different aspects related to luting fiber posts

DIFFERENT ASPECTS

RELATED TO LUTING FIBER POSTS

Ivana Radovi�

1

UNIVERSITY OF SIENA

School of Dental Medicine

PhD PROGRAM:

“DENTAL MATERIALS AND THEIR CLINICAL

APPLICATIONS”

PhD THESIS OF:

Ivana Radovi�_________________________________________________

TITLE:

Different aspects related to luting fiber posts

Academic Year 2008/09

2

December 11th 2009

Siena, Italy

Committee:

Promoter Prof. Marco Ferrari

Co-Promoter Prof. Zoran R. Vuli�evi�

Prof. Leopoldo Forner Navarro

Prof. Andrea Borracchini

Prof. Cecilia Goracci

Prof. Lorenzo Breschi

Prof. Simone Grandini

TITLE:

Different aspects related to luting fiber posts

CANDIDATE

Ivana Radovi�

3

Table of contents

Chapter 1: Introduction _______________________________ 5�

1.1. Fiber posts – general facts __________________________________ 5�

Chapter 2: Treatments of fiber post surface _____________ 23�

2.1. The effect of sandblasting on adhesion of a dual-cured resin composite

to methacrylic fiber posts: microtensile bond strength and SEM evaluation

__________________________________________________________ 23�

2.2. Accelerated aging of adhesive-mediated fiber post-resin composite

bonds: a modeling approach ___________________________________ 44�

2.3. Coupling of composite resin cements to quartz fiber post: a

comparison of industrial and “chair-side” treatments of the post surface _ 64�

Chapter 3: Selection of resin cement for fiber post

cementation ________________________________________ 91�

3.1. Self-adhesive resin cements: a literature review ________________ 91�

3.2. Evaluation of the adhesion of fiber posts cemented using different

adhesive approaches ________________________________________ 118�

Chapter 4: Light transmission through fiber post ________ 144�

4.1. Light transmission through fiber post: The effect on adhesion, elastic

modulus and hardness of dual-cure resin cement __________________ 144�

Summary _________________________________________ 169�

Conclusions _______________________________________ 172�

4

Sommario e conclusioni _____________________________ 173�

Sommaire et conclusions ____________________________ 178�

Zusammenfassung und schlussfolgerungen _____________ 184�

Sažetak i zaklju�ci __________________________________ 189�

Complete list of references ___________________________ 195�

Curriculum vitae ___________________________________ 218�

Acknowledgements _________________________________ 226�

5

Chapter 1: Introduction

1.1. Fiber posts – general facts

Fiber reinforced composite posts are the newest in line of endodontic posts

that are available to clinicians today. They have been used for more than

twenty years (Duret et al. 1990). The first posts were made of carbon fibers.

Even though carbon fiber posts demonstrated favorable clinical behavior

(Fredriksson et al. 1998), nowadays they have been almost entirely replaced

by quartz and glass fiber posts, primarily for esthetic reasons. Beside fibers,

posts may contain epoxy or methacrylate resin.

The most widely known feature of fiber posts is their elasticity, which

is similar to dentin and composite resins (Asmussen et al. 1999). The

modulus of elasticity of cast, titanium and ceramic posts is several times

higher which implies that these posts are much more rigid than fiber posts

(Table). Due to favorable elasticity, stress distribution during clinical

function is uniform and spreads along the entire root. On the other side, when

rigid metallic posts are used, stress concentrates in isolated points and the

risk of root fracture is much higher (Figure).

This feature may be particularly important and beneficial in pediatric

dentistry, especially in cases when teeth have to be restored following

apexification procedures, since in such short roots with extremely thin walls,

fiber posts may prevent root fractures that are otherwise quite common

(Katebzadeh et al. 1998). Even in fully developed roots, young patients’ teeth

still have fairly wide root canals that may benefit too from the placement of

fiber post instead of much more rigid metallic posts that some time ago used

to be the only option. Good clinical performance of endodontically treated

6

teeth restored with fiber posts and direct composite restorations has been

reported (Grandini et al. 2005c), which is also of importance for pediatric

dentistry. Besides favorable mechanical properties, fiber posts provide a fine

esthetic base for direct composite restorations or full ceramic crowns (Ferrari

2008).

Table: Modulus of elasticity of dentin and different post materials (Tay and

Pashley 2007)

Material Modulus of elasticity [GPa] Dentin 14 – 19 Fiber posts 18 – 22 Ceramic posts (ZrO2) 96 Titanium posts 120 Cast posts 200

Figure: Fiber posts provide balanced stress distribution along the root (left),

whereas considerably stiffer metallic posts may cause stress concentration in

isolated points (right).

7

It was noted long time ago that endodontically treated teeth are

weaker than vital teeth. It is now known that the main reason for this is the

loss of crown tissue due to decay or trauma (Reeh et al. 1989). Further

weakening takes place when access cavity is prepared (Panitvisai and Messer

1995). Additionally, following pulp removal, the protective feed-back

mechanism that the pulp provides is lost, and roots are prone to fractures

(Randow and Glantz 1986).

Even though a strengthening effect is often needed when restoring

endodontically treated teeth, research has clearly shown that metallic posts

cannot fulfill this task (Guzy and Nicholls 1979; Trope et al. 1985).

Therefore, the main indication for post placement is the need for additional

retention for crown restoration (Schwartz and Robbins 2004). This applies to

all endodontic posts, including fiber posts. However, knowing the favorable

fiber post properties that provide well balanced stress distribution and root

fracture prevention, it makes sense to assume that adhesively cemented fiber

posts may also strengthen teeth to a certain extent, apart from providing

additional retention. Indeed, it was reported that strengthening effect is

present immediately after adhesive post cementation (Saupe et al. 1996;

Mannocci et al. 1999). Nevertheless, it is believed that this strengthening

effect is lost during function (Schwartz and Robbins 2004). Therefore, in

order to better understand the strengthening effect and its duration, it was

recommended to include simulations of clinical function into studies that

investigate this topic (Schwartz and Robbins 2004).

Apart from the usual indications, fiber posts may be extremely useful

in traumatology, for reattaching fractured crown fragments following

endodontic treatment (Durkan et al. 2008), or in case of complicated crown-

root fractures (Fidel et al. 2006). This approach follows the general trend of

minimal intervention dentistry (Mount and Ngo 2000), and may provide

8

functional and economical treatments regardless of patient’s age. However,

in pediatric dentistry, it may be particularly important, as it enables to

postpone the crown placement and preserve the integrity of the epithelial

junction in a young patient. Orthodontic extrusion may also be performed

with an aid of fiber post after a traumatic injury, if indicated (Yuzugullu et al.

2008).

Different shapes of fiber posts are available: parallel, tapered, or posts

may have additional macro retentive grooves. Similar survival rates were

reported for parallel and tapered fiber posts in a recent clinical study (Signore

et al. 2009). However, greater removal of root canal dentin is usually

inevitable in order to fit in a parallel shaped post. For this reason, tapered

posts are generally recommended, especially in teeth with thin roots and

delicate morphology, as tapered posts respect root canal's anatomy and

require only minimal removal of root canal dentin (Schwartz and Robbins

2004).

Even though all fiber posts consist of fibers and matrix, they don’t all

have similar mechanical properties. This was clearly demonstrated when

posts were subjected to cyclic loading of 2 million cycles that roughly

simulated four years of clinical function (Grandini et al. 2005b). Only one

post was able to withstand this loading while the others fractured at less than

2 million cycles. The authors stated that a slightly different design might

have provided findings of higher clinical relevance. Nevertheless, from the

two clinical studies by Naumann (Naumann et al. 2005a; Naumann et al.

2005b), a correlation may be observed between in vitro findings and actual

clinical behavior of some posts. Fiber posts that exhibited poor mechanical

properties in the study by Grandini et al. were reported to fail by post fracture

in the two clinical studies (Naumann et al. 2005a; Naumann et al. 2005b). On

the other side, when post with superior mechanical properties was used,

9

fractures of the posts were never reported to be a cause of clinical failure

(Monticelli et al. 2003; Cagidiaco et al. 2007; Cagidiaco et al. 2008a).

Several factors are believed to influence the success of fiber post

cementation and fiber post-retained restorations. It is often recommended to

avoid eugenol based sealers, due to risk that remnants of eugenol in dentinal

tubules may interfere with complete polymerization of resin cements and

adhesives. Literature is not consistent on this topic. Kurtz et al. have shown

that post retention is not impaired with eugenol based sealers (Kurtz et al.

2003). On the other side, lower fiber post retention in roots treated with

eugenol based sealers was also reported (Baldissara et al. 2006). Etch-and-

rinse adhesives may attain higher adhesion to eugenol contaminated dentine

surfaces than self-etching adhesives (Carvalho et al. 2007). This was

explained by the self-etching adhesives’ mechanism of action, which is based

on incorporation of the eugenol containing smear layer into the hybrid layer.

Conversely, phosphoric acid removes the smear layer, and hence it is much

more effective in removing the remnants of eugenol from the dentine surface.

For this reason, etch-and-rinse adhesive system may be preferable for fiber

post cementation in roots treated with eugenol based endodontic sealers

(Ferrari 2008).

There are many clinical studies that have shown that failures happen

more often when crown destruction is extensive. Therefore, clinically every

effort should be made to preserve as much coronal tissue as possible

(Cagidiaco et al. 2008b). More importantly, in case of crown placement,

literature is in agreement that preparation of a 2mm-high 1mm-thick ferrule

will give the restoration the highest chances for long lasting successful

clinical function (Stankiewicz and Wilson 2002). It was also demonstrated

that even the preparation of a non-uniform ferrule, which is clinically often

10

the only option, provides higher fracture resistance than no ferrule at all (Tan

et al. 2005).

During fiber post cementation, it is recommended to keep the resin

cement layer as thin as possible. Even though one study showed that cement

layer does not influence fiber post retention (Perez et al. 2006), the

recommendation remains. As resin cements are formulated to be used in thin

films, their mechanical properties allow only a thin layer around the post, in

order to provide the most favorable stress distribution along the root. In case

of oval canals, in which a circular post cannot fit perfectly, since recently

small, so called accessory posts are available that may be placed in addition

to the main post (Porciani et al. 2008). The placement of accessory posts can

be roughly compared to lateral gutta-percha condensation, with an aim to

reduce the amount of resin cement as much as possible. For the same purpose

oval or anatomic posts (Grandini et al. 2005a) may be used, too.

The standard rules for endodontic post length in root canal apply for

fiber posts too. The most important two rules to follow are to leave 4-5 mm

of gutta-percha and sealer apically in order to prevent apical microleakage,

and to assure that the ratio between the root part of the post and the crown is

at least one to one or more whenever possible (Schwartz and Robbins 2004).

Clinical studies of fiber posts have shown good clinical performance

of this treatment option. Nevertheless, it was noted that if the treatment fails,

it usually does due to debonding of the post (Cagidiaco et al. 2008b). For this

reason, adequate attention needs to be given to both of the interfaces that

form when post is cemented: fiber post-cement interface and cement-root

dentin interface. It was recently assumed that the amount of light

transmission through the post may affect both these interfaces (Goracci et al.

2008, Ferrari 2008). Fiber post-cement interface may be influenced through

different treatments of the post surface, whereas cement-root dentin interface

11

is primarily affected by the type of resin cement/adhesive approach used.

Therefore, fiber post surface treatment, resin cement selection and light

transmission through the post were the three aspects of post cementation that

this thesis focused on. Studies assessing each aspect are presented in

Chapters 2, 3 and 4, respectively.

Fiber post surface treatment

It was reported that the fiber post-cement interface is one of the levels where

a debonding failure can occur (Perdigao et al. 2006), and a number of

investigations focused on improving the adhesion at this interface. Coupling

between fiber posts and resin cements may be influenced by post surface

treatments. Various post surface treatments have been investigated so far. It

appears from the current literature that the majority of fiber posts benefit

from some kind of surface treatment, though the best treatment is not the

same for every post (Monticelli et al. 2008). Fiber post surface treatment

procedures fall within three categories (Monticelli et al. 2008):

1. treatments that result in chemical bonding between composite and

post (coating with primer solutions)

2. treatments that roughen the surface (sandblasting and etching)

3. treatments that combine both a micromechanical and chemical

component, either by a combination of the two above-mentioned

treatments or by the use of specific systems (e.g. Co-Jet®)

Chapter 2 of this thesis presents three studies that investigated various

treatments of fiber post surface. In order to determine the influence of surface

treatments to fiber post adhesion, post-composite microtensile bond strength

tests (Goracci et al. 2005a) and SEM investigations were performed.

12

Resin cement selection

According to the curing mode, resin cements may be light-curing, dual-

curing or self-curing materials. Additionally, resin cements may be

categorized into the following three groups, based on the adhesive system

they use, i.e. – their adhesive approach.

1. Cements with etch-and-rinse adhesives

2. Cements with self-etching adhesives

3. Self-adhesive cements.

Resin cements with etch-and-rinse adhesives have been successfully

used with fiber posts for the longest period of time, and the vast majority of

clinical studies investigated this type of cements (Ferrari et al. 2000a; Ferrari

et al. 2000b; Malferrari et al. 2003; Mannocci et al. 2005; Monticelli et al.

2003; Grandini et al. 2005c; Naumann et al. 2005a; Naumann et al. 2005b;

Cagidiaco et al. 2007; Ferrari et al. 2007a; Ferrari et al. 2007b). Application

steps of etch-and-rinse adhesives in root dentin do not differ from coronal

dentin. However, etch and rinse adhesives are generally considered to be

technique sensitive (Van Meerbeek et al. 2003). The main reason for widely

discussed technique sensitivity of etch-and-rinse systems is the questionable

degree of surface wetness needed after rinsing the acid. While enamel should

preferably be dry to allow penetration of adhesive monomers, proper treating

of dentin is more complex. The etching and rinsing step leaves dentin surface

demineralized to a depth of 3-5μm (Perdigao et al. 1996). More importantly,

collagen fibers are exposed and left without inorganic support of

hydroxyapatite. In order to achieve penetration of resin monomers into such a

structure and assure interlocking, collapse of collagen fibers needs to be

prevented. It has been described that overdrying of dentin surface induces

collapse of collagen fibers which form a coagulate, thereby impeding proper

resin penetration (Pashley and Carvalho 1997). Depending on the kind of

13

solvent of the primer (or primer/adhesive in two-step systems), two different

clinical approaches have been described: wet and dry bonding (Gwinnett

1992; Kanca 1992). Regardless of the bonding technique used, the possibility

for discrepancy between depth of dentin demineralization and monomer

infiltration was recognized as a main drawback of etch-and-rinse adhesives

(Van Meerbeek et al. 1992; Sano et al. 1994; Wang and Spencer 2003).

Considering that in fiber post cementation these adhesives have to be applied

to the surface that cannot be properly visualized, it would be reasonable to

assume that they are even more technique sensitive when used in the root

canal. For this reason, it is often recommended to adapt every step to the

specific conditions of the post space. Phosphoric acid should be applied and

rinsed-off through a needle or a long tip, in order to reach the apical third of

the post space. Drying should be performed using paper points in order to

avoid desiccation of the dentin surface, while for adhesive application,

microbrushes should be used (Ferrari et al. 2002).

Cements used with self-etching adhesives are simpler and more user

friendly. Since rinsing phase is excluded, so is the need for establishing the

debatable optimal level of moisture on dentin surface, which significantly

reduces technique sensitivity. These systems are user-friendly due to reduced

number of application steps and reduced application time. Another

characteristic of self-etching systems is simultaneous demineralization and

infiltration of resin monomers as well as incorporation of smear layer into

hybrid layer.

The newest group of resin cements consists of self-adhesive cements,

which are by far the easiest to use and are becoming very popular. Some

products have application tips exclusively made for easy and efficient fiber

post cementation. These materials are still new and for this reason they were

given particular attention in a literature review that is presented in Chapter 3

14

of this thesis. The second study of Chapter 3 assessed fiber post adhesion

with resin cements from each of the above-mentioned three categories. In

order to determine the retentive strength of fiber posts, microtensile

(Bouillaguet et al. 2003; Mallmann et al. 2005; Monticelli et al. 2006) and

push-out (Kurtz et al. 2003; Bell et al. 2005; Goracci et al. 2005b) tests may

be used. In the study presented in Chapter 3, the thin-slice push-out strength

test was performed, since it was shown to be more reliable than the

microtensile technique for measuring the retentive strength of fiber posts to

root canal walls (Goracci et al. 2004).

Light transmission through fiber post

The vast majority of posts that are available to clinicians are claimed by the

manufacturers to transmit light. However, a study by Goracci et al

demonstrated that posts differ in the amount of transmitted light and that

some of the posts that are declared to transmit light do not transmit any light

at all (Goracci et al. 2008). Fiber posts were therefore divided into three

categories based on their light transmitting ability (Ferrari 2008):

1. Posts that permit light to pass in a consistent entity

2. Posts that permit light to pass only partially and do not transmit light

at the apical end of the post

3. Posts that do not permit light to irradiate at all.

It is advisable not to use light curing resin cements and adhesives

because of the post space depth that cannot be entirely reached by light. For

this reason, self curing and dual curing resin cements are strongly

recommended (Ferrari 2008). It appears that in clinical practice dual-curing

cements are most frequently used. Moreover, dual-curing resin cements were

used in several clinical studies on fiber posts (Ferrari et al. 2000b; Monticelli

et al. 2003; Grandini et al. 2005c; Naumann et al. 2005a; Naumann et al.

15

2005b; Cagidiaco et al. 2007; Ferrari et al. 2007b). These materials have the

advantage of adequately long working time, and still they can be cured on

demand when convenient for the clinician. They cure by light in areas that

light can reach, whereas in areas non reachable by light, chemical

polymerization takes place. However, it was reported that dual curing

cements reach far better mechanical properties in the presence of light, and it

is hence recommended to light cure them whenever possible (Caughman et

al. 2001; Kumbuloglu et al. 2004). The question remained whether this

property of dual curing cements in relation with light transmitting ability of

the post may in fact make a difference in fiber post cementation. It was not

known whether light transmission through the post may influence the quality

of post/cement/dentin interfaces. In an attempt to give an answer to these

questions, a study presented in Chapter 4 was performed.

16

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reinforced dowel system in the intraradicular restoration of structurally

compromised roots. Quintessence Int 27(7): 483-91.

Schwartz RS, Robbins JW (2004). Post placement and restoration of

endodontically treated teeth: a literature review. J Endod 30(5): 289-301.

Signore A, Benedicenti S, Kaitsas V, Barone M, Angiero F, Ravera G

(2009). Long-term survival of endodontically treated, maxillary anterior teeth

restored with either tapered or parallel-sided glass-fiber posts and full-

ceramic crown coverage. J Dent 37(2): 115-21.

Stankiewicz NR, Wilson PR (2002). The ferrule effect: a literature

review. Int Endod J 35(7): 575-81.

22

Tan PL, Aquilino SA, Gratton DG, Stanford CM, Tan SC, Johnson

WT, Dawson D (2005). In vitro fracture resistance of endodontically treated

central incisors with varying ferrule heights and configurations. J Prosthet

Dent 93(4): 331-6.

Tay FR, Pashley DH (2007). Monoblocks in root canals: a

hypothetical or a tangible goal. J Endod 33(4): 391-8.

Trope M, Maltz DO, Tronstad L (1985). Resistance to fracture of

restored endodontically treated teeth. Endod Dent Traumatol 1(3): 108-11.

Van Meerbeek B, De Munck J, Yoshida Y, Inoue S, Vargas M, Vijay

P, Van Landuyt K, Lambrechts P, Vanherle G (2003). Buonocore memorial

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Oper Dent 28(3): 215-35.

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(1992). Morphological aspects of the resin-dentin interdiffusion zone with

different dentin adhesive systems. J Dent Res 71(8): 1530-40.

Wang Y, Spencer P (2003). Hybridization efficiency of the

adhesive/dentin interface with wet bonding. J Dent Res 82(2): 141-5.

Yuzugullu B, Polat O, Ungor M (2008). Multidisciplinary approach to

traumatized teeth: a case report. Dent Traumatol 24(5): e27-30.

�

23

Chapter 2: Treatments of fiber post surface

2.1. The effect of sandblasting on adhesion of a dual-cured resin

composite to methacrylic fiber posts: microtensile bond strength and

SEM evaluation

Ivana Radovic, Francesca Monticelli, Cecilia Goracci, Àlvaro Hafiz Cury,

Ivanovic Coniglio, Zoran R. Vulicevic, Franklin Garcia-Godoy, Marco

Ferrari. Journal of Dentistry 2007; 35(6): 496-502.

Introduction

Reconstructing endodontically treated teeth with prefabricated fiber post and

core systems has been widely accepted as a treatment option offering both

esthetics and function (Schwartz and Robbins 2004; Schwartz and Fransman

2005). The advantages of fiber post and core restorations have been

demonstrated in in vitro studies (Martinez-Insua et al. 1998; Sirimai et al.

1999; Cormier et al. 2001; Akkayan and Gulmez 2002; Newman et al. 2003;

Fokkinga et al. 2004; Hayashi et al. 2006). These systems can reduce the

incidence of non-retrievable root fractures when compared to prefabricated

metallic posts or conventional cast posts (Martinez-Insua et al. 1998; Sirimai

et al. 1999; Cormier et al. 2001; Akkayan and Gulmez 2002; Newman et al.

2003; Fokkinga et al. 2004; Hayashi et al. 2006). Retrospective (Fredriksson

et al. 1998; Ferrari et al. 2000; Ferrari et al. 2000) and prospective (Glazer

2000; Mannocci et al. 2002; Malferrari et al. 2003; Monticelli et al. 2003;

Naumann et al. 2005a; Naumann et al. 2005b) clinical studies have shown

overall satisfactory performance of endodontically treated teeth restored with

fiber post and core systems.

24

An important characteristic of fiber posts is a modulus of elasticity

similar to dentin, resin cements and resin core materials (Asmussen et al.

1999). This feature is most beneficial in the presence of a homogeneous post-

composite-dentin structure that would allow optimal stress distribution (De

Santis et al. 2000). Therefore, the importance of optimal coupling between

fiber post system components has been recognized and investigated. A

number of studies focused particularly on the possibility to improve adhesion

at the fiber post-composite interface through various treatments of post

surface (Sahafi et al. 2003; Sahafi et al. 2004a; Asmussen et al. 2005;

Goracci et al. 2005; Balbosh and Kern 2006; Bitter et al. 2006; Monticelli et

al. 2006a; Monticelli et al. 2006b; Monticelli et al. 2006c).

An increase in bond strength to flowable composites was observed

when fiber posts were silanized (Goracci et al. 2005), treated with a

combination of hydrogen peroxide etching and silanization (Monticelli et al.

2006c) as well as when chemical pretreatment with potassium permanganate

followed by silanization was employed (Monticelli et al. 2006b).

Furthermore, application of the silane/adhesive coupling was shown to

improve bond strength to hybrid composite (Monticelli et al. 2006a).

Adhesion of dual-cure resin composite to epoxy resin-based fiber posts was

improved when the post surface was treated with a dual cured bonding agent

or was silanized (Aksornmuang et al. 2004).

The possibility of improving the adhesion between fiber posts and

resin cements has been investigated to a somewhat lesser extent.

Sandblasting followed by silane coating, sandblasting alone and

tribochemical treatment (CoJet) significantly increased shear bond strength of

resin cements to methacrylate based glass fiber posts (Sahafi et al. 2003).

CoJet treatment significantly increased the resistance to cyclic loading of

teeth restored with adhesively luted glass fiber posts, which was assumed to

25

derive from an effective bonding of resin cement to the posts with a

reinforcing effect on the teeth (Sahafi et al. 2005). Sandblasting of the

surface of the glass-fiber epoxy resin posts significantly improved the

retention of posts adhesively luted with dual cured resin cement (Balbosh and

Kern 2006).

Sandblasting is routinely applied in general industry to provide

surface roughening making materials more bondable. It is commonly

employed in ceramic (Chung and Hwang 1997) and composite repair

procedures (Swift et al. 1992; Pontes et al. 2005; Papacchini et al. 2008),

indirect composite bonding (Swift et al. 1992), for pretreatment of metal

surface in metal-ceramic restorations (Winkler and Wongthai 1986), or as a

part of a tribochemical silica-coating process (Kern and Thompson 1993).

Nevertheless, the information on the effect of sandblasting alone or

combined with additional “chair-side” treatments on bond strength to fiber

posts is lacking. Therefore, the aim of this investigation was to evaluate the

influence of sandblasting pretreatment and different “chair-side” treatments

of methacrylate based fiber posts on the microtensile bond strength with a

dual-cured resin composite. The null hypothesis tested was that various

combinations of surface pre-treatment and “chair-side” treatment did not

influence the adhesion of methacrylate based fiber posts to dual-cured resin

composite.

Materials and Methods

Thirty two translucent methacrylate-based glass fiber posts (GC Corporation,

Tokyo, Japan) with a diameter of 1.6 mm were used in the study. Posts were

divided into two groups, according to the surface pretreatment performed.

Group 1: Sandblasting with 110μm aluminum oxide particles (Rocatec-Pre,

26

3M ESPE, St. Paul, MN, USA) for 5 seconds at 2.8 bar (0.28 MPa) from a

distance of 1 cm. In Group 2 no pretreatment was performed. Each group was

further divided into three subgroups (n=5), according to the additional “chair-

side” treatment performed. Subgroup 1: silane application (Monobond S,

Ivoclar Vivadent, Schaan, Liechtenstein); Subgroup 2: adhesive application

(Unifil Core self-etching bond, GC Corporation); Subgroup 3: no additional

“chair-side” treatment. The materials were used according to the

manufacturers’ instructions. The chemical composition, batch numbers and

the application modes are reported in Table 1.

Composite build-up and microtensile bond strength test procedures

A dual-cured resin composite (Unifil Core, GC Corporation) was applied on

the posts to produce cylindrical specimens with the post in the center, using a

transparent plastic matrix. The procedure previously described by Goracci et

al. for core build-up materials was followed (Goracci et al. 2005). All

specimens were prepared by one investigator to ensure standardization. Each

post was positioned upright on a glass slab, and secured with a drop of sticky

wax. A cylindrical plastic matrix was placed around the post and adjusted so

that the post would be exactly in the middle. The matrix was 10 mm in

diameter. In height, the matrix was extended only to the cylindrical portion of

the post (about 10 mm), since for an appropriate cutting of the microtensile

specimens, it is desirable that the post diameter is constant throughout the

post length. The two components of resin composite were mixed, applied on

the post filling the matrix completely, and light cured for 40 s with a halogen

curing light (600 mW/cm2 output; VIP; Bisco, Schaumburg, IL, USA)

directly from the open upper side of the matrix and through the post.

27

Table 1: Composition, batch numbers and the application mode of the

materials used in the study

Material Composition1 Application mode Rocatec-Pre Aluminum oxide

(particle size: 110 μm)

Sandblasting from a distance of 1 cm at 2.8 Bar (0.28 MPa) for 5 sec.2

Monobond S (Ivoclar Vivadent) Batch no. F68158

1% 3-methacryloxypropyltrimethoxysilane (3-MPS), ethanol/water-based solvent

Apply to the post surface. Air dry after 60 seconds.

Unifil Core self-etching bond (GC Corporation) Batch no. 0511251

Liquid A: Ethanol, water, 4-MET, dimethacrylate, silica, catalyst Liquid B: Ethanol, catalyst

Mix liquid A and Liquid B; (1:1) apply mixture to the post surface for 1-2 seconds; gently air dry; light cure

Unifil Core Resin Cement/Core material (GC Corporation) Batch no. 0511251

Pastes A and B: Urethane dimethacrylate, dimethacrylate, photo/chemical initiator, fluoro-amino silicate glass

Mix components; seat the post immediately; light cure.

GC fiber post (GC Corporation) Batch no. 21700BZZ00408000

Glass fibers (77% vol), methacrylate resin matrix (23% vol)

-

1 Information from the manufacturers. 2 Manufacturer’s recommended procedure is: sandblast from the distance of 1cm2 at 2.8 Bar for 15 seconds for the area of approximately 1cm2. Considering the size of fiber posts, the sandblasting time was reduced to 5 seconds.

28

Additional 40 s irradiations were performed from each side of the cylinder

prior to the removal of the matrix to ensure optimal polymerization of the

composite material.

Cylinders were mounted in a cutting machine (Isomet 1000, Buehler,

Lake Bluff, IL, USA) and sectioned under water cooling to obtain a slab of

uniform thickness, with the post in the center and composite on each side.

From each slab, 6-8 sticks of 1-mm in thickness were obtained, resulting in

the multiple specimens (32 on average per subgroup) that were available for

microtensile bond strength testing. Beams were glued (Super Attak Gel,

Henkel Loctite Adesivi S.r.l., Milano, Italy) to the two free sliding

components of a jig, which was mounted on a universal testing machine

(Triax, Controls S.P.A., Milano, Italy) and loaded in tension at a crosshead

speed of 0.5 mm/min until failure occurred at either side of the post-

composite interface. The dimensions of the interface on each beam were

measured with a digital caliper to the nearest 0.01 mm. No pretesting failures

occurred during cutting and testing procedures. Schematic drawing of

specimen preparation for microtensile testing is shown in Figure 1.

Failure modes were evaluated with a stereomicroscope (Nikon

SMZ645, Tokyo, Japan) at 40x magnification and recorded as adhesive (at

the post/composite interface), cohesive (within the post or the composite) or

mixed (a combination of the two modes of failure in the same interface).

Bond strength was expressed in MegaPascals (MPa), dividing the load at

failure in Newtons by the bonding surface area. As the bonded interface was

curved, its area was calculated using a mathematical formula previously

applied by Bouillaguet et al (Bouillaguet et al. 2003).

29

Figure 1: Schematic drawing of specimen preparation for microtensile bond

strength testing. C: composite; P: post.

SEM evaluation

One post was randomly selected from each of the two main groups for SEM

examination of the surface morphology. The posts were ultrasonicated in

96% alcohol for 2 min and air dried. Following core build-up procedure, one

post-composite cylinder from each subgroup was randomly chosen for the

SEM evaluation of the bonded interface. Samples were cut into 1.5 mm thick

cross-sections (Isomet 1000; Buehler). Sections were polished with wet

abrasive SiC papers, cleaned with orthophosphoric acid for 15 s, rinsed with

water, ultrasonicated in 96% alcohol for 2 min and air dried. Each specimen

was mounted on a metallic stub, sputtered with gold-palladium (Polaron

Range SC7620; Quorum Technology, Newhaven, UK), and observed under

an SEM (JSM 6060 LV, JEOL, Tokyo, Japan) at different magnifications.

30

Statistical analysis of the microtensile bond strength data

A preliminary linear regression analysis showed that the post–composite

cylinder did not have a significant influence on the measured bond strength;

therefore, the sticks were considered as independent within each group. After

analyzing the bond strength data for the normality of data distribution

(Kolmogorov–Smirnov test) and homogeneity of variances (Levene’s test), a

two-way ANOVA was applied with bond strength as the dependent variable,

and types of surface pretreatment and “chair-side” treatment as factors. The

Tukey test was used for post hoc comparisons. In all the tests, the level of

significance was set at p<0.05 and calculations were handled by the SPSS

13.0 software (SPSS Inc.; Chicago, IL, USA).

Results

Interfacial Bond Strength

Results of microtensile bond strength testing are summarized in Table 2 and

Figure 2. Statistical analysis revealed that post surface pretreatment was not a

significant factor (p=0.08), while ‘‘chair-side’’ treatment had a significant

influence on bond strength (p<0.001). When the results were pooled for each

‘‘chair-side’’ treatment regardless of the pretreatment, post hoc comparisons

(Tukey test) revealed that no ‘‘chairside’’ treatment and silanization resulted

in comparable bond strengths while the values were significantly lower when

the adhesive was applied. The interaction of the two factors was also

significant (p<0.001). This lead to post hoc comparisons (Tukey test) in

which all six groups were compared to assess which group means differed

from which others. The Tukey test revealed that sandblasting significantly

improved bond strength when no ‘‘chair-side’’ treatment was performed

(Table 2). The values in this group were comparable to experimental groups

31

‘‘sandblasting/Monobond S’’ and ‘‘no pretreatment/Monobond S’’. Adhesive

application resulted in significantly lower bond strength on sandblasted posts,

while on conventional posts results were comparable with no ‘‘chair-side’’

treatment. Application of silane had no influence on bond strength, regardless

of the pretreatment. In group ‘‘sandblasting/Monobond S’’ and

‘‘sandblasting/no treatment’’ cohesive failures within the fiber post occurred

in 47 and 35% of tested beams, respectively. In the other groups the most

frequent type of failure was adhesive (Figure 3).

Table 2: Post-composite microtensile bond strength [MPa]. Numbers are

means. Values in brackets are standard deviations. Different superscript

letters indicate statistically significant differences.

Pretreatment

Treatment Sandblasting None

Monobond S 19.76 [6.16]AB 21.67 [7.13]AB

Unifil Core self-etching bond 14.29 [6.02]C 14.12 [4.90]C

None 23.97 [6.82]A 17.67 [5.31]BC

32

Figure 2: Post-composite microtensile bond strength

SANDBLASTINGNO PRETREATMENT

� � �

Monobond SUnifil Core self-etching bond

No treatment

�

�

�

�

10

20

30

40

[MPa

]

Figure 3: Failure distribution. M: mixed failure. CC: cohesive failure within

the cement. CP: cohesive failure within the post. A: adhesive failure.

33

SEM evaluation

Sandblasting created a rough surface along the entire post length (Figure 4A),

providing additional spaces for micromechanical retention compared to the

surface of a conventional post (Figure 4B). Cross-sections of the post-

composite interfaces exhibited a good adaptation of the resin composite to

the post surface in groups: “sandblasting/Monobond S”, “sandblasting/no

treatment”, “no pretreatment/Monobond S” and “no pretreatment/no

treatment” (not shown). No defects and no discontinuities occurred along the

interface, and no significant differences in the morphology of the interface

between these groups were noticed. In groups where adhesive was applied,

gaps between the post surface and the adhesive layer were frequently

observed, both on sandblasted and conventional posts (not shown), without

significant differences in gap occurrence and morphological appearance.

34

Figure 4. Representative SEM micrographs of a post-surface. After

sandblasting (A) the surface appeared more retentive compared to the

conventional post surface (B).

A

B

35

Discussion

Unifil Core belongs to the group of materials that are formulated to be used

both for cementation and core-build-up procedures. However, the

experimental set-up employed in this investigation has limitations that render

it more appropriate for simulating a core-build-up procedure than a luting

procedure. The amount of material that was placed around the posts is

considerably thicker than the cement layer between the fiber post and root

canal. In the clinical situation, a much higher C-factor is present, as well as

an unfavorable interaction between C-factor and shrinkage stress that could

interfere with bond strength values (Tay et al. 2005). However, microtensile

tests allow bond strength measurements between resin cements or core

materials and surface of fiber posts. Assessing fiber post-resin cement bond

strength with conventional shear bond strength tests required the post surface

to be removed (Sahafi et al. 2003), while tensile bond strength tests have

been conducted with discs of post materials (O'Keefe et al. 2000; Sahmali et

al. 2004). Therefore, microtensile bond strength values measured after

bonding to the original post surface may be advantageous and more clinically

relevant.

Significant differences in bond strength were found between

experimental groups, which led to the rejection of the null hypothesis. The

highest bond strength was recorded on sandblasted posts with no additional

“chair-side” treatment. Results in this group were significantly better than the

results on conventional posts with no additional treatment. SEM evaluation

supported bond strength data (Figure 4A), revealing a more retentive surface

created by sandblasting. This finding is in accordance with others

demonstrating the beneficial influence of sandblasting on retention of epoxy

resin based fiber posts (Balbosh and Kern 2006). Significantly higher bond

36

strengths of resin cements to sandblasted posts were also observed on

methacrylate (Sahafi et al. 2003) and epoxy resin-based fiber posts (Wang et

al, unpublished data, 2006).

Application of silane did not result in increase in bond strength,

regardless of the pretreatment. This finding is in contrast with previous

studies that reported beneficial influence of silanization on bond strength to

conventional (Goracci et al. 2005) and sandblasted fiber posts (Sahafi et al.

2003). The mechanism of silane action relies on formation of bonds between

its functional alkoxy groups and OH-covered inorganic substrates. Since the

resin matrix of fiber posts contains highly cross-linked monomers, only the

exposed fibers on the post surface could provide sites for chemical bonding

with the silane molecules. As the contribution of such a chemical interaction

to fiber post-composite bond strength is considered to be fairly low, it is

assumed that the increase in surface wettability induced by silane application

plays a more important role (Goracci et al. 2005). However, it was shown

that surface energy characteristics of adherend and adhesive determine fiber

post-composite bond strength in the minor part, while the other factors

remained to be identified (Asmussen et al. 2005). Bond strength of Unifil

Core to epoxy resin fiber posts silanized with Monobond S (Sadek et al.

2007) was noticeably lower than in the present investigation. Since GC fiber

post is methacrylate based, it can be speculated that the dual-cured resin

composite bonded to the organic matrix of fiber posts, consequently

influencing bond strength to a greater extent than the potential surface

wetting capacity of the silane applied. Nevertheless, bond strength to

conventional silanized posts (“no pretreatment/Monobond S”) was

comparable to bond strength to sandblasted posts (“sandblasting/no

treatment”) (Table 2).

37

Monobond S is a single component pre-hydrolyzed silane. On the

other side, two-component systems have been introduced for “on-demand”

hydrolysis. In these systems the silane is rapidly hydrolyzed when mixed

with the acidic phosphate monomers like 10-MDP (10-methacryloloxydecyl

dihydrogenphosphate), which are present in the water-containing dentin

adhesives. It would be of interest to investigate whether the beneficial effect

of a two-component system on epoxy resin-based fiber posts (Aksornmuang

et al. 2004; Monticelli et al. 2006a) could be observed using fiber posts that

contain methacrylate matrix.

Coating the posts with the proprietary self etching adhesive (Unifil

Core self-etching bond) resulted in the lowest bond strengths, regardless of

the pretreatment. Moreover, gaps were frequently observed between the post

and the adhesive layer. No discontinuities were seen between the adhesive

layer and the cement. In contrast to these findings, the application of a dual

cured bonding agent significantly improved adhesion to epoxy resin based

fiber posts (Aksornmuang et al. 2004). The authors speculate that the water

content and acidity of the self-etching adhesive used in this study may have

influenced bonding to fiber post surface. A possible mechanism involved

could be the phase separation of adhesive monomers from water upon

evaporation of ethanol solvent, that was demonstrated to occur in HEMA-

free (2-hydroxyethyl methacrylate) one-step self-etching adhesives (Van

Landuyt et al. 2005). Remnants of water may have affected the

polymerization of the adhesive, decreasing bond strength and influencing gap

formation at the adhesive-post interface.

In general, higher bond strengths resulted in a superior percentage of

cohesive failures (Figure 3), correlating with previous investigations of other

authors (O'Keefe et al. 2000; Sahmali et al. 2004). The vast majority of

cohesive failures occurred within the fiber post, which may be the result of an

38

unfavorable coupling between glass fibers and methacrylate matrix of the

fiber post.

Although sandblasting may give an increase in microtensile strength

to methacrylate-based glass fiber posts, its effects should be further

investigated. Concern was raised regarding the possible volume loss induced

by sandblasting or tribochemical coating procedures (Sahafi et al. 2004b).

Therefore, further research is necessary in order to agree on the optimal

particle size, distance, pressure and time of application. Additional

application of a self-etching adhesive to methacrylate-based fiber posts

should be avoided, since no increase in bond strength could be observed.

Moreover, long term durability of fiber post-composite bonds following

various treatments of post surface under clinical and laboratory conditions

remains to be determined.

Conclusion

Sandblasting may give an increase in microtensile strength to methacrylate-

based glass fiber posts, eliminating the need to apply additional ‘‘chair-side’’

treatments. Reducing the number of clinical steps could contribute to

simplify the clinical procedures.

39

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composite surfaces for indirect bonding. Dent Mater 8(3): 193-6.

Swift EJ, Jr., LeValley BD, Boyer DB (1992). Evaluation of new

methods for composite repair. Dent Mater 8(6): 362-5.

Tay FR, Loushine RJ, Lambrechts P, Weller RN, Pashley DH (2005).

Geometric factors affecting dentin bonding in root canals: a theoretical

modeling approach. J Endod 31(8): 584-9.

Van Landuyt KL, De Munck J, Snauwaert J, Coutinho E, Poitevin A,

Yoshida Y, Inoue S, Peumans M, Suzuki K, Lambrechts P, Van Meerbeek B

(2005). Monomer-solvent phase separation in one-step self-etch adhesives. J

Dent Res 84(2): 183-8.

Winkler S, Wongthai P (1986). Increasing the bond strength of metal-

ceramic restorations. J Prosthet Dent 56(4): 396-401.

44

2.2. Accelerated aging of adhesive-mediated fiber post-resin composite

bonds: a modeling approach

Ivana Radovic, Francesca Monticelli, Federica Papacchini, Elisa Magni,

Àlvaro Hafiz Cury, Zoran R. Vulicevic, Marco Ferrari. Journal of Dentistry

2007; 35(8): 683-689.

Introduction

The importance of coronal seal for the long-term clinical success of

endodontically treated teeth is well established (Saunders and Saunders 1994;

Begotka and Hartwell 1996; Tronstad et al. 2000). If fiber reinforced

composite (FRC) post-retained adhesive restorations are chosen, the resin

composite used for the build-up as well as the luting cement play a

significant role in the establishment and maintenance of a durable coronal

seal (Bachicha et al. 1998; Mannocci et al. 2001; Rogic-Barbic et al. 2006).

Although resin cements resulted in a significantly lower microleakage extent

than conventional zinc phosphate (Bachicha et al. 1998; Mannocci et al.

2001; Rogic-Barbic et al. 2006) or glass ionomer cement (Bachicha et al.

1998), it has been reported that none of the luting materials is able to

completely prevent leakage. Furthermore, it has been reported that the

combination of some simplified adhesives and resin cements for luting to

radicular dentin may result in a fluid movement phenomenon across the

adhesive layer in vivo, with the formers behaving as permeable membranes

even after polymerization (Chersoni et al. 2005). Thus, the importance of

investigating and improving the coupling between FRC posts and the

materials used for luting has been recognized.

In particular, the link established between the FRC post and the resin

cement or core material may contribute to the coronal seal and homogeneity

45

of post-retained adhesive restorations, as well as to optimal stress distribution

during clinical function (De Santis et al. 2000). Since failure may eventually

occur at this interface (Pirani et al. 2005; Perdigao et al. 2006), numerous

post surface treatments have been recently investigated, aiming to enhance

the adhesion between prefabricated FRC posts and resin composites (Sahafi

et al. 2003; Aksornmuang et al. 2004; Sahafi et al. 2004; Goracci et al. 2005;

Aksornmuang et al. 2006; Balbosh and Kern 2006; Bitter et al. 2006;

Monticelli et al. 2006a; Monticelli et al. 2006b; Radovic et al. 2007). The

adhesion of resin cements to FRC posts with a semi-interpenetrating polymer

network (IPN) polymer matrix has been recently investigated. It was reported

that these posts bonded better to resin cements in comparison with

prefabricated FRC posts with a cross-linked polymer matrix (Le Bell et al.

2004; Mannocci et al. 2005).

The application of a dual-cured adhesive on FRC post surface

represents a simple and effective chair-side treatment that can improve the

adhesion of core materials to epoxy resin-based quartz fiber posts

(Aksornmuang et al. 2004; Aksornmuang et al. 2006). Nevertheless, the

information about the stability of this interface in the presence of an aging

medium is missing in the literature. The hydrolytic stability of fiber post-core

bonds has been assessed in only one study, revealing that silane-mediated

bonds were susceptible to hydrolytic degradation in vitro when a highly

hydrophilic silane was used, with a subsequent decline in post-core bond

strength (Monticelli et al. 2006). In the light of these findings, it may be of

interest to evaluate the stability of fiber post-composite bonds mediated by a

resinous coupling agent like an adhesive layer rather than methacrylate-based

silanes. Sandblasting followed by silane application is a beneficial procedure

for enhancing the bond strength of resin cements to methacrylate-based glass

FRC posts (Sahafi et al. 2003; Magni et al. 2007). However, it should be

46

evaluated whether bond strength to epoxy resin-based FRC posts can be

further enhanced if adhesive application is preceded by sandblasting.

The objectives of this study were: 1. to evaluate the influence of water

storage on adhesive-mediated FRC post-resin cement and FRC post-flowable

composite bonds using a model of accelerated aging, and 2. to investigate

whether previous sandblasting influences post-composite bond strength. The

following null hypotheses were tested:

(1) Pretreatment of FRC post surface has no influence on bond strength to

resin cement and flowable composite;

(2) there is no difference between FRC post-cement and FRC post-flowable

composite bond strength;

(3) the accelerated water aging procedure does not influence bond strength of

resin cement and flowable composite to epoxy resin-based FRC posts,

regardless of post surface treatment.

Materials and Methods

Forty translucent epoxy resin-based quartz FRC posts (DT Light Post #3 –

RTD, St Egrève, France) with a diameter of 2.14 mm were used in the study.

Posts were randomly divided into two groups of 20 each, according to the

surface treatment to be performed. In group I posts were treated with an etch-

and-rinse adhesive XPBond (Dentsply Caulk, Milford, DE, USA). In group II

posts were sandblasted (aluminum oxide, particle size 110 μm; Rocatec-Pre,

3M ESPE, St. Paul, MN, USA) for 5 seconds at 0.28 MPa from a distance of

1cm, and then treated with XPBond adhesive. Posts were manually rotated

during the sandblasting procedure. On all the posts the adhesive was used in

the self-curing mode. Each experimental group was then divided into two

subgroups (n=10), according to the resin cement/core material to be applied

47

on the posts. FRC posts were coupled with a dual-cured resin cement

(Calibra, Dentsply Caulk; Subgroup 1) and a flowable composite (X-Flow,

Dentsply Caulk; Subgroup 2). The materials were used according to the

manufacturer’s instructions. The chemical composition, batch numbers and

the application modes are reported in Table 1.

Coupling of resin cement/flowable composite and microtensile bond strength

test procedures

Schematic flow chart of specimen preparation for microtensile testing is

shown in Figure 1. Resin cement and flowable composite were applied on the

posts to produce cylindrical specimens with the post in the center, using a

transparent plastic matrix. The procedure previously described by Goracci et

al. for core build-up materials was followed (Goracci et al. 2005). All

specimens were prepared and cut by the same investigator to ensure

standardization. Each post was positioned up-right on a glass slab, and

secured with a drop of sticky wax. A cylindrical disposable plastic matrix

was placed around the post and adjusted so that the post would be exactly in

the middle. The matrix was 10 mm in diameter.

48



Material Composition Application mode

Rocatec-Pre (3M ESPE)

Aluminum oxide (particle size: 110 μm)

Sandblasting from a distanceof 1 cm at 0.28 MPa for 5 seconds.3

XPBond adhesive (Dentsply Caulk) Batch no. 0503004020

carboxylic acid modified dimethacrylate (TCB resin), phosphoric acid modified acrylate resin (PENTA), urethane dimethacrylate (UDMA), triethyleneglycol dimethacrylate (TEGDMA), 2-hydroxyethylmethacrylate (HEMA), Butylated benzenediol (stabilizer), ethyl-4-dimethylaminobenzoate, camphorquinone, functionalised amorphous silica, t-butanol

Mix XPBond adhesive with Self-Cure Activator (1:1); apply mixture to the post surface for 1-2 s; gently air dry.

Self-cure activator (Dentsply Caulk) Batch no. 040901

Aromatic Sodium Sulfinate, (Self cure initiator), Acetone, Ethanol

Calibra Esthetic Resin Cement (Dentsply Caulk) Batch no. 050412 Batch no. 0506142

Base: Dimethacrylate Resins; Camphorquinone (CQ) Photoinitiator; Stabilizers; Glass Fillers; Fumed silica; Titanium Dioxide; Pigments Catalyst: Dimethacrylate Resins; Catalyst; Stabilizers; Glass Fillers; Fumed Silica

Mix cement components; seat the post immediately; light cure.

X-Flow flowable composite (Dentsply Caulk) Batch no. 0412000740

Strontium alumino sodium fluoro phosphor silicate glass, Di- and multifunctional acrylate and methacrylate resins, Diethylene glycol dimethacrylate (DGDMA), Highly dispersed silicon dioxide, UV stabiliser, Ethyl-4-dimethylaminobenzoate, Camphor quinone, Butylated hydroxy toluene (BHT), Iron pigments, Titanium dioxide

Dispense directly into the matrix in 2 mm layers; light cure.

DT Light Post (RTD St Egreve France) Batch no. 00447200506

Epoxy resin (40%); quartz fibers (60%) -

3 Manufacturer’s recommended procedure is: sandblast from the distance of 1cm at 0.28 MPa for 15 seconds for the area of approximately 1cm2. Considering the size of fiber posts, the sandblasting time was reduced to 5 seconds.

49


strength testing. C: cement/composite; P: fiber post.

In height, the matrix was extended only to the cylindrical portion of the post

(about 10 mm), since for an appropriate cutting of the microtensile


post length. The resin cement was mixed, applied on the post filling the

matrix completely, and light cured for 40 s with a halogen curing light (600

mW/cm2 output; VIP; Bisco, Schaumburg, IL, USA) directly from the open

upper side of the matrix and through the post. Additional 40 s irradiations

were performed from each side of the cylinder prior to the removal of the

matrix to ensure optimal polymerization of the material. The flowable

composite was applied to the post in 1–2mm thick increments. Each

increment was carefully adapted to the post surface and light-cured

separately.

50

The bond strength at the interface between post and

cement/composite was measured with the microtensile non-trimming

technique (Shono et al. 1999). The sectioning of the specimens began on

completion of the cementation/core build-up procedure. In each subgroup, 5

cylinders were used to obtain microtensile sticks that were to be tested

immediately (Subgroups 1A and 2A, Figure 1). Sticks obtained from the

remaining 5 cylinders (Subgroups 1B and 2B, Figure 1) were stored in

deionized water at 37ºC for 1 month prior to microtensile bond strength

testing. Cylinders were mounted in a cutting machine (Isomet 1000, Buehler,

Lake Bluff, IL, USA) and sectioned under water cooling to obtain a slab of

uniform thickness, with the post in the center and cement/flowable composite

on each side. Each slab was further sectioned into sticks of 1 mm in

thickness, resulting in the mean of 30 specimens per final experimental

condition (Group/Subgroup/time of bond strength test: A or B). The cylinder

of origin was noted for every stick. The number of prematurely failed sticks

during the cutting procedures was noted and is reported in Table 2. For each

of the prematurely failed sticks bond strength value was recorded as 0 MPa

and included in the statistical analysis. Sticks were glued (Super Attak Gel,

Henkel Loctite Adesivi S.r.l., Milano, Italy) to the two free sliding

components of a jig, which was mounted on a universal testing machine

(Triax, Controls S.P.A., Milano. Italy) and loaded in tension at a crosshead

speed of 0.5 mm/min until failure occurred at either side of the post-

composite interface. No sticks failed prematurely during the testing step.

Failure modes were evaluated with a stereomicroscope (Nikon

SMZ645, Nikon Co., Tokyo, Japan) at 40x magnification and recorded as

adhesive (at the post/cement or post/composite interface), cohesive (within

the post, cement or the composite) or mixed (a combination of the two modes

of failure in the same interface). Bond strength was expressed in

51

MegaPascals (MPa), dividing the load at failure in Newtons by the bonding

surface area. As the bonded interface was curved, its area was calculated

using a mathematical formula previously applied by Bouillaguet et al. for

similar purposes (Bouillaguet et al. 2003).

SEM evaluation

Two additional post/cement or post/flowable composite cylinders were

prepared per each subgroup in order to evaluate the adhesive interface prior

and after water aging. The cylinders were immediately cut into 1.5 mm thick

cross-sections. Half of the sections obtained was immediately processed for

SEM evaluation while the other half was evaluated after 1 month of water

storage at 37ºC. Sections were cleaned with 32% silica-free phosphoric acid

gel (Uni-Etch, Bisco, Schaumburg, IL, USA) for 15 seconds, rinsed with

water, rinsed in 96% alcohol solution for 1 minute and air-dried. Each section

was mounted on a metallic stub, sputter-coated with gold (Polaron Range

SC7620; Quorum Technology), and observed under a scanning electron

microscope (JSM 6060 LV, JEOL) at different magnifications.


As a preliminary linear regression analysis showed that neither the post-

cement nor the post-flowable composite cylinder had a significant influence

on the measured bond strength, sticks were considered as independent within

each experimental group (i.e. final experimental condition -

Group/Subgroup/time of bond strength test: A or B). As the bond strength

data was not normally distributed (Kolmogorov–Smirnov test), Kruskal-

Wallis analysis of variance was applied, followed by Dunn’s multiple range

test for the post-hoc comparisons. In all the tests, the level of significance

52

was set at p<0.05 and calculations were handled by the SPSS 13.0 software

(SPSS Inc.; Chicago, IL, USA).

Results


Results of microtensile bond strength testing are reported in Table 2.

Sandblasting followed by adhesive coating significantly improved immediate

post-composite bond strength in comparison to adhesive alone, for each of

the two materials tested. After water aging, the two post surface treatments

attained comparable bond strengths, when comparing groups in which the

same material was used. Resin cement achieved higher bond strength to fiber

posts than flowable composite when the groups with the same post surface

treatment were compared, both immediately and after 1 month. Fiber post-

resin cement and fiber post-flowable composite bond strengths were

significantly lower after accelerated water aging. Failure distribution is

reported in Table 3. In general, higher bond strengths resulted in a superior

percentage of cohesive or mixed failures.

53

Table 2: Post-cement and post-flowable composite microtensile bond

strength (MPa) prior and after water storage and number of pretesting failures

(pf). Values are means. Numbers in brackets are standard deviations.

Different letters indicate statistically significant differences within the

column. Different numbers indicate statistically significant differences within

the row (Kruskal-Wallis analysis of variance followed by Dunn’s multiple

range test, p<0.05)

Storage

Treatment Material No storage 1 month water

XPBond

Calibra 21.32 (5.18) B1

pf: 0 of 29 15.59 (5.67) A2

pf: 0 of 39

X-Flow 9.77 (8.68) C1

pf: 9 of 25 3.93 (3.26) B2

pf: 7 of 36

Sandblasting + XPBond

Calibra

26.57 (7.61) A1 pf: 0 of 26

15.65 (6.48) A2 pf: 0 of 28

X-Flow

18.03 (6.31) B1 pf: 0 of 30

7.57 (3.53) B2 pf: 0 of 33

Table 3: Percentage of different types of testing failures. A: adhesive failure;

M: mixed failure; CP: cohesive failure in the fiber post; CC: cohesive failure

in cement/flowable composite.

Treatment Material Storage Type of testing failure (%) A M CP CC

XPBond

Calibra

No storage 76 0 21 3

1 month, water 85 5 10 0

X-Flow



Sandblasting + XPBond

Calibra



X-Flow



54

SEM evaluation

SEM evaluation of the immediately processed cross-sections revealed a good

adaptation of the resin cement (Figure 2A and 2C) and the flowable

composite (Figure 2E and 2G) to the post surface, irrespective of the

pretreatment. No defects and no discontinuities occurred along the interface,

and no significant differences in the morphology of the interface between

these groups were noticed. In cross-sections that were stored in water for 1

month, gaps between the post surface and resin cement (Figure 2B and 2D)

or flowable composite (Figure 2F and 2H) were frequently observed,

regardless of the pretreatment and without significant differences in gap

occurrence and morphological appearance.

Figure 2: SEM micrographs of the post-cement (A-D) and post-flowable

composite (E-H) interfaces prior (A, C, E, G) and after water aging (B, D, F,

H). Immediately examined interfaces revealed the absence of any defects or

discontinuities. No differences were noticed between the groups where post

surface was treated with XPBond adhesive (A, E) and the groups where

adhesive application was preceded with sandblasting (C, G). One-month

water storage resulted in the frequent occurrence of gaps at the interface, both

on posts treated with the adhesive (B, F) and the posts that were previously

sandblasted (D, H).

56

Discussion

A general agreement on how to statistically treat the prematurely failed

specimens during microtensile bond strength testing is presently lacking in

the literature. They may be excluded, considered as zero or greater than zero

values (Pashley et al. 1999). In the present study, it was decided to include

the prematurely failed sticks to the statistical analysis as “zero bonds”,

assuming that specimens that fail prior to testing are most likely the

expression of a relatively weaker bond (Pashley et al. 1999).

The three study variables (post surface treatment, material and aging

condition) had an influence on bond strength of fiber posts to resin cement

and flowable composite leading to the rejection of the null hypotheses. It is

important to emphasise that the applied method is a simplified model of

accelerated aging (De Munck et al. 2005) which has been commonly

performed for challenging resin-dentin adhesion (Okuda et al. 2002; Reis et

al. 2004; Carrilho et al. 2005). Clinically, the post-composite bond in a

restored tooth cannot be directly exposed to the wet environment in a manner

comparable to an in vitro experimental design, which precludes a direct

correlation with the clinical conditions. In the present study, the observed

decrease in bond strength may be related only to the exposure to water of the

adhesive interface on the sticks, as the surface of the posts was not exposed.

In the clinical conditions a direct intraoral exposure of the post-composite

interface is routinely avoided by immediately restoring a tooth with a direct

composite restoration or a crown. In the case of crown placement, the core

material covers the post-composite interface protecting it during crown

fabrication. In the worst case scenario, assuming that the coronal restoration

fails in preventing leakage during clinical service, and that oral fluids

subsequently reach the post-composite interface, it is reasonable to assume

57

that it would take a considerably longer period of time for the fiber post-

composite bond to weaken. Despite of these limitations, the experimental set-

up employed in this study allowed to evaluate the effect of accelerated water

diffusion phenomena on the FRC post-cement/flowable composite interface

and the effectiveness of adhesive in preventing it within a shorter period of

time (De Munck et al. 2005).

Previous studies performed on the same epoxy resin-based fiber post

reported significantly higher bond strengths on adhesive-treated posts when

compared with no surface treatment (Aksornmuang et al. 2004;

Aksornmuang et al. 2006). All the posts tested in the present study were

treated with the same adhesive system, in order to evaluate whether the

enhanced immediate bond strength is unaffected by accelerated challenging

procedures. However, significantly lower bond strengths were recorded in all

groups after aging, regardless of previous sandblasting and the resinous

material that was placed on the posts. SEM evaluation supported bond

strength data, revealing gaps at the post-adhesive interface after aqueous

challenge. The mechanism involved may be related to the presence of

hydrophilic monomers in XPBond adhesive layer (Table 1), such as HEMA,

TEGDMA and TCB resin, which may be susceptible to water sorption

(Malacarne et al. 2006). The hydrophilicity of TEGDMA is explained by the

presence of hydrophilic ether linkages (Ferracane 2006), while TCB resin is a

reaction product between tetracarboxylic acid and HEMA, which contains

two carboxyl groups (Yap et al. 1998). Complex reactions that occur in

polymer networks exposed to the wet environment are related to water

sorption and solubility that affect their dimensions (Ferracane 2006).

Exposure to water was also reported to result in the formation of microcracks

in HEMA- containing polymer networks (Ghi et al. 2001; George et al. 2004)

depending on the concentration of HEMA (Ghi et al. 2001). The occurrence

58

of cracks was explained by stresses generated between the hydrated swollen

outer layer and the inner portions of the polymer, when water begins to

diffuse into the polymer network. Although self-healing and closing of the

cracks inside of the polymer is possible (Ghi et al. 2001), it can be assumed

that the interaction between these processes played a role in the gradual

separation at the interface between the fiber post and the adhesive.

Sandblasting of the posts prior to the adhesive application improved

only immediate bond strength. In the light of the overall reduction in bond

strength after accelerated aging, the role of sandblasting is probably of minor

importance if the posts are subsequently coated with a relatively hydrophilic

adhesive. It is possible that FRC post-composite bonds mediated by

sandblasting alone would not be affected by the detrimental effect of water,

being the adhesion mechanism mediated only by a physical interaction

between components. Another potential approach to avoid the concern

related to hydrophilicity of adhesives or silane solutions would be the use of

more hydrophobic industrial coatings. In a similar experimental design as in

the present study, industrially coated FRC posts resulted in immediate bond

strengths that were lower if compared to XPBond adhesive treatment, but

were not affected by one month accelerated water aging (Zhang et al,

unpublished results).

59

Conclusions

The investigated dual-cured resin cement exhibited higher bond strength to

fiber posts than flowable composite when the groups with the same post

surface treatment were compared, both immediately and after 1 month.

Sandblasting followed by adhesive application may improve immediate bond

strength in comparison to the adhesive alone. After accelerated water aging

the two post surface treatments resulted in comparable bond strengths. Fiber

post-resin cement and fiber post-flowable composite bonds may be impaired

by accelerated water aging if mediated by hydrophilic adhesive coatings.

60

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Introduction

Since their introduction back in 1990’s (Duret et al. 1990), fiber post and core

systems have been extensively investigated (Schwartz and Robbins 2004;

Schwartz and Fransman 2005). In vitro studies have demonstrated the

advantages of these systems over conventional cast posts or prefabricated

metallic posts (Martinez-Insua et al. 1998; Sirimai et al. 1999; Cormier et al.

2001; Akkayan and Gulmez 2002; Newman et al. 2003; Fokkinga et al.

2004; Hayashi et al. 2006). The satisfactory clinical performance of fiber

post and core systems has been reported in short or medium-term clinical

studies (Fredriksson et al. 1998; Ferrari et al. 2000a; Glazer 2000; Malferrari

et al. 2003; Naumann et al. 2005; Naumann et al. 2005). Conversely, a recent

retrospective long-term study reported shorter survival times for carbon fiber

reinforced epoxy resin posts than those previously documented for cast posts

(Segerstrom et al. 2006). In some clinical studies debonding of the post was

frequently observed as the main failure mode (Ferrari et al. 2000b; Mannocci

et al. 2002; Monticelli et al. 2003; Cagidiaco et al. 2007) , which may

question the real efficacy of the employed adhesive procedures. Fiber post

placement involves the formation of two equally important interfaces both at

the dentin/resin composite and resin composite/fiber level where a failure can

eventually occur. The achievement of an optimal coupling at the interfaces is

65

considered to be crucial for ensuring the restoration homogeneity and

durability, as well as for favorable stress distribution (De Santis et al. 2000).

In a recently published investigation on luting fiber posts to

hybridized root canals, 60% of the failures during push-out testing occurred

between the fiber post and the cement (Perdigao et al. 2006). Various post

surface “chair-side” treatments have been recommended with the purpose of

enhancing the adhesion of resin cements and different resin based core

materials to fiber posts. Hydrogen peroxide etching and chemical

pretreatment with potassium permanganate followed by silanization

increased bond strength to flowable composites (Monticelli et al. 2006b;

Monticelli et al. 2006c). Adhesion of composite resins to quartz fiber posts

was improved when the post surface was treated with a bonding agent

(Aksornmuang et al. 2004; Aksornmuang et al. 2006) or was silanized

(Aksornmuang et al. 2004; Aksornmuang et al. 2006; Monticelli et al. 2006a;

Magni et al. 2007). Sandblasting followed by silane coating (Sahafi et al.

2003) and sandblasting alone (Sahafi et al. 2003; Radovic et al. 2007)

significantly increased bond strength of resin cements to glass fiber posts.

Adhesion to fiber posts may also be improved by the use of tribochemical

systems which allow the creation of chemical bonds between non-ceramic

surfaces and resin composites (Sahafi et al. 2003; Sahafi et al. 2005;

Valandro et al. 2006). However, both laboratory (Rocatec, 3M ESPE) and

intraoral (CoJet, 3M ESPE) tribochemical systems consist of three

components that need to be successively applied. Therefore, an industrial

employment of the fiber post surface treatment that would eliminate the need

for additional chair-side treatments may be advantageous, allowing for a

simplification of the clinical procedures.

An experimental patented industrial treatment has been recently

developed with the intention of improving post-composite coupling.

66

According to the manufacturer’s information, the treatment comprises two

main steps: a 1�m-thick coating of zirconium oxide followed by silanization

with 3–(trimethoxysilyl) propyl methacrylate. This treatment is claimed to

keep the initial surface roughness of the fiber post in order to provide

micromechanical retention and to create a chemical bond between the silane

and the adhesive or cement. Electrolitically deposited zirconium oxide

coatings on dental cobalt-chromium alloys prevent corrosion and release of

metal ions (Hsu and Yen 1998). Zirconium oxide sandblasting was used to

treat the surface of titanium endosseus dental implants (Franchi et al. 2004).

However, no information is available on the potential application of

zirconium oxide coatings on fiber post surface.

The aim of this investigation was to evaluate the influence of an

industrial treatment and conventional “chair-side” treatments of fiber post

surface on the microtensile bond strength to luting resin cements. The null

hypothesis tested is that the treatment of the post surface does not influence

the bond strength of fiber posts to dual cured resin cements.

Materials and methods

Forty-two translucent quartz fiber posts (Light Post, RTD) with a diameter of

1.8mm were used in the study. Posts were divided into 7 groups (n=6)

according to the surface treatment performed. Groups I and II: experimental

patented industrial treatment consisting of a coating with a layer of zirconium

oxide followed by silanization with a 3–(trimethoxysilyl)propyl methacrylate

(RTD, St Egrève, France). Group III: industrial coating (the same as in

groups I and II, RTD) followed by etch-and-rinse adhesive application

(XPBond, Dentsply Caulk, Milford, DE, USA). Group IV: adhesive

application (XPBond). Group V: adhesive application (Prime&Bond NT,

67

Dentsply Caulk). Group VI: silane application (Calibra Silane, Dentsply

Caulk). Group VII: no treatment (control group). The materials were used

according to the manufacturers’ instructions; their chemical composition,

batch numbers and application modes are reported in Table 1. Both adhesives

were used in the self-cure mode.

Coupling of resin cements and microtensile test procedures

Two resin cements (Sealbond, RTD – Group I and Calibra, Dentsply Caulk –

Groups II to VII) were applied on the posts to produce cylindrical specimens

with the post in the center, using a transparent plastic matrix. A procedure

previously described by Goracci et al. for core build-up materials was

followed (Goracci et al. 2005). All specimens were prepared by a single

investigator to avoid the risk of operator’s variability. Each post was

positioned upright on a glass slab, and secured with a drop of sticky wax. A

cylindrical plastic matrix was placed around the post and adjusted so that the

post would be exactly in the middle (Figure 1). The matrix was 10 mm in

diameter. In height, the matrix was extended to the end of the coronal taper of

the post (about 10 mm). For an appropriate cutting of the microtensile


post length. Since the coronal taper of Light Post is parallel sided, it was used

in its complete length.

68


strength testing. C: cement; P: post.

69



Material Composition Application mode Prime & Bond NT adhesive (Dentsply Caulk) Batch no. 0501001760

Di- and Trimethacrylate resins, PENTA (dipentaerythritol penta acrylate monophosphate), Photoinitiators, Stabilizers, Nanofillers - Amorphous Silicone Dioxide, Cetylamine hydrofluoride, Acetone

Mix Prime&Bond NT (XPBond) adhesive with Self-Cure Activator (1:1); apply mixture to the post surface for 1-2 s; gently air dry.

XPBond adhesive (Dentsply Caulk) Batch no. 0503004020

carboxylic acid modified dimethacrylate (TCB resin), phosphoric acid modified acrylate resin (PENTA), urethane dimethacrylate (UDMA), triethyleneglycol dimethacrylate (TEGDMA), 2-hydroxyethylmethacrylate (HEMA), Butylated benzenediol (stabilizer), ethyl-4-dimethylaminobenzoate, camphorquinone, functionalised amorphous silica, tertiary butanol

Self-cure activator (Dentsply Caulk) Batch no. 040901

Aromatic Sodium Sulfinate, (Self cure initiator), Acetone, Ethanol

Calibra Silane Coupling Agent (Dentsply Caulk) Batch no. 0503242

Acetone; Ethyl Alcohol; Organo Silane Treat the post surface with the silane; air dry.

Calibra Esthetic Resin Cement (Dentsply Caulk) Batch no. 050412 Batch no. 0506142

Base: Dimethacrylate Resins; Camphorquinone (CQ) Photoinitiator; Stabilizers; Glass Fillers; Fumed silica; Titanium Dioxide; Pigments Catalyst: Dimethacrylate Resins; Catalyst; Stabilizers; Glass Fillers; Fumed Silica Mix cement

components; seat the post immediately; light cure.

Sealbond Resin Cement (RTD St Egreve France) Batch no. 01379200511

Base: Bis-GMA, Hexane diol dimethacrylate, Camphorquinone; Stabilizers; Barium glass fillers; Silica; Pigments Catalyst: Bisgma, Hexane diol dimethacrylate, Peroxide, Stabilizers; Barium glass fillers; Silica; Pigments

Light Post (RTD St Egreve France) Batch no. 00210200504 Batch no. 05/65 (ind. treatment)

Epoxy resin (40%); quartz fibers (60%) Industrial treatment: coating with a layer of zirconium oxide followed by silanisation with a 3–(trimethoxysilyl)propyl methacrylate.

-

70

The resin cements were mixed, applied on the post filling the matrix

completely, and light cured for 40 s with a halogen curing light (600 mW/cm2

output; VIP; Bisco, Schaumburg, IL, USA) directly from the open upper side

of the matrix and through the post. Additional 40 s irradiations were

performed from each side of the cylinder prior to the removal of the matrix to

ensure optimal polymerization of the cement material. The sectioning and

loading of the specimens began on completion of the cementation procedure,

in order to simulate the clinical situation of immediate loading applied in the

procedures of core preparation, impression, and temporary crown adaptation

and cementation.

The cylinders were mounted in a cutting machine (Isomet 1000,

Buehler, Lake Bluff, IL, USA) and sectioned under water cooling to obtain a

slab of uniform thickness, with the post in the center and the cement build-up

on each side. Six to eight sticks of 1-mm in thickness were obtained from

each slab, resulting in multiple specimens (33 per group) that were available

for microtensile bond strength testing. During the experimental industrial

coating procedure, 3mm at the coronal end of the post were not coated.

Therefore, sticks obtained from this part of the post in groups I-III were

excluded. Sticks were glued (Super Attak Gel, Henkel Loctite Adesivi S.r.l.,

Milano, Italy) to the two free sliding components of a jig, which was

mounted on a universal testing machine (Triax, Controls S.P.A., Milano.

Italy) and loaded in tension at a crosshead speed of 0.5 mm/min until failure

occurred at either side of the post-composite interface. Failure modes were

evaluated with a stereomicroscope (Nikon SMZ645) at 40x magnification

and recorded as adhesive (at the post/cement interface), cohesive (within the

post or the cement) or mixed (a combination of the two modes of failure in

the same interface). Bond strength values were expressed in MegaPascals

(MPa), dividing the load at failure in Newtons by the bonding surface area.

71

As the bonded interface was curved, its area was calculated using a

mathematical formula previously applied by Bouillaguet et al. (Bouillaguet et

al. 2003). Nine beams from group VI and eleven beams from group VII failed

prematurely during the cutting procedure. For each of the prematurely failed

beams bond strength value was recorded as 0 MPa and included in the

statistical analysis.

SEM evaluation

One sample from each group was randomly chosen for scanning electron

microscopic evaluation (SEM) of the fiber post-cement interface. The

cylinders were cut into 1.5mm thick cross sections (Isomet 1000). Sections

were polished with wet abrasive SiC papers, cleaned with 37%

orthophosphoric acid for 15 seconds, rinsed with water, ultrasonicated in

96% ethanol for 2 min and air dried. Each slice was mounted on a metallic

stub, sputtered with gold-palladium (Polaron Range SC7620; Quorum

Technology, Newhaven, UK), and observed under a SEM (JSM 6060 LV,

JEOL, Tokyo, Japan) at different magnifications, using secondary electron

beam. Additionaly, back scattered mode was used to observe the post-cement

interfaces on industrialy coated posts. Four additional fiber posts were

examined with a scanning electron microscope in order to detect differences

in the surface texture between industrially coated (n=2) and conventional

posts (n=2). One industrially coated and one conventional post were observed

longitudinally, while the remaining two were cross-sectioned with a diamond

saw (Isomet 1000) and polished with wet abrasive SiC papers. The specimens

were rinsed in deionised water, air-dried, gold-sputtered (Polaron Range

SC7620) and observed under a scanning electron microscope (JSM 6060

LV). The surface of the industrialy coated posts was also examined using

72

Energy Dispersive Analysis by X-ray (EDAX) in a scanning electron

microscope.


A preliminary linear regression analysis showed that the post–cement

cylinder did not have a significant influence on the measured bond strength;

therefore, the sticks were considered as independent within each group. Since

the bond strength data were not normally distributed (Kolmogorov–Smirnov

test, p>0.05), a Kruskal-Wallis analysis of variance was performed with bond

strength as the dependent variable, and the type of surface treatment as the

factor. Dunn’s multiple range test for was used for the post-hoc comparisons.

The level of significance was set at p<0.05 and calculations were handled

by the SPSS 13.0 software (SPSS Inc.; Chicago, IL, USA).

Weibull analysis was performed to determine failure probability at

specific loads, Weibull modulus (m) and characteristic bond strength (�; the

strength at the failure probability of 63.2%) in the experimental groups. The

calculations were handled by the Weibull++ 7 software (ReliaSoft

Corporation, Tucson, AZ, USA).

Results


The post surface treatment significantly influenced the measured bond

strengths (p<0.001). Significantly higher bond strengths (p<0.001) were

achieved in Groups I, II and III, when the industrial treatment was performed,

and in Group IV, when the surface was treated with the XPBond adhesive

(Figure 2). Additional adhesive application did not influence bond strength

on industrially coated posts (Group III). No significant differences between

73

the two tested luting cements were recorded. Bond strengths to silanized

(group VI) and no treated fiber posts (Group VII) were the lowest (p<0.001)

and comparable. The application of Prime&Bond NT adhesive resulted in

significantly higher bond strengths compared to no treatment and

silanization, but lower than in groups I-IV.

The data were shown to fit a 2-parameter Weibull distribution curve.

Probability of failure as a function of stress, Weibull modulus (m) and

characteristic bond strength (�) are shown in Figure 3. The lowest probability

of failure was found in groups I-IV (industrialy treated and XPBond coated

posts), followed by groups V (Prime & Bond NT), VI (Calibra Silane) and

VII (no treatment).

During microtensile testing, the recorded failure mode in Groups I-III

and V-VII was 100% adhesive in nature. In Group IV, six beams (20%)

failed cohesively within the post, and one beam (3%) failed cohesively within

luting cement.

SEM evaluation

Cross-sections of the post-cement interfaces revealed a good adaptation of

the resin cements to the post surface in all groups. No defects and no

discontinuities occurred along the interface between the fiber post and the

cement. An intimate contact of quartz fibers with the resin cement was

frequently observed along the interface in all groups. No significant

differences in the morphology of the interface between the groups were

noticed (Figure 4). In back scattered mode, tight adaptation of the cement to

industrialy coated post surface was visible (Figure 5). A uniform coating

could be seen both at the low magnification (Figure 5A; x500) and high

magnification (Figure 5B; x5000).

74

Figure 2: Post-cement microtensile bond strength. The length of each box

represents the interquartile range of microtensile bond strengths. The ends of

the box are the upper and lower quartiles. A horizontal line inside the box

marks the median. The whiskers extend to the highest and lowest

microtensile bond strengths. Different letters in brackets indicate statistically

significant differences. IND: Industrial treatment; SEAL: Sealbond cement;

CAL: Calibra cement; XPB: XPBond adhesive; PBNT: Prime&Bond NT

adhesive; SIL: Calibra Silane; NO: No treatment.

IND/SEAL (A)IND/CAL (A)

IND+XPB/CAL (A)XPB/CAL (A)

PBNT/CAL (B)SIL/CAL (C)

NO/CAL (C)

0

10

20

30

40

[MPa

]

75

Figure 3: Weibull distribution plots of a probability of failure as a function of

stress. m: Weibull modulus; �: characteristic bond strength (the strength at

the failure probability of 63.2%).

76

B

A

Figure 4: SEM images of the post-cement interfaces. Tight and continuous

adaptation of the cement to the post surface can be seen, with a frequent

occurrence of direct contact between the fibers and the cement. A: SEM

image of the interface between industrially treated fiber post and Sealbond

cement; B: SEM image of the interface between conventional fiber post

treated with XP Bond adhesive and Calibra cement.

77

Figure 5: Images of the post-cement interface between Calibra cement and

industrialy coated posts made using back scattered mode. Tight adaptation of

the cement to post surface and a uniform coating are visible both at the low

magnification (A; x500) and high magnification (B; x5000).

B

A

78

Fiber post surface observation revealed a modification of the surface

morphology of industrially coated fiber posts (Figure 6A, 6B) when

compared to conventional posts (Figure 6C). A uniform coating was visible

on industrially treated posts.

Figure 6: SEM images

of the fiber post

surface prior to

performing the build-

up. A fairly uniform

coating is visible on

industrially treated

posts (A). B: The

transition (arrow)

between the coronal

end of the post (not

treated) and the

experimental industrial

coating; C: surface of a

conventional quartz

fiber post.

B

C

A

79

B

A

Cross-sectional views of industrially coated (Figure 7A) and conventional

post (Figure 7B) revealed that the action of the industrial treatment resulted

in partial removal of the resin matrix and impregnation of the exposed quartz

fibers with the coating (Figure 7A).

Figure 7: Cross-sectional views of industrially coated (A) and conventional

fiber post (B). The resin matrix was partialy removed from the post surface

by the industrial treatment (A); the coating covers the exposed quartz fibers

(arrow). The uniformity and integrity of the coating may have been affected

by polishing during the sample preparation.

80

The EDAX revealed the presence of zirconium, silicon, oxygen, calcium,

carbon and natrium (Figure 8). Zirconium and silicon were the predominant

elements.

Figure 8: EDAX of the industrialy treated fiber post surface revealed the

presence of zirconium, silicon, oxygen, calcium, carbon and natrium.

81

Discussion

Significant differences in bond strengths were found between the

experimental groups. Both industrial coating and adhesive application

resulted in a superior outcome than silanization or no treatment of the fiber

post surface. Therefore, the null hypothesis was rejected.

The highest post-to-cement bond strengths were recorded on

industrially coated fiber posts. The experimental treatment performed was

still under development at the time this investigation was conducted.

However, general information on its composition was available from the

manufacturer (Table 1). The chemical nature of the industrial coating was

determined using Energy Dispersive Analysis by X-ray in a scanning electron

microscope and these findings correlated with the manufacturer’s information

(Figure 8). The industrial employment of zirconium oxide coating followed

by silanization to create fiber post surface coatings seems promising, as it

may simplify the clinical procedures during post cementation. The two

investigated resin cements, Sealbond and Calibra, achieved comparable bond

strengths to industrialy coated posts. It would also be of interest to investigate

whether similar results could be obtained with different types of luting

cements, such as resin modified glass ionomers and/or self-adhesive cements.

Significantly higher bond strengths were also obtained by the

application of the tested etch-and-rinse adhesive systems used in the self-cure

mode (Prime&Bond NT and XPBond) when compared to the control group.

This finding supports previous investigations conducted on the same type of

fiber post (Aksornmuang et al. 2004; Aksornmuang et al. 2006).

Enhancement of composite to composite bond strength was also reported

when adhesives were used as intermediate layers in composite repair

procedures (Saunders 1990; Shahdad and Kennedy 1998; Tezvergil et al.

82

2003). One of the explanations for the enhanced post-cement bond strength

may be the low viscosity of adhesive and a small contact angle that facilitates

micromechanical retention by penetration of monomer components into

microiregularities of the post surface. Furthermore, adhesive application may

have improved surface wettability resulting in a better distribution of the

resin cements. An interesting observation is the superior performance in

terms of bond strength of the new adhesive XPBond when compared to

Prime&Bond NT, resulting comparable to industrial treatment. It is possible

that the presence of a different solvent in XPBond (tertiary butanol instead of

acetone) influenced its wetting properties and consequently coupling with

fiber post surface. According to the manufacturer’s information, tertiary

butanol is for the first time employed in clinical dentistry as the solvent in

XPBond adhesive. Thanks to its high solvation forces (Pashley et al. 2002) it

is claimed to increase the resin content of bonded interfaces. It may be

speculated that better evaporation of buthanol increased resin concentration,

wettability and adaptation of the resin cement to the post surface. These

properties might have played a role in the favorable post-cement bond

strength recorded by XPBond. Both tested adhesives were used in the self-

curing mode, thus a frank adhesive layer was not visible at the post-cement

interfaces and its thickness could not have been determined (Figure 4B).

The beneficial effect of adhesive observed in the present study is in

contrast with the investigation of Ferrari et al. (Ferrari et al. 2006) that

reported no improvement in fiber post-core bond strength after coating the

methacrylate resin-based post with different adhesives. However, the matrix

of Light Post is epoxy resin-based, which may have accounted for the

disagreement in the results. Artopoulou et al. have shown that the effect of

adhesive coating on post retention depended on the core material placed

around the fiber post (Artopoulou et al. 2006). It may be speculated that the

83

effect of adhesive depends on the type of fiber post, type of core

material/resin cement and type of adhesive. This topic deserves further

research.

Although adhesive application significantly improved bond strength

compared to control group, it did not further increase bond strength on

industrially treated posts (Group IV). The industrial treatment induced

micromechanical and chemical changes in the surface of the posts (Figure

5A). The zirconium oxide coating followed by silanization apparently

improved the surface wettability to a sufficient extent, eliminating the need

for additional adhesive application, and at the same time offered sites

available for chemical bonding with the resin monomers.

The lowest bond strengths were recorded in the silanized post group

and when no treatment was performed. Moreover, premature failures were

observed in these two groups only, indicating an unfavorable post-cement

coupling. Although silanization tended to increase bond strength compared to

no treatment (Table 2, Figures 2 and 3), the difference was not statistically

significant. Sahafi et al. (Sahafi et al. 2003) reported that silanization did not

improve bond strength between fiber posts and resin cements unless it was

preceded by sandblasting, and this finding is consistent with the results of the

present study. The external surface of Light Post is mainly covered by epoxy

resin (Figure 6C). It can be assumed that previous surface treatment which

would expose the fibers would increase the surface available for chemical

bonding with the alcoxy groups of the silane molecules, and therefore result

in increased post-cement bond strength. Conversely, beneficial influence of

silanization without preceding sandblasting was demonstrated in

investigations of other authors that used DT Light Post (Aksornmuang et al.

2006; Monticelli et al. 2006a). Nevertheless, the silane applied in these

investigations was a two-component silane/adhesive system in which the

84

silane molecule is hydrolyzed “on demand” when mixed with the acidic

phosphate monomers which are present in water-containing dentin adhesives,

while in a present study a prehydrolized single-component silane was used.

The different strategy of the tested coupling agents may explain the

discrepancy with the results of the present investigation.

The cement layer that was placed around fiber posts was noticeably

thicker than the layer that formes in the root canal in a clinical situation. It

was recently demonstrated that different core diameters did not affect

retention values of glass fiber posts (Artopoulou et al. 2006). Nevertheless,

this limitation of the experimental set-up may have influenced the bond

strength results obtained. Higher values of Weibull modulus indicate systems

in which values of tensile strength show higher consistency, while low values

indicate systems with large data variability and are characteristic for brittle

materials. The Weibull moduli were generally low for all the materials tested.

This might indicate the need for additional methods for assessing the quality

of post-cement interfaces. Sectioning and loading of the specimens was

performed immediately after the cementation procedure with the intention of

assessing interfacial strength at the time when procedures of core preparation,

impression, and temporary crown adaptation/cementation are carried out.

Further investigations need to be conducted in order to assess the durability

of fiber post-composite bonds in clinical and accelerated aging conditions, as

well as the fatigue and fracture resistance of teeth restored with industrially

coated posts.

85

Conclusions

The experimental industrial surface treatment and the adhesive application

enhanced fiber post to resin cement interfacial strength. Industrial treatment

may simplify the clinical luting procedure. Cementation of epoxy resin-based

fiber posts without any treatment of the post surface is not recommended.

86

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(2006a). Improving the quality of the quartz fiber postcore bond using

sodium ethoxide etching and combined silane/adhesive coupling. J Endod

32(5): 447-51.

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(2006b). Post-surface conditioning improves interfacial adhesion in post/core



(2006c). A simple etching technique for improving the retention of fiber











Pashley DH, Carvalho RM, Tay FR, Agee KA, Lee KW (2002).

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Saunders WP (1990). Effect of fatigue upon the interfacial bond

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Segerstrom S, Astback J, Ekstrand KD (2006). A retrospective long

term study of teeth restored with prefabricated carbon fiber reinforced epoxy

resin posts. Swed Dent J 30(1): 1-8.

Shahdad SA, Kennedy JG (1998). Bond strength of repaired anterior

composite resins: an in vitro study. J Dent 26(8): 685-94.




Tezvergil A, Lassila LV, Vallittu PK (2003). Composite-composite

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91

Chapter 3: Selection of resin cement for fiber post cementation

3.1. Self-adhesive resin cements: a literature review

Ivana Radovic, Francesca Monticelli, Cecilia Goracci, Zoran R. Vulicevic,

Marco Ferrari. Journal of Adhesive Dentistry 2008; 10(4): 251-258.

Introduction

The clinical success of an indirect restorative procedure depends in part on

the cementation technique used to create a link between the restoration and

the tooth. The different luting cements that are available to the clinicians

have been categorized into five main classes: zinc phosphate cements,

polycarboxylate cements, glass ionomer cements, resin-modified glass

ionomer cements and resin composite cements (Diaz-Arnold et al. 1999).

Although each of the five classes has been widely investigated, the correct

clinical choice between them is not always clear (Rosenstiel et al. 1998).

None of the five cement types is suitable to be used for the entire broad range

of indirect restorative procedures. Therefore, their proper application requires

a thorough understanding and awareness of each material’s advantages and

disadvantages, taking into account the restorative material, moisture control

and preparation design (retentive or adhesive) (Diaz-Arnold et al. 1999).

Until recently resin cements were divided into two subgroups

according to the adhesive system used to prepare the tooth prior to

cementation. One group utilizes etch-and-rinse adhesive systems (e.g.

Variolink and Variolink II, Ivoclar-Vivadent, Schaan, Lichtenstein; Calibra,

Dentsply Caulk, Milford, DE, USA; Nexus, Kerr, Orange, CA, USA). In the

92

other group, enamel and dentin are prepared using self-etching primers (e.g.

Panavia 21, Panavia F and Panavia F 2.0, Kuraray Medical Inc., Tokyo,

Japan; Multilink, Ivoclar-Vivadent). Self-adhesive cements were introduced

in 2002 as a new subgroup of resin cements (e.g. RelyX Unicem, 3M ESPE,

St. Paul, MN, USA). These materials were designed with an intention to

overcome some of the shortcomings of both conventional (zinc phosphate,

polycarboxylate and glass ionomer cements) and resin cements, as well as to

bring the favorable characteristics of different cement classes into a single

product.

Self-adhesive cements do not require any pretreatment of the tooth

surface. Once the cement is mixed, its application procedure is extremely

simple. Application is accomplished through a single clinical step, similarly

to the application procedures of zinc-phosphate and polycarboxylate cements.

According to the manufacturers’ information, as the smear layer is not

removed, no post-operative sensitivity is expected. Unlike zinc phosphate,

polycarboxylate and resin cements, self-adhesive cements are claimed to be

moisture tolerant and to release fluoride ions in a manner comparable to glass

ionomer cements. Furthermore, they are expected to offer esthetics, optimal

mechanical properties, dimensional stability and micromechanical adhesion,

analogous to resin cements. Such a combination of favorable features of

conventional and resin cements is claimed to render self-adhesive cements

suitable for a wide range of applications. At the same time, the clinicians’

demands for simplification of luting procedures are addressed, as the

application procedure purportedly leaves little or no room for mistakes

induced by technique sensitivity.

Self-adhesive cements are still relatively new and detailed

information on their composition and adhesive properties is limited.

Although the basic adhesion mechanism appears to be the same for all self-

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adhesive cements, features of RelyX Unicem (3M ESPE) are by far the most

extensively explained by the manufacturer (3M ESPE product profile; RelyX

Unicem). This cement was the first product from the class of self-adhesive

cements to be introduced to the market. Its multifunctional monomers with

phosphoric acid groups simultaneously demineralize and infiltrate enamel

and dentin. The dominant setting reaction is the radical polymerization that

can be initiated by light exposure or through the self-cure mechanism. This

results in extensive cross linking of cement monomers and the creation of

high molecular weight polymers. Additionally, in order to assure

neutralization of this initially acidic system, a glass ionomer concept was

applied, resulting in the pH increase from 1 to 6 through reactions between

phosphoric acid groups and alkaline filer. Phosphoric acid groups also react

with the tooth apatite. Water that is formed in these neutralization processes

is claimed to contribute to cement’s initial hydrophylicity, which provides

improved adaptation to the tooth structure and moisture tolerance.

Subsequently, water is expected to be reused by reaction with acidic

functional groups and during the cement reaction with ion-releasing basic

filler particles. Such a reaction would finally result in an intelligent switch to

a hydrophobic matrix. The adhesion obtained is claimed to rely on

micromechanical retention and chemical interaction between monomer acidic

groups and hydroxyapatite.

Several products are currently available on the market (Table). They

differ in terms of delivery systems, working/setting times, number of

available shades and composition. According to the manufacturers, all

currently available self-adhesive cements release fluoride ions. All these

products are dual-cured radiopaque materials that are indicated for adhesive

cementation of virtually any indirect restoration: ceramic, composite, metal,

inlays (composite or metal), onlays, bridges, crowns, posts and screws

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(including fiber posts) made of metal, composite and ceramic. The only

procedure in which the use of self-adhesive cements is not indicated is the

cementation of veneers. In this case light curing veneer cements are

recommended, as the practitioners usually require longer working time that

allows the positioning and adjustment of several veneers simultaneously,

prior to light initiation of the cement polymerization.

This literature review aimed at summarizing research conducted on

self-adhesive cements and at providing information on their properties, based

on the results of original scientific full-papers from peer-reviewed journals

listed in PubMed. The search was conducted using the term: self-adhesive

cement OR biscem OR gcem OR wetbond OR maxcem OR monocem OR

multilink sprint OR unicem.

Literature data

RelyX Unicem is undoubtedly the most thoroughly investigated self-adhesive

cement in the current literature. The vast majority of the articles published in

Medline cited journals investigated some of the properties of this cement.

Limited information is also available on Maxcem (Bishara et al. 2006a;

Goracci et al. 2006; Frankenberger et al. 2007), while no studies that

investigated other currently marketed self-adhesive cements have been

published so far. One study assessed the handling properties of Relyx

Unicem in clinical use through a practice-based evaluation (Burke et al.

2006). All the other published articles are based on in vitro investigations.

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Table: Features of commercially available self-adhesive cements

Product Working / setting time Composition BisCem (Bisco Inc, Schaumburg, IL, USA)

1min / 6min at 22°C (72°F)

Bis (Hydroxyethyl methacrylate) phosphate (Base) Tetraethylene glycol dimethacrylate Dental Glass

Breeze Pentron Clinical Technologies, Wallingford, CT, USA

(information not available)

Mixture of BisGMA, UDMA, TEGDMA, HEMA, & 4-MET resins, silane-treated bariumborosilicate glasses, silica with initiators, stabilizers and UV absorber, organic and/or inorganic pigments, opacifiers

GCem GC Corp, Tokyo, Japan

2min / 4min (based on oral temperature)

Powder: fluoro-alumino-silicate glass, initiator, pigment Liquid: 4-MET, phosphoric acid ester monomer, water, UDMA, dimethacrylate, silica powder, initiator, stabilizer

Embrace WetBond resin cement (Pulpdent, Watertown, MA, USA

completely auto-cures in 7 minutes


Maxcem (Kerr; Orange, CA, USA)

gel time is 2 minutes – set time is 3 minutes (based on oral temperature)

GPDM (glyceroldimethacrylate dihydrogen phosphate), comonomers (mono-, di-, and tri-functional methacrylate monomers), proprietary self-curing redox activator, photoinitiator (camphorquinone), stabilizer, barium glass fillers, fluoroaluminosilicate glass filler, fumed silica (filler load 67% wt, particle size 3.6 μm)

MonoCem Shofu Dental Corporation, San Marcos, CA, USA

Unlimited working time. Completely auto-cures in 7 minutes in anaerobic conditions.


Multilink Sprint Ivoclar Vivadent, Schaan, Lichtenstein

Working time: 130+/-30s Setting time: 270+/-30s (based on oral temperature)

Dimethacrylates and acidic monomers. The inorganic fillers are barium glass, ytterbium trifluoride and silicon dioxide. The mean particle size is 5 μm. The total volume of inorganic fillers is approx. 48 %.

RelyX Unicem 3M ESPE, St. Paul, MN, USA

2min / 5min at 22°C (72°F)

Powder: glass fillers, silica, calcium hydroxide, self-curing initiators, pigments, light-curing initiators (filler load 72% wt, particle size <9.5 μm) Liquid: methacrylated phosphoric esters, dimethacrylates, acetate, stabilizers, self-curing initiators, light-curing initiators

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Adhesion to tooth substrates

Enamel

Self-adhesive cements adhesion to ground enamel was assessed in several

studies that evaluated bond strength (De Munck et al. 2004; Abo-Hamar et

al. 2005; Goracci et al. 2006; Hikita et al. 2007) and cement-enamel interface

micromorphology (De Munck et al. 2004; Goracci et al. 2006). Bond

strength of self-adhesive cements used for cementation of orthodontic

brackets to unground enamel was also investigated (Vicente et al. 2005;

Bishara et al. 2006a; Bishara et al. 2006b). In all the studies self-adhesive

cements were light cured.

Bond strength of RelyX Unicem (De Munck et al. 2004; Abo-Hamar

et al. 2005; Goracci et al. 2006; Hikita et al. 2007) and Maxcem (Goracci et

al. 2006) to enamel was investigated using shear (Abo-Hamar et al. 2005)

and microtensile (De Munck et al. 2004; Goracci et al. 2006; Hikita et al.

2007) bond strength tests. Shear bond strength of RelyX Unicem to enamel

was evaluated prior and after thermocycling (Abo-Hamar et al. 2005). Before

thermocycling this cement produced bond strength of 14.5 MPa which was

significantly lower than the bond strengths of other resin luting systems

investigated, that ranged between 17 and 32 MPa. Moreover, its shear bond

strength to enamel was significantly lower after thermocycling, in contrast to

other resin cements that were not influenced by the same aging condition

(Abo-Hamar et al. 2005). However, since the bond strength of RelyX

Unicem was higher than the bond strength of a glass ionomer cement both

before and after thermocycling, it was pointed out that this self-adhesive

cement may be considered an alternative to glass ionomer cement for

cementation of high-strength ceramic or metal-based restorations. It was also

commented that RelyX Unicem may be used for luting conventional ceramic

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crowns with little or no enamel left, but that it might not be the ideal material

for luting inlays and partial crowns, if a considerable enamel surface area is

present (Abo-Hamar et al. 2005).

Similar results in terms of enamel bond strengths were reported in

microtensile bond strength investigations. Enamel microtensile bond

strengths of RelyX Unicem ranged between 10.7 MPa (Goracci et al. 2006)

and 19.6 MPa (De Munck et al. 2004; Hikita et al. 2007) and were

significantly lower compared to the bond strengths of self-etching cement

Panavia F 2.0 (De Munck et al. 2004; Goracci et al. 2006; Hikita et al. 2007)

and other resin cements (Hikita et al. 2007) that ranged between 25 and 49

MPa (De Munck et al. 2004; Goracci et al. 2006; Hikita et al. 2007).

Microtensile bond strength of Maxcem to enamel was significantly lower

compared to RelyX Unicem (Goracci et al. 2006). Conversely, RelyX

Unicem microtensile bond strength to enamel was comparable to other resin

cements when its application was preceded by phosphoric acid etching (De

Munck et al. 2004; Hikita et al. 2007).

Morphological evaluations revealed that RelyX Unicem should be

applied using some pressure in order to ensure its close adaptation to the

cavity wall (De Munck et al. 2004). However, the pressure twice as high as

the finger pressure had no effect on RelyX Unicem and other investigated

cements (Maxcem and Panavia F 2.0) microtensile bond strength to flat

ground enamel surfaces (Goracci et al. 2006). Under scanning electron

microscope, different self-adhesive cements resulted in comparable interfaces

with ground enamel, without microscopic signs of micromechanical

retention.

The manufacturers did not include cementation of orthodontic

appliances in the indications for use of self-adhesive cements. Nevertheless,

the shear bond strength of orthodontic brackets cemented to unground enamel

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with RelyX Unicem (Vicente et al. 2005; Bishara et al. 2006b) and Maxcem

(Bishara et al. 2006a) was assessed in order to evaluate the potential benefits

of self-adhesive cements in orthodontic clinical procedures. Both cements

revealed significantly lower bond strengths in comparison to conventional

orthodontic resin adhesive systems that utilize phosphoric acid etching of the

enamel surface (Vicente et al. 2005; Bishara et al. 2006a; Bishara et al.

2006b). However, the lower bond strength of orthodontic brackets cemented

to enamel by RelyX Unicem was thought to be clinically acceptable (Vicente

et al. 2005).

Dentin

The adhesion of RelyX Unicem (De Munck et al. 2004; Abo-Hamar et al.

2005; Walter et al. 2005; Escribano and de la Macorra 2006; Goracci et al.

2006; Yang et al. 2006; Al-Assaf et al. 2007; Hikita et al. 2007;

Piwowarczyk et al. 2007) and Maxcem (Goracci et al. 2006) to coronal

dentin was evaluated by bond strength (De Munck et al. 2004; Abo-Hamar et

al. 2005; Walter et al. 2005; Goracci et al. 2006; Yang et al. 2006; Al-Assaf

et al. 2007; Hikita et al. 2007; Piwowarczyk et al. 2007) and morphological

investigations (De Munck et al. 2004; Goracci et al. 2006; Yang et al. 2006;

Al-Assaf et al. 2007). The retentive strength of zirconia crowns cemented

with RelyX Unicem was also assessed (Ernst et al. 2005; Palacios et al.

2006). In the majority of the studies self-adhesive cements were light-cured

(De Munck et al. 2004; Walter et al. 2005; Escribano and de la Macorra

2006; Goracci et al. 2006; Palacios et al. 2006; Hikita et al. 2007) while in

two studies materials were left to autopolymerize (Yoshida et al. 2004; Al-

Assaf et al. 2007). The effect of curing mode to shear bond strength to dentin

of dual-cured resin cements, including RelyX Unicem, was assessed in two

studies (Abo-Hamar et al. 2005; Piwowarczyk et al. 2007). Light curing

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resulted in higher bond strengths and therefore it was recommended for

clinical procedures (Abo-Hamar et al. 2005; Piwowarczyk et al. 2007).

Bond strength studies were conducted using shear (Abo-Hamar et al. 2005;

Piwowarczyk et al. 2007) tensile(Al-Assaf et al. 2007) and microtensile bond

strength test (De Munck et al. 2004; Walter et al. 2005; Escribano and de la

Macorra 2006; Goracci et al. 2006; Yang et al. 2006; Hikita et al. 2007), and

the recorded bond strength values vary greatly depending on the applied test

methodology. Nevertheless, the majority of the results obtained is consistent

and demonstrate that in contrast to enamel adhesion, RelyX Unicem performs

comparably to other multi-step systems on coronal dentin. Its bond strengths

were often compared to Panavia F, and no significant differences (De Munck

et al. 2004; Abo-Hamar et al. 2005; Goracci et al. 2006; Al-Assaf et al. 2007;

Hikita et al. 2007; Piwowarczyk et al. 2007) or higher bond strength of

RelyX Unicem were reported (Walter et al. 2005). In comparison to resin

cements that utilize etch-and-rinse adhesive systems RelyX Unicem bonded

equally effectively when compared to Variolink II (Ivoclar Vivadent) (Abo-

Hamar et al. 2005; Hikita et al. 2007), Nexus 2 (Kerr) (Hikita et al. 2007),

RelyX ARC (3M ESPE) and Calibra (Dentsply Caulk) (Piwowarczyk et al.

2007). Unlike previous findings, significantly lower microtensile bond

strength of RelyX Unicem to dentin compared to Panavia F 2.0 (Escribano

and de la Macorra 2006; Yang et al. 2006), Multilink (Escribano and de la

Macorra 2006) and Variolink II (Piwowarczyk et al. 2007) was also reported.

In contrast to the positive effect observed on enamel, acid etching was

detrimental to RelyX Unicem dentin adhesion (De Munck et al. 2004; Hikita

et al. 2007). Its microtensile bond strength following acid etching was

significantly lower compared to the one obtained when the cement was used

without any treatment of the dentin surface (De Munck et al. 2004; Hikita et

al. 2007). This was attributed to the self-adhesive cements inability to

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infiltrate the collagen depleted by the etching step (De Munck et al. 2004).

Although higher seating force had no effect on enamel adhesion, it improved

microtensile bond strengths of RelyX Unicem and Panavia F 2.0 to dentin

(Goracci et al. 2006). Conversely, the microtensile bond strength of Maxcem

to dentin was significantly lower compared to RelyX Unicem, and was not

influenced by the heavier seating pressure (Goracci et al. 2006).

The application of RelyX Unicem (De Munck et al. 2004; Goracci et

al. 2006; Yang et al. 2006; Al-Assaf et al. 2007) and Maxcem (Goracci et al.

2006) to coronal dentin does not result in the formation of a hybrid layer and

resin tags. The morphological findings at the cement-dentin interface formed

by self-adhesive cements were noticeably different in comparison to the

interface formed with resin cements that require pretreatment of the dentin

surface (De Munck et al. 2004; Goracci et al. 2006; Yang et al. 2006; Al-

Assaf et al. 2007).

Zirconium oxide crowns and fixed partial dentures may be cemented

using conventional non-bonding cements due to their high fracture resistance.

However, these restorations may also benefit from adhesive cementation

(Blatz et al. 2003). Retention of zirconia crowns cemented with RelyX

Unicem was investigated in two studies (Ernst et al. 2005; Palacios et al.

2006). The retentive strength of Lava crowns (3M ESPE) cemented with the

self-adhesive cement was not significantly different in comparison to the

other multi-step resin luting agents tested (Ernst et al. 2005). Likewise,

comparable retentive strengths of Procera AllZirkon copings (Nobel Biocare)

were found between RelyX Unicem, Panavia F and a resin modified glass

ionomer cement (RelyX Luting, 3M ESPE) (Palacios et al. 2006).

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Root dentin

Since root dentin is different in nature from coronal dentine and variations in

its structure may affect bonding, the adhesion to this substrate is usually

assessed separately (Ferrari et al. 2000; Mjor et al. 2001). The adhesion of

RelyX Unicem to root dentin was investigated in light-cure mode when this

cement was used for the cementation of fiber posts (Bateman et al. 2005;

Goracci et al. 2005; Bitter et al. 2006a; Sadek et al. 2006) and titanium

dowels (Balbosh et al. 2005). In order to evaluate the effectiveness of

cementation, thin-slice push out tests (Goracci et al. 2005; Bitter et al. 2006a;

Sadek et al. 2006), retention tests (Balbosh et al. 2005; Bateman et al. 2005)

and morphological evaluations of the cement-root dentin interface (Goracci

et al. 2005) were performed.

Similarly to bond strengths on coronal dentin, the push-out strength of

RelyX Unicem was comparable to Panavia F 2.0. However, both cements

resulted in significantly lower push-out strengths compared to Variolink II

cement in combination with an etch-and-rinse dual cured adhesive Excite

DSC (Ivoclar Vivadent) (Goracci et al. 2005). Different results were reported

in another investigation, where RelyX Unicem push-out strength was

significantly higher than the push-out strengths of Panavia F, Variolink II and

other resin cements investigated (Bitter et al. 2006a). Moreover, its push-out

strength was significantly higher after thermocycling. The authors speculated

that the self-adhesive cements moisture tolerance, purported by the

manufacturer, may partly explain its favorable adhesion in the root canals

(Bitter et al. 2006a). A significant increase in RelyX Unicem push-out

strength was found after 24 hours of water storage in comparison to

immediate testing (Sadek et al. 2006).

Retention of quartz fiber posts cemented with RelyX Unicem was

comparable to the retention obtained with the conventional resin cement

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RelyX ARC in combination with an etch-and-rinse adhesive (Bateman et al.

2005). When RelyX Unicem was used for titanium dowel cementation it

performed comparably to a zinc phosphate, glass ionomer and a resin cement

(Panavia 21) (Balbosh et al. 2005).

Similarly to coronal dentin, no hybrid layer and inability to etch

through the smear layer formed in the root canal were observed when RelyX

Unicem (Goracci et al. 2005) was used for adhesive cementation of fiber

posts.

Adhesion to restorative materials

Endodontic posts

Only one study assessed the adhesion of RelyX Unicem to endodontic posts,

using the thin-slice push out test after the tribochemically coated (CoJet, 3M

ESPE) zirconia (CosmoPost, Ivoclar Vivadent) and fiber posts (FRC Postec,

Ivoclar Vivadent) were cemented in artificial post spaces (Bitter et al.

2006b). The push-out strength of RelyX Unicem was significantly higher to

fiber posts than to zirconia posts. On both substrates it performed comparably

to the cements that resulted in the highest push-out strengths (Bitter et al.

2006b).

Ceramics

Several studies investigated shear (Piwowarczyk et al. 2004; Kumbuloglu et

al. 2005; Piwowarczyk et al. 2005b; Reich et al. 2005; Kumbuloglu et al.

2006; Luthy et al. 2006) and microtensile (Pisani-Proenca et al. 2006) bond

strength of RelyX Unicem to different types of ceramic: high-strength

cylindrical aluminum oxide (Piwowarczyk et al. 2004), leucite-reinforced

(Piwowarczyk et al. 2004), lithium disilicate (Piwowarczyk et al. 2004;

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Kumbuloglu et al. 2005; Pisani-Proenca et al. 2006), machinable feldspatic

(Reich et al. 2005) and zirconia ceramics (Piwowarczyk et al. 2005b;

Kumbuloglu et al. 2006; Luthy et al. 2006). The bond strength values varied

in different studies, depending on the ceramic treatment and the aging

conditions. However, the obtained results are in agreement, demonstrating

that this cement achieves bond strength that is either higher or comparable to

other investigated materials. In the majority of the studies, RelyX Unicem

was light cured (Kumbuloglu et al. 2005; Reich et al. 2005; Kumbuloglu et

al. 2006; Luthy et al. 2006; Pisani-Proenca et al. 2006). Two studies

investigated the influence of the curing mode on bond strength of dual-curing

resin cements to high-strength cylindrical aluminum oxide, leucite-

reinforced, lithium disilicate (Piwowarczyk et al. 2004) and zirconia

ceramics (Piwowarczyk et al. 2005b). It was reported that light

polymerization of the investigated dual-curing resin cements, including

RelyX Unicem, significantly increased bond strengths in comparison to

autopolymerization.

In comparison with 10 cements from different classes, only RelyX

Unicem resulted in high shear bond strengths after 14 days of water storage

and thermocycling to all the investigated substrates: high-strength cylindrical

aluminum oxide ceramic (following sandblasting), leucite-reinforced and

lithium disilicate ceramic (following etching with hydrofluoric acid and

silanization). Interestingly, water storage and thermocycling increased the

bond strength of all resin cements and the self-adhesive universal resin

cement (Piwowarczyk et al. 2004). In a study by Kumbuloglu et al, RelyX

Unicem revealed lower shear bond strengths to lithium disilicate ceramics

than the other resin cements investigated (Kumbuloglu et al. 2005).

However, in this study no pretreatment of the ceramic surface was

performed, in contrast to the previous study in which the ceramic surface was

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etched and silanized (Piwowarczyk et al. 2004). following the manufacturer’s

directions (3M ESPE product profile, RelyX Unicem). Microtensile bond

strengths of RelyX Unicem, Multilink and Panavia F increased when lithium

disilicate ceramics (IPS Empress 2) was etched and silanized, in comparison

to bond strengths to untreated ceramic surfaces (Pisani-Proenca et al. 2006).

RelyX Unicem microtensile bond strength was comparable to Multilink

following etching and silanization, and higher in comparison to Panavia F,

regardless of the ceramic surface treatment (Pisani-Proenca et al. 2006). High

bond strengths that were increased after thermocycling were also reported to

etched and silanized machinable feldspatic ceramic (Reich et al. 2005). This

study reported that etching with hydrofluoric acid and silanization was the

most beneficial treatment to gain a reliable bond strength to the majority of

materials investigated, including RelyX Unicem (Reich et al. 2005).

RelyX Unicem shear bond strength to sandblasted (110 �m aluminum

oxide) or tribochemically coated (Rocatec, 3M ESPE) zirconia ceramics

(Lava, 3M ESPE) was investigated and compared with 10 luting cements

from different material classes (Piwowarczyk et al. 2005b). Similarly to the

previous study using the same materials and methodology for different

ceramic substrates (Piwowarczyk et al. 2004), the shear bond strength of this

cement increased after 14 days of water storage and thermocycling. It was

also the highest in comparison with other investigated materials regardless of

the ceramic surface treatment (Piwowarczyk et al. 2005b). High shear bond

strengths, comparable to Panavia F, were also reported to zirconia ceramics

with and without previous tribochemical treatment of the ceramic surface

(Rocatec) and regardless of the aging condition (Kumbuloglu et al. 2006;

Luthy et al. 2006).

105

Titanium abutments

Retention forces of noble alloy castings cemented on titanium abutments with

different cements were investigated (Wolfart et al. 2006). The retention

achieved using RelyX Unicem was comparable to retention achieved using

polycarboxylate cement, and significantly higher in comparison to retention

following the cementation with zinc oxide, zinc phosphate and glass ionomer

cements (Wolfart et al. 2006).

Marginal adaptation

In vitro marginal adaptation of RelyX Unicem (Behr et al. 2004; Rosentritt

et al. 2004; Frankenberger et al. 2008) and Maxcem (Frankenberger et al.

2008) was evaluated following the cementation of all-ceramic MOD inlay

restorations (IPS Empress, Ivoclar Vivadent) (Rosentritt et al. 2004;

Frankenberger et al. 2008) and all-ceramic crowns (IPS Empress 2, Ivoclar

Vivadent) (Behr et al. 2004). Marginal adaptation of all-ceramic MOD inlays

was assessed in enamel and in dentin. These authors reported over 90% of

perfect margin in RelyX Unicem specimens, which was comparable to resin

cements Variolink and Panavia F both before and after thermocycling and

mechanical loading. Marginal integrity deteriorated after loading for all the

cements investigated, but significantly lower percentage of perfect margin

was recorded only for Variolink in dentin, at both tooth-cement and cement-

inlay interface (Rosentritt et al. 2004). Another investigation reported that

RelyX Unicem offers a tight seal at dentin margins, while Maxcem resulted

in a significantly lower percentage of perfect margin (Frankenberger et al.

2008). However, it was ponted out that self-adhesive cements cannot

compete with cements which utilize etch-and-rinse adhesives in terms of

enamel bonding performance (Frankenberger et al. 2008).

106

Marginal adaptation of RelyX Unicem used for the cementation of all

ceramic crowns was assessed in dentin, before and after thermal and

mechanical loading that was applied with the intention to simulate a five-year

period of intraoral stress. Over 90% of perfect margin was observed in RelyX

Unicem specimens. Its adaptation was not influenced either by previous

application of Prompt-L-Pop adhesive or by loading, and was comparable to

Variolink resin cement (Behr et al. 2004).

Microleakage

Microleakage of RelyX Unicem was evaluated subsequently to cementation

of porcelain veneers (Ibarra et al. 2007), all-ceramic inlay restorations

(Rosentritt et al. 2004; Fabianelli et al. 2005), all-ceramic crowns (Behr et al.

2004), gold inlays (Fabianelli et al. 2005) and full cast crowns (Piwowarczyk

et al. 2005a). Porcelain veneers enamel microleakage was significantly

higher when the self-adhesive cement was used in comparison to resin

cement Variolink combined with the etch-and-rinse adhesive Excite (Ivoclar

Vivadent). However, in accordance with bond strength data (De Munck et al.

2004; Hikita et al. 2007) enamel microleakage decreased to values

comparable to Variolink if RelyX Unicem was used with the etch-and-rinse

adhesive (Single Bond, 3M ESPE) or a strong self-etch adhesive (Adper

Prompt-L-Pop, 3M ESPE) (Ibarra et al. 2007). Conversely, the application of

these adhesives on dentin had an unfavorable effect on microleakage, while

the self-adhesive cement used without any dentin pretreatment resulted in

microleakage values comparable to Variolink (Ibarra et al. 2007). When the

self-adhesive cement was used for the cementation of all-ceramic MOD

inlays, microleakage in enamel and dentin was comparable to resin cements

Variolink (Rosentritt et al. 2004; Fabianelli et al. 2005) and Panavia F

107

(Rosentritt et al. 2004). Microleakage of this cement following the

cementation of all-ceramic crowns was investigated in dentin, and was

significantly lower compared to Variolink (Behr et al. 2004).

In a microleakage investigation of various cementing agents for full

cast crowns, RelyX Unicem revealed the lowest microleakage both in enamel

and in dentin (Piwowarczyk et al. 2005a). Enamel microleakage was

significantly lower compared to RelyX ARC resin cement used with the etch-

and-rinse adhesive Single Bond and the zinc phosphate cement, and

comparable to glass ionomer cements and the self-etching cement Panavia F

(Piwowarczyk et al. 2005a). The authors speculated that the specific

multifunctional phosphoric-acid methacrylates that this cement contains are

able to react with the tooth surface in multiple ways, resulting in an effective

seal. Apart from the formation of complex compounds with calcium ions,

different kinds of physical interactions like hydrogen bonding or dipole-to-

dipole interactions were assumed to favorably influence self-adhesion

(Piwowarczyk et al. 2005a). In another microleakage investigation, RelyX

Unicem performed significantly better than the zinc phosphate cement with

gold inlays (Fabianelli et al. 2005).

Mechanical properties

Mechanical properties of RelyX Unicem cement were assessed by surface

microhardness (Kumbuloglu et al. 2004), degree of conversion (Kumbuloglu

et al. 2004), compressive strength (Piwowarczyk and Lauer 2003;

Kumbuloglu et al. 2004) and flexural strength (Piwowarczyk and Lauer

2003) investigations. Fatigue (Baldissara et al. 2006; Uy et al. 2006) and

fracture resistance (Komine et al. 2004; Burke et al. 2006) of teeth restored

using RelyX Unicem were also evaluated.

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After 1 week of water storage, RelyX Unicem in light-cure mode had

the highest values of hardness and compressive strength when it was

compared with three other resin cements (RelyX ARC, Panavia F and

Variolink). However, in the same study it was reported that its degree of

conversion was the lowest: 56% when the cement was light cured and only

26% when it was autopolymerized (Kumbuloglu et al. 2004). In another

study, the same three resin cements had the highest flexural and compressive

strengths, followed by RelyX Unicem, while all four materials were

statistically stronger than resin-modified glass ionomer cements, glass

ionomer cements and zinc phosphate cements (Piwowarczyk and Lauer

2003). This study also assessed the influence of curing mode on flexural and

compressive strengths of dual-curing resin cements. No significant

differences between the properties of light-cured and autopolymerized

cements were found (Piwowarczyk and Lauer 2003).

Fatigue resistance of sandblasted (110 �m aluminum oxide) glass-

infiltrated alumina ceramic (In Ceram Alumina, Vita) bonded to dentin was

lower when RelyX Unicem was used in comparison to Panavia F (Baldissara

et al. 2006). Both cements were used in the self-cure mode (Baldissara et al.

2006). In the assessment of load-fatigue performance of gold crowns luted

with resin cements, RelyX Unicem survived lower number of cycles

compared to C & B Opaque (Bisco Inc., Schaumburg, IL, USA) and Calibra

Esthetic resin cement (Dentsply Caulk) but behaved comparably to Panavia F

and zinc phosphate cement (Uy et al. 2006). The marginal areas in teeth

where the crowns were luted with resin cements were light polymerized (Uy

et al. 2006). Fracture resistance of teeth restored with all ceramic crowns

luted with RelyX Unicem in light-cure (Burke et al. 2006b) and self-cure

(Komine et al. 2004) mode was comparable to fracture resistance of teeth

restored using a conventional resin cement Mirage ABS/FLC (Mirage Dental

109

Systems, Kansas City, KS, USA) (Burke et al. 2006b) and Super-Bond C&B

(Sun Medical, Shiga, Japan) (Komine et al. 2004).

Biocompatibility

In a study by de Souza Costa et al. pulpal response to RelyX Unicem and

Variolink II used to bond inlay restorations was investigated and compared

(de Souza Costa et al. 2006). Although slight tissue disorganization was

observed in the RelyX Unicem samples at the 7-day period, no pulpal

response was present in most of the samples evaluated at 60 days.

Conversely, Variolink II associated with the adhesive system Excite

demonstrated more aggressive effects to the pulp–dentin complex. A

discrete-to-moderate initial pulpal inflammatory response was observed that

persisted until the 60-day period. The authors speculated that RelyX Unicem

benefited from its chemical adhesion to tooth structure, low solubility and a

self-neutralizing mechanism during the setting reaction. These manufacturer-

declared properties were assumed to prevent hydrolysis and diffusion of

cement’s components across dentinal tubules. The mild inflammatory

reaction that was observed at the 7-day period was explained by the initially

low pH of the cement (de Souza Costa et al. 2006).

Chemical adhesion and fluoride release

Until recently, chemical adhesion to hydroxyapatite was proven for glass

ionomer cements (Wilson et al. 1983; Yoshida et al. 2000) and 10-MDP (10-

methacryloxydecyl dihydrogen phosphate) and 4-MET (4-methacryloxyethyl

trimellitic acid) functional monomers used in some self-etching adhesive

systems (Yoshida et al. 2004). In a study by Gerth et al (Gerth et al. 2006)

110

the potential for chemical interaction between RelyX Unicem and

hydroxyapatite was investigated and compared to resin cement Bifix (Voco,

Cuxhaven, Germany) in combination with an etch-and-rinse adhesive system.

It was reported that RelyX Unicem showed high chemical interaction with Ca

ions derived from hydroxyapatite, which was enhanced in comparison to

Bifix (Gerth et al. 2006).

The same authors investigated the exact composition of RelyX

Unicem and Bifix and detected a fluoride content of 10% with RelyX

Unicem and 2% with Bifix. Although fluoride release from restorative

materials depends on their fluoride content, this process is also influenced by

several other factors (Wiegand et al. 2007). More importantly, a direct

relationship between fluoride release from restorative materials and its actual

anticariogenic effects has not been determined in vivo (Burke et al. 2006).

Therefore, the clinical significance of fluoride release from self-adhesive

cements in terms of their cariostatic properties remains to be determined.

Ratings in clinical use

No clinical studies that investigated self-adhesive cements have been

published yet. However, some information on the handling properties of

these materials is available. Product Research and Evaluation by Practitioners

(PREP) Panel, a United Kingdom-based group conducted a practice-based

evaluation of RelyX Unicem handling. The authors reported that this cement

achieved ratings for ease of use that were superior to the pre-study resin-

based and conventional luting materials in the practices of 13 United

Kingdom dental practitioners (Burke et al. 2006a).

111

Conclusions

Based on the literature in vitro data, adhesion of the most investigated self-

adhesive cement to dentin and various restorative materials is satisfactory and

comparable to other multi-step resin cements. An interesting and clinically

relevant concept is the possibility for dentin bond strength enhancement by

the application of higher seating pressure. Light curing provided higher bond

strengths than autopolymerization to dentin and to various types of ceramic

materials. Some investigations have reported that artificial aging resulted in

increased push-out strength to root dentin and increased bond strengths to

various fixed prosthodontic restorative materials. Adhesion to enamel

appears to be a weak link in bonding properties of self-adhesive cements.

Although it may benefit from previous acid etching, this procedure is

detrimental to dentin adhesion. Therefore, its potential employment would

require an extreme precision in applying the acid solely on enamel, which is

difficult to achieve in clinical conditions. Chemical adhesion and fluoride

release may play a role in durability and cariostatic properties of these

materials, which remains to be determined in vivo.

Self-adhesive cements appear to offer a promising new approach in

indirect restorative procedures. However, the available literature data is based

on studies that investigated only one of the cements that are currently

available to clinicians. More importantly, long term clinical performance of

these materials needs to be assessed prior to making a general

recommendation for their use.

112

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118

3.2. Evaluation of the adhesion of fiber posts cemented using different

adhesive approaches

Ivana Radovic, Claudia Mazzitelli, Nicoletta Chieffi, Marco Ferrari.

European Journal of Oral Sciences 2008; 116(6): 557-563.

Introduction

Reconstructing endodontically treated teeth with fiber post and core systems

has been widely investigated (Schwartz and Robbins 2004; Schwartz and

Fransman 2005). This treatment option may offer advantages over

conventional cast posts or prefabricated metallic posts (Martinez-Insua et al.

1998; Sirimai et al. 1999; Cormier et al. 2001; Akkayan and Gulmez 2002;

Newman et al. 2003; Fokkinga et al. 2004; Hayashi et al. 2006).

Notwithstanding the satisfactory clinical performance of fiber post and core

systems (Cagidiaco et al. 2008), debonding of the post was observed as the

main failure mode (Ferrari et al. 2000; Mannocci et al. 2002; Monticelli et al.

2003; Cagidiaco et al. 2007; Ferrari et al. 2007a).

The success of fiber post and core restorative procedure depends in

part on the cementation technique used to create a link between the post and

root canal dentin. Contemporary resin cements may be divided into three

subgroups according to the adhesive approach used to prepare the tooth prior

to cementation. The first group utilizes etch-and-rinse adhesive systems. In

the second group, enamel and dentin are prepared using self-etching primers.

The third and the most recently introduced group of resin cements is

represented by self-adhesive cements.

In the majority of clinical investigations fiber posts were cemented

using etch-and-rinse adhesives in combination with self-cured (Ferrari et al.

2000a; Ferrari et al. 2000b; Malferrari et al. 2003; Mannocci et al. 2005;

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Ferrari et al. 2007a) and dual-cured resin cements (Ferrari et al. 2000b;

Monticelli et al. 2003; Grandini et al. 2005; Naumann et al. 2005a; Naumann

et al. 2005b; Cagidiaco et al. 2007; Ferrari et al. 2007b). It was reported that

the level of operator’s experience does not influence retention of fiber posts

cemented using etch-and-rinse adhesive in laboratory conditions (Simonetti

et al. 2006). Nevertheless, scientists and manufacturers have been

continuously challenged by a general trend to simplify the clinical

procedures. The simpler, self-etching adhesive approach, offers the shorter

adhesive application time and reduced number of clinical steps. It is

considered to be less technique sensitive as the clinical assessment of optimal

dentin wetness after rinsing the phosphoric acid is avoided (Van Meerbeek et

al. 2003). However, the most simple, one-step self-etching adhesives, are

also associated with permeability and phase separation which may affect

bond durability (Van Meerbeek et al. 2005).

The adhesion of fiber posts luted using self-etching adhesives has

been assessed only in laboratory studies, most commonly by comparing them

with the performance of etch-and-rinse adhesives. The findings on self-

etching adhesives performance in fiber post cementation are not consistent. It

was reported that microleakage at the cement/root dentin interface was

significantly higher when self-etching primer was used for fiber post

cementation, in comparison to etch-and-rinse adhesive (Mannocci et al.

2001a). Likewise, resin-root dentin interdiffusion zone was less pronounced

following self-etching approach than with etch-and-rinse adhesive approach

(Mannocci et al. 1999). On the other side, no differences between self-

etching and etch-and-rinse approach were found when representative

materials were investigated using microtensile bond strength test (Mannocci

et al. 2001b) and push-out strength test (Kurtz et al. 2003; Akgungor and

Akkayan 2006).

120

Self-adhesive cements represent the least investigated group of resin

cements. Their in vitro performance in fiber post cementation was

investigated using push-out strength test (Goracci et al. 2005; Bitter et al.

2006; de Durao Mauricio et al. 2007; Huber et al. 2007; Wang et al. 2008),

and the results are contradictory. In comparison with etch-and-rinse

approach, both lower (Goracci et al. 2005; de Durao Mauricio et al. 2007;

Wang et al. 2008) and higher (Bitter et al. 2006) push-out strength of self-

adhesive cement was reported. In comparison to self-etching approach,

inferior (de Durao Mauricio et al. 2007), comparable (Goracci et al. 2005)

and superior (Huber et al. 2007) behaviour of the self-adhesive approach was

reported, even though the same self-adhesive cement was investigated in all

the studies. In the only clinical study available, no failures were recorded

after 2-year follow-up of restorations retained by fiber posts cemented with

self-adhesive cement (Naumann et al. 2007).

Self-etching and self-adhesive approach offer simplicity and chair-

time reduction, which may be beneficial in the clinical setting. However, the

information on the most favourable fiber post cementation technique is

lacking in the present literature. Therefore, the aim of the study was to

investigate the adhesion of fiber posts cemented to intraradicular dentin with

luting agents that utilize three currently available adhesive approaches: etch-

and-rinse, self-etch and self-adhesive. The working hypothesis was that the

simpler, self-etching and self-adhesive approaches are equally effective as the

clinically proven etch-and-rinse approach. The null hypothesis tested is that

there are no differences in the retention of fiber posts cemented with different

luting agents.

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Material and methods

Specimens preparation

Forty two intact human premolars with a single root canal, extracted due to

orthodontic reasons were selected for the study. The teeth were hand-scaled

and stored in 1% chloramine T at 4°C for no more than six months until use.

The crown of each tooth was removed at 1mm above the cementoenamel

junction, using a slow speed diamond saw (Isomet, Buehler, Lake Bluff, IL,

USA) under copious water-cooling. The roots were endodontically

instrumented at a working length of 1 mm from the apex to a #35 master

apical file (Maillefer), Gates-Glidden drills #2 to #4 (Maillefer), and 2.5%

sodium hypochlorite irrigation. For canal obturation, thermoplasticized,

injectable gutta-percha (Obtura, Texceed Corp, Costa Mesa, CA, USA) and a

resin sealer (AH Plus Jet, Dentsply DeTrey, Konstanz, Germany) were

employed. Teeth were randomly divided into six groups. In each group,

different resin cement with its adhesive system (if needed) and fiber post was

used. The groups were classified according to the adhesive approach into

three categories: etch-and rinse, self-etch and self-adhesive.

Etch-and-rinse groups:

� Calibra resin cement, XPBond adhesive/Self curing activator, RadiX

Fiber Post (Dentsply Caulk, Milford, DE, USA).

� FluoroCore 2 core build-up material, XPBond adhesive/Self curing

activator, RadiX Fiber Post (Dentsply Caulk)

� MultiCore Flow luting/core build-up material, Excite DSC adhesive,

FRC Postec Plus fiber post (Ivoclar Vivadent, Schaan, Liechtenstein)

122

Self-etch group:

� Panavia F 2.0, ED primer (Kuraray, Osaka, Japan), RadiX Fiber Post

(Dentsply Caulk)

Self-adhesive groups:

� Experimental self-adhesive cement, RadiX Fiber Post (Dentsply

Caulk)

� RelyX Unicem, RelyX Fiber Post (3M ESPE, Seefeld, Germany)

In each root-treated tooth, a 9 mm deep post space was prepared with low-

speed drills provided by the post manufacturer. The materials were strictly

handled according to the manufacturer’s instructions. The application mode

of all materials used in each group, their composition and their batch

numbers are reported in Table 1 and 2 respectively.

123

Table 1: Application mode of the materials used in the study

Luting agent (manufacturer)

Fiber post treatment

Post space dentin treatment Cementation

Calibra (Dentsply Caulk)

Clean RadiX Fiber Post with alcohol; air dry; treat surface with Calibra Silane; air dry

Apply Caulk 34% Tooth Conditioner Gel to the post space through a needle; rinse off after 15 seconds with water using an endodontic syringe; remove excess water with a gentle air blast; use paper points to remove residual moisture without desiccating the etched dentin surfaceMix XPBond adhesive with Self-Cure Activator (1:1); apply mixture to the post space with a microbrush for 20 seconds; gently air dry and then remove excess with paper points.

Mix Calibra cement components 1:1; spread mixed cement on surface of post and into the post preparation with a lentulo spiral; seat the post immediately; light cure for 40 seconds

FluoroCore 2 (Dentsply Caulk)

Clean RadiX Fiber Post with alcohol; air dry

Mix FluoroCore 2 base and catalyst 1:1 for 30 seconds; apply the material on the post and seat the post immediately; allow the material to self-cure for 7 minutes, then light cure for 40 seconds

MultiCore Flow (Ivoclar Vivadent)

Clean FRC Postec Plus post with phosphoric acid gel (Total Etch) for 60 seconds, rinse and dry. Apply Monobond S and dry after 60 seconds.

Apply Total Etch to the post space through a needle; rinse off after 15 seconds with water using an endodontic syringe; remove excess water with a gentle air blast; use paper points to remove residual moisture without desiccating the etched dentin surface. Apply activated Excite DSC adhesive to the post space with a proprietary microbrush for 10 seconds; gently air dry and then remove excess with paper points.

Mix the components of MultiCore Flow and apply the mixed material to the post; seat the post into the root canal and hold it in place using slight pressure; light cure for 60 seconds.

124

Table 1 (continued): Application mode of the materials used in the study

Luting agent (manufacturer)

Fiber post treatment

Post space dentin treatment Cementation

Panavia F 2.0 (Kuraray)

Clean RadiX Fiber Post with alcohol; air dry

Mix ED primer II (Liquid A and Liquid B 1:1); apply mixture to the post space with a microbrush for 30 seconds; gently air dry and then remove excess with paper points.

Mix Panavia F 2.0 paste A and paste B for 20 seconds; apply the mixed paste to the post and seat it in place; light cure for 40 seconds.

Experimental self-adhesive (Dentsply Caulk)

No treatment

Apply experimental cement directly to the post space through an endodontic application tip that is attached to the double syringe; place the post; allow the cement to self-cure for 5 min, then light cure for 40 seconds.

RelyX Unicem (3M ESPE)

Clean RelyX Fiber Post with alcohol, air dry

Mix the capsule; apply RelyX Unicem cement directly to the post space through a disposable application tip that is attached to the capsule; place the post; leave the cement to self- cure for 5 min and then light cure for 40 seconds.

125

Table 2: Composition and batch numbers of the materials used in the study Material (manufacturer)

Composition Batch number

Caulk 34% Tooth Conditioner Gel (Dentsply Caulk)

34% phosphoric acid 0704001801

XPBond adhesive (Dentsply Caulk)

carboxylic acid modified dimethacrylate (TCB resin), phosphoric acid modified acrylate resin (PENTA), urethane dimethacrylate (UDMA), triethyleneglycol dimethacrylate (TEGDMA), 2-hydroxyethylmethacrylate (HEMA), Butylated benzenediol (stabilizer), ethyl-4-dimethylaminobenzoate, camphorquinone, functionalised amorphous silica, tertiary butanol

0702001786

Self-cure activator (Dentsply Caulk)

Urethane Dimethacrylate (UDMA); 2-hydroxyethylmethacrylate (HEMA); Catalyst; Photoinitiators; Stabilizers; Acetone; Water

070119

Calibra Esthetic Resin Cement (Dentsply Caulk)

Base: Dimethacrylate Resins; Camphorquinone (CQ) Photoinitiator; Stabilizers; Glass Fillers; Fumed silica; Titanium Dioxide; Pigments Catalyst: Dimethacrylate Resins; Catalyst; Stabilizers; Glass Fillers; Fumed Silica

070525 0705291

Calibra Silane Coupling Agent (Dentsply Caulk)

Acetone; Ethyl Alcohol; Organo Silane 070511

FluoroCore 2 (Dentsply Caulk)

Base: Urethane Dimethacrylate; Di- & Tri-functional Methacrylates; Barium Boron; Catalyst: Fluoroaluminosilicate Glass; Camphorquinone (CQ) Photoinitiator; Photoaccelerators; Silicon Dioxide; Benzoyl Peroxide

0705041

RadiX Fiber Post (Dentsply Caulk)

Zirconium-enriched glass fibers (60%), Epoxy resin matrix (40%)

8626460

Total Etch (Ivoclar Vivadent)

37% phosphoric acid gel J25470

Excite DSC adhesive (Ivoclar Vivadent)

HEMA, dimethacrylates, phosphonic acid acrylate, highly dispersed silicon dioxide, initiators and stabilizers in an alcohol solution. The Excite DSC Brush is coated with initiators.

J23127

MultiCore Flow (Ivoclar Vivadent)

Bis-GMA, urethane dimethacrylate and triethylene glycol dimethacrylate; barium glass, ytterbiumtrifluoride, Ba-Al-fluorosilicate glass and highly dispersed silicon dioxide; catalysts, stabilizers and pigments.

H20666

Monobond S (Ivoclar Vivadent)

1% 3-methacryloxypropyltrimethoxysilane (3-MPS), ethanol/water-based solvent

H34023

FRC Postec Fiber Post (Ivoclar Vivadent)

Glass fibers. Matrix: urethane dimethacrylate, triethylene glycol dimethacrylate. Additional contents: ytterbium trifluoride, highly dispersed silicon dioxide.

K13203

126

Table 2 (continued): Composition and batch numbers of the materials used in

the study

Material (manufacturer)

Composition Batch number

ED primer (Kuraray)

Liquid A: HEMA, 10-methacryloyloxydecyl dihydrogen phosphate (MDP), N-methacryloyl 5-aminosalicylic acid (5-NMSA), dimethacrylate, sodium aromatic sulphinate, water, accelerator Liquid B: 5-NMSA, accelerator, water, sodium benzene sulphinate

00238B 00116B

Panavia F 2.0 (Kuraray)

Base: Hydrophobic aromatic and aliphatic dimethacrylate, sodium aromatic sulphinate, N,N-diethanol-p-toluidine, functionalized sodium fluoride, silanized barium glass sodium benzene sulphinate Catalyst: MDP, hydrophobic aromatic and aliphatic dimethacrylate, photoinitiator, dibenzoyl peroxide, hydrophilic dimethacrylate, silanized silica

00249A 00058D

Experimental self-adhesive cement (Dentsply Caulk)

Information not available HL6-91-1T

RelyX Fiber Post (3M ESPE)

glass fibers (60 - 70% by weight) embedded in epoxy-resin matrix containing zirconia filler

050230703

RelyX Unicem cement (3M ESPE)

Powder: glass fillers, silica, calcium hydroxide, self-curing initiators, pigments, light-curing initiators, substituted pyrimidine, peroxy compound Liquid: methacrylated phosphoric esters, dimethacrylates, acetate, stabilizers, self-curing initiators, light-curing initiators

288418

127

Following the placement of fiber post, the excess of luting agent was

removed prior to light curing. Light-curing was performed through the post

using a conventional quartz–tungsten–halogen light (600 mW/cm2 output;

VIP; Bisco, Schaumburg, IL, USA). The exposed dentin along the coronary

part of the root and the coronal part of luting agent/fiber post were

completely covered with glass ionomer cement (Fuji II, GC corp., Tokyo,

Japan). After storage in water for 24 h at 37°C (ISO/TS 11405:2003), the

roots were processed for the evaluation of push-out strength.

Push-out strength evaluation

In order to assess the adhesion of fiber posts, thin-slice push-out test was

used (Goracci et al. 2004). The portion of each root that contained the

bonded fiber post was sectioned into five to six 1 mm-thick serial slices with

the Isomet saw under water cooling (Figure 1). Seven bonded roots from

each group resulted in 35-42 slices per group for push-out strength

evaluation. None of the slices failed during sectioning process and all

fabricated slices were used for the evaluation of push-out strength. The

number of slices in each experimental group of at least 35 was determined

from a preliminary power analysis that was conducted in order to assure the

power of at least 90% for finding the statistically significant differences

given the standard value of type I errors (0.05) and assuming the difference

of 4 MPa as relevant for this investigation. The within group standard

deviation that was used in the calculations was assumed to be 4 MPa, based

on the previous investigations of push-out strength (Sadek et al. 2006). The

sample size and power calculations were handled by SigmaStat (Systat

Software Inc, San Jose, California, USA).

128

Figure 1: Schematic drawing of the specimen preparation for push-out

strength testing. Each root was sectioned into 1 mm-thick slices. The apical

surface of each root slice was marked (M) in order to assure that the loading

force would be applied in the apical-coronal direction, so as to move the post

toward the larger part of the slice. P: fiber post; C: luting agent; D: root

dentin.

The thickness of each slice was individually measured by a digital calliper,

and then firmly fixed with cyanoacrylate glue to a loading fixture. A

compressive load was applied on the apical aspect of the slice via a universal

testing machine (Controls, Spa, Milano, Italy) that was equipped with a 1

mm-diameter cylindrical plunger.

129

The plunger was positioned so that it only contacted the bonded post

on loading, introducing shear stresses along the bonded interfaces. The

loading force was extended in an apical-coronal direction, so as to move the

post toward the larger part of the root slice. Loading was performed at a

speed of 0.5 mm/min until failure, as manifested by the extrusion of the post

segment from the root slice. This was further confirmed by the appearance of

a sharp drop along the load/time curve recorded by the testing machine. The

push-out strength (MPa) was computed by dividing the load at debonding

(Newtons) by the area (A) of the bonded interface. The latter was calculated

through the formula: A=��R+r)[(h2 + (R-r)2]0.5 where R represents the

coronal post radius, r represents the apical post radius and h is the thickness

of the slice in mm. The diameters of the post and the thickness of the slice

were individually measured using a digital calliper with 0.01 mm accuracy.

The failure mode of each debonded specimen after push-out test was assessed

with a stereomicroscope (Nikon SMZ645) at 40x magnification and

classified by the following criteria:

1. Adhesive failure between dentin and luting agent;

2. Adhesive failure between luting agent and post;

3. Cohesive failure within luting agent;

4. Cohesive failure within post;

5. Mixed failure.

One slice representative of each failure mode was processed for scanning

electron microscopy (SEM) evaluation in order to obtain SEM images of the

failure patterns. The slices were rinsed in 96% alcohol solution for 1 minute

and air-dried. Each slice was mounted on a metallic stub, sputter-coated with

gold (Polaron Range SC7620; Quorum Technology), and observed under a

scanning electron microscope (JSM 6060 LV, JEOL).

130

Statistical analysis

Regression analysis was firstly conducted in each group to check if the root

of origin was a significant factor for differences in push-out strengths of root

slices. The regression analysis revealed that in none of the groups the root of

origin was significant. Therefore, the slices were considered as independent

statistical units within each group. The normal distribution of the push-out

strength data was first checked and verified by the Kolmogorov-Smirnov test.

A one-way analysis of variance (ANOVA) was subsequently performed, to

assess the significance of the differences in push-out strength between the

luting agents. As variances were homogeneous (Levene’s test), one-way

ANOVA was followed by the Tukey test for post hoc comparisons. In all the

analyses the level of significance was set at the 0.05 probability level and

calculations were handled by the SPSS 15.0 software (SPSS Inc.; Chicago,

IL, USA).

Results

The type of luting agent significantly influenced the measured push-out

strengths (p<0.001). The results of push-out strength testing are summarized

in Table 3. Multiple comparisons revealed that push-out strengths of Calibra

(etch-and-rinse approach) and RelyX Unicem (self-adhesive approach) were

comparable and significantly higher than push-out strengths of FluoroCore 2

(etch-and-rinse approach) and Panavia F 2.0 (self-etch approach). Push-out

strengths in groups where posts were cemented with MultiCore Flow (etch-

and-rinse approach) and Experimental self-adhesive cement were comparable

to push-out strengths in all the other groups (Table 4). The distribution of

failure modes is reported in Table 3. In the majority of groups the most

frequent type of failure was adhesive between dentin and cement (Figure

131

2A), followed by adhesive failures between post and cement, and mixed

failures (Figure 2B). No cohesive failures within the post were observed in

this study.

Table 3: Push-out strengths and the percentage of slices that failed in the

respective failure mode for each luting agent. Different letters indicate

statistically significant differences (1-way ANOVA and Tukey test, p<0.05).

SD: standard deviation; Med: median value; 25%: lower quartile; 75%: upper

quartile; AD: adhesive failure between dentin and luting agent; AP: adhesive

failure between luting agent and post; CC: cohesive failure within the luting

agent; M: mixed failure.

Adhesive approach

Luting agent

Push-out strength Failure modes [%] Mean (SD)

Med 25% 75% AD AP CC M

Etch-and-rinse

Calibra 12.70

(4.33) A 13.64 10.12 16.39 50 38 0 12

FluoroCore 2

8.07 (4.76) B

7.93 4.70 12.17 49 30 0 21

MultiCore Flow

11.14 (3.88) AB

12.62 8.39 13.88 32 50 0 18

Self-etch Panavia F 2.0

8.68 (5.29) B

8.41 3.67 12.42 47 20 18 15

Self-adhesive

Exp. 10.61

(5.01) AB 9.69 5.40 15.38 56 25 0 19

RelyX Unicem

12.52 (5.47) A

11.33 8.88 15.63 62 5 0 33

132

Table 4: The resultant p values of post-hoc comparisons between the groups

(1-way ANOVA and Tukey test). Significant p values are underlined

(p<0.05)

Calibra FluoroCore

2

MultiCore

Flow

Panavia F

2.0Exp.

RelyX

Unicem

Calibra - 0.001 0.745 0.009 0.491 1.000

FluoroCore 2

0.001 - 0.050 0.994 0.213 0.001

MultiCore Flow

0.745 0.050 - 0.254 0.997 0.820

Panavia F 2.0

0.009 0.994 0.254 - 0.578 0.012

Exp. 0.491 0.213 0.997 0.578 - 0.574

RelyX Unicem

1.000 0.001 0.820 0.012 0.574 -

133

Figure 2: SEM micrographs of failed slices. A: The slice that failed

adhesively between root dentin and luting agent. B: The slice representative

of mixed failure. Remnants of luting agent are visible (asterisk).

134

Discussion Thin-slice push-out strength test is considered to be a valid method to

evaluate fiber post adhesion to root canal walls (Goracci et al. 2007). It was

shown to be more reliable than microtensile technique for measuring the

adhesion of fiber posts (Goracci et al. 2004). Thin-slice push-out strength test

is not difficult to handle, it allows fabrication of several specimens out of one

root, as well as testing for regional differences between root sections

(Goracci et al. 2007). On the other side, the manner in which fiber post in 1

mm-thick root slice is exposed to dislodging forces during push-out testing

cannot be directly compared to functional forces that the post needs to

withstand during clinical service. It is also possible that the sectioning

process may induce artefacts that could influence test results. This may partly

serve as an explanation for the relatively high coefficient of variation in some

groups.

In each group, resin cement/adhesive was used with the manufacturer

recommended fiber post. The only exception was made in case of Panavia F

2.0, as no specific fiber post is recommended by the manufacturer (Kuraray).

This experimental set-up has limitations, as it was previously reported that

push-out strength may be influenced by a type of fiber post to a greater extent

than by a luting agent (Kurtz et al. 2003). Nevertheless, it was assumed that

combining all the fiber post system components (resin cement, adhesive and

fiber post) from the same manufacturer would prevent possible

incompatibility between the materials and allow assessing the full potential of

each system in laboratory conditions.

Significant differences were found between experimental groups

which led to the rejection of the null hypothesis. Both self-adhesive groups

were comparable with Calibra and MultiCore Flow etch-and-rinse groups.

135

This finding is in contrast with some previous investigations (Goracci et al.

2005; de Durao Mauricio et al. 2007; Wang et al. 2008). The favourable

push-out strength of RelyX Unicem may be partly explained by the fact that

in the present investigation it was used with RelyX Fiber Post. According to

the manufacturer’s claims, this post-cement system offers both chemical

compatibility and strong micromechanical post/cement interlocking. In

previous investigations RelyX Unicem was used with FRC Postec post

(Goracci et al. 2005; de Durao Mauricio et al. 2007), Aestheti Plus post

(RTD) (Wang et al. 2008) and C-Post (RTD) (Wang et al. 2008), which may

account for the discrepancy in the results. In the study by De Durao Mauricio

et al. (de Durao Mauricio et al. 2007), the vast majority of testing failures

was found between post and cement, and no failures were observed between

dentin and cement, which may imply unsatisfactory RelyX Unicem/FRC

Postec coupling. On the contrary, in the present study the majority of failures

were located between dentin and cement (Table 3). Furthermore, after the

initial 5 min period of self-curing RelyX Unicem was light-cured in the

present study, whereas in the previous investigations it was used only in the

self-cure mode (de Durao Mauricio et al. 2007; Wang et al. 2008). It was

reported that light curing significantly increased bond strength of RelyX

Unicem to various types of ceramics (Piwowarczyk et al. 2004; Piwowarczyk

et al. 2005). Taking into account the low degree of conversion of this cement

when it is self-cured (Kumbuloglu et al. 2004), it might be advisable to use it

in dual-cure mode.

Retention of quartz fiber posts cemented with dual-cure resin cement

RelyX ARC in combination with an etch-and-rinse adhesive was comparable

to the retention obtained with RelyX Unicem (Bateman et al. 2005) and these

findings are in accordance with the present investigation. Push-out strength

of Panavia F was significantly lower than RelyX Unicem push-out strength

136

and this result is consistent with previous reports (Bitter et al. 2006; Huber et

al. 2007). It is interesting to notice that cohesive failures within the luting

agent were only seen in the Panavia F 2.0 group. This may be the result of the

unfavourable cohesive strength of this cement.

MultiCore Flow is the material which is formulated to be used both as

the cement and core material. Its push-out strength in the present

investigation was comparable to Calibra. Having in mind the favourable

adhesion of this material to silanized FRC Postec post (Magni et al. 2007), its

clinical use could offer advantages. Besides the procedure being easier and

faster, it also results in less interfaces between different types of materials

and therefore in less potentially critical areas where failure could occur.

Although FluoroCore 2 is a core build-up material, it was included into this

investigation following the suggestion of the manufacturer, in order to

explore its potential use in luting fiber posts. However, its push-out strength

was significantly lower in comparison with Calibra (Table 3), even though

both materials were used with the same adhesive (XPBond). It may be

speculated that the application mode and higher viscosity of FluoroCore 2 in

comparison with Calibra precluded its close adaptation to root canal walls, as

FluoroCore 2 was applied to the post only, whereas Calibra was firstly

introduced into post space by a lentulo spiral.

This study assessed push-out strength of fiber posts after 24 hours of

water storage. It is possible that longer storage and/or thermal cycling would

give different results. Within the limitations of the present investigation, it

may be concluded that 24 h push-out strength of fiber posts was significantly

influenced by luting agents. The study findings do not allow favorizing any

of the three investigated adhesive approaches with certainty. Nevertheless, in

the test arrangement used, the self-etching approach may offer less

137

favourable adhesion to root canal dentin in comparison to etch-and-rinse and

self-adhesive approaches.

138

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and polymerization modes on the bond strength between translucent fiber

posts and three dentin regions within a post space. J Prosthet Dent 95(5):

368-78.



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K, Kielbassa AM (2006). Effects of luting agent and thermocycling on bond


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de Durao Mauricio PJ, Gonzalez-Lopez S, Aguilar-Mendoza JA,

Felix S, Gonzalez-Rodriguez MP (2007). Comparison of regional bond

strength in root thirds among fiber-reinforced posts luted with different

cements. J Biomed Mater Res B Appl Biomater 83(2): 364-72.

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Tay F (2007a). Long-term retrospective study of the clinical performance of



(2007b). Post placement affects survival of endodontically treated premolars.

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Goracci C, Grandini S, Bossu M, Bertelli E, Ferrari M (2007).

Laboratory assessment of the retentive potential of adhesive posts: A review.

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22(5): 477-85.

Huber L, Cattani-Lorente M, Shaw L, Krejci I, Bouillaguet S (2007).

Push-out bond strengths of endodontic posts bonded with different resin-

based luting cements. Am J Dent 20(3): 167-72.













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Mannocci F, Ferrari M, Watson TF (2001a). Microleakage of



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Mannocci F, Innocenti M, Ferrari M, Watson TF (1999). Confocal

and scanning electron microscopic study of teeth restored with fiber posts,

metal posts, and composite resins. J Endod 25(12): 789-94.





Mannocci F, Sherriff M, Ferrari M, Watson TF (2001b). Microtensile

bond strength and confocal microscopy of dental adhesives bonded to root

canal dentin. Am J Dent 14(4): 200-4.













Naumann M, Sterzenbac G, Alexandra F, Dietrich T (2007).

Randomized controlled clinical pilot trial of titanium vs. glass fiber

prefabricated posts: preliminary results after up to 3 years. Int J Prosthodont

20(5): 499-503.

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Piwowarczyk A, Lauer HC, Sorensen JA (2005). The shear bond











Simonetti M, Radovic I, Vano M, Chieffi N, Goracci C, Tognini F,

Ferrari M (2006). The influence of operator variability on adhesive

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Oper Dent 28(3): 215-35.

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Van Meerbeek B, Van Landuyt K, De Munck J, Hashimoto M,

Peumans M, Lambrechts P, Yoshida Y, Inoue S, Suzuki K (2005).

Technique-sensitivity of contemporary adhesives. Dent Mater J 24(1): 1-13.

Wang VJ, Chen YM, Yip KH, Smales RJ, Meng QF, Chen L (2008).

Effect of two fiber post types and two luting cement systems on regional post

retention using the push-out test. Dent Mater 24(3): 372-7.

144

Chapter 4: Light transmission through fiber post

4.1. Light transmission through fiber post: The effect on adhesion, elastic

modulus and hardness of dual-cure resin cement

Ivana Radovic, Gabriele Corciolani, Elisa Magni, Goranka Krstanovic,

Vladimir Pavlovic, Zoran R. Vulicevic, Marco Ferrari. Dental Materials

2009; 25(7): 837-844.

Introduction

The use of fiber post and core systems has been extensively investigated and

supported by clinical (Bitter and Kielbassa 2007; Cagidiaco et al. 2008) and

laboratory studies (Bitter and Kielbassa 2007; Goracci et al. 2007). In order

to allow for optimal retention and favorable stress distribution inside the root

canal (De Santis et al. 2000), resin-based luting agents are indicated for fiber

post cementation (Goracci et al. 2007).

Light curing resins are not recommended for fiber post cementation

because of inadequate depth of cure in the apical portions of the root, even if

translucent posts are used (Roberts et al. 2004). Therefore, dual-cured and

self-cured resin cements have been advised for fiber post cementation. Dual-

cured resin cements have been widely used by the clinicians and were

investigated in a number of clinical studies (Ferrari et al. 2000; Monticelli et

al. 2003; Grandini et al. 2005; Naumann et al. 2005a; Naumann et al. 2005b;

Cagidiaco et al. 2007; Ferrari et al. 2007; Naumann et al. 2007). These

cements are expected to adequately polymerize in areas which cannot be

entirely reached by light as well as in complete absence of light.

Nevertheless, it was reported that in the absence of light some dual-cured

145

cements may not reach an adequate degree of conversion (Caughman et al.

2001; Kumbuloglu et al. 2004). Therefore, light curing was recommended for

dual-cured resin cements. Having in mind the depth of post space

preparations, translucent fiber posts were introduced in order to facilitate

light curing. Adequate curing is considered to be especially important in the

apical portions of the root canals which have presented impaired adhesion in

the vast number of studies that dealt with differences in adhesion along the

post space (Goracci et al. 2007).

Recent investigations pointed out that the amount of transmitted light

differs between different fiber posts. Limited or no light transmission was

recorded through some fiber posts that were claimed to be translucent by the

manufacturers (Teixeira et al. 2006; dos Santos Alves Morgan et al. 2008;

Goracci et al. 2008). A significant reduction of the quantity of transmitted

light as the depth increased was also reported (dos Santos Alves Morgan et

al. 2008). Concern was raised regarding the ability of fiber posts to transmit

light in the amount sufficient for polymerization of dual-cured resin cements

in the apical portion of the post space.

No attempt was made in the literature so far to investigate the effect

of fiber post light transmitting ability to the adhesive potential of dual-cured

resin cements used for post cementation. One study investigated the influence

of fiber post translucency on the degree of conversion of dual-cured resin

cement (Faria e Silva et al. 2007). The use of non light transmitting carbon

fiber post resulted in lower degree of conversion at medium depth of the post

space in comparison to translucent fiber post (Faria e Silva et al. 2007). It

may be assumed that the amount of light transmitted through the post affects

dual-cured resin cement’s coupling to root dentin and fiber post, as well as

micromechanical properties of the cement itself. Therefore, the aim of this

study was: 1. to determine the light transmission at different post levels and

146

at the apical tip through two fiber posts that differ in light-conducting aspect

by taking spectrophotometric measurements; 2. to investigate whether the

type of fiber post influences the continuity of resin cement-root dentin (C-

RD) and resin cement-fiber post (C-FP) interface, keeping all other variables

constant; 3. to investigate whether the type of fiber post influences the elastic

modulus and hardness of the cement layer. The null hypothesis was that there

are no statistically significant differences in the continuity of C-RD/C-FP

interface and in elastic modulus/hardness of the cement layer following the

cementation of two fiber posts with different light transmitting properties.

Materials and methods

Measurements of light transmission through the posts

A pilot investigation was firstly conducted in order to select two fiber posts

that differ in light transmission. Several fiber posts that are claimed by the

manufacturers to transmit light were used. Each post was placed

perpendicular through a black cardboard taken from the Q-14 color

separation scale (Kodak Co, Rochester, USA). The distance between the card

and the apical tip of each post was set at 10 mm and light curing unit

(L.E.Demetron 1, Kerr, Danbury, CT, USA) was placed on the opposite end

of the post. Two fiber posts that appeared to differ the most in the amount of

light that could be visually observed below the black cardboard were then

selected for further investigation.

Two groups were formed according to the fiber post investigated. Ten

posts were used in each group.

Group 1: Tech 21 X-OP fiber post #12 (Isasan, Rovello Poro, Italy) which

consists of silica-zirconia fibers (55%), diphenilpropane and methyloxirane

(45%). Its coronal diameter is 1.2 mm and its apical diameter is 0.8 mm.

147

Group 2: DT Light Post #2 (RTD, St Egreve, France) which consists of

epoxy resin (40%), and quartz fibers (60%). Its coronal diameter is 1.8 mm

and its apical diameter is 1 mm.

Each post was placed through a black cardboard in the same manner

as in pilot investigations. The system light-curing unit/post was positioned on

a stand. A 50 �m fiber optic (P50-2-UV-VIS, Ocean Optics, FL, USA)

connected to a Spectrophotometer (PSD1000, Ocean Optics, FL, USA) was

oriented perpendicular to the post and stabilized. The fiber was placed at

three different levels along the post - 2mm, 5 mm and 8 mm from the apical

tip (Figure 1 A), and at the tip of the post (Figure 1 B). These distances were

always verified by an electronic digital caliper with a 10 �m resolution (1651

DGT, Beta, Milan, Italy).

The spectrophotometer was connected to a computer running

spectrum analyzer software (OOIBase 32, Ocean Optics, FL, USA). The

software was set in “Scope” mode, in order to evaluate the light counts that

correlated to the amount of photons received from the Charge Coupled

Device detector of the spectrophotometer. At 470 nm, for each count 30

photons were received from the detector of the instrument.

148

Figure 1: Schematic drawing of the test set-up for the measurements of light

transmission through the posts. Each post was placed through a black

cardboard. The distance between the card and the apical tip of each post was

set at 10 mm and light curing unit was placed on the opposite end of the post.

A 50 �m fiber optic connected to a Spectrophotometer was oriented

perpendicular to the post and stabilized. The fiber was placed at three

different levels along the post - 2mm, 5 mm and 8 mm from the apical tip

(A), and at the tip of the post (B).

Counts were recorded at each level. In both groups a radiometer was used

prior to measurements (Optilux Radiometer, sds/Kerr, Orange, CA, USA) in

order to check that the output of the light tip (Light Guide Curved 11mm

1020898, Kerr, Danbury, CT, USA) remained over 700 mW/cm2.

149

Specimen preparation for interface observations

Twenty intact single-rooted human premolars, extracted due to orthodontic

reasons, were selected for the study. The teeth were stored in 1% chloramine

T at 4°C for no more than six months until use. The crown of each tooth was

removed at 1mm above the cement-enamel junction, using a slow speed

diamond saw (Isomet, Buehler, Lake Bluff, IL, USA) under water-cooling.

A crown-down preparation technique was followed, using stainless

steel K-files (Union Broach, New York, NY) combined with 2.5% sodium

hypochlorite irrigation. The canals were filled with gutta-percha and a sealer

(Acroseal, Septodont, Saint Maur Des Fosses, France; batch R1 077, R1 081)

following the lateral condensation technique. The filled roots were coronally

sealed with glass ionomer cement (Fuji IX, GC Corporation, Tokyo, Japan;

batch 0711071) and stored in water for 48 hr to allow the sealer to set. The

roots were then divided into two experimental groups (n=10) according to the

fiber post used.

Group 1: Tech 21 X-OP fiber post #12

Group 2: DT Light Post #2.

After removing the temporary coronal seal, 8-mm post space was

prepared in each root with drills provided by post manufacturers. In both

groups, XPBond Dual Cure adhesive system was used (XPBond and Self-

Cure Activator; Dentsply Caulk, Milford, DE, USA; batch 0604001288) in

combination with the dual-cure resin cement Calibra (Dentsply Caulk; batch

base 060112, batch catalyst 060605). Caulk 34% Tooth Conditioner Gel

(34% phosphoric acid; Dentsply Caulk) was applied to the post space through

a needle, and after 15 seconds it was completely rinsed off with water carried

into the canal with an endodontic syringe. Excess water was removed from

the post space with a gentle air blast. Paper points were used to remove

residual moisture. XPBond was mixed with Self-Cure Activator following

150

the manufacturer’s instructions. The adhesive/activator mixture was applied

to post preparation with a microbrush, maintaining the contact of

adhesive/activator with tooth structure for 20 seconds. The adhesive/activator

solution in excess was absorbed from the post space by a paper point and

light-cured for 40s (L.E.Demetron 1). Resin cement components were mixed

and introduced into the post preparation with a lentulo spiral. The post was

seated immediately and the excess was removed. Light-curing was performed

through the post for 40 seconds. The exposed dentin along the coronal part of

the root was covered with flowable composite (Tetric Flow, Ivoclar

Vivadent, Schaan, Liechtenstein; batch G08479). All the post-cemented roots

were placed in water at room temperature.

After 7 days each root was longitudinally cut through the post using a

low speed diamond saw (Isomet). Only one section per root was randomly

selected and used for interface evaluation, in order to allow that the sections

can be treated as independent statistical units. Sections were polished with

silicon carbide papers (600, 800, 1000, 1200) under running water and gently

decalcified for 15 seconds with silica-free phosphoric acid gel (Uni-Etch,

Bisco, Schaumburg). After rinsing with water and air drying, polyvinyl

siloxane (Elite HD+, Zhermack, Badia Polesine, Italy; batch 47233)

impressions of the surfaces to be observed were taken. Positive replicas were

then obtained using epoxy resin (i-pox plus, AuDent AG, Triesenberg,

Liechtenstein).

SEM interface observations

Each replica was mounted on a metallic stub, sputtered with gold (BAL-TEC

SC-RD 005, BAL-TEC AG, Balzers, Liechtenstein), and observed under a

scanning electron microscope (JSM-6390 LV, JEOL, Tokyo, Japan) at

different magnifications. Measurements were made using the JEOL’s image

151

analysis software directly on the sections in the microscope. Firstly the exact

length of the entire cement-dentin (C-RD) and cement-post (C-FP) bonding

interface was measured. The bonding interface on each side of the post was

further divided into coronal, middle and apical third. In each third gaps and

discontinuities at the C-RD and C-FP interface were measured. The integrity

of the interface in each third was then expressed as the percentage of the

continuous (gap-free) interface. The percentage of the continuous interface

along the entire C-RD and C-FP interface was also calculated.

Elastic modulus and hardness measurements

Three sections were randomly selected per group for the analysis of the

micromechanical properties of the cement layer in each third of the post-

space. The specimens were fixed to glass slabs with methacrylate resin

(Technovit 4004, Heraeus Kulzer, Wehrheim, Germany), with the flat surface

to be tested parallel to the slab. Prior to testing, the surfaces were polished

with 1 �m-polycrystalline diamonds (DP-Spray, P; Struers) under water

cooling. Modulus of elasticity (E) and Vickers hardness (VH) of the cement

layer were assessed. The measurements were performed by means of a micro

hardness indenter (Fischerscope H100C; Fischer, Sindelfingen, Germany). A

constant distance of 200 �m was maintained between the measurement

points, which were located from the most coronal to the most apical limits of

the post-space. The test procedure was carried out force controlled. The test

load increased and decreased at a constant speed between 0.4 mN and 500

mN. The force application time can be non-standardly varied. The force

increased from 0.4 mN to 500 mN in 20s, the maximal force of 500 mN was

kept constant for 5s, then the force decreased from 500 mN to 0.4 mN in 20s

and the minimal force of 0.4 mN was kept constant for 5s. The load and the

penetration depth of the indenter (Vickers pyramid: diamond right pyramid

152

with an angle �=136° between the opposite faces at the vertex) were

continuously measured during the load-unload-hysteresis.

The Universal Hardness is defined as the test force divided by the

apparent area of the indentation at maximal force. From a multiplicity of

measurements stored in a database supplied by the manufacturer, a

conversion factor between Universal Hardness and Vickers hardness (VH)

was calculated and implemented into the software, so that the measurements

were expressed in Vickers hardness units.

The indentation modulus was calculated from the slope of the tangent

of the indentation depth-curve at maximal force and is comparable with the

modulus of elasticity of the material (E).

Statistical analysis of the interface continuity data

Since the interface continuity data were not normally distributed

(Kolmogorov–Smirnov test, p<0.05), non-parametric statistical tests were

selected to assess significant differences. Mann Whitney U-test was applied

to compare DT Light Post to Tech 21 X-OP in the percentage of continuous

C-RD and C-FP interface in each third as well as in the percentage of

continuity along the entire two interfaces. Wilcoxon signed ranks test was

used to compare the percentage of continuous interface among the thirds for

each fiber post separately. Wilcoxon signed ranks test was also used to

compare C-RD to C-FP interface in each third and along the entire interface

for each of the two posts separately.

Statistical analysis of the elastic modulus and Vickers hardness data

Since the elastic modulus (E) and Vickers hardness (VH) data were normally

distributed (Kolmogorov–Smirnov test, p>0.05), parametric statistical tests

were selected. Repeated measures analysis of variance (ANOVA) was used

153

to compare E and VH measurements between the post space thirds for each

fiber post. Independent samples t-tests were used to compare E and VH

measurements between DT Light Post and Tech 21 X-OP in each post space

third. In all the statistical tests, the level of significance was set at p<0.05 and

calculations were handled by the SPSS 15.0 software (SPSS Inc.; Chicago,

IL, USA).

Results

Light transmission

No light transmission was detected through Tech 21 X-OP. For DT Light

Post light intensity decreased from the coronal to apical portion and peaked at

the apical tip (Table 1).

Table 1: Light transmission through Tech 21 X-OP and DT Light Post

Level Mean (counts)

Standard deviation (counts)

Tech 21 X-OP Coronal 0 0

Middle 0 0

Apical 0 0

Tip 0 0 DT Light Post Coronal 900 14.9

Middle 820 15.6

Apical 620 12.3

Tip 4096 0.0

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Interface continuity at C-RD interface

When two fiber posts were compared, Tech 21 X-OP specimens presented

significantly lower percentage of the continuous interface in the apical third

and along the entire interface (Table 2). The comparisons between the post

space thirds revealed that in Tech 21 X-OP apical third exhibited lower

percentage of continuous interface than coronal third. In DT Light Post group

no differences were found among the interface thirds. In both groups the gaps

at the C-RD interface were mostly located between the adhesive and the

cement (Figure 2 A). In some Tech 21 X-OP specimens conglomerates of

poorly polymerized adhesive and resin cement could be seen, particularly in

the apical third (Figure 2 B).

Interface continuity at C-FP interface

When two fiber posts were compared, Tech 21 X-OP specimens presented

significantly lower percentage of the continuous interface in the apical third

and along the entire interface (Table 2). DT Light Post specimens presented

no gaps at the C-FP interface (Table 2 and 3, Figure 3). The comparisons

between the post space thirds revealed no significant differences for neither

of the posts.

Comparisons between C-RD and C-FP interface for each fiber post

For Tech 21 X-OP, C-FP interface had a significantly higher percentage of

continuity than C-RD interface in middle and coronal third (Table 3). In DT

Light Post specimens, percentage of continuous C-FP interface along the

entire interface and in coronal third was significantly higher than the

percentage of the continuous C-RD interface.

155

Table 2: Percentage of the continuous C-RD and C-FP interface. Numbers

are means; values in brackets are standard deviations. Groups marked with

the same superscript letters/symbols are not statistically significantly

different. Upper case letters indicate statistically significant differences at the

C-RD interface between two fiber posts for each root third and for the entire

cement-dentin interface (Mann-Whitney U test, p<0.05). Symbols indicate

statistically significant differences at the C-FP interface between two fiber

posts for each root third and for the entire cement-dentin interface (Mann-

Whitney U test, p<0.05). Lower case letters indicate statistically significant

differences within the column, i.e. between the post space thirds for each

fiber post, at C-RD and C-FP interface (Wilcoxon signed ranks test, p<0.05).

C-RD interface (%) C-FP interface (%)

Tech 21 X-OP DT Light Post Tech 21 X-OP DT Light Post Coronal third 87.56 (24.01)Aa 94.47 (4.73)Aa 93.69 (13.85)�a 100.00 (0.00)�a Middle third 68.96 (19.10)Aab 81.61 (25.65)Aa 92.97 (11.69)�a 100.00 (0.00)�a Apical third 58.47 (29.02)Ab 94.97 (8.52)Ba 75.97 (31.58)�a 100.00 (0.00)�a Entire interface 71.66 (22.60)A 90.35 (11.02)B 87.54 (12.50)� 100.00 (0.00)�

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Table 3: Percentage of the continuous C-RD and C-FP interface. Numbers

are means; values in brackets are standard deviations. Groups marked with

the same superscript letters are not statistically significantly different. Letters

indicate statistically significant differences within the row, i.e. between C-RD

and C-FP interface in each root third and at the entire interface for each of the

two fiber posts (Wilcoxon signed ranks test, p<0.05).

C-RD interface (%)

C-FP interface (%)

Tech 21 X-OP

Apical third 58.47 (29.02)A 75.97 (31.58)A

Middle third 68.96 (19.10)A 92.97 (11.69)B

Coronal third 87.56 (24.01)A 93.69 (13.85)B

Entire interface 71.66 (22.60)A 87.54 (12,50)B

DT Light Post

Apical third 94.97 (8.52)A 100.00 (0.00)A

Middle third 81.61 (25.65)A 100.00 (0.00)A

Coronal third 94.47 (4.73)A 100.00 (0.00)B

Entire interface 90.35 (11.02)A 100.00 (0.00)B

157

Figure 2: SEM micrographs of Tech 21 X-OP specimens. A: the gaps at the

C-RD interface were most often located between the adhesive and the cement

while resin tags could be seen in dentinal tubules. B: In some Tech 21 X-OP

specimens areas of poorly polymerized adhesive and cement could be seen,

especially in the apical third. c: resin cement; d: dentin; r: resin tag.

A

B

158

Figure 3: SEM micrographs of DT Light Post specimens. A: In DT Light

Post specimens all the gaps were located at the C-RD interface (asterisk)

whereas C-FP interface was 100% continuous. c: resin cement; d: dentin; p:

fiber post.

B

A

159

Elastic modulus and Vickers hardness

E and VH decreased from coronal to apical for both fiber posts. Significant

differences in E and VH were found between the post space thirds (Table 4).

In Tech 21 X-OP specimens E and VH in middle and apical third were

significantly lower than in coronal third. For DT Light Post, no differences

were found between coronal and middle third in E and VH measurements,

whereas significantly lower E and VH were found in apical third. When two

fiber posts were compared, E was significantly lower in Tech 21 X-OP

specimens in all post space thirds. VH in coronal third did not significantly

differ between two fiber posts, while it was significantly lower in middle and

apical third in Tech 21 X-OP specimens (Table 5).

Table 4: Elastic modulus and Vickers hardness. Numbers are means; values

in brackets are standard deviations. Groups marked with the same superscript

letters are not statistically significantly different. Letters indicate statistically

significant differences within the column, i.e. between the post space thirds

for each fiber post (repeated measures ANOVA, p<0.05)

Tech 21 X-OP DT Light Post

Elastic modulus (GPa)

Vickers hardness (N/mm2)



9.60 (1.53)A 59.23 (15.32)A 10.75 (1.51)A 63.12 (13.79)A

8.70 (2.40)B 42.27 (11.36)B 10.91 (1.18)A 61.57 (12.58)A

5.88 (1.60)C 37.62 (11.57)B 9.69 (1.18)B 49.09 (11.80)B

160

Table 5: Elastic modulus and Vickers hardness. Numbers are means; values

in brackets are standard deviations. Groups marked with the same superscript

letters are not statistically significantly different. Letters indicate statistically

significant differences within the row, i.e. between Tech 1 X-OP and DT

Light Post in each post space third (independent samples t-test, p<0.05).

Post space third Tech 21 X-OP DT Light Post


Coronal 9.60 (1.53)A 10.75 (1.51)B

Middle 8.70 (2.40)A 10.91 (1.18)B

Apical 5.88 (1.60)A 9.69 (1.18)B


Coronal 59.23 (15.32)A 63.12 (13.79)A

Middle 42.27 (11.36)A 61.57 (12.58)B

Apical 37.62 (11.57)A 49.09 (11.80)B

161

Discussion

SEM method used in this study has been widely used for investigation of

adhesion in root canals following cementation of fiber posts (Vichi et al.

2002a; Vichi et al. 2002b; Grandini et al. 2004). In order to avoid possible

influence of shrinkage under vacuum in the SEM chamber on the presence of

gaps along the investigated interfaces, epoxy resin replicas were made.

Significant differences were found in the percentage of the continuous C-RD

and C-FP interface between the experimental groups. Likewise, elastic

modulus and microhardness of the cement layer were significantly influences

by the fiber post used. Therefore, the null hypothesis had to be rejected.

Both investigated fiber posts are claimed to transmit light by the

manufacturers. Nevertheless, no light transmission was detected through

Tech 21 X-OP. It is possible that the presence of silica-zirconia fibers in Tech

21 X-OP fiber post adversely influenced its light transmitting properties. In

the previous investigation of fiber post light transmission that used the same

spectrophotometric method as the present study, somewhat lower readings

were recorded for DT Light Post (Goracci et al. 2008). Nevertheless, the

same trend of reduction in light transmission from coronal to apical, followed

by the increase at the tip of the posts was found. Previous study investigated

DT Light Post size 1, whereas size 2 was used in the present study. The

difference in sizes as well as variations in composition of posts originating

from two different batches may clarify the difference in spectrophotometric

counts that were recorded.

The occurrence of gaps in general may be related to the high C-factor

in bonded root canals (Tay et al. 2005). The lower percentage of continuous

C-RD and C-FP interface in Tech 21 X-OP specimens may be the

consequence of the lack of light transmission through this fiber post. The

162

absence of light may have impaired complete polymerization of the cement

(Figure 2 B), particularly in the apical third, and may have adversely affected

its coupling with root dentin and post surface. Resin cement polymerization

in the apical third relied solely on chemical catalysts. This may clarify the

significantly lower percentage of continuous C-RD interface in Tech 21 X-

OP specimens in comparison to coronal third that was accessible to light

(Table 2).

On the other side, no regional differences were found along the C-RD

interface in DT Light Post specimens. Spectrophotometric measurements

revealed a reduction in light transmission from coronal to apical third of this

fiber post. Nevertheless, a considerably high peak in counts was measured at

the tips of the posts. This may be explained by the unidirectional longitudinal

orientation of the reinforcing quartz fibers that could facilitate the

transmission of light up to the tip of the post. Therefore, light could

participate in resin cement polymerization in the apical third in a manner

similar to coronal third. The presence of light in the apical third may thus

clarify the lack of regional differences along the C-RD interface in DT Light

Post specimens.

The absence of gaps at C-FP interface in DT Light Post specimens

indicates more predictable adhesion at the post-cement in comparison to

cement-dentin level. In Tech 21 X-OP specimens no difference in continuity

of the entire interface was found between C-RD and C-FP interface. Apart

from differences in post surface properties between the two posts that may

have affected adhesion to resin cement, it may be speculated that light

transmission contributed to favorable post-cement coupling in DT Light Post

specimens.

Markedly lower percentage of continuous resin cement-root dentin

interface was reported in the study that investigated cementation of Fibrekor

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fiber post (Jeneric Pentron Incorporated, Wallingford, CT, USA) with a self-

cured, dual-cured and light-cured resin cement, using a similar method as in

the present study (Bonfante et al. 2008). The authors of the present study

believe that this difference in case of dual-cured and light-cured cement may

be partly attributed to the lack of light transmitting ability of Fibrekor fiber

post (Teixeira et al. 2006). However, it remains unclear why cementation of

Fibrekor post with a self-cured cement did not result in a higher percentage

of the continuous C-RD interface (Bonfante et al. 2008). A reduction in

interface continuity from coronal to apical third was also reported (Bonfante

et al. 2008), which is in accordance with the present study.

Universal occurrence of interfacial gaps was also reported when

carbon fiber posts Tech 2000 (Isasan) and Endopost (RTD) were cemented

using dual-cured resin cements (Pirani et al. 2005). The percentage of

continuous interface was not reported in this study (Pirani et al. 2005) which

precludes direct comparisons with the present study. Nevertheless, it may be

speculated that the lack of light transmission through carbon fiber posts

contributed to the high incidence of gaps.

E and VH decreased from coronal to apical for both fiber posts. This

finding correlates with previous study that evaluated hardness of dual-cured

resin cement used for the cementation of DT Light Post (Teixeira Cda et al.

2008). However, in Tech 21 X-OP specimens, significant differences in

comparison to coronal third were found in middle third of the post space

already. On the other side, coronal and middle third in DT Light Post

specimens were comparable, whereas only measurements in the apical third

were significantly lower. Moreover, E and VH were significantly higher

when DT Light Post was used. Superior micromechanical properties of resin

cement in DT Light Post specimens may be attributed to the enhanced

cement polymerization in the presence of light. It was previously reported

164

that composite resin micromechanical properties may serve as an indicator

for the extent of monomer conversion (Ferracane 1985; Rueggeberg and

Craig 1988; Bouschlicher et al. 2004). Therefore, the results of hardness

measurements performed in this study indirectly indicate that higher degree

of conversion of dual-cured resin cement may be attained by the use of light

transmitting fiber post.

The authors are aware that the specific choice of dual-cured resin

cement might have influenced the results of the present study. It is possible

that adhesion of different resin cement to root dentin in terms of the

percentage of continuous C-RD and/or C-FP interface would not be

influenced by the type of fiber post and its light transmitting ability.

Conclusion

In conclusion, cementation of fiber post with no light transmitting ability

using dual-cured resin cement resulted in lower percentage of continuous C-

RD and C-FP interface in comparison to cementation of light transmitting

fiber post. Elastic modulus and Vickers hardness of the cement layer

significantly decreased from coronal to apical third of the post space

regardless of the fiber post used. However, cementation of light transmitting

fiber post resulted in higher elastic modulus and Vickers hardness of the

cement layer in comparison to cementation of fiber post with no light

transmitting ability.

165

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observation of the bond integrity of fiber-reinforced composite posts

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Bouschlicher MR, Rueggeberg FA, Wilson BM (2004). Correlation

of bottom-to-top surface microhardness and conversion ratios for a variety of

resin composite compositions. Oper Dent 29(6): 698-704.



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(2007). Influence of fiber-post translucency on the degree of conversion of a

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light exposure time on composite resin hardness after root reinforcement

using translucent fibre post. J Dent 36(7): 520-8.

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Teixeira EC, Teixeira FB, Piasick JR, Thompson JY (2006). An in

vitro assessment of prefabricated fiber post systems. J Am Dent Assoc

137(7): 1006-12.

Vichi A, Grandini S, Davidson CL, Ferrari M (2002a). An SEM

evaluation of several adhesive systems used for bonding fiber posts under

clinical conditions. Dent Mater 18(7): 495-502.

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169

Summary

This thesis aimed at assessing three aspects related to fiber post cementation:

post surface treatment, the type of resin cement used for cementation and

light transmission through the post. It was hypothesized that these aspects

may influence cementation success. In order to verify author’s assumptions,

several laboratory investigations were performed. The thesis consists of four

chapters in which six studies are presented.

Chapter 1 covers general introduction to the main topic. The use of

fiber posts in endodontically treated teeth was presented. Basic features of

fiber posts, such as composition, elasticity and esthetics were discussed, as

well as clinical benefits that these features provide. Indications in which fiber

posts may show their full potential were described, including the specific

benefits of fiber posts use in pediatric dentistry and traumatology. Even

though all fiber posts available to clinicians consist of same basic

components, mechanical properties and clinical behavior of different brands

may vary substantially. Therefore, some factors that may influence the choice

of fiber post were presented. Besides the three aspects of fiber post

cementation that this thesis focused on, several other factors are believed to

influence the success of fiber post cementation. The following factors were

briefly discussed in Chapter 1: the type of endodontic sealer, the amount of

remaining coronal dentine, ferrule preparation and resin cement thickness.

Fiber post surface preparation and its influence to adhesion between

fiber posts and resin cements were assessed in Chapter 2. This chapter

consists of three studies in which microtensile bond strength between posts

and resin cements was investigated following various treatments of fiber post

surface. SEM observations of treated/untreated fiber post surfaces and

adhesive interfaces were performed as well. The first study evaluated the

170

influence of sandblasting pretreatment and different “chair-side” treatments

of methacrylate based fiber posts on the microtensile bond strength with a

dual-cured resin composite. The focus of the second study was the influence

of surface treatments of epoxy resin-based fiber posts to microtensile bond

strength with resin cement and flowable composite. Dual-cured adhesive was

applied to all posts in this study as this treatment had been shown to

effectively increase bond strength to epoxy resin-based fiber posts. The study

had two objectives: 1. to investigate whether previous sandblasting of the post

surface influences post-composite bond strength; 2. to evaluate the influence

of water storage on adhesive-mediated FRC post-resin cement and FRC post-

flowable composite bonds using a model of accelerated aging. In the third

study of Chapter 2, the aim was to evaluate the influence of an experimental

industrial treatment and conventional “chair-side” treatments of epoxy resin-

based fiber post surface on the microtensile bond strength to luting resin

cements. The experimental industrial treatment comprised two main steps: a

1�m-thick coating of zirconium oxide followed by silanization with 3–

(trimethoxysilyl) propyl methacrylate. This treatment was claimed to keep the

initial surface roughness of the fiber post in order to provide micromechanical

retention and to create a chemical bond between the silane and the adhesive

or cement. Conventional “chair-side” treatments that were performed in this

study were silane coating and adhesive application, whereas no treatment was

performed in the control group. Apart from SEM observations of

treated/untreated fiber post surfaces and adhesive interfaces, the surface of the

industrially coated posts was also examined using Energy Dispersive

Analysis by X-ray (EDAX) in a scanning electron microscope.

Resin cements and adhesive approaches for fiber post cementation

were the theme of Chapter 3, which consists of two studies. Particular

attention was given to self-adhesive cements as the newest and least

171

investigated group of materials. The first study of Chapter 3 is a literature

review that aimed at summarizing research conducted on self-adhesive

cements and at providing information on their properties, based on the results

of original scientific full-papers from peer-reviewed journals listed in

PubMed. The results were summarized into the following categories:

adhesion to tooth substrates (enamel, dentin, root dentin), adhesion to

restorative materials (endodontic posts, ceramics, titanium abutments),

marginal adaptation, microleakage, mechanical properties, biocompatibility,

chemical adhesion and fluoride release, ratings in clinical use. The second

study of Chapter 3 investigated the adhesion of fiber posts cemented to root

dentin with luting agents that utilize three currently available adhesive

approaches. It was assumed that the simpler, self-etching and self-adhesive

approaches are equally effective as the clinically proven etch-and-rinse

approach. In order to assess the adhesion of fiber posts, thin-slice push-out

test was used.

In Chapter 4 a study which focuses on importance of light

transmission through the post is presented. This study investigated whether

light transmission through fiber posts influences the adhesive potential of

dual-cured resin cement used for post cementation, as well as

micromechanical properties of the cement itself. Firstly spectrophotometric

measurements were taken to determine the light transmission at different post

levels and at the apical tip through two fiber posts that appeared to differ

substantially in light-conducting aspect based on visual observation. The

measurements detected no light transmission through one of the posts,

whereas for the other one light intensity decreased from the coronal to apical

portion and peaked at the apical tip. Following the measurements, it was

investigated whether the type of fiber post influences the continuity of resin

cement-root dentin and resin cement-fiber post interface, keeping all other

172

variables constant. Moreover, it was assessed whether the type of fiber post

influences the elastic modulus and hardness of the cement layer.

Conclusions

The following conclusions may be drawn from the basic evaluation of the

following aspects related to fiber post cementation - post surface treatment,

the type of resin cement used for cementation and light transmission through

the post:

1. Sandblasting may give an increase in microtensile strength to

methacrylate-based glass fiber posts, eliminating the need to apply

additional ‘‘chair-side’’ treatments. Reducing the number of clinical steps

could contribute to simplify the clinical procedures.

2. Sandblasting followed by adhesive application may improve immediate

bond strength to epoxy resin-based fiber posts in comparison to the

adhesive alone. Fiber post-resin cement and fiber post-flowable composite

bonds may be impaired by accelerated water aging if mediated by

hydrophilic adhesive coatings.

3. The experimental industrial surface treatment and the adhesive application

enhance fiber post to resin cement interfacial strength. Industrial treatment

may simplify the clinical luting procedure. Cementation of epoxy resin-

based fiber posts without any treatment of the post surface is not

recommended.

4. Self-adhesive cements appear to offer a promising new approach in

indirect restorative procedures, including fiber post cementation. However,

the vast majority of available literature data is based on studies that

investigated only one of the cements that are currently available to

173

clinicians. More importantly, long term clinical performance of these

materials needs to be assessed prior to making a general recommendation

for their use in fiber post cementation.

5. 24 h push-out strength of fiber posts was significantly influenced by luting

agents. This thesis findings do not allow favorizing any of the three

investigated adhesive approaches with certainty. Nevertheless, in the test

arrangement used, the self-etching approach may offer less favorable

adhesion to root canal dentin in comparison to etch-and-rinse and self-

adhesive approaches.

6. Cementation of fiber post with no light transmitting ability using dual-

cured resin cement resulted in lower percentage of continuous cement-root

dentin and cement-fiber post interface in comparison to cementation of

light transmitting fiber post.

7. Elastic modulus and Vickers hardness of the cement layer significantly

decreased from coronal to apical third of the post space regardless of the

light transmitting ability of fiber post used. However, cementation of light

transmitting fiber post resulted in higher elastic modulus and Vickers

hardness of the cement layer in comparison to cementation of fiber post

with no light transmitting ability.

Sommario e conclusioni

Questa tesi ha avuto lo scopo di valutare tre aspetti relativi alla cementazione

del perno in fibra: il trattamento di superficie del perno, il tipo di cemento

resinoso utilizzato per la cementazione e la trasmissione della luce attraverso

il perno. Allo scopo di verificare l’influenza di questi aspetti sul successo

della cementazione, sono stati condotti diversi studi di laboratorio. La tesi

consiste in quattro capitoli nei quali sono presentati sei studi.

174

Il Capitolo 1 contiene un’introduzione generale all’argomento della

tesi. Viene descritto l’uso dei perni in fibra nei denti trattati

endodonticamente. Le caratteristiche di base dei perni in fibra come la

composizione, l’elasticità e l’estetica sono discusse, così come i benefici

clinici apportati da queste caratteristiche. Vengono descritte le indicazioni

nelle quali i perni in fibra possono mostrare il loro pieno potenziale, compresi

i benefici specifici derivanti dall’uso dei perni in fibra in pedodonzia e in

traumatologia. Nonostante tutti i perni in fibra a disposizione del clinico

presentino gli stessi componenti di base, le proprietà meccaniche e il

comportamento clinico di perni di varie marche possono variare in modo

significativo. Vengono pertanto presentati alcuni fattori che possono

influenzare la scelta del perno in fibra. Oltre ai tre aspetti relativi alla

cementazione del perno in fibra su cui si basa questa tesi, molti altri fattori

sono ritenuti influenzare il successo della cementazione. I seguenti fattori

vengono brevemente discussi nel Capitolo 1: il tipo di cemento endodontico,

la quantità di dentina coronale residua, l’effetto ferula e lo spessore del

cemento resinoso.

La preparazione della superficie del perno e la sua influenza

sull’adesione tra perno in fibra e cementi resinosi sono stati valutati nel

Capitolo 2. Questo capitolo consiste di tre studi in cui è stata misurata la

forza di adesione microtensile tra perni e cementi resinosi in seguito a diversi

trattamenti di superficie del perno in fibra. Sono state condotte anche

osservazioni SEM delle superfici trattate/non trattate così come delle

interfacce adesive. Il primo studio ha valutato l’influenza della sabbiatura

come pretrattamento del perno e di differenti trattamenti “alla poltrona” di

perni in fibra a base di metacrilato sulla forza di adesione microtensile con

una resina composita duale. L’obiettivo del secondo studio è stato quello di

valutare l’influenza di trattamenti di superficie di perni a base di resina

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epossidica sulla forza di adesione microtensile con cemento resinoso e

composito fluido. Un adesivo resinoso duale è stato applicato su tutti i perni

poiché questo trattamento è risultato essere efficace nell’aumentare la forza di

adesione ai perni epossidici. Lo studio ha avuto due obiettivi: 1. studiare se la

preventiva sabbiatura della superficie del perno è in grado di influenzare la

forza di adesione perno-composito; 2. valutare l’influenza della

conservazione in acqua sui legami mediati dall’adesivo tra perno-cemento

resinoso e perno-composito fluido usando un modello di invecchiamento

accelerato. Nel terzo studio del Capitolo 2, lo scopo è stato quello di valutare

l’influenza di un trattamento industriale sperimentale e di diversi trattamenti

“alla poltrona” della superficie di un perno a base di resina epossidica sulla

forza di adesione microtensile a cementi resinosi. Il trattamento industriale

sperimentale comprendeva due passaggi: un rivestimento di 1�m di ossido di

zirconio seguito dalla silanizzazione con 3-(trimetossisilil) propilmetacrilato.

Questo trattamento aveva lo scopo di migliorare l’iniziale ruvidità di

superficie del perno in fibra in modo da favorire una ritenzione

micromeccanica e di creare un’adesione chimica tra il silano e l’adesivo o il

cemento. I trattamenti convenzionali “alla poltrona” eseguiti in questo studio

erano la silanizzazione e l’applicazione di adesivo, mentre nessun trattamento

è stato eseguito nel gruppo controllo. Oltre alle osservazioni SEM delle

superfici dei perni trattate/non trattate e delle interfacce adesive, la superficie

dei perni rivestiti industrialmente è stata esaminata con analisi EDX (Energy

Dispersive by X-ray) in un microscopio elettronico a scansione.

I cementi resinosi e diverse strategie adesive per la cementazione del

perno in fibra sono stati il tema del Capitolo 3, il quale consiste di due studi.

Un’attenzione particolare è stata data ai cementi auto-adesivi come il più

nuovo e meno studiato gruppo di materiali dentali. Il primo studio del

Capitolo 3 è una revisione della letteratura volta a sintetizzare la ricerca

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condotta sui cementi auto-adesivi e a fornire informazioni sulle loro proprietà,

in base ai risultati di lavori scientifici originali pubblicati su riviste impattate

presenti su PubMed. I risultati sono stati sintetizzati nelle seguenti categorie:

adesione ai substrati dentali (smalto, dentina, dentina radicolare), adesione ai

materiali da restauro (perni endodontici, ceramica, monconi di titanio),

adattamento marginale, microinfiltrazione, proprietà meccaniche,

biocompatibilità, adesione chimica e rilascio di fluoro, rilevanza clinica. Il

secondo studio del Capitolo 3 ha valutato l’adesione tra perni in fibra

cementati alla dentina intraradicolare con agenti che utilizzano tre attuali e

diverse strategie adesive. Si è stabilito che gli approcci più semplici, auto-

mordenzanti e auto-adesivi sono efficaci quanto la tecnica etch-and-rinse.

Allo scopo di determinare l’adesione dei perni in fibra, è stata usato il test di

push-out.

Nel Capitolo 4 viene presentato uno studio basato sull’importanza

della trasmissione della luce attraverso il perno. Questo studio ha valutato se

la trasmissione della luce attraverso i perni in fibra può influenzare il

potenziale adesivo del cemento resinoso duale usato per la cementazione del

perno, così come le proprietà meccaniche del cemento stesso. In primo luogo,

sono state effettuate misurazioni spettrofotometriche per determinare la

trasmissione della luce a diversi livelli del perno e in zona apicale in due

perni in fibra che sembravano differire in modo sostanziale riguardo alla

conduzione della luce ad un esame visivo. Le misurazioni non hanno

riscontrato alcuna trasmissione di luce in uno dei perni, mentre nell’altro

l’intensità della luce è diminuita dalla parte coronale a quella apicale del

perno, con un decremento significativo nella punta. Continuando le

misurazioni, si è studiato se il tipo di perno in fibra è in grado di influenzare

la continuità dell’interfaccia cemento resinoso-dentina radicolare e cemento

resinoso-perno in fibra, mantenendo costanti tutte le altre variabili. Inoltre, è

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stato determinato se il tipo di perno in fibra influenza il modulo elastico e la

durezza dello strato di cemento.

Le seguenti conclusioni possono essere tratte dalla valutazione di base di

alcuni aspetti relativi alla cementazione del perno in fibra – trattamento di

superficie del perno, tipo di cemento resinoso utilizzato per la cementazione e

trasmissione di luce attraverso il perno:

1. La sabbiatura può aumentare la forza di adesione microtensile a perni in

fibra a base di metacrilato, eliminando la necessità di eseguire ulteriori

trattamenti “alla poltrona”. La riduzione del numero dei passaggi clinici

può contribuire alla semplificazione delle procedure cliniche.

2. La sabbiatura seguita dall’applicazione di adesivo può migliorare l’iniziale

forza di adesione a perni in fibra a base di resina epossidica rispetto all’uso

del solo adesivo. I legami perno in fibra-cemento resinoso e perno in fibra-

composito fluido possono essere compromessi da un invecchiamento

accelerato in acqua in presenza di adesivi idrofilici.

3. Il trattamento di superficie industriale sperimentale e l’applicazione di

adesivo migliorano la resistenza interfacciale del legame tra perno in fibra

e cemento resinoso. Il trattamento industriale può semplificare la

procedura clinica di cementazione. La cementazione dei perni in fibra a

base di resina epossidica senza alcun trattamento di superficie non è

raccomandata.

4. I cementi auto-adesivi sembrano rappresentare un approccio nuovo e

promettente nelle procedure di restauro indiretto, compresa la

cementazione dei perni in fibra. Tuttavia, la grande maggioranza dei dati

disponibili in letteratura è basata su studi che hanno valutato solo uno dei

cementi attualmente in commercio. Inoltre, il comportamento clinico a

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lungo termine di questi materiali deve essere valutato prima di poterli

consigliare per la cementazione del perno in fibra.

5. La resistenza push-out a 24 h dei perni in fibra è stata significativamente

influenzata dai cementi utilizzati. I risultati di questa tesi non consentono

di favorire con certezza nessuno dei tre approcci adesivi studiati. Tuttavia,

in questo test, l’approccio auto-mordenzante può portare ad una adesione

meno favorevole alla dentina radicolare rispetto agli approcci auto-adesivo

e etch-and-rinse.

6. La cementazione del perno in fibra senza trasmissione di luce usando un

cemento duale è risultato in una più bassa percentuale di continuità

all’interfaccia cemento-dentina radicolare e cemento resinoso-perno in

fibra rispetto alla cementazione di perni in grado di trasmettere la luce.

7. Il modulo elastico e la durezza Vickers dello strato di cemento è diminuita

in modo significativo dal terzo coronale a quello apicale del post space,

indipendentemente dalla capacità del perno nel trasmettere la luce.

Comunque, la cementazione del perno capace di trasmettere la luce è

risultato in un più alto modulo elastico e in una maggiore durezza Vickers

dello strato di cemento rispetto alla cementazione del perno in fibra senza

alcuna capacità di trasmissione di luce.

Sommaire et conclusions

La thèse vise d'examiner trois facteurs de cimentation des tenons

composites renforcés de fibres: préparatifs de la surface des tenons, type du

ciment composite destiné à la cimentation des tenons et la conductivité de

lumière par tenons. L'hypothèse de départ était que ces facteurs pourraient

influencer le succès de cimentation des tenons. Aux fins de vérifier

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l'hypothèse, plusieurs examens de laboratoire ont été effectués. La thèse

comprend quatre chapitres dans lesquels six études publiées sont présentées.

Chapitre 1 comprend une introduction au sujet principal.

L'application des tenons composites après le traitement endodontique des

dents y est présentée. Les caractéristiques fondamentales des tenons

composites, soit leur composition, leur élasticité et leur esthétique, ainsi que

les avantages cliniques fournis par ces caractéristiques. Les indications où les

tenons composites peuvent démontrer leur plein potentiel ont été décrites, y

compris les avantages spécifiques de ces tenons utilisés dans la dentisterie

pédiatrique et la traumatologie. Même si tous les tenons composites

comprennent les mêmes composantes de base, leurs caractéristiques

mécaniques et leur qualité peuvent considérablement varier dans les

conditions cliniques en fonction du producteur. Par conséquent, certains

facteurs pouvant influencer le choix du tenon y étaient présentées. Outre ces

trois aspects développés par la thèse, l'on considère qu'il y encore quelques

facteurs qui peuvent influencer le succès de cimentation des tenons. Dans le

Chapitre 1 la brève discussion concerne les facteurs suivants: le type de la

résine servant d'obturation définitive du canal radiculaire, la quantité restante

de la dentine coronaire, la préparation des viroles et l'épaisseur de la couche

du ciment composite.

Les préparatifs de la surface du tenon et son influence à l'adhérence

entre le tenon et le ciment composite ont été examinés dans le cadre de trois

études présentées dans le Chapitre 2. Dans ces études, après l'application de

différentes modalités de préparation de la surface du tenon, l'on a examiné la

puissance de liaison entre le tenon et le ciment par le teste de résistance à la

traction des micro-échantillons (“microtensile bond strength test”). Les

surfaces des tenons traités et de ceux non-traités étaient prises en

considération, ainsi que les interfaces adhérentes ciment-tenon au microscope

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électronique à balayage (MEB). Dans la première étude l'on a examiné

l'influence de sablage et de différents procédés dans le cabinet, concernant les

préparatifs des tenons à matrice méthacrylique à la puissance de liaison avec

le composite double-polymérisé. Dans la deuxième étude il a été examiné

l'influence du préparatif du tenon à matrice en résine époxy à la puissance de

liaison avec le ciment composite et le composite liquide. L'adhésif double-

polymérisé était appliqué sur tous les tenons, étant donné qu'il a été déjà

constaté que ce traitement augmente, d'une manière efficace, la puissance de

liaison entre les matériaux composites et les tenons contenant la résine époxy.

Ces deux études ont eu deux objectifs: 1. de définir si le sablage avant

l'application de l'adhésif influence la puissance de liaison tenon-ciment et

tenon-composite liquide; 2. d'examiner l'influence de l'eau à la liaison tenon-

ciment et tenon-composite liquide, en utilisant le modèle de vieillissement

accéléré du matériau. L'objectif de la troisième étude du Chapitre 2 était

d'examiner l'influence des préparatifs expérimentaux industriels et de diverses

modalités des préparatifs au cabinet, de la surface du tenon à matrice en

résine époxy, à la puissance de liaison avec les ciments composites. Les

préparatifs expérimentaux industriels comprenaient deux pas: application de

la couche de l'oxyde de zirconium d'épaisseur de 1 �m et ensuite la

silanisation par 3- (trimethoxysilyl) propylméthacrylate. D'après les

confirmations du producteur, ces préparatifs assurent la rétention

micromécanique, ainsi que la liaison chimique entre le silane et l'adhésif ou le

ciment. Les procédés du cabinet relatifs aux préparatifs des tenons, examinés

dans cette étude comprenaient l'application du silane et l'application d'adhésif,

tandis que dans le groupe de contrôle la surface des tenons n'a pas subi aucun

traitement. Les surfaces des tenons traités et de ceux non-traités, ainsi que les

interfaces adhésives ciment-tenon étaiemt examinées au microscope (MEB).

La surface des tenons industriellement préparés a été également examinée par

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l'analyse EDAX (Energy Dispersive Analysis by X-ray) au microscope

électronique à balayage.

Le sujet du Chapitre 3 concernait les ciments composites et divers

abords adhésifs qui peuvent être utilisés pour la cimentation des tenons

composites. Ce chapitre comprend deux études. Une attention particulière

était prêtée aux ciments composites auto-adhésifs qui font une catégorie la

plus récente et la moindre étudiée des ciments composites. La première étude

du Chapitre 3 est la revue de la littérature ayant pour objectif de donner les

informations sur les ciments composites auto-adhésifs en vertu d'études

scientifiques originales publiées dans les magasins recensés, indexées dans la

base PubMed. Les résultats sont classifiés dans les catégories suivantes:

adhésion avec les tissues dentaires (émail, dentine, dentine du canal

radiculaire), l'adhésion avec les matériaux de restauration (tenons

endodontiques, céramique, titane), adaptation marginale, micro-perméabilité,

propriétés mécaniques, biocompatibilité, adhésion chimique et échappement

des fluorure, l'évaluation de la qualité pendant utilisation clinique. La seconde

étude du Chapitre 3 a examiné l'adhésion des tenons composites, cimentés par

trois approches actuelles d'adhésion. L'hypothèse de départ était que les

approches simples, auto-adhésifs et automordançants sont aussi efficaces que

l'approche de mordançage total cliniquement confirmée. Aux fins d'examiner

l'adhésion des tenons, il a été fait le mesurage de rétention par le test des

découpes minces transversales (thin-slice push-out test).

Dans le Chapitre 4 il est présenté l'étude qui a examiné l'importance

de la conductivité lumineuse à travers le tenon. Y était examiné l'influence de

la conductivité lumineuse du tenon à l'adhésion du ciment composite à

double-polymérisé, ainsi qu'aux caractéristiques micromécaniques du ciment.

Par les mesurages spectrophotométriques, il a été défini la conductivité

lumineuse de deux tenons et se basant sur les observations visuelles, l'on a

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supposé qu'ils se distinguent essentiellement par cette caractéristique. Les

mesurages étaient effectués aux niveaux différents des tenons et à l'apex. Il a

été constaté l'absence de la conductivité lumineuse à travers un tenon parmi

deux, tandis qu'à travers le second tenon l'intensité de la lumière diminuait à

partir du niveau coronaire vers la région apicale, tandis qu'à la région apicale,

l'intensité était la plus élevée. Après les mesurages, il a été examiné

l'influence du type du tenon à la continuité de liaison adhésive ciment-dentine

et ciment-tenon. Il a été, également, examiné l'influence du type du tenon au

module d'élasticité et à la fermeté du ciment.

Se basant sur l'examen des facteurs suivants de cimentation des tenons

composites: préparatifs de la surface des tenons, type du ciment composite et

la conductibilité lumineuse des tenons, l'on peut faire les conclusions

suivantes:

1. Le sablage permet d'améliorer l'intensité de la liaison des matériaux

composites avec les tenons composites méthacryliques et d'éliminer le

besoin des traitements supplémentaires de la surface du tenon au cabinet.

La diminution du nombre des démarches cliniques donne sa contribution à

la simplicité des procédures cliniques.

2. Le sablage suivi d'application d'adhésif fait l'amélioration de l'intensité de

la liaison entre les matériaux composites (ciment et composite liquide)

avec les tenons composites en résine époxy, mesurée immédiatement après

la cimentation des tenons. La liaison adhésive des tenons préparés par

l'adhésif à ciment composite et le composite liquide peut être abîmée par

vieillissement accéléré dans l'eau.

3. Les préparatifs expérimentaux industriels et l'application des adhésifs

augmentent l'intensité de la liaison entre le ciment et le tenon composite

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avec la matrice en résine époxy. Le traitement industriel peut simplifier le

procédé clinique de cimentation. La cimentation des tenons composites

avec la matrice en résine époxy sans traitement de la surface des tenons

n'est pas recommandée.

4. Les ciments composites auto-adhésifs puissent offrir une nouvelle

approche prometteuse pour procédés indirects de restauration, y compris la

cimentation des tenons composites. Pourtant, la plupart des données de la

littérature sur ces ciments proviennent des recherches aux laboratoires d'un

des ciments étant actuellement à la disposition des cliniciens. Les études

cliniques de ces matériaux à long terme sont indispensables avant de

donner la recommandation générale pour l'utilisation des ciments auto-

adhésifs destinés à la cimentation des tenons.

5. La rétention des tenons composites, mesurée 24 heures après la

cimentation était considérablement différente par rapport aux diverses

ciments composites. En vertu des résultats de la thèse, il n'est pas possible

de constater avec certitude qu'une sur trois approches adhésives donne des

résultats meilleurs par rapport à deux autres approches. Pourtant, la

méthode utilisée a permis de constater une plus mauvaise adhésion des

tenons en utilisant l'approche d'automordançage par rapport à la méthode

autoadhésive et à celle de mordançage totale.

6. Le pourcentage de liaison adhésive continue ciment-dentine et ciment-

tenon été considérablement plus élevé après la cimentation du tenon qui

laisse passer la lumière par rapport au tenon qui ne la laisse pas.

7. Le module d'élasticité et de dureté du ciment d'après Vickers ont

considérablement baissé à partir du niveau coronaire vers la région apicale,

nonobstant la conductivité lumineuse des tenons. Pourtant, le module

d'élasticité et de dureté d'après Vickers étaient considérablement plus

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élevés après la cimentation des tenons à conductivité lumineuse par

rapport au tenon qui n'a pas la capacité de conduire la lumière.

Zusammenfassung und schlussfolgerungen

Diese Dissertation hatte das Ziel drei Aspekte, die mit der Zementierung von

Faserstiften im Zusammenhang sind, festzustellen: die Behandlung der

Oberfläche des Faserstiftes, der Resin-Zement, der für die Zementierung

angewendet wird, und die Lichtdurchlässigkeit durch den Faserstift. Es

wurde angenommen, dass diese Aspekte den Erfolg der Zementierung

beeinflussen könnten. Verschiedene Labor-Studien wurden durchgeführt, um

diese Annahmen zu bestätigen. Diese Dissertation besteht aus vier Kapiteln,

in denen sechs Studien dargestellt wurden.

Im Kapitel 1 gibt es eine allgemeine Einleitung über das Hauptthema.

Die Anwendung von Faserstiften in endodontisch behandelten Zähnen wurde

dargestellt. Die wesentlichen Eigenschaften der Faserstifte - wie die

chemische Zusammensetzung, die Elastizität und die Ästhetik - wurden

diskutiert so wie die klinischen Vorteile, die diese Eigenschaften anbieten.

Die klinischen Indikationen, in denen die Faserstifte ihres totale Potenzial

zeigen können, wurden beschreibt und die spezifischen Vorteile der

Anwendung der Faserstifte in der Kinderzahnheilkunde und in der

Traumatologie wurden aufgenommen. Auch wenn alle Faserstifte, die zur

Verfügung für die Zahnärzte stehen, aus den gleichen wesentlichen

Komponenten bestehen, können die mechanischen Eigenschaften und das

klinische Verhalten verschiedener Arten von Faserstiften beträchtlich

variieren. Daher wurden einige Faktoren, die die Auswahl des Faserstiftes

beeinflussen können, dargestellt. Außer den drei Aspekten der Zementierung

der Faserstifte, auf die diese Dissertation sich konzentrierte, sind andere

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Faktoren gedacht, den Erfolg der Zementierung der Faserstifte zu

beeinflussen. Die folgenden Faktoren wurden im Kapitel 1 kurz diskutiert:

die Art des Wurzelfüllmaterials, die Menge des restlichen Kronendentins, die

Ferrule-Vorbereitung und die Dicke des Resin-Zementes.

Die Behandlung der Oberfläche des Faserstiftes und ihr Einfluss auf

die Adhäsion zwischen Faserstiften und Resin-Zementen wurden im Kapitel

2 festgestellt. Dieses Kapitel besteht aus drei Studien, in denen die

Microtensile-Verbundfestigkeit zwischen Faserstiften und Resin-Zementen

nach verschiedenen Behandlungen der Oberfläche der Faserstifte erforscht

wurde. Beobachtungen der behandelten/unbehandelten Oberfläche des

Faserstiftes und der adhäsiven Schnittstellen wurden auch mit einem REM

ausgeführt. Die erste Studie hat den Einfluss von dem Sandstrahlen und von

verschiedenen „Chair-Side“ Behandlungen auf die Microtensile-

Verbundfestigkeit zwischen Methacrylat-Faserstiften und einem

dualhärtenden Komposit-Zement bewertet. Das Thema der zweiten Studie

war der Einfluss von den Behandlungen der Oberfläche des Faserstiftes auf

die Microtensile-Verbundfestigkeit zwischen Epoxydharz-Faserstiften und

einem Resin-Zement bzw. einem Flowable-Komposit. Ein dualhärtendes

Adhäsiv wurde in dieser Studie auf allen Faserstiften appliziert, weil es

gezeigt worden war, dass diese Behandlung die Verbundfestigkeit mit den

Epoxydharz-Faserstiften erhöhte. Die Studie hatte zwei Ziele: 1. es zu

untersuchen, ob das Sandstrahlen der Oberfläche des Faserstiftes die

Verbundfestigkeit zwischen Faserstiften und Komposit-Zement beeinflusst;

2. den Einfluss der Wasserlagerung auf die von dem Adhäsiv vermittelte

Verbindung zwischen FRC Faserstiften und Resin-Zement und zwischen

FRC Faserstiften und Flowable-Komposit mit einem „Model of accelerated

Aging“ zu bestimmen. Das Ziel der dritten Studie vom Kapitel 2 war es, den

Einfluss von einer experimentellen industriellen Behandlung und von

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konventionellen „Chair-Side“ Behandlungen der Oberfläche von

Epoxydharz-Faserstiften auf die Microtensile-Verbundfestigkeit mit Resin-

Zementen festzustellen. Die experimentelle industrielle Behandlung bestand

aus zwei Schritten: eine 1�m-dicke Zirkoniumoxid-Schicht, die von der

Silanisierung mit 3-(Trimethoxysilyl) Propyl Methacrylat gefolgt wurde. Es

wurde behauptet, dass diese Behandlung den anfänglichen Rillenabstand des

Faserstiftes erhielt, um mikromechanische Retention anzubieten und um eine

chemische Verbindung zwischen dem Silan und dem Adhäsiv bzw. dem

Zement herzustellen. Die konventionellen „Chair-Side“ Behandlungen, die in

dieser Studie angewendet wurden, waren die Silanisierung und die

Anwendung eines Adhäsives. Dagegen wurde keine Behandlung in der

Kontrolle-Gruppe verwendet. Außer den REM Beobachtungen der

behandelten/unbehandelten Oberfläche des Faserstiftes und der adhäsiven

Schnittstellen wurde die Oberfläche der industriell behandelten Faserstifte

auch mit der „Energy Dispersive Analysis by X-Ray (EDAX)“ in einem

REM bewertet.

Resin-Zemente und adhäsive Techniken für die Zementierung der

Faserstifte waren die Themen vom Kapitel 3, das aus zwei Studien besteht.

Die selbst-adhäsiven Zemente wurden besonders berücksichtigt, weil sie die

neuesten und weniger untersuchten Gruppe von Materialien sind. Die erste

Studie vom Kapitel 3 ist eine Literaturübersicht, die das Ziel hatte, die

Forschung über die selbst-adhäsiven Zemente zusammenzufassen und

Auskunft über ihre Eigenschaften zu geben. Sie stützte sich auf die

Ergebnisse wissenschaftlicher Artikel von „peer-reviewed“ Zeitschriften, die

in Pub-Med gelistet sind. Die Ergebnisse wurden in den folgenden

Kategorien zusammengefasst: Adhäsion mit den Zahnhartsubstanzen

(Schmelz, Kronendentin, Wurzeldentin), Adhäsion mit den Restauration-

Materialien (Wurzelstifte, Keramik, Titanium-Abutments), marginale

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Anpassung, Microleakage, mechanische Eigenschaften, Biokompatibilität,

chemische Adhäsion und Abgabe von Fluorid, Bewertungen der klinischen

Anwendung. Die zweite Studie vom Kapitel 3 erforschte die Adhäsion von

Faserstiften, die in Wurzeldentin mit Zementen, die drei derzeit verfügbaren

adhäsiven Techniken benutzen, zementiert wurden. Es wurde angenommen,

dass die simplifizierten Self-Etch und selbst-adhäsiven Techniken so

wirksam wie die klinisch nachgewiesene Etch-and-Rinse Technik sind. Um

die Adhäsion von Faserstiften festzustellen, wurde den „Thin-Slice Push-out“

Test verwendet.

Im Kapitel 4 wurde eine Studie, die die Wichtigkeit der

Lichtdurchlässigkeit durch den Faserstift scharf umriß, dargestellt. Diese

Studie erforschte, ob die Lichtdurchlässigkeit durch den Faserstift das

adhäsive Potenzial und die mikromechanischen Eigenschaften eines

dualhärtenden Resin-Zementes, der für die Zementierung von Faserstiften

angewendet wurde, beeinflusst. Erstens wurden spektrophotometriche

Messungen gemacht, um die Lichtdurchlässigkeit in verschiedenen Teilen

und in der Spitze des Faserstiftes von zwei Faserstiften, die sich nach einer

visuellen Beobachtung in ihren Lichtdurchlässigkeiten beträchtlich

voneinander zu unterscheiden schienen, festzustellen. Die Messungen zeigten

keine Lichtdurchlässigkeit in einem der Faserstifte, dagegen sank die

Lichtstärke von dem koronalen bis zum apikalen Teil des anderen Faserstiftes

und sie erreichte den Höchstwert in der Spitze. Nach den Messungen wurde

es untersucht, ob die Art des Faserstiftes die Kontinuität der Resin-

Zement/Wurzeldentin bzw. Resin-Zement/Faserstift Schnittstelle beeinflusst,

wenn die anderen Variablen konstant bleiben. Außerdem wurde es

festgestellt, ob die Art des Faserstiftes den Elastizitätsmodul bzw. die Härte

des Zementes beeinflusst.

188

Die folgenden Schlussfolgerungen können aus der Bewertung der folgenden

Aspekte, die mit der Zementierung von Faserstiften korrelieren, -

Behandlung der Oberfläche des Faserstiftes, Art des Resin-Zementes und

Lichtdurchlässigkeit durch den Faserstift – gezogen werden:

1. Das Sandstrahlen kann die Microtensile-Verbundfestigkeit mit

Methacrylat-Faserstiften erhöhen, daher wird die Notwendigkeit

zusätzlicher „Chair-Side“ Behandlungen vermieden. Die reduzierte

Anzahl der klinischen Schritte kann das klinische Verfahren

simplifizieren.

2. Verglichen mit dem Adhäsiv allein, kann das Sandstrahlen gefolgt von der

Anwendung eines Adhäsives die sofortige Verbundfestigkeit mit

Epoxydharz-Faserstiften verbessern. Das „accelerated Water Aging“ kann

den Faserstift/Resin-Zement bzw. Faserstift/Flowable-Komposit

Verbindungen, die von einem hydrophilen Adhäsiv vermittelt werden,

schaden.

3. Die experimentelle industrielle Behandlung der Oberfläche des

Faserstiftes und die Anwendung eines Adhäsives erhöhen die

Verbundfestigkeit zwischen Faserstift und Resin-Zement. Die industrielle

Behandlung kann die Zementierung simplifizieren. Die Zementierung von

Epoxydharz-Faserstiften ohne Behandlung der Oberfläche des Faserstiftes

ist nicht zu empfehlen.

4. Die selbst-adhäsiven Zemente scheinen eine erfolgversprechende neue

Technik für die indirekten Restaurationen inklusiv die Zementierung von

Faserstiften zu sein. Trotzdem stützt sich die Mehrheit der Daten der

Literatur auf Studien, die nur einen der Zemente, die derzeit zur

Verfügung für die Zahnärzte stehen, erforschten. Es wäre noch wichtiger

das langfristige klinische Verhalten dieser Materialien festzustellen, bevor

189

allgemeine Hinweise für ihre Anwendung für die Zementierung von

Faserstiften zu geben.

5. Die 24 St. Push-out Verbundfestigkeit mit Faserstiften wurde von den

Zementen signifikant beeinflusst. Die Ergebnisse dieser Dissertation

ermöglichen nicht, eine der drei untersuchten adhäsiven Techniken mit

Sicherheit zu bevorzugen. Trotzdem zeigt die Self-Etching Technik unter

den ausgewählten experimentellen Bedingungen eine schlechtere

Adhäsion mit dem Wurzeldentin, verglichen mit den Etch-and-Rinse bzw.

Total-etch Techniken.

6. Verglichen mit der Zementierung von lichtdurchlässigen Faserstiften,

zeigte die Zementierung von lichtundurchlässigen Faserstiften mit einem

dualhärtenden Resin-Zement einen geringeren Prozentsatz von Kontinuität

der Resin-Zement/Wurzeldentin bzw. Resin-Zement/Faserstift

Schnittstellen.

7. Elastizitätsmodul und Vickershärte des Zementes sanken signifikant von

dem koronalen bis zum apikalen Drittel des Post-Space unabhängig von

der Lichtdurchlässigkeit des Faserstiftes. Trotzdem zeigte die

Zementierung von lichtdurchlässigen Faserstiften höhere Werte des

Elastizitätsmoduls und der Vickershärte des Zementes, verglichen mit der

Zementierung von lichtundurchlässigen Faserstiften.

Sažetak i zaklju�ci

Cilj ove teze bio je da ispita tri faktora cementiranja kompozitnih ko�i�a

oja�anih vlaknima: priprema površine ko�i�a, vrsta kompozitnog cementa za

cementiranje ko�i�a i svetlosna provodljivost ko�i�a. Radna hipoteza bila je

da ovi faktori mogu uticati na uspešnost cementiranja ko�i�a. Kako bi se ova

190

hipoteza proverila, sprovedeno je nekoliko laboratorijskih istraživanja. Tezu

�ine �etiri poglavlja u kojima je predstavljeno šest publikovanih radova.

Poglavlje 1 obuhvata uvod u osnovnu temu. Predstavljena je primena

kompozitnih ko�i�a u zbrinjavanju endodontski le�enih zuba. Diskutovano je

o osnovnim svojstvima kompozitnih ko�i�a, kao što su sastav, elasti�nost i

estetika, kao i o klini�kim pogodnostima koje ova svojstva pružaju. Opisane

su indikacije u kojima kompozitni ko�i�i mogu u potpunosti ispoljiti svoj

potencijal, uklju�uju�i i posebne prednosti koje primena ovih ko�i�a donosi u

de�joj stomatologiji i traumatologiji. Iako se svi kompozitni ko�i�i sastoje od

istih osnovnih komponenti, njihova mehani�ka svojstva i kvalitet u klini�kim

uslovima mogu zna�ajno da variraju u zavisnosti od proizvo�a�a. Zbog toga

su predstavljena neka od svojstava koja mogu da uti�u na izbor ko�i�a. Osim

tri faktora kojima se bavi ova teza, smatra se da još nekoliko drugih faktora

može uticati na uspešnost cementiranja ko�i�a. U Poglavlju 1 su ukratko

diskutovani slede�i: vrsta paste za definitivno punjenje kanala korena,

koli�ina preostalog kruni�nog dentina, preparacija ferula i debljina sloja

kompozitnog cementa.

Priprema površine ko�i�a i njen uticaj na adheziju izme�u ko�i�a i

kompozitnog cementa ispitivani su u tri rada predstavljena u Poglavlju 2. U

ovim radovima, nakon primene razli�itih na�ina pripreme površine ko�i�a,

ispitivana je ja�ina veze izme�u ko�i�a i cementa pomo�u testa otpornosti

mikrouzoraka na istezanje (“microtensile bond strength test”). Tako�e su

posmatrane površine tretiranih i netretiranih ko�i�a, kao i adhezivni spojevi

cement-ko�i� skening elektronskim mikroskopom (SEM). U prvom radu

ispitivan je uticaj peskiranja i razli�itih ordinacijskih postupaka pripreme

ko�i�a sa metakrilatnim matriksom na ja�inu veze sa dvostruko-

polimerizuju�im kompozitom. U drugom radu ispitivan je uticaj pripreme

ko�i�a sa matriksom od epoksi smole na ja�inu veze sa kompozitnim

191

cementom i te�nim kompozitom. Na sve ko�i�e bio je nanesen dvostruko-

polimerizuju�i adheziv, imaju�i u vidu da je ranije utvr�eno da ovakav

tretman efikasno pove�ava ja�inu veze kompozitnih materijala sa ko�i�ima

koji sadrže epoksi smolu. Rad je imao dva cilja: 1. utvrditi da li peskiranje pre

nanošenja adheziva uti�e na ja�inu veze ko�i�-cement i ko�i�-te�ni kompozit;

2. ispitati uticaj vode na vezu ko�i�-cement i ko�i�-te�ni kompozit koriste�i

model ubrzanog starenja materijala. U tre�em radu Poglavlja 2 cilj je bio da

se ispita uticaj eksperimentalne fabri�ke pripreme i razli�itih ordinacijskih

na�ina pripreme površine ko�i�a sa matriksom od epoksi smole na ja�inu

veze sa kompozitnim cementima. Eksperimentalnu fabri�ku pripremu �inilo

je dva koraka: nanošenje sloja cirkonijum oksida debljine 1�m, a zatim

silanizacija 3-(trimetoksilil) propil metakrilatom. Prema tvrdnji proizvo�a�a,

ovakvom pripremom obezbe�uje se mikromehani�ka retencija, kao i hemijska

veza izme�u silana i adheziva ili cementa. Ordinacijski postupci pripreme

ko�i�a koji su ispitivani u ovom radu obuhvatili su nanošenje silana i

nanošenje adheziva, dok u kontrolnoj grupi površina ko�i�a nije tretirana.

Mikroskopski su posmatrane površine tretiranih i netretiranih ko�i�a, kao i

adhezivni spojevi cement-ko�i� (SEM). Površina fabri�ki pripremljenih

ko�i�a tako�e je ispitivana pomo�u EDAX analize (Energy Dispersive

Analysis by X-ray) u skening elektronskom mikroskopu.

Tema Poglavlja 3 bili su kompozitni cementi i razli�iti adhezivni

pristupi koji se mogu koristiti pri cementiranju kompozitnih ko�i�a. Ovo

poglavlje �ine dva rada. Posebna pažnja posve�ena je samoadhezivnim

kompozitnim cementima, koji �ine najnoviju i najmanje ispitivanu kategoriju

kompozitnih cemenata. Prvi rad Poglavlja 3 je pregled literature �iji je cilj bio

da pruži informacije o samoadhezivnim kompozitnim cementima na osnovu

originalnih nau�nih radova objavljenih u recenziranim �asopisima koji su

indeksirani u bazi PubMed. Rezultati su klasifikovani u slede�e kategorije:

192

adhezija sa zubnim tkivima (gle�, dentin, dentin kanala korena), adhezija sa

restaurativnim materijalima (endodontski ko�i�i, keramika, titanijum),

marginalna adaptacija, mikropropustljivost, mehani�ka svojstva,

biokompatibilnost, hemijska adhezija i otpuštanje fluorida, ocena kvaliteta

tokom klini�ke upotrebe. U drugom radu Poglavlja 3 ispitivana je adhezija

kompozitnih ko�i�a cementiranih pomo�u tri aktuelna adhezivna pristupa.

Radna hipoteza bila je da su jednostavniji, samoadhezivni i samonagrizaju�i

pristup, jednako efektivni kao klini�ki potvr�en pristup potpunog nagrizanja.

Kako bi se ispitala adhezija ko�i�a merena je retencija pomo�u testa tankih

popre�nih preseka (thin-slice push-out test).

U Poglavlju 4 predstavljen je rad koji ispituje važnost svetlosne

provodljivosti ko�i�a. U ovom radu ispitivan je uticaj svetlosne provodljivosti

ko�i�a na adheziju dvostruko-polimerizuju�eg kompozitnog cementa, kao i na

mikromehani�ka svojstva cementa. Spektrofotometrijskim merenjima

utvr�ena je svetlosna provodljivost dva ko�i�a za koje je na osnovu vizuelnih

zapažanja pretpostavljeno da se u ovom svojstvu zna�ajno razlikuju. Merenja

su izvršena na razli�itim nivoima ko�i�a i na apikalnom vrhu. Utvr�eno je

odsustvo svetlosne provodljivosti kroz jedan od dva ko�i�a, dok je kroz drugi

intenzitet propuštene svetlosti opadao od koronarnog ka apikalnom nivou, a

na apikalnom vrhu dostizao najvišu vrednost. Nakon merenja, ispitivan je

uticaj tipa ko�i�a na kontinuitet adhezivnog spoja cement-dentin i cement-

ko�i�. Tako�e, ispitivan je uticaj tipa ko�i�a na modul elasti�nosti i tvrdo�u

cementa.

Na osnovu ispitivanja slede�ih faktora cementiranja kompozitnih ko�i�a:

priprema površine ko�i�a, tip kompozitnog cementa i svetlosna provodljivost

ko�i�a, mogu se izvesti slede�i zaklju�ci:

193

1. Peskiranje može da poboljša ja�inu veze kompozitnih materijala sa

metakrilatnim kompozitnim ko�i�ima i da eliminiše potrebu za dodatnim

ordinacijskim tretmanima površine ko�i�a. Smanjenje broja klini�kih

koraka doprinosi jednostavnosti klini�kih procedura.

2. Peskiranje pra�eno aplikacijom adheziva poboljšava ja�inu veze

kompozitnih materijala (cementa i te�nog kompozita) sa kompozitnim

ko�i�ima od epoksi smole, izmerenu neposredno nakon cementiranja

ko�i�a. Adhezivni spoj ko�i�a pripremljenih adhezivom sa kompozitnim

cementom i te�nim kompozitom može biti ugrožen ubrzanim starenjem u

vodi.

3. Eksperimentalna fabri�ka priprema i aplikacija adheziva poboljšavaju

ja�inu veze izme�u cementa i kompozitnog ko�i�a sa matriksom od epoksi

smole. Fabri�ki tretman može pojednostaviti klini�ki postupak

cementiranja. Cementiranje kompozitnih ko�i�a sa matriksom od epoksi

smole bez pripreme površine ko�i�a se ne preporu�uje.

4. Samoadhezivni kompozitni cementi mogli bi da ponude obe�avaju�i novi

pristup u indirektnim restaurativnim postupcima, uklju�uju�i cementiranje

kompozitnih ko�i�a. Me�utim, najve�i broj podataka iz literature o ovim

cementima poti�e iz laboratorijskih istraživanja samo jednog od više

cemenata koji su trenutno na raspolaganju klini�arima. Neophodne su

dugotrajne klini�ke studije kako bi se mogla dati generalna preporuka za

upotrebu samoadhezivnih cemenata u cementiranju ko�i�a.

5. Retencija kompozitnih ko�i�a merena nakon 24 sata od cementiranja

zna�ajno se razlikovala kod razli�itih kompozitnih cemenata. Na osnovu

rezultata ove teze nije mogu�e sa sigurnoš�u tvrditi da jedan od tri

adhezivna pristupa daje bolje rezultate u odnosu na ostala dva. Ipak,

metodom koji je koriš�en ustanovljena je lošija adhezija ko�i�a

194

koriš�enjem samonagrizaju�eg pristupa u odnosu na samoadhezivni i

pristup potpunog nagrizanja.

6. Procenat kontinualnog adhezivnog spoja cement-dentin i cement-ko�i� bio

je zna�ajno viši nakon cementiranja ko�i�a koji propušta svetlost u

pore�enju sa ko�i�em koji ne propušta svetlost.

7. Modulus elasti�nosti i tvrdo�a po Vikersu cementa zna�ajno su opadali od

koronarnog ka apikalnom nivou nezavisno od svetlosne provodljivosti

ko�i�a. Me�utim, modulus elasti�nosti i tvrdo�a po Vikersu bili su

zna�ajno viši nakon cementiranja ko�i�a sa svetlosnom provodljivoš�u u

odnosu na ko�i� koji ne provodi svetlost.

195

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218

Curriculum vitae

Dr. Ivana Radovic

Date of birth: April 9th, 1976

Place of birth: Belgrade, Serbia

Civil status: Married (former last name: Davitkov)

Citizenship: Serbian

Work address: Dr Subotica 11, 11000 Beograd, Serbia

Home address: Dr Agostina Neta 24, 11070 Novi Beograd, Serbia

Telephone number: +381 11 2684581

E-mail address: [email protected]

2001: Degree in Dentistry, Faculty of dentistry, University of Belgrade,

Serbia

Research activity

2004: Nova Southeastern University, Fort Lauderdale, Florida, USA

(conducting experiments within the scope of Master thesis).

2002 – 2005: Postgraduate studies at the Faculty of Dentistry, Belgrade,

Serbia. Master thesis “Bond strength, microleakage and SEM investigation of

self-etching adhesive systems” defended on September 27th 2005.

2006: Master of Science in Dental Materials and their clinical applications,

University of Siena.

219

Professional position

2002 – Teaching and research assistant, Clinic for pediatric and preventive

dentistry, Faculty of dentistry, University of Belgrade, Serbia.

Membership in Dental Societies

2002 - Serbian doctors’ society

2004 - International Organization for Dental Research (IADR)

2006 - Serbian Society of Pediatric and Preventive Dentists

2009 - European Academy of Paediatric Dentistry (EAPD)

International publications

Beloica M, Goracci C, Carvalho CAR, Radovic I, Margvelashvili M, Vulicevic ZR, Ferrari M (2010). Microtensile vs microshear bond strength of all-in-one adhesives to unground enamel. Journal of Adhesive Dentistry: In press

Beloica M, Carvalho CAR, Radovic I, Margelashvili M, Goracci C,

Vulicevic ZR, Ferrari M (2008). Efficacy of all-in-one adhesive systems on unground enamel. International Dentistry South Africa 10(5): 12-9.

Cagidiaco MC, Radovic I, Simonetti M, Tay F, Ferrari M (2007). Clinical performance of fiber post restorations in endodontically treated teeth: 2-year results. Int J Prosthodont 20(3): 293-8. Coniglio I, Magni E, Goracci C, Radovic I, Carvalho CA, Grandini S, Ferrari M (2008). Post space cleaning using a new nickel titanium endodontic drill combined with different cleaning regimens. J Endod 34(1): 83-6.

220

Dall'oca S, Papacchini F, Radovic I, Polimeni A, Ferrari M (2008). Repair potential of a laboratory-processed nano-hybrid resin composite. J Oral Sci 50(4): 403-12. Ferrari M, Cagidiaco MC, Goracci C, Vichi A, Mason PN, Radovic I, Tay F (2007). Long-term retrospective study of the clinical performance of fiber posts. Am J Dent 20(5): 287-91. Magni E, Coniglio I, Radovic I, Goracci C, Ilie N, Hickel R, Cagidiaco MC (2009). Effect of diagnostic method and operator’s experience on the detection of occlusal caries in posterior permanent teeth: an in vivo pilot study. International Dentistry South Africa 11(1): 32-40. Magni E, Mazzitelli C, Papacchini F, Radovic I, Goracci C, Coniglio I, Ferrari M (2007). Adhesion between fiber posts and resin luting agents: a microtensile bond strength test and an SEM investigation following different treatments of the post surface. J Adhes Dent 9(2): 195-202. Magni E, Radovic I, Coniglio I, Papacchini F, Mazzitelli C, Ferrari M (2007). Bonding of self-etching adhesive/flowable composite combinations to enamel and dentin: a microtensile bond strength evaluation. . International Dentistry South Africa 9(4): 6-18. Mazzitelli C, Magni E, Radovic I, Papacchini F, Goracci C, Ferrari M (2007). The adhesion between FRC posts and resin core materials following different treatments of the post surface. . International Dentistry South Africa 9(2): 30-40. Monticelli F, Osorio R, Sadek FT, Radovic I, Toledano M, Ferrari M (2008). Surface treatments for improving bond strength to prefabricated fiber posts: a literature review. Oper Dent 33(3): 346-55. Papacchini F, Magni E, Radovic I, Mazzitelli C, Monticellia F, Goracci C, Polimeni A, Ferrari M (2007). Effect of intermediate agents and pre-heating of repairing resin on composite-repair bonds. Oper Dent 32(4): 363-71. Papacchini F, Monticelli F, Hasa I, Radovic I, Fabianelli A, Polimeni A, Ferrari M (2007). Effect of air-drying temperature on the effectiveness of silane primers and coupling blends in the repair of a microhybrid resin composite. J Adhes Dent 9(4): 391-7.

221

Papacchini F, Monticelli F, Radovic I, Chieffi N, Goracci C, Tay FR, Polimeni A, Ferrari M (2007). The application of hydrogen peroxide in composite repair. J Biomed Mater Res B Appl Biomater. Papacchini F, Radovic I, Magni E, Goracci C, Monticelli F, Chieffi N, Polimeni A, Ferrari M (2008). Flowable composites as intermediate agents without adhesive application in resin composite repair. Am J Dent 21(1): 53-8. Papacchini F, Toledano M, Monticelli F, Osorio R, Radovic I, Polimeni A, Garcia-Godoy F, Ferrari M (2007). Hydrolytic stability of composite repair bond. Eur J Oral Sci 115(5): 417-24. Porciani PF, Vano M, Radovic I, Goracci C, Grandini S, Garcia-Godoy F, Ferrari M (2008). Fracture resistance of fiber posts: combinations of several small posts vs. standardized single post. Am J Dent 21(6): 373-6. Radovic I, Corciolani G, Magni E, Krstanovic G, Pavlovic V, Vulicevic ZR, Ferrari M (2009). Light transmission through fiber post: The effect on adhesion, elastic modulus and hardness of dual-cure resin cement. Dent Mater 25(7): 837-44. Radovic I, Mazzitelli C, Chieffi N, Ferrari M (2008). Evaluation of the adhesion of fiber posts cemented using different adhesive approaches. Eur J Oral Sci 116(6): 557-63. Radovic I, Monticelli F, Cury AH, Bertelli E, Vulicevic ZR, Ferrari M (2008). Coupling of composite resin cements to quartz fiber posts: a comparison of industrial and chairside treatments of the post surface. J Adhes Dent 10(1): 57-66. Radovic I, Monticelli F, Goracci C, Cury AH, Coniglio I, Vulicevic ZR, Garcia-Godoy F, Ferrari M (2007). The effect of sandblasting on adhesion of a dual-cured resin composite to methacrylic fiber posts: Microtensile bond strength and SEM evaluation. J Dent 35(6): 496-502. Radovic I, Monticelli F, Goracci C, Vulicevic ZR, Ferrari M (2008). Self-adhesive resin cements: a literature review. J Adhes Dent 10(4): 251-8. Radovic I, Monticelli F, Papacchini F, Magni E, Cury AH, Vulicevic ZR, Ferrari M (2007). Accelerated aging of adhesive-mediated fiber post-resin composite bonds: A modeling approach. J Dent 35(8): 683-9.

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Radovic I, Vulicevic ZR, Garcia-Godoy F (2006). Morphological evaluation of 2- and 1-step self-etching system interfaces with dentin. Oper Dent 31(6): 710-8. Simonetti M, Radovic I, Vano M, Chieffi N, Goracci C, Tognini F, Ferrari M (2006). The influence of operator variability on adhesive cementation of fiber posts. J Adhes Dent 8(6): 421-5. Vulicevic ZR, Radovic I, Cury AH, Krstanovic G, Mandic J, Ferrari M (2008). Microtensile bond strength of self-etching adhesives to dentin. Metalurgija – Journal of Metallurgy 14(2): 101-9. Zhang L, Magni E, Radovic I, Wang YJ, Chen JH, Ferrari M (2008). Effect of curing modes of dual-curing luting systems and root regions on retention of translucent fiber posts in root canals. J Adhes Dent 10(3): 219-26. Zhang L, Wang YJ, Radovic I, Chieffi N, Chen JH, Ferrari M (2006). Adhesion of two dual-cure core resins to silica fiber posts treated with different bonding agents. International Dentistry South Africa 8(6): 38-47. Abstracts 1. Radovic I, Mazzitelli C, Chieffi N, Ferrari M. Adhesion of fiber posts

cemented using different adhesive approaches. J Dent Res 87(Spec Iss B):(abstract no. 1750), 2008 (www.dentalresearch.org). 86th General Session and Exhibition of the International and Canadian Associations for Dental Research, July 2-5. 2008, Toronto, Canada. Poster presentation.

2. Radovic I, Monticelli F, Papacchini F, Magni E, Cury AH, Vulicevic ZR, Ferrari M. Accelerated aging of adhesive-mediated fiber post-resin composite bonds. J Dent Res 86(Spec Iss B):(abstract no. 0429), 2007 (www.dentalresearch.org). 42nd Annual Meeting IADR-Continental European and Israeli Divisions, September 26-29. 2007, Thessaloniki, Greece. Poster presentation.

3. Papacchini F, Ferrari M, Radovic I, Monticelli F, Toledano M, Osorio R, Garcia-Godoy F, Polimeni A. Effect of thermocycling on composite-to-composite adhesion. J Dent Res 86(Spec Iss B):(abstract no. 0303), 2007

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(www.dentalresearch.org). 42nd Annual Meeting IADR-Continental European and Israeli Divisions, September 26-29. 2007, Thessaloniki, Greece. Poster presentation.

4. Radovic I, Monticelli F, Cury AH, Bertelli E, Vulicevic ZR, Ferrari M. Comparison of Industrial and “Chair-Side” Treatments of Fiber Post Surface. J Dent Res 86(Spec Iss A):(abstract no. 1532), 2007 (www.dentalresearch.org). 85th General Session and Exhibition of the International, American and Canadian Associations for Dental Research, March 21-24. 2007, New Orleans, Louisiana, USA. Poster presentation.

5. Papacchini F, Monticelli F, Radovic I, Polimeni A, Ferrari M. Influenza dell’agente intermedio sulla stabilità idrolitica dell’adesione composito-composito (Effect of the intermediate agent on the hydrolytic stability of the composite-repair bond). XI National Congress SIDOC (Società Italiana di Odontoiatria Conservatrice) "Adesione, estetica e funzione", February 15-17. 2007, Rome, Italy. Poster presentation.

6. Cury AH, Radovic I, Goracci C, Chieffi N, Ferrari M. Strategies to lute

fiber post: immediate and 1week push-out retention. Academy of Dental Materials Meeting 2006, October 23-25. 2006, Sao Paulo, Brazil. Poster presentation.

7. Papacchini F, Radovic I, Magni E, Monticelli F, Goracci C, Chieffi N,

Ferrari M. The effect of intermediate agents in composite repair bond strength. J Dent Res 85(Spec Iss C):(abstract no. 0308), 2006 (www.dentalresearch.org). IADR Pan European Federation 2006, September 13-16. 2006, Dublin, Ireland. Poster presentation.

8. Radovic I, Monticelli F, Cury AH, Goracci C, Cantoro A, Coniglio I,

Ferrari M. Surface treatment influence on fiber post - resin cement bond strength. J Dent Res 85(Spec Iss C):(abstract no. 0245), 2006 (www.dentalresearch.org). IADR Pan European Federation 2006, September 13-16. 2006, Dublin, Ireland. Oral presentation.

9. Radovic I, Cury AH, Vulicevic ZR, Garcia-Godoy F, Ferrari M.

Microtensile bond strength of two- and one-step self-etching systems to dentin. The Third CONSEURO 2006 on Across European Borders Prevention, Restorations and Esthetics, February 9-11. 2006, Rome, Italy. Poster presentation.

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10. Davitkov I, Vulicevic ZR, Garcia-Godoy F. The influence of flowable composite as an initial layer on microleakage of self-etching systems. 10th Congress of the Balkan Stomatological Society, May 12-14. 2005, Belgrade, Serbia and Montenegro. Oral presentation.

11. Davitkov I, Vulicevic ZR, Garcia-Godoy F. SEM investigation of different self-etching systems interface with dentin. J Dent Res 84(Spec Iss A):(abstract no. 0158), 2005 (www.dentalresearch.org). 83rd General Session and Exhibition of the International, American and Canadian Associations for Dental Research, March 9-12. 2005, Baltimore, Maryland, USA. Oral presentation.

12. Davitkov I, Vulicevic ZR. SEM investigation of self-etching primers

influence on unground and ground enamel. 4th Congress of Serbia and Montenegro dentists, October 13-16. 2004, Herceg Novi, Serbia and Montenegro. Poster presentation.

13. Davitkov I, Vulicevic ZR. Microleakage of a total-etch and a self-etch

bonding system under composite resins with various filler content. 7th Congress of the European Academy of Pediatric Dentistry, Jun 10-13. 2004, Barcelona, Spain. Oral presentation.

14. Davitkov I, Vulicevic ZR. Microleakage of three different self-etching

adhesive systems. 9th Congress of the Balkan Stomatological Society, May 13-16. 2004, Ohrid, Macedonia. Oral presentation.

15. Vulicevic ZR, Todorovic A, Davitkov I. Adhesive bridges as space

maintainers. First International Congress of Serbia and Montenegro Orthodontists, October 2-5. 2003, Belgrade, Serbia and Montenegro. Poster presentation.

16. Beloica D, Vulicevic ZR, Davitkov I. FRC Postec in pediatric dentistry.

8th Congress of the Balkan Stomatological Society, May 2003, Tirana, Albania. Poster presentation.

17. Vulicevic ZR, Davitkov I, Todorovic A, Spadijer A. Ribbond reinforced

Class II composite fillings – a case report. 7th Congress of the Balkan Stomatological Society, March 28-30. 2002, Cushadasi, Turkey. Poster presentation.

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18. Vulicevic ZR, Todorovic A, Davitkov I. Occlusal reconstruction with prefabricated ceramic inlays. 8th Symposium of Serbia prosthetitians, Jun 22-23. 2001, Zlatibor, Yugoslavia. Poster presentation.

19. Davitkov I (author), Vulicevic ZR (mentor). Ribbond reinforced composite bridges. 42nd Congress of medicine and dentistry students of Yugoslavia, April 17-21. 2001, Lepenski Vir, Yugoslavia. Oral presentation.

20. Vulicevic ZR, Davitkov I. Composite-compomer sandwich technique

(case report). 3rd Congress of Yugoslavia dentists, September 20-23. 2000, Novi Sad, Yugoslavia. Poster presentation.

21. Davitkov I (author), Vulicevic ZR (mentor). The use of compomers in

pediatric dentistry. 41st Congress of medicine and dentistry students of Yugoslavia, April 25-29. 2000, Zlatibor, Yugoslavia. Oral presentation.

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Acknowledgements

This thesis is respectfully submitted to Prof. Silvano Focardi, Rector of the University of Siena, to Prof. Gian Maria Rossolini, Dean of the Faculty of Medicine of the University of Siena, to Prof. Marco Ferrari, Director of the Department of Dental Science, Dean of School of Dental Medicine, Director of the PhD Program in “Biotechnologies: section of Dental Biomaterials”, University of Siena.

It is also submitted to Prof. Branko Kova�evi�, Rector of the University of Belgrade and to Prof. Dragoslav Stamenkovi�, Dean of the Faculty of Dentistry, University of Belgrade. The Siena PhD program has been one of the greatest adventures and experiences in my life. Having the possibility to take this journey and encounter numerous wonderful people on the way made me feel as a truly rich person. The quality of Siena PhD programme that I appreciated and enjoyed the most was the opportunity to work in a team. This thesis is a result of a joint effort. It would never have become reality without the generous help of my professors and a large supportive network of colleagues and friends. Even though I don’t have the possibility to mention everyone by name, I truly cherish each contribution. I am heartily thankful to my Promoter, Prof. Marco Ferrari, whose encouragement, guidance and clear broad vision have been the continuous source of positive energy and motivation for me. He has always been a strong and supportive advisor to me throughout the program, and at the same time he encouraged me to pursue and implement independent ideas. My Co-Promoter, Prof. Zoran Vuli�evi�, introduced me to the world of science almost 10 years ago. Since then, he has been providing me with various opportunities and challenges in the academic world which have boosted my confidence. I am deeply grateful for his guidance and advice I know I can always count on. I would also like to express gratitude to my committee members for time and attention they put in reviewing my thesis. Prof. Francesca Monticelli taught me how to expand my views and how to build a solid research protocol and put it in clear and concise written form. I am grateful to her for experience and knowledge that she generously shared with me, both in laboratory work and in writing papers.

Prof. Cecilia Goracci introduced the world of statistics to me patiently and clearly. This made all the time I spent in front of seemingly endless data on SPSS screen a stimulating challenge I truly enjoyed and was happy to take.

Dr. Federica Papacchini and Dr. Alvaro Cury welcomed me the first time I visited Siena. Besides providing all the help I needed in the lab, they also made my first stay a joyful memory I often go back to. Throughout the entire time I spent in Siena we shared many hours working and laughing together as colleagues and friends.

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Dr. Elisa Magni helped me many times with clear reasoning and a fast constructive approach when it was needed the most. I am also grateful to Elisa for the hospitality she generously showed during my visits to her beautiful city. It is a pleasure to thank many dear PhD colleagues who have made significant contributions and invested their time, ideas and energy into improving my work: especially Dr. Claudia Mazzitelli, Dr. Gabrielle Corciolani and Dr. Nicoletta Chieffi. I gratefully acknowledge the translations of Summary and conclusions that were made by Dr. Federica Papacchini (Italian) and Dr. Elisa Magni (German). A unique part of Siena living experience had been the stay in Santa Chiara College for PhD students. I thank all the friends I met there for happy times we spent together in small everyday joys of College life and in numerous field trips around Toscana. I owe an exceptional dept to the “Serbian side” of my PhD road. Firstly, to all the Professors and colleagues from the Clinic for pediatric and preventive dentistry. I am deeply grateful for the kind support they showed during the year I spent in Siena, as well as during several shorter leaves of absence that I had to take in order to complete the program. I especially appreciated the instantly positive attitude and confidence in me that the late Prof. Marko Vulovi�, former Clinic director, expressed in the early stages of preparation to apply for the program. I thank the Clinic director, Prof. Mirjana Ivanovi�, for her warmth and for always having time to share caring and encouraging words. Prof. Vuli�evi�’s, Prof. Vulovi�’s and Prof. Ivanovi�’s supportive presence during my Master thesis defence in Siena in December 2006 had a great impact on my self-esteem and created an especially valued page in the book of my Siena memories. Special thanks go to Professor Dragoslav Stamenkovi�, the Dean of the Faculty of dentistry. I appreciate his catching enthusiasm, positive energy and the trust he has been showing me.

I am grateful to Professor Vladimir Pavlovi� for his assistance with Scanning Electron Microscope, as well as for the time we spent in discussions of our findings. I also thank Dr. Goranka Krstanovi�, a very dear friend and colleague, for her precious help that was very important and significant for me in the final stages of this project.

Architect Milan Stefanovi�, my brother in law and a dear friend, made beautiful 3-D schemes and drawings that considerably enhanced the way this thesis is reported. I truly appreciate the time he spent doing this, as well as his infinite kindness and patience.

My sister Nevena and my parents have always been there for me with unconditional love, support and encouragement. My overwhelming feeling of awareness of being blessed with such a family only begins to explain how much I am grateful to them.

I deeply thank my love, Marko, for his patience, sacrifice, understanding, for having faith in me and being proud of me, for listening to my problems and for gladly taking part in resolving them countless times. I thank him for being so perceptive to my dreams and wishes and for enabling me to live them.

different aspects related to luting fiber posts

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