“fracture resistance of endodontically treated …

“FRACTURE RESISTANCE OF ENDODONTICALLY

TREATED MAXILLARY INCISORS WITH

DIFFERENT POST AND CORE MATERIALS: A

COMPARITIVE EVALUATION”

Dissertation submitted to

THE TAMILNADU Dr. M.G.R. MEDICAL UNIVERSITY

In partial fulfillment for the Degree of

MASTER OF DENTAL SURGERY

BRANCH IV

CONSERVATIVE DENTISTRY AND ENDODONTICS

MAY 2020

CERTIFICATE

This is to certify that DR. GANESHAMOORTHY.T post graduate student

(2017-2020) from the Department Of Conservative Dentistry and Endodontics,

J.K.K.Nataraja Dental College, Komarapalayam, Namakkal District–

638183,Tamilnadu has done the dissertation titled “FRACTURE RESISTANCE

OF ENDODONTICALLY TREATED MAXILLARY INCISORS WITH

DIFFERENT POST AND CORE MATERIALS: A COMPARITIVE

EVALUATION” under my direct guidance and supervision in the partial fulfillment

of the regulations laid down by THE TAMIL NADU DR. M.G.R MEDICAL

UNIVERSITY, CHENNAI, FOR M.D.S BRANCH – IV CONSERVATIVE

DENTISTRY AND ENDODONTICS DEGREE EXAMINATION. It has not been

submitted (partial or full) for the award of any other degree or diploma.

Dr. J.V. Karunakaran. M.D.S,

Professor & Head, Department of Conservative Dentistry & Endodontics, J.K.K.Nataraja Dental College Komarapalayam, Namakkal Dist – 638183, Tamilnadu.

Dr. A. Siva Kumar. M.D.S,

Principal, J.K.K.Nataraja Dental College Komarapalayam, Namakkal Dist – 638183, Tamilnadu.

CERTIFICATE – II

This is to certify that this dissertation work titled “FRACTURE

RESISTANCE OF ENDODONTICALLY TREATED MAXILLARY INCISORS

WITH DIFFERENT POST AND CORE MATERIALS: A COMPARITIVE

EVALUATION” of the candidate DR. GANESHAMOORTHY.T with registration

number 241717101 for the award of MDS in the branch of CONSERVATIVE

DENTISTRY AND ENDODONTICS. I personally verified the urkund.com website

for the purpose of plagiarism check. I found that the uploaded thesis file contains from

introduction to conclusion pages and result and result shows ONE percentage of

plagiarism in the dissertation.

Guide & Supervisor Sign with Seal

ACKNOWLEDGEMENT

I take this opportunity to sincerely thank my post graduate teacher and my

guide Dr.J.V.Karunakaran.M.D.S, Professor and Head, Department of

Conservative Dentistry & Endodontics, J.K.K.Nattrajah Dental College, for his

academic and technical assistance, perseverance in motivating and supporting

me throughout my study period.

My sincere thanks to Dr.A.Sivakumar.M.D.S, Principal, J.K.K. Nattrajah

Dental College,who had helped with his advice and immense support throughout my

postgraduate curriculum.

I would like to express my sincere gratitude to Dr.N.S.Mohan Kumar.M.D.S,

Professor, Dr.S.Senthil Kumar.M.D.S, Reader, Department of Conservative

Dentistry & Endodontics J.K.K.Nattraja Dental College, for his valuable

suggestions, support and encouragement throughout my post graduate curriculum.

I extend my sincere thanks to Mr. Rajaganeshan, Chief Administrative

Officer, J.K.K.Nattraja Dental College & Hospital, for his constant support

throughout my study period.

I thank Dr.Satyanarayanan.M.D.S, Reader Dr.JayaprakashM.D.S, Senior

Lecturer, Dr.Ragavendran.M.D.S, Senior Lecturer, Dr.Chris Susan Abraham

M.D.S, Dr.C.S.Anagha M.D.S Senior Lecturer for their support, guidance and

constant encouragement throughout the completion of this work.

I am profoundly thankful to Mr. Muthukumar, in PSG Institute of

Technology, for helping in fracture resistance testing and I thank Dentcare Dental,

for guiding in processing the samples.

I extend my gratefulness to Mr. Ramakrishnan, our College Librarian’s for

their valuable assistance rendered during the course of the study.

I am thankful to Mr. Chinnarasu, Dental Technician, and our department

support staff for their help throughout my thesis.

My sincere thanks to Mr.M.Prasad Krishnan, for his guidance in

biostatistics. I thank Mr. Murali Sundar Chakra Printers, SPY Printers, Erode for

processing the dissertation.

I thank all my batchmates, colleagues, friends and family for their eternal

support. Above all, am thankful to God Almighty, to have given me the strength to

choose the right path and to have given these wonderful people in my life.

CONTENTS

S.No. INDEX PAGE No.

1. INTRODUCTION 1

2. REVIEW OF LITERATURE 7

3. MATERIALS AND METHODS 26

4. RESULTS 38

5. DISCUSSION 43

6. SUMMARY 61

7. CONCLUSION 62

8. BIBLIOGRAPHY 63

INTRODUCTION

Introduction

1

Endodontically treated teeth have been reported to be more susceptible to

fracture when compared to vital teeth. This necessitates adequate protection of

remaining tooth structure by proper restoration protocols. Excessive tooth structure

removal during endodontic therapy and subsequent dehydration of both coronal and

radicular dentin are principal factors which have been responsible for affecting the

fracture resistance of restored tooth structure after completion of endodontic

treatment procedure.The remaining dentin in a endodontically treated tooth should

be preserved as resistance to fracture depends primarily on remaining root dentin

thickness, especially in the buccolingual direction. (Sedgley and Messer in 1992)80

A number of reasons have been put forward for the tooth being susceptible

for fracture of root structure. This includes loss of tooth structure due to caries or

trauma, excessive removal of tooth structure during root canal preparation, the

dehydration of dentin subsequent to endodontic treatment, excessive radicular

dentinal structural loss during post space preparation, creation of excessive stress

during obturation and increased use of higher concentration of irrigants with

prolonged exposure times. This in a clinical situation would mean a reduction in the

long term survival rate, which is undesirable. The achievable target of endodontic

therapy should be reinforcement of the residual tooth structure in such a way that it

prevents untoward events in the long term. (Johnson M.E., et al in 2000)38

.

The anatomy of the root canal system and its variations, curvature of the

roots especially in posterior teeth pose a challenge to the clinician during preparation

of the root canal space, irrigant delivery, replacement and debridement in the apical

one third. In the case of curved canals this becomes even more difficult where in

order to access the apical third of the canal system and to achieve sufficient

Introduction

2

cleansing and debridement, a considerable amount of dentin in the coronal and

middle third of the root is removed which weakens the root structure and decreases

fracture resistance. (Sornkul E al in 1992)91

Earlier with hand instrumentation it was common practice to enlarge the

canal to three sizes from the first initial file to bind at the apical third of the root.

This enlargement allowed efficient cleansing and allowed the irrigants and

medicaments to reach the entire length of the canal system. The introduction of NiTi

hand instruments in endodontics almost two decades ago, improved preparations as

they were flexible. The most significant advantage was the predictable control of the

preparation. The alloy was resistant to corrosion, had the property of super-elasticity

and shape memory. With the advent of nickel titanium rotary instrumentation, things

changed and negotiation of even severely curved canals became much easier to

accomplish, was more complete and reduced the clinical working time. These rotary

instruments when used to prepare the canal exert considerable stresses in certain

areas resulting in formation of microcracks or craze lines which later predisposes the

tooth to vertical root fracture. These areas of most stress are mostly located in the

mid root canal wall area. It has been observed that lateral forces result in high stress

concentrations in radicular dentin in the coronal one-third of the root, and make the

teeth susceptible to fracture at the cemento enamel junction. There is a direct

proportional correlation between thickness of the root and the ability of the tooth to

resist lateral dislodging forces. The amount of remaining radicular and coronal

dentin in a tooth is directly proportional to the fracture resistance. (Lertchirakarn

V., et al in 2002)44

Introduction

3

A potential relationship between nickel titanium rotary instrument design and

the incidence of vertical root fractures has been reported. (Kim H.C et al in 2010)42

The geometry of the rotary instruments and their mechanical cutting action decide

the kind of difficulty and complications encountered during usage, as also the

operator training and skill.

Different types of fractures occur in roots of endodontically treated teeth and

can either be horizontal and vertical root fractures. Clinical studies have shown that

11% - 13% of extracted teeth with endodontic treatment done have been associated

with vertical fractures of the root (Fuss Z., et al in 1999)28. Craze lines and cracks

occur on the walls of the root canal which become areas of increased stress

concentration. These cracks can spread or extend slowly over a period of time to the

surface eventually resulting in a vertical root fracture (Yoldas O., et al in 2012)107.

Vertical fracture of the root is one of the serious complications of root canal

treatment procedure with a very unfavourable prognosis. This can occur before,

during, or after root canal obturation and most often leads to the removal of the

affected tooth. (Meister F et al in 1980)49

This has lead to various researchers looking to reinforce the structure of both

the crown and the root after the completion of endodontic treatment. The commonly

used root canal filling material is gutta percha in combination with a sealer. The low

elastic modulus of gutta percha presents little or no capacity to reinforce roots after

completion of endodontic therapy. (Ribero F.C., et al in 2008)64 Thus there is a

compelling need to develop materials and techniques to overcome the shortcomings

of current endodontic obturation materials and post endodontic restorations to

reinforce root structure post therapy. Coronal leakage after endodontic treatment

Introduction

4

procedure can be effectively prevented by use of intra orifice barriers. (Yavari H R.,

et al in 2012)106 This procedure involves placing additional material into the canal

orifices immediately after removal of the coronal portion of gutta-percha and sealer.

This also improves the fracture resistance of the root structure. (Roghanizad N.,

et al in 1996)70 Materials like resin modified glass ionomers, flowable composites,

and bonded amalgam can ideally be used as intra-orifice barriers. Swartz D B., et al

in 198395

stated that failure rates of endodontically treated teeth was almost double

in cases where the process of adequate post endodontic restoration has not been

followed. Newer generation of materials tend to improve the bond between radicular

dentin and the sealer and the sealer core interface which helps to increase the

fracture resistance and reduces ingress pathways. To reinforce the roots, the modulus

of elasticity of the root filling material should approximate that of radicular dentin.

(Williams C., et al in 2006)105 This presents the concept of a monoblock, which

aims at creating mechanically sound homologous units with radicular dentin.

This is easier said than done as the complexity of the canal system,

difficulties in access and cleansing present difficulties in predictably achieving the

target of a monoblock unit. Priming the radicular dentinal surface and creating a

bond between the sealer and dentin, sealer and core material would effectively

achieve this. A number of sealer and core materials have been formulated with the

aim of achieving this objective. The modulus of elasticity of the post, the filling

material and the sealer has to match that of radicular dentin so that the load stresses

are evenly distributed and borne by the components of the monoblock (Tay F.R.,

et al in 2007)96.

Introduction

5

Traditionally the rotary NiTi file systems were designed to be used in a

sequence and consisted of multiple rotary tools. Recently the advances in metallurgy

have seen introduction of newer file systems with a single rotary file which are

efficient. Also rotary files for use in reciprocating motion have been designed. A new

concept of endodontic file adjusting to the size of the canal and which works with

vibration and continuous irrigation, the self adjusting file system has been developed

and this system also prepares the canal system symetrically centered in the root

following the path of the canal limiting excessive removal of the radicular dentinal

structure. (Metzger Z, et al in 20)35 These single file systems have been based on

practicality, simplicity, reduce clinical working time and have been reported to

reduce the amount of stresses on the canal walls. They have also been recommended

and designed for a single use which tackles the issue of sterilization and cross

contamination.

The cast post and core method of post endodontic reconstruction has been

traditionally used and can be considered as gold standard. This technique has its own

limitations. There is a greater removal of radicular dentinal structure, need for

multiple clinical leading to more turnover time and has a elastic modulus which is

high compared to tooth structure. (200 Gpa) which can lead to fractures. (Sarkis-

Onofre R et al in 2014)85 Glass fiber posts have been used to restore

endodontically treated teeth, mainly because they are aesthetic, faster to execute and

have an elastic modulus near that of tooth structure (30-50 GPa).

For post preparations survival rates ranging from 71 to 100% for fiber posts

and 50 to 97.1% for metal posts have been reported. No difference in the survival

among different kinds of metallic posts were reported. No differences were reported

Introduction

6

between fiber and metal posts by most studies conducted. Studies also showed that

the longevity of the restored teeth is increased by remaining dentine height, number

of walls and ferrule. Post loss of retention was the reason for failure fiber posts.

Metallic post failures were mostly related to root fracture, post fracture or crown

or post retention loss. Metal based and fiber posts present similar clinical behavior

at short to medium term follow-up. Remaining dental structure and ferrule increase

the survival of nonvital teeth and long term analysis has been recommended.

(Malferrari et al in 2003)45

This study aims to comparatively analyse resistance to fracture of metallic

and fibre reinforced post and core preparations in upper central incisor teeth.

REVIEW OF

LITERATURE

Review of Literature

7

CampanellaV., et al in 201922 attempted to analyse the clinical fitting of

a cast metal post and core obtained by means of an intraoral optical scanning and

digital workflow. They noted that Customization of post-and-cores using computer-

aided-design and computer-aided-manufacturing (CAD-CAM) requires the scanning

of a pattern and the subsequent digital design. The case report describes the

production of a CAD-CAM customized post-and-core designed from an intraoral

scan and milled from a metal block. The use of an intraoral scanner for post-

endodontic rehabilitation could lead to a faster and more efficient CAD-CAM

customized post and core realization. The use of a high resistance material such as

metal is paramount in cases with high loss of coronal structure. The patient has been

treated with bisphosphonate for years. The risk of osteonecrosis of the jaw after

extraction was high.

Stankiewicz NR and Wilson in 199893 reviewed the literature regarding the

use of a ferrule for post and core preparations. They noted that a ferrule is a metal

ring or cap used to strengthen the end of a stick or tube. It has been proposed that the

use of a ferrule as part of the core or artificial crown may be of benefit in reinforcing

root-filled teeth. They observed that literature demonstrates that a ferrule effect

occurs owing to the artificial crown bracing against the dentin extending coronal to

the crown margin. Overall, it can be concluded that a ferrule is desirable, but should

not be provided at the expense of the remaining tooth or the root structure.

Robbins JW., et al in 200268 in their article aimed to provide a rationale for

the restoration of endodontically treated teeth. Treatment recommendations have

been made in the areas of post design, placement technique, cements, core materials,

and definitive restorations, based on a review of the clinical and laboratory data.


8

Fokkinga WA., et al in 200426 did a structured analysis of in vitro failure

loads and failure modes of fiber, metal, and ceramic post-and-core systems and

sought to aggregate literature data on in vitro failure loads and failure modes of

prefabricated fiber-reinforced composite post systems and to compare them to those

of prefabricated metal, custom-cast, and ceramic post systems. They found that

significantly more favorable failures occurred with prefabricated post systems than

with prefabricated and custom-cast metal post systems. The authors concluded that

the variable "post system" had a significant effect on mean failure loads and that the

fibre reinforced post systems more frequently showed favorable failure modes than

did metal post systems.

Aritopoulou II., et al in 20062 in their review of materials used in post and

core systems discuss a plethora of prefabricated post and core materials currently

available for the restoration of endodontically treated teeth. The materials presented

demonstrate a variety of mechanical properties and esthetic potential, while the

selection of the optimum post and core system depends upon clinical judgment and

the specific clinical situation.

A comparative study of fracture resistance of endodontically treated teeth

filled with Resilon and guttapercha in a in-vitro setting was done by Shetty R.R.,

et al in 200982 and they found that Resilon was superior and the results were

statistically significant. The weakest tooth in terms of fracture resistance were those

that belonged to the guttapercha without sealer. The authors also note that in this

clinically relevant comparison between Resilon and guttapercha, the monoblock

concept is important not only to resist microbial leakage through the material, but

also holds the root as a single unit thereby increasing fracture resistance.


9

A new concept in endodontic files, the self adjusting files was discussed by

Metzger Z., et al in 201035 and they compared it with the rotary nickel titanium file

systems. This was a single file system which was designed as a hollow thin

cylindrical nickel titanium lattice that adapts to the cross section of the root canal.

This file is used after preparation of the canal to # 20 k-file. It was operated with a in

and out motion with vibration and continuous irrigant flow which is also activated

by vibration. The self adjusting file is operated with a transline vibration resulting in

circumferential pressure which allows the files abrasive surface to remove a thin

uniform hard tissue layer from the entire root canal surface resulting in a canal with

similar cross-section but with larger dimensions. The straightening of the root canals

was also reduced due to lack of a rigid metal core and high pliability. This concept

allowed the file to retain the original shape of the root canal both in cross-section as

well as longitudinally. The author claims that the file has got a high amount of

mechanical endurance and failure when it occurs happens as small tears in the metal

lattice network. They proposed this as a method of overcoming the many

shortcomings of the rotary nickel titanium file systems.

The mechanical properties of the self adjusting files system was evaluated by

Hof R., et al in 201035 and they observed that this file system was mechanically

sound and was able to endure the canal preparation procedure with very little loss of

efficiency under the recommended operating conditions. They noted that the irrigant

flow was within the confines of the canal and did not cross the apical constriction.

The reduction in efficiency was found to be about 40% after continuous operation

for 30 minutes. They also found that the self adjusting file was elastically

compressible from a dimension of 1.5mm to the size of a #20 k-file and that


10

compressing the self adjusting file creates a circumferential force which coupled

with in and out vibration and rough surface removes dentin from the canal walls.

The current developments in rotary root canal instrument technology and

clinical use was reviewed by Peters O.A., et al in 201060. The review summarised

clinical and laboratory findings for several current instruments with some guidelines

and usage parameters. This discuss the development of the nickel titanium alloy

developed first for the U.S. navy which has got a shape memory and super elasticity.

They compare it with steel instruments which can withstand a maximum of 3%

elastic deformation while Nickel titanium instruments can withstand a 7% elastic

deformation without permanent damage or plastic deformation. Steel can also

withstand upto 20 bending cycles whereas nickel titanium can be bent upto 1000

times and the difference is due to the atomic structure of the two alloys. They

discuss in detail the rotary instrument design, usage and fracture prevention of

nickel titanium instruments, and usage parameters and strategies. They observe that

clinical studies on the rotary instruments are sparse and that the results of the current

studies indicate that their use leads to a reduced incidence of gross preparation errors

and possibly improved clinical outcomes.

Vallabhaneni S., et al in 2012103 in their review of single file rotary

endodontic systems observe that the recently introduced files such as self adjusting

file, twisted file, wave one, protaper next and reciproc etc., claim to be able to

completely prepare and clean the root canals with only use of a single instrument

after the preparation of a glide path. This reduces clinical time, reduces instrument

fatigue, cost effective and reduces cross contamination. The advent of nickel

titanium rotary files removes the smear and debris effectively even from curved root


11

canals. They suggest further clinical studies of these single file systems and discuss

in detail the individual method and technique of use of these systems.

In a in-vitro study of comparison of fracture resistance of roots of

endodontically treated teeth using different root canal filling materials Ravi N., et al

in 201261 found that the highest fracture resistance of almost more than 75% was

found in the resilon obturated roots when compared with other filling materials

(guttapercha) independent of the filling technique used. The authors suggest long

term clinical studies which are evidence based to assess whether resilon reduces the

vertical root fractures clinically.

Rippe M.P., et al in 201347 evaluated the effect of the root canal filling

methods on resistance to root fracture. They also used finite element analysis to

assess the expansion of the root canal sealer in two different filling techniques. The

authors observed that vertical root fractures have been the cause of fracture of many

root canal treated teeth and are most likely caused by the propagation of small

critical and less pronounced defects rather than the force exerted during the filling

procedure or the canal preparation. These fractures occur in the area of increased

occlusal stresses during mastication that originate in small defects and propagate

through small and constant impulses which result in root fracture. They also

discussed the role of the sealer expansion as one of the cause of stress concentration

in the root canal which would weaken the root. They found that the filling technique

influenced the fracture strength but did not influence the fracture type. The finite

element analysis revealed that greater the sealer thickness the greater the

concentration of the stresses in the root canal.


12

Capar I.D, et al in 201413 in their evaluation of the fracture strength of roots

instrumented with self adjusting file and the protaper rotary systems concluded that

instrumentation with both the systems did not change the fracture strength of the

standardized roots with respect to their cross-sectional diameter and weight within

the limitation and standardization conditions of this study. This study was a in-vitro

study on mandibular premolars with straight canals. They observe that

standardization of the samples is an important step and a lot of variables could affect

the results of the study. The filling of the canals with a adhesive sealer did not

significantly strengthen the roots compared with instrumented but not filled canals.

Ertas H et al in 201425 evaluated the effects of the physical and

morphological properties of roots on the fracture resistance. The authors observed

that for study of fracture resistance of roots standardization is very important and the

roots if not distributed among the groups equally the variables could possibly affect

the results. This leads to large standard deviations within the groups rendering the

results meaningless prompting the researchers to use more number of samples. This

study principally aimed to determine how the physical properties of weight volume

and density and morphological properties of mesio-distal dimensions affect the

fracture resistance and the important criteria for standardization in fracture

resistance studies. They concluded that the volume or weight of the root as the most

important determining factor in root fracture and that the roots should be equally

distributed according to their volumes or weights rather than the morphological

dimensions which cannot closely simulate the entire strength of the root.

The fracture resistance of roots instrumented with three different single file

systems in curved root canals of the mesial root of maxillary molars was studied by


13

Nur B.G. et al in 201557. They hypothesized that the instrument design, kinematics

and mechanical behaviour of the single file rotary systems affect the extent of

dentinal defects which subsequently translates into vertical root fracture

susceptibility. They compared three file systems namely Waveone, Reciproc and

Oneshape which are single file Niti systems. They concluded that the oneshape

rotary file system enhances the fracture strength of the roots as compared with the

control group within the limitations of this study. The Waveone and Reciproc rotary

file systems were found to be similar to the control group. All the three single file

systems had different designs and kinematics.

Muttlib N.A et al in 201553 in their study compared the adaptation of fiber

reinforced composite post system and cast post-and-core and found that both

cast post-and-core and fiber reinforced composite post systems showed similar

adaptation to the canal.

Mankar S et al in 201546 in their invitro assessment of the fracture

resistance of teeth restored with cast posts and cores with or without cervical ferrule

and cemented with zinc phosphate, glass ionomer, or resin cement. The authors

concluded that the inclusion of ferrule in tooth preparations for posts increased the

fracture resistance regardless of the luting agent.

Dastjerdi R et al in 201563 in their study compared the fracture resistance

of endodontically treated maxillary central incisors restored with different posts and

cores. And found that within the limitations of this study fiber reinforced posts

showed acceptable fracture resistance with favorable fracture patterns for

reconstruction of upper central incisors.


14

Sreedevi S et al in 201592 an invitro study on the effects of post-

core design and ferrule on the fracture resistance of endodontically treated maxillary

central incisors observed that endodontically treated teeth have significantly

different physical and mechanical properties compared to vital teeth and are more

prone to fracture. The study aimed to compare the fracture resistance of

endodontically treated teeth with and without post reinforcement, custom cast post-

core and prefabricated post with glass ionomer core and to evaluate the ferrule effect

on endodontically treated teeth restored with custom cast post-core. Reinforcement

of endodontically treated maxillary central incisors with post and core, improved

their fracture resistance to be at par with that of endodontically treated maxillary

central incisor, with natural crown. The fracture resistance of endodontically treated

maxillary central incisors is significantly increased when restored with

custom cast post-core and 2 mm ferrule. The authors concluded that with the use of

a 2 mm ferrule, teeth restored with custom cast post-core had a significantly higher

fracture resistance than teeth restored with custom cast post-core or

prefabricated post and glass ionomer core without ferrule

Shamseddine L et al in 201681 investigated the influence of a contra bevel

on the fracture resistance of teeth restored with cast post and core and found that in

the presence of a ferrule and a crown in the anterior teeth, adding a secondary

ferrule to the cast post and core will not increase the resistance to fracture.

Shamseddine L et al in 201681 in a randomized clinical trial assessed the

influence of impression technique on the fabrication of cast metal posts. Direct and

indirect techniques are used for intra canal impression and fabrication of cast metal

posts. However, whether those techniques affect the accuracy of cast metal posts is


15

unknown. The purpose of this randomized clinical trial was to evaluate the accuracy

of cast metal posts depending on tooth position and impression technique. Both of

the intra canal impression techniques resulted in cast posts that were shorter than the

impressed post space. The authors concluded that the discrepancy was greatest for

the indirect technique. Nevertheless, all posts were considered clinically acceptable

and were cemented.

Upadhyaya V., et al in 2016100 in their in vitro study to evaluated the effect

of design and material of post with or without ferrule on stress distribution using

finite element analysis. The highest amount of stress was seen in the cervical region.

Overall, the stress in the tapered post system was more than the parallel one.

FRC post and composite resin core recorded minimal stresses within the post but the

stresses transmitted to cervical dentin were more as compared to other systems.

Minimal stresses in cervical dentine were observed where the remaining coronal

dentin was strengthening by ferrule. The authors concluded that a rigid material

with high modulus of elasticity for post and core system creates most uniform stress

distribution pattern. Ferrule provides uniform distribution of stresses and decreases

the cervical stresses.

Schwendicke F., et al in 201678 in their study assessed the cost effectiveness

of a metal and fiber post systems to provide post-retained restorations. The risk of

tooth loss and other complications differs between different post systems, as do the

initial treatment costs. They assesses the cost-effectiveness of cast metal, preformed

metal, glass fiber, and carbon fiber post-retained restorations. The authors concluded

that patients not willing to invest additional money for longer tooth retention,

preformed metal seemed most suitable to retain restorations. For payers with


16

additional willingness to pay, glass fibre post seemed suitable. Cast metal was only

cost effective under very high willingness to pay. Carbon fibre is not

recommendable on the basis of their cost effectiveness.

Kar S., et al in 201739 in their study compared the effect of ferrule length

on fracture resistance of endodontically treated mandibular premolar teeth, restored

with prefabricated glass fiber post luted with resin cement, composite core and a

full coverage metal crow. A ferrule has been described as a key element of tooth

preparation when using a post and a core. It is a vertical band of tooth structure at

the gingival aspect of crown preparation. It lessens the stress transmission to the

root which is due to forces from posts or bending during seating of the post. The

incorporation of a ferrule can help to withstand the forces of occlusion, preserve the

hermetic seal of the luting cement, and minimize the concentration of stresses at the

junction of post and core. The authors observed that the results of this study showed

that fracture resistance of endodontically treated teeth increases as ferrule length

increases.

MarchionattiA M E., et al in 20178 in their systematic review was to

compare the clinical performance and failure modes of teeth restored with intra

radicular retainers. Evaluated retainers were fiber (prefabricated and customized)

and metal (prefabricated and cast) posts, and follow-up ranged from 6 months to 10

years. Most studies showed good clinical behavior for evaluated intra-radicular

retainers. Reported survival rates varied from 71 to 100% for fiber posts and 50 to

97.1% for metal posts. Studies found no difference in the survival among different

metal posts and most studies found no difference between fiber and metal posts. Two

studies also showed that remaining dentine height, number of walls and ferrule


17

increased the longevity of the restored teeth. Failures of fiber posts were mainly due

to post loss of retention, while metal post failures were mostly related to either root

fracture, post fracture and crown and/or post loss of retention. In conclusion, metal

and fiber posts present similar clinical behavior at short to medium term follow-up.

Remaining dental structure and ferrule increase the survival of restored pulpless

teeth. The authors felt that studies with longer follow up would throw more light on

the issue.

Savychuk A., et al in 201777 compared the impact of the post type (glass

fiber post-and-resin core or cast post-and-core) along with the ferrule effect on the

stress fields generated in endodontically treated mandibular lateral incisors and

canines using a finite element analysis. Maximum principal stresses in dentin were

highest in incisors, with a ferrule. Stress parameters in composite resin core in both

incisors and canines were critically close to the tensile failure limit of

the core material. Cast post-and-cores cemented in incisors without a ferrule

accumulated the highest stresses, exceeding the tensile failure limit of resin-

modified glass ionomer cement. They also observed that the tooth preparations with

a ferrule led to a remarkable rise in stress in the dentin of mandibular incisors but

favored the mechanical integrity of the restoration.

Tsintsadze N et al in 201797

assessed the push out strength, the cement

layer thickness and the interfacial nanoleakage of prefabricated fiber posts,

CAD/CAM fiber posts and metal cast posts cemented into oval-shaped root canals.

Sections from six roots per group were used to measure the cement thickness and

subsequently for the thin-slice push-out test, whereas the sections from the

remaining four teeth were assigned to interfacial nanoleakage test. The cement


18

thickness around the posts was measured in micrometers on the digital images

acquired with a digital microscope using the Digimizer software. Thin-slice push-

out test was conducted using a universal testing machine at the crosshead speed of

0.5 mm/minute. The interfacial nanoleakage was observed under light microscope

and quantified by scoring the depth of silver nitrate penetration along the post-

cement dentin-interfaces. CAD/CAM-fabricated fiber posts achieved retention that

was comparable to that of cast metal posts and significantly higher than that of

prefabricated fiber posts. The cement layer thickness around CAD/CAM-fabricated

fiber posts was significantly lower than around prefabricated fiber posts, but higher

than that around cast metal posts. No differences were observed in interfacial

nanoleakage between CAD/CAM fabricated and prefabricated fiber posts, while

nanoleakage recorded in cast metal posts was significantly lower. CAD/CAM

fabricated fiber posts could represent a valid alternative to traditionally used posts

in the restoration of endodontically-treated teeth with oval or wide root canals,

offering the advantages of better esthetics, retention, and cement thickness values

that are comparable to cast post and cores.

Pantaleon S., et al in 201873 in this in vitro study examined the effect of

varying residual axial wall heights, residual coronal tooth structure, and the absence

of 1 proximal axial wall on the fracture resistance and failure mode of

endodontically treated teeth restored with metal posts. The authors found that the

specimens with 2-mm ferrule of uniform height were more resistant to fracture than

specimens with a 2-mm ferrule and 1 missing interproximal wall. An increased wall

height of 3 or 4 mm was associated with a significant increase in fracture resistance

and can compensate for the missing interproximal wall.


19

Khiavi H A S., et al in 201841 in their study compared the fracture strength

of endodontically treated maxillary central incisors restored with nickel chromium

(Ni-Cr) and non-precious gold alloys. As fiber posts are not recommended for teeth

under lateral loads, a new alloy containing >80% copper was introduced with a

modulus of elasticity closer to that of dentin and easier preparation. Based on the

results of this study the authors concluded that the fracture strength of teeth restored

with cast non precious gold post and cores was significantly higher than that of

teeth restored with cast nickel chromium post and cores. Due to adequate

mechanical properties, non-precious post and cores seem to be a suitable choice for

restoration of severely damaged anterior teeth, provided that other properties are

proven to be acceptable.

Nokar S., et al in 201856 investigated the stress distribution of

different post and core materials in radicular dentin by three-dimensional finite

element analysis method. The authors were able to detect two stress concentration

sites with the first group showing the lowest stress levels in the cervical region,

while the stress levels detected in the second group were higher than those in the

first group and lower than those found in the third group. Fiber-reinforced posts

induced a higher stress concentration between the middle and cervical thirds of the

root compared to other posts. Based on the observations the authors concluded that

since cast posts induce lower stresses in dentin, they are recommended for clinical

use. Fiber reinforced posts and all ceramic restorations caused the maximum

stresses in dentin.

Hendi A R., et al in 201934 in an vitro study compared the retention of posts

and cores fabricated using full-digital, half-digital, and conventional techniques.


20

They assessed the accuracy of these techniques in terms of the presence of apical

gap. They observe that Conventional cast metal posts and cores are fabricated using

direct and indirect techniques, both of which need impression materials and

considerable laboratory time and work scheduling and that Digital techniques have

the capacity to substitute for conventional methods in fabricating the posts and

cores but their accuracy remains unknown. The apical gap of each post in the canals

was defined with parallel digital radiography. The data were analyzed using the

Kruskal-Wallis test (α=.05) and Mann-Whitney test at the adjusted α=.016. They

came to the conclusion that the conventional technique was more accurate and

resulted in higher retention than both the full and half digital techniques. However,

the retention and gap of all the posts fell within clinical guidelines recommended.

Alkhatri R., et al in 20191 measured the fracture resistance and failure

modes of endodontically treated teeth restored with three different computer aided

design or computer aided manufacturing (CAD/CAM) fabricated post and core

systems. Fracture of the post and core or fracture of the root above the level of the

acrylic resin was considered as a favorable fracture, while nonfavorable fractures

were those where the root fracture occurred below the level of the acrylic resin. The

authors found that there was no significant difference between metal and zirconia

samples in terms of nonfavorable fracture, and that PICN material can be used in the

fabrication of post and core assemblies using CAD/CAM.

In their retrospective clinical study Martino N., et al in 201948 evaluated the

clinical survival rate of custom fabricated cast metal and prefabricated (both metal

and fiber reinforced composite resin post) post and cores as a function of patient

and restoration related variables. They found that the mean survival time for each


21

group to be 12.0 years for fiber reinforced composite resin posts, 11.8 years

for cast metal post-and-cores, and 10.2 years for prefabricated metal posts. Although

the mean survival time differed by 1.8 years among groups, with prefabricated metal

posts having a slightly higher risk of failure, this effect was not statistically

significant (P=.067). The effect of post type also failed to reach significance when

controlling for patient demographics and post position in a Cox proportional hazards

analysis (P=.106). However, the Cox model did show that survival was associated

with tooth position (P=.003), cement (P=.021), and type of restoration (P<.001).

Fontana PE., et al in 201927 investigated the influence of ferrule thickness

on fracture resistance after mechanical cycling of teeth restored with different

intracanal posts. A thicker ferrule statistically increased the fracture resistance only

for cast post and core when it was at least 1 mm thick, despite causing more

unfavorable failures. The authors suggest that the ferrule thickness should be

considered when choosing different intracanal posts, to reduce the occurrence of

unfavorable failures. In the absence of a ferrule, the use of a cast post and core

presents more favorable failures, and in the presence of a 1 mm thick ferrule, the use

of a glass fiber post seemed a better clinical decision.

Schwindling F S., et al in 201979 proposed the concept and feasibility of a

three dimensional guided removal and preparation of dental rot posts. They

presented a novel method to remove glass fiber reinforced composite root posts in a

minimally invasive way while simultaneously shaping the canal for a new post

endodontic restoration. A conebeam computed tomography scan was imported into

conventional implant-planning software and matched to a stone cast of the intraoral

situation. Position, length, and axis of the future post were planned virtually. Based


22

on this planning, a tooth-supported splint was three dimensionally printed. This

splint allowed use of a 2.2-mm spiral drill for removal of the fractured post and

shaping of the root canal for a new cast post-and-core. This metal post-and-core was

adhesively cemented and prepared for a zirconia single crown veneered in the labial

aspect. This method currently requires use, ionizing three dimensional imaging.

Additional refinements to this approach can be made regarding spiral drill design

and coating as well as regarding the post-and-core workflow. The authors concluded

that guided post endodontic management is feasible. More research is needed to

balance higher radiation doses against therapeutic success.

Byakova SF., et al in 201911 compared the accuracy of cone beam

tomography ex vivo and in vivo for the detection of artificially created large and

small vertical root fractures in extracted teeth restored with post and core. They

found that the width of the fracture affected the detectability of vertical root

fractures invitro in teeth with metal cast post cores. Root fractures in vivo was less

detectable because of low image quality, making the assessment of sound tooth

tissue impossible.

Ozturk C., et al in 201958 compared the fracture resistance and fracture

mode of endodontically treated thin walled teeth restored with different post

systems. Restoration of the teeth with extensive root canals with different post

systems is a challenge for clinicians. Evaluation of these systems is important for

clinical success. The authors observed that the type of fracture encountered with

fibre posts mode would permit repair of the tooth and was favourable.

Bacchi A., et al in 20193 evaluated the influence of ferrule and the post type

on the fracture strength and stress distribution in premolar teeth. They were prepared


23

with a cast post and core or a glass fiber post with a core with or without a ferrule

and fracture strength and failure patterns assessed. Stress distribution was evaluated

using finite element analysis. The authors concluded that the Ferrule effect was

shown to be more important than type of post used in the analysis. Both posts

showed potential to withstand functional loads irrespective of presence of ferrule.

Bakirtzoglou E., et al in 20194 in their in vitro analysis of the retention and

resistance form of complete coverage restorations with two different types of cast

post and core designs. The authors concluded that the standard cast post and core

design with a 2 mm of ferrule height offers superior resistance, although not

statistically significant (p=0.061), when compared to the core design encircling the

axial wall ferrule. Both cast post and core designs offered equal retention with

different failure modes during decementation.

Sary SB., et al in 201976

studied the effect of technique of restoration of the

fracture resistance of endodontically treated teeth with flared root canals. This study

was done in anterior teeth and compared the impact of post and core systems on

resistance to fracture of endodontically treated anterior teeth with flared root canals

and to assess their fracture pattern. The authors observed that the resistance to

fracture of wide root canals can be enhanced by using one piece CAD-

CAM post and core as an alternative to the use of either glass fiber post relined with

composite resin increasing the thickness of luting cement or the use of cast post and

core system. They also noted that as this was an in vitro investigation and further in

vivo studies are needed to confirm the same.

Haralur S B., et al in 201831 evaluated the efffect of multiple fiber

reinforced composite and Ni-Cr cast posts on the resistance to fracture of


24

endodontically treated teeth with wide root canals. The endodontically treated teeth

with thin remaining radicular dentin thickness are inherently predisposed to fracture.

Therefore it requires the proper selection and the execution of post and core

technique used. The posts were cemented with self-adhesive resin cement and

subsequently restored with full veneer metal crown. The restoration of

endodontically treated teeth with larger canals by multiple fibre reinforced

composite and metal posts provides substantially higher fracture resistance in

comparison to wider single post.

Carvalho M A., et al in 201814 in this critical present a survey of the current

knowledge on adhesive approaches to restore endodontically treated teeth with and

without extensive coronal tissue loss. Adhesive procedures have changed the way to

restore endodontically treated teeth. It started with the shift from cast post and core

to fiber post. The original focus on strength also shifted towards failure modes,

revealing that catastrophic failures are still a concern when restoring endodontically-

treated teeth even with fiber posts. As an alternative, postless approaches have been

proposed in order to improve the chances of repair. The preservation of tooth

structure of endodontically treated teeth is paramount. Partial versus full coverage of

the treated tooth, the role of the ferrule, the post type effect on catastrophic failures

and postless alternatives as endocrowns and postless buildups are reviewed. There is

a consensus that the remaining tooth structure plays an important role in tooth

survival, although the current literature still is contradictory on the influence

of post type on root fractures as well as the benefits of avoiding a post or partially

restoring a tooth. More clinical studies should be carried out with the modern

postless adhesive alternatives to conventional approaches.


25

Munaga S., et al in 201852 in their comparative clinical evaluation of

composite overcast gold post and core buildups in endodontically treated teeth

observe that the management of non-vital teeth includes endodontic treatment and

restoration followed by post and core restoration in selected cases. And conducted

the present study to compare the indirect cast post, and core buildup with direct

composite post build up in patients. The authors concluded that both composite

post buildup and cast gold post and core build-up exhibited similar properties and

therefore have recommended both of these techniques for clinical use.

Haralur S B., et al in 201931 in their study compared the teeth restored with

custom-made cast metal posts and cores cemented with different luting agents in

terms of coronal microleakage after thermocycling. The apical seal provided by a

root canal filling may be breached via coronal leakage. The authors observed that in

this study a complete coronal seal was not achieved with any of the luting agents.

The highest and the lowest degree of microleakage was by zinc phosphate and

Panavia luting agents, respectively.

MATERIALS AND

METHODS

Materials and Methods

26

ARMAMENTARIUM

Collection of teeth

1. Disposable gloves (Dispodent, Chennai)

2. 2% Thymol solution (Alpha chemicals, Maharastra, India)

3. Normal saline solution (Nirlife Health Care, Nirma products, India)

4. Vented labelled glass bottles

5. Tissue forceps (GDC Fine Crafted Pvt Ltd, Hosiarpur)

6. Large bore needles

Selection & standardization of samples

1. Stainless steel trays (GDC Fine Crafted Pvt Ltd, Hosiarpur)

2. Glass beakers

3. Ultrasonic scaler unit (Woodpecker)

4. Illuminated Magnifying Lens

5. Electronic weighing Scale

6. Vernier Calipers Digital

7. Diamond disc (AXIS,SYBRON ENDO, Kevakarr group, Denaher USA)

8. Indelible marker pen bold and fine (Camlin)

9. DG-16 Endodontic probe (Dentsply Maillefer, Ballaigues, Switzerland)

10. Operating microscope (AM-3000 Series, China)

11. Stainless steel tweezers(GDC Fine Crafted Pvt Ltd,Hosiarpur)

12. RadioVisiography unit (Skanray Technologies Pvt Ltd, India)

13. RVG analysis software

Canal preparation

1. Size 8, 10, 15 K file of 21mm length (Dentsply, Maillefer, Ballaigues,

Switzerland) Endo block (Dentsply Maillefer, Ballaigues, Switzerland)


27

1. X-smart plus (Dentsply Maillefer, Ballaigues, Switzerland)

2. 28 gauge side-vent needle (Prime dent)

3. 5ml syringe with leur-lock needle (Dispovan, Hindustan Syringes and

Medical Devices Ltd, Faridabad, India)

4. 5ml, 10ml Unolock Syringe (Hindustan Syringes and Medical Devices Ltd,

Faridabad, India)

5. Endoprep RC (Anabond Stedman Pharma Research, India)

Irrigating solutions

1. Normal saline (Nirlife Health Care, Nirma products, India)

2. 5% Sodium Hypochlorite solution (Nice chemicals Pvt Ltd, India)

3. Sterile Distilled water (Ives drugs, Pvt Ltd, India)

4. 17% EDTA solution (pulpdent corporation, USA)

Obturation of samples

2. Lentulospiral size 25 (Mani Inc, Tochigi, Japan)

3. Hand spreaders 21mm size:15-40 (Mani Inc, Tochigi, Japan)

4. AH plus resin sealer (Dentsply Maillefer, Ballaigues, Switzerland)

5. Gutta percha points and paper points 2%,4% ,6% (Dentsply Maillefer,

Ballaigues, Switzerland)

6. Mixing pad and agate spatula (GC Corporation, Tokyo, Japan)

7. Spirit lamp (GDC Fine Crafted Pvt Ltd, Hosiarpur)

8. GP condenser (Dispodent , India )

9. GP cutter (Generic)

10. Cotton holder

11. Stainless steel tray (GDC Fine Crafted Pvt Ltd, Hosiarpur)

12. Heat carrier Touch N Heat (Sybron Endo, Kavo Kerr, Germany)


28

Post space preparation

1. Reamers (Mani Inc, Tochigi, Japan)

2. Files (Mani Inc, Tochigi, Japan)

Fabrication of post and core

1. Air rotor unit (NSK, Nakanishi INC, Tochigi, Japan)

2. Crown preparation kit (Diatech, Coltene Whaldent, Pvt Ltd, Mumbai)

3. Mouth mirror (GDC Fine Crafted Pvt Ltd, Hosiarpur)

4. Probe (GDC Fine Crafted Pvt Ltd, Hosiarpur)

5. Tweezer (GDC Fine Crafted Pvt Ltd, Hosiarpur)

6. Stainless steel tray (GDC Fine Crafted Pvt Ltd, Hosiarpur)

7. Fornax centrifugal induction casting machine (BEGO, Canada)

8. Phosphate bonded investment material (Adantatec)

9. Laser sintering machine (SISMA MYSINT 100, S.p.A. via dell'Industria,

136013 Piovene Rocchette (VI) Italy)

10. Geo crowax pattern material, Modelling wax (Renfert, Hilzingen, Germany)

11. Inlay wax Medium, Dental inlay casting wax, GC corporation, Tokyo, Japan)

12. Luxacore, (DMG Dental Milestones Guaranteed, Germany)

13. Reforpost, Angelus (Dental Avenue India Pvt Ltd, Mumbai)


29

Luting procedure

1. Cementation media type I Glass ionomer luting cement (Fuji GC corporation,

Tokyo, Japan)

2. Rely x (U200Self adhesive resin cement, 3M ESPE)

3. Mixing pad (GC Corporation, Tokyo, Japan)

4. Agate spatula (generic)

Preparation for Fracture testing

1. Sterile self sealing pouches (AK Product; West Bengal; India)

2. Base former unit – custom stainless steel (1.5” X 1.5” X 1.5”)

3. Epoxy resin polymer and monomer (ROTEX Roto Polymers And Chemicals

Orakkadu Village Chennai, India)

4. Emery paper (3M 100,180,400)

5. Storage containers (genric)

6. Mounted 3mm diameter Stainless Steel Tip or fracture testing

7. Stainless steel millimetre scale

8. Wax knife and carver set (GDC INDIA)

9. White soft paraffin (Medisan, Trichy, India)

10. Sticky wax (DPI Model Cement,Dental products of India, Mumbai)

11. Stainless steel wire - 19 Gauge (Sendent, Salem, TN)

12. Bunsen burner


30

Fracture testing

1. Universal testing machine (Zwick Roell Z010,Germany)

2. Storage media (SonyDVD-RW. Sandisk Ultra, Sandisk)

3. Digital SLR camera (Canon EOS 1300D)

Fracture strength analysis and tabulation

1. HP and DELL computing systems

2. Zip lock covers(5cmx5cm)

3. Storage boxes for individual groups

4. Magnifying loupe with illumination

5. Observation sheets

6. Software for fracture recording and analysis (Zwick Roell, 2125 Barrett Park

Drive, Suite 107 44 Kennesaw, GA, USA)

Fracture type analysis and tabulation

1. Magnifying loupe – Illuminated (Generic)

2. Observation sheets.

Statistical Analysis

1. SPSS Version 16.0 software for statistical analysis.


31

MATERIALS AND METHODS

1. Collection of teeth:

Seventy two extracted human permanent maxillary central incisor teeth were

collected and stored in isotonic saline solution for a maximum of 72 hours.

Sufficient protocols for infection control as per OSHA and CDC guideline

regulations in collection, storing, sterilization and handling were followed.

2. Selection of samples:

Teeth with mature and intact root apices were selected for the purpose of the

study. Teeth with gross destruction, restorations and those that were treated

endontically were discarded. They were then observed for presence of cracks under

magnification and those with such damage were excluded. The teeth thus selected

were cleansed ultrasonically and stored in normal saline solution at 4°C until use. A

total of forty eight teeth were selected for the purpose of the study.

3. Standardization of samples

The teeth which confirmed to the inclusion criteria were kept moist with

normal saline throughout the experimental procedure to avoid dehydration. The

mesiodistal and buccolingual diameters of the selected teeth at the level of the

cemento enamel junction was then tabulated with the help of digital Vernier

callipers. The samples were then weighed using a precision weighing machine and

the results tabulated. The samples were evenly distributed based on their weights

across the six experimental and control groups (n=8). The selected teeth were then

rinsed with distilled water and stored in normal saline at 4°C in separate glass

bottles.


32

4. Preparation of the Sample:

Access preparation was done and the working length was determined by

passively placing a size 15K file (Dentsply Maillefer, Ballaigues, Switzerland) into

the canal until the tip was visualized at the apical foramen using a magnifying loupe

and was adjusted to the apical foramen. Then the actual canal length was measured

and working length was calculated by subtracting 0.5mm from this measurement

and recorded for each sample.

5. Root Canal Preparation Technique

Canal preparation was done using hand files to a master apical file size of 40

using step back technique. 3% Sodium hypochlorite irrigation (8 ml) was used as

initial rinse during the cleansing and shaping of the canal system. The canal systems

of the experimental groups were prepared with hand files with care not to remove

excessive dentin.

6. Final Rinse of Samples

Subsequent to the canal preparation the samples were irrigated with a final

rinse of 5ml of the irrigant solution. 5ml of 17% EDTA was delivered using a 28-

gauge side vent needle (Neo endo). The exposure time of the final rinse solution was

three minutes. After the completion of three minutes a post-final rinse irrigation of

5ml of distilled water was done to flush out the remaining final rinse irrigant from

within the canal system.

7. Obturation of the samples

The canals were then dried and then coated with a sealer using a

lentulospiral. The roots were obturated using the cold lateral condensation technique


33

using gutta-percha points (2%) with a zinc oxide eugenol sealer. Excess gutta-percha

was removed using a gutta-percha cutter and entrance filling done with zinc oxide

eugenol cement. The filled samples were then stored at 24 degree Celsius. The

quality of root canal fillings were confirmed with radiovisiography. The samples

were then stored at 37°C at 100% relative humidity for 72 hours. Each group was

processed and stored separately for further analysis.

8. Post space preparation

With the use of a diamond disc (Mani Inc, Japan), the teeth were decoronated

3mm from the deepest point of cemento enamel junction by comparing mesial and

distal surfaces using, at a level corresponding to the clinical gingival margin Digital

Vernier Caliper. After decoronation, one fourth of length of entire samples were

marked using marker and the gutta percha has been removed using Touch N Heat

device.(Sybron Endo). The walls were cleared of the sealer using hedstrom files and

a size-1 peeso reamer with care not to remove radicular dentin. The samples were

assessed using radiovisiography for consistent finish and gutta-percha removal

from within the canal system.

9. Crown preparation

Crown preparation was done using TF–12 flat end tapered fissure bur (SS

White burs) with the tip diameter of 1mm around the finish line, core ferrule was

given using thin tapered fissure burs. A anti rotation notch was given for a depth of

about 2mm using Flat end tapered fissure bur on the thickest portion of the root to

prevent the rotational displacement of the cast post preparation.


34

10. Indirect Pattern Procedure For Cast Post And Core

In all groups, the excess gutta percha was removed using TOUCH N HEAT

(Sybron Endo, Kavo Kerr, Germany) after removal of the entrance filling. The post

space preparation was refined using Hedstrom files, Reamers and size 1 Peeso

reamers. A minimum apical seal of 5 mm of gutta-percha filling was retained. The

apical end of the post space preparation was assessed, gauged and standardised to a

specific width. The walls were cleansed so no sealer remained and sealed with

cotton plugs and stored.

14. Fabrication Of Cast Post And Core

GROUP I (ORDEN ALLOY POST AND CORE)

Direct technique was used to fabricate a post and core pattern using a

prepared stainless steel sprue former (18 g) with a medium Inlay wax (Dental inlay

casting wax, GC). The core height of all samples in the group was standardized to

3mm. A separating media was used to aid the easy removal and insertion of the

pattern. Subsequently after debubblizing and investing the pattern was cast (BEGO

Induction casting machine) with Non precious gold alloy (Orden alloy) using a lost

wax technique.

GROUP- II (GOLD ALLOY POST AND CORE)


prepared stainless steel sprue former (18 g) with a medium Inlay wax (Dental inlay

casting wax, GC). The core height of all samples in the group was standardized to

3mm. A separating media was used to aid the easy removal and insertion of the


35

pattern. Subsequently after debubblizing and investing the pattern was cast (BEGO

Induction casting machine) with gold alloy (20 carats) using a lost wax technique.

GROUP -III (COBALT CHROMIUM POST AND CORE)


prepared sprue former (18 g) with a modeling wax (Geo Crowax, Renfert, Hilfingen,

Germany). The core height of all samples in the group was standardized to 3mm. A

separating media was used to aid the easy removal and insertion of the pattern.

Subsequently after debubblizing and investing the pattern was cast (BEGO

Induction casting machine) with cobalt chromium alloy (Co Cr alloy (Colado CC,

Ivoclar,Vivadent) using a lost wax technique.

GROUP- IV (TITANIUM ALLOY)

Root canal impressions that were obtained using direct wax patterns were

scanned with a digital scanner to generate and transfer the data to digital design

software for three dimensional image generation. A special software was used to

design post and core which was then fabricated using a laser sintering process.

(SISMA MYSINT 100, laser metal fusion)

12. Post luting Core Preparation Technique For Glass And Carbon Fiber Post:

GROUP- V (GLASS FIBER POST)

The length of the post in the canal was marked and the trimmed glass fiber

post was replaced in the canal to confirm its length. A 37% phosphoric acid etchant

was applied into the canal for 15 seconds and the canal flushed with distilled water

(5ml). The canal was dried subsequently with paper points. The Rely X U200 Self

adhesive resin cement (3M ESPE) base and catalyst were mixed in 1:1 ratio on a


36

mixing pad for 10 seconds and applied into the post space with a lentulo spiral (size

25). The presilanated fiber Post (Luxapost, DMG Dental Milestones Guaranteed,

Germany) was then seated in the canal and the adhesive resin cement was light

cured for 30 seconds on each surface. The core was established with the successive

layered addition of a core buildup resin (Luxacore, (DMG Dental Milestones

Guaranteed , Germany) and finishing done.

GROUP- VI (CARBON FIBER POST)

The same procedure as in the glass fiber post was followed and a Carbon

Fiber Post (Reforpost, Angelus, Dental Avenue India Pvt Ltd, Mumbai) was then

seated in the canal and the adhesive resin cement was light cured for 30sec on each

surfaces. The core was established with the successive addition of composite resin

(Luxacore, (DMG Dental Milestones Guaranteed, Germany).

13. Luting the cast post and core

The metallic cast posts and cores were cut from the sprues tested for seating

and assessed with radiovisiography for apical fit after which they were luted to the

respective prepared teeth using type I glass ionomer cement (Fuji GC corporation,

Japan).

14. Finishing the crown preparation

The excess cement was removed and after 24 hours the refining of the crown

preparation was done with a tapering fissure bur flat end.

15. Preparation for fracture testing

The samples belonging to each group were removed from the temporary

bases and mounted on formers (1.5” X 1.5” X 1.5”) with the help of a custom made


37

stainless steel base block. The apical root ends embedded vertically along the long

axis of the block at an angle of 30 degrees in such a way that the crown of the tooth

was visible. The clear epoxy resin was prepared. poured and allowed to set for 72

hours and the sample blocks coded. The samples were kept covered by moist cotton

and wet towel to prevent dehydration till they were ready for fracture testing.

17. Fracture testing procedure:

The samples were tested with the help of a universal testing machine. A

custom made metal indenter of size 3 millimetres was mounted on the upper arm jig

and the tooth specimen block was mounted on the lower arm jig. A cross head speed

of 1mm/min was set and the load applied on the surface of the tooth vertically

parallel to the long axis of the tooth from above. The force required to fracture the

tooth sample was recorded in Newton.

18. Tabulation of result:

The result of the fracture testing was tabulated after recording the maximum

load at which fracture occurred. The fracture strength results and the type of fracture

were analysed. The type of fractures which have taken place in each sample were

observed under magnification, grouped and recorded. The results were assessed by

two different operators and the results compared and tabulated.

19. Statistical analysis:

The samples were distributed across the groups based on their weights and

homogeneity. They were subjected to a statistical test to assess the normality of

these continuous variables. The results of the fracture test were statistically analysed

using one way ANOVA test of variance with Tukey post hoc test for multiple

comparisons.

Table 1: GROUPING – POST AND CORE

GROUPS (n= 8) POST AND CORE TYPE

I ORDEN ALLOY

II GOLD ALLOY

III NICKEL CHROMIUM ALLOY

IV TITANIUM

V GLASS FIBER POST

VI CARBON FIBER POST

RESULTS

TABLE 2: TYPES OF FRACTURE -INCIDENCE

TOTAL

SAMPLES

PERCENTAGE OF INCIDENCE

Buccolingual Mesiodistal Communited Transverse Others

(n=48) 12.5% 60.5% 18.7% 4.15% 4.15%

CHART I: FRACTURE TYPES - INCIDENCE

TABLE 3: TYPE OF FRACTURE – DISTRIBUTION

Experimental

Groups (n=8)

PERCENTAGE OF INCIDENCE

Buccolingual Mesiodistal Communited Transverse Others

GROUP I 0 62.5 25 0 12.5

GROUP II 0 50 25 12.5 12.5

GROUP III 0 62.5 37.5 0 0

GROUP IV 12.5 50 25 12.5 0

GROUP V 25 75 0 0 0

GROUP VI 37.5 62.5 0 0 0

OVERALL 12.5 60.4 18.8 4.2 4.2

CHART II: FRACTURE TYPES - DISTRIBUTION

TABLE 4: FRACTURE LOAD ANALYSIS

EXPERIMENTAL

GROUPS (n=8)

MAXIMUM

VALUE

MINIMUM

VALUE MEAN

CONFIDENCE INTERVAL

AT 95% STANDARD

DEVIATION MEDIAN

LOWER

BOUND

UPPER

BOUND

I 579.53 285.71 427.92 340.8238 510.4283 101.70 410.91

II 650.71 216.54 361.11 247.8979 474.3266 135.42 357.50

III 928.84 444.74 742.88 591.8977 893.8758 180.60 790.42

IV 672.36 284.32 482.32 349.5759 615.0758 158.78 484.46

V 472.62 203.12 336.96 255.6189 418.3055 97.29 322.05

VI 690.27 182.54 323.67 181.9662 465.3924 169.50 287.12

CHART III – EXPERIMENTAL GROUPS - FRACTURE MEAN

TABLE 5: SAMPLE DISTIBUTION DATA

EXPERIMENTAL GROUPS

(n=8)

PERENTAGE OF INCIDENCE

Buccolingual width

(A)mm

Mesiodistal width

(B)mm (A*B) (A+B) Weight(g)

GROUP I 5.716±0.15 6.135±0.38 35.118±3.15 11.851±0.53 0.97±0.06

GROUP II 5.772±0.14 6.165±0.31 35.622±2.63 11.937±0.44 0.97±0.07

GROUP III 5.771±0.16 6.036±0.23 34.870±2.37 11.807±0.40 0.97±0.06

GROUP IV 5.833±0.22 6.051±0.26 35.353±2.98 11.885±0.49 0.97±0.07

GROUP V 5.756±0.07 5.930±0.08 34.139±0.91 11.686±0.15 0.97±0.06

GROUP VI 5.768±0.06 5.936±0.06 34.246±0.66 11.705±0.11 0.96±0.06

OVERALL 5.769±0.14 6.042±0.25 34.891±2.27 11.812±0.38 0.971±0.06

38

TABLE 6: NORMALITY ANALYSIS FOR SAMPLES

SL. NO. GROUPS COMPARED SIGNIFICANCE

1 Buccolingual Width (B) NORMAL

2 Mesiodistal Width (B) NORMAL

3 A*B NORMAL

4 A+B NORMAL

5 Weight(G) NORMAL

Since the p-values of all the groups are more than 0.05, it can be concluded that the distribution is normal at 5% level of significance.

ANALYSIS AND INTERPRETATION:

Normality Testing is used to test whether the distribution is normal at 5% level of significance.

Note 1: If “p” value is more than 0.05, then we can conclude that the distribution is normal.

Note 2: If “p” value is less than 0.05, then we can conclude that the distribution is non-normal.

39

TABLE 7: STATISTICAL ANALYSIS – VALUE CORRELATION

SL.NO. GROUPS COMPARED CORRELATION

1 Buccolingual Width (A) and Weight positive correlation

2 Mesiodistal Width (B) and Weight positive correlation

3 A*B and Weight positive correlation

4 A+B and Weight positive correlation

5 Groups Combined positive correlation


Correlation is a statistical tool that is used to determine the degree of relationship between two or more variables.

• When r = +ve, there is positive correlation between the variables.

• When r = –ve, there is negative correlation between the variables.

• When r = 0, there is no relationship between the variables.

The co-efficient of correlation “r” will lie between –1 and +1, (i.e.) –1 ≤ r ≤ +1.

Note 1: If “p” value is more than 0.05, then we can conclude that the correlation is not statistically significant.

Note 2: If “p” value is less than 0.05, then we can conclude that the correlation is statistically significant.

40

TABLE 8: METALLIC AND NON-METALLIC POST AND CORE GROUP COMPARISON

Student’s t- test

Group N Mean Std.

Deviation

I-IV 32 503.56 202.84407

V-VI 16 330.32 133.69303

SL.NO. GROUPS COMPARED t-value p-value SIGNIFICANCE

1

[Groups I-IV]

&

[Groups V-VI]

t = 3.089 p= 0.003 Significant

Combination of groups I-IV is comparatively better/higher than the combination of groups V-VI.


Student’s “t” test for two independent groups is used to compare the significance of difference between means of two groups at 5% level of

significance.

Note 1: If “p” value is more than 0.05, then we can conclude that there is no significant difference between the two groups considered with

regard to mean.

Note 2: If “p” value is less than 0.05, then we can conclude that there is a significant difference between the two groups considered with

regard to mean.

41

TABLE 9: STATISTICAL COMPARISON BETWEEN GROUPS -

FRACTURE RESISTANCE

TWO GROUP COMPARISON Student’s t- test

SL.NO. GROUPS COMPARED t-value p-value SIGNIFICANCE

1 GROUP I ,II 1.116 0.283 non significant

2 GROUP I,III 4.298 0.001 significant

3 GROUP I,IV 0.816 0.428 non significant

4 GROUP I,V 1.828 0.089 non significant

5 GROUP I,VI 1.492 0.158 non significant

6 GROUP II,III 4.784 0.000 significant

7 GROUP II,IV 1.643 0.123 non significant

8 GROUP II,V 0.410 0.688 non significant

9 GROUP II,VI 0.488 0.633 non significant

10 GROUP III,IV 3.065 0.008 significant

11 GROUP III,V 5.597 0.000 significant

12 GROUP III,VI 4.787 0.000 significant

13 GROUP IV,V 2.208 0.044 significant

14 GROUP IV,VI 1.932 0.074 significant

15 GROUP V,VI 0.192 0.850 non significant


Student’s “t” test for two independent groups is used to compare the significance of

difference between means of two groups at 5% level of significance.

Note 1: If “p” value is more than 0.05, then we can conclude that there is no

significant difference between the two groups considered with regard to mean.

Note 2: If “p” value is less than 0.05, then we can conclude that there is a significant

difference between the two groups considered with regard to mean.

42

TABLE 10: COMPARISON BETWEEN GROUPS - Analysis of Variance (ANOVA)

SL.NO. GROUPS COMPARED SIGNIFICANCE

1 Multiple Comparisons

Tukey HSD

Significant difference Group III with

other Groups

SL.NO. GROUPS COMPARED f-value p-value SIGNIFICANCE

1 Groups I, II, III, IV, V AND VI F = 9.533 p = 0.000 Significant difference between six groups


ANOVA (Analysis of Variance) is used to compare the significance of difference between means of more than two independent groups at 5%

level of significance.

Note 1: If “p” value is more than 0.05, then we can conclude that there is no significant difference between the two groups considered with

regard to mean.

Note 2: If “p” value is less than 0.05, then we can conclude that there is a significant difference between the two groups considered with

regard to mean.

CHART IV: FRACTURE RESISTANCE ANALYSIS – EXPERIMENTAL GROUPS

METALLIC POST AND CORE

GROUP I GROUP II

GROUP III GROUP IV

CHART V: FRACTURE RESISTANCE ANALYSIS – EXPERIMENTAL GROUPS

NON METALLIC POST AND CORE

GROUP V GROUP VI

DISCUSSION

Discussion

43

The objective and aim of the root canal treatment procedure is to achieve a

three dimensional hermetic seal during canal obturation and adequately reinforce the

root canal space so as to increase resistance to fracture of the remaining tooth

structure. Endodontically treated teeth have been reported to be more susceptible to

fracture when compared to vital teeth. This necessitates adequate protection of

remaining tooth structure by proper restoration protocols.

During endodontic therapy the entire root canal system has to be adequately

accessed, cleansed of all the necrotic tissues, remnants, debris, microbes and

subsequently appropriately restored. This process of cleansing of the root canal

space is called the biomechanical preparation. The root canal system presents a

complex structure and is colonized by the microorganisms during an infection which

have been demonstrated in the dentinal tubules half way through radicular dentin.

Therefore while treating the infected root canal space the process of shaping and

cleansing i.e., the biomechanical preparation of the canal is viewed as a vital step

during endodontic therapy. The inherent variations of anatomy of the canal system,

the curvature of the roots especially in the mandibular and maxillary posterior teeth

pose a challenge during biomechanical preparation. The occlusal one third of the

canal system is highly accessible, middle one is third fairly accessible and the apical

one third is the least accessible. In the case of curved roots in order to access the

apical third of the canals and to achieve sufficient cleansing and debridement,

considerable amount of radicular dentin in the coronal and middle third is removed

intentionally which would possibly can affect the structural integrity of the of the

tooth. This makes the endodontically treated tooth more prone to fracture. (Sornkul

et al in 199291)

Discussion

44

Excessive tooth structure removal during endodontic therapy and subsequent

dehydration of both coronal and radicular dentin are principal factors which have

been responsible for affecting the fracture resistance of restored tooth structure after

completion of endodontic treatment procedure. Dentin in a endodontically treated

tooth should be preserved as much as possible. The resistance to fracture depends

primarily on remaining root dentin thickness, especially in the buccolingual

direction. (Sedgley and Messer in 1992)80

A number of reasons have been put forward for the tooth being susceptible

for fracture which includes loss of tooth structure due to caries or trauma, excessive

removal of tooth structure during root canal preparation, the dehydration of dentin

subsequent to endodontic treatment, excessive radicular dentinal structural loss

during post space preparation, creation of excessive stress during obturation and

increased use of higher concentration of irrigants with prolonged exposure times.

This in a clinical situation would mean a reduction in the long term survival rate,

which is highly undesirable. The major achievable goal of endodontic therapy

should be reinforcement of the residual tooth structure in such a way that it prevents

untoward events in the long term. (Johnson M.E., et al in 2000)38

.

Earlier with hand instrumentation it was common practice to enlarge the

canal to three sizes from the first initial file to bind at the apical third of the root.

This enlargement allowed efficient cleansing and allowed the irrigants and

medicaments to reach the entire length of the canal system. The introduction of

nickel titanium hand instruments in endodontics almost two decades ago, improved

preparations as they were flexible. The most significant advantage was the more

predictable control of the preparation. The alloy was resistant to corrosion, had the

Discussion

45

property of super elasticity and shape memory. With the advent of nickel titanium

rotary instrumentation, things changed and negotiation of even severely curved

canals became much easier to accomplish, was more complete and reduced the

clinical working time. These rotary instruments when used to prepare the canal exert

considerable stresses in certain areas resulting in formation of microcracks or craze

lines which later predisposes the tooth to vertical root fracture. These areas of most

stress are mostly located in the mid root canal wall area. It has been observed that

lateral forces result in high stress concentrations in radicular dentin in the coronal

one third of the root, and make the teeth susceptible to fracture at the cemento

enamel junction. There is a direct proportional correlation between thickness of the

root and the ability of the tooth to resist lateral dislodging forces. The amount of

remaining radicular and coronal dentin in a tooth is directly proportional to the

fracture resistance. (Lertchirakarn V., et al in 2002)44

Studies have pointed out a potential relationship between the design of the

nickel titanium rotary instruments and the incidence of vertical root fractures. (Kim

H.C et al in 201042). Traditionally the rotary nickel titanium file systems were

designed to be used in a sequence and consisted of multiple rotary tools. Advances

in metallurgy have seen introduction of newer file systems for canal preparation

with a single rotary file which are effective. Also rotary files for use in reciprocating

motion have been designed. A new rotary file adjusting to the size of the canal and

which works with vibration and continuous irrigation, the self adjusting file system

has been developed successfully. These single file systems have been formulated

due to the advances in metallurgy and have practicality, simplicity, reduce clinical

working time and have been reported to reduce the amount of induced stresses on

Discussion

46

the canal walls. The self adjusting file is hollow, flexbile and compressible and the

system works with a up and down grinding motion with the help of which it

removed dentin from the canal walls. The file literally adapts to the anatomical

pathway of the canal wall which reduces over preparation and subsequent

weakening. The self adjusting file is made of medical grade nickel titanium alloy to

form a metal lattice hollow cylinder design and sand blasted to enable it to remove

radicular dentin. The straightening of the curved canals is reduced because of the

absence of a rigid core and the pliability of the file. (Metzger Z, et al in 201035)

The file as it is inserted into the canal removes a surface layer of dentin which

results in a canal of larger dimensions but a similar cross-section. (Hof R, et al in

201035)

Next concept was the innovative migration from a continuous rotary motion

to a reciprocating motion involving different clockwise and counterclockwise

angles. The reciprocating motion has been used to rotate stainless steel files since

1958. These systems used a 90 degress clockwise and counterclockwise motion

which later evolved to 30 degrees. The reciprocation file systems that have been

introduced of late which use the superior reciprocating motion based on the Roane

technique of canal preparation which is a balanced force concept put forward by

Roane J B, et al in 198567

. The use of the reciprocating movement reduces the

various risks of continuously rotating the file through the curvature of the canal

system. The equal angle reciprocating motors reduce the cutting efficiency, increase

the required pressure, require multiple files and are poor at debridement. The use of

unequal angles of reciprocation has distinct advantages of efficient debridement and

easy advancement of the file to the established working length. The incorporation of

Discussion

47

these newer techniques have made the single file reciprocating systems more safer

and achieve the target preparation faster. The reciprocating motion shifted from the

use of equal to unequal counterclockwise angles. The use of a reciprocating motion

results in a minimal torsional and flexural stresses. This translates into a less binding

effect of the instruments on the radicular dentin. This also creates a less invasive

preparation of the canal space due to the increased canal centering.

The waveone gold reciprocating single file system (Dentsply Mallieifer

Ballaigues, Switzerland) is made with a M-wire NiTi alloy and is used with a

dedicated reciprocating motor system with a 170 degree counter clockwise motion

followed by a 50 degree clockwise motion with a rotational speed of 350rpm. This

can be used in any canal irrespective of its length, diameter or curvature. These

edges minimise the screwing effect, thereby reducing torque which along with the

enhanced cutting efficiency, allows for smoother operation.

This reciprocating single file system Reciproc (VDW Munich Germany) is

made with M-wire NiTi alloy and uses a 150 degree counter clockwise rotation

followed by a 30 degree clockwise motion with a speed of 300 rpm. It has a

continuous taper over the first 3mm of the file and followed by a decreased taper

until the shaft with an S-shaped cross section. These angles are designed in such a

way that prevents the rotation of the instrument past the angle of fracture and has

good canal centering ability. The S- shaped cross section reduces friction while

cutting and deeper flutes offers a huge capacity for debris removal from the canal

system. Both the Reciproc and Waveone reciprocation systems have been found to

be similar in their cleaning efficiency (Carvalho M S, et al in 201515) The Reciproc

Discussion

48

system single file has been found to be more efficient at cutting when compared to

the waveone system.

The single file reciprocating systems Reciproc and Waveone have been

found to be superior and suitable for canal preparation when compared to other

single file rotary systems. The reciprocating motion was found to be superior to the

rotary motion of canal preparation in terms of canal transportation, cervical dentinal

thickness and cross sectional area (Dhingra A, et al in 201523) The reciprocating

single file systems have been found to be superior in shaping severely curved canals

when compared with rotary multi file systems. They also have been found to have a

lesser preparation time and procedural errors. (Bane K, et al in 20155)

Different presentations of fractures in roots of endodontically treated teeth

have been reported. They can be classified broadly as transverse and vertical root

fractures. Vertical root fracture is one of the most serious complications of root canal

procedures with an unfavorable prognosis that can occur before, during, or after root

canal obturation and most often leads to the removal of the affected tooth. (Meister

F et al in 198049) Numerous clinical studies have shown that 11%- 13% of extracted

teeth with endodontic treatment are associated with vertical root fractures. (Fuss Z.,

et al in 199928) Various predisposing factors like age, tooth type, degree of

calcification, excessive forces applied during obturation, the wedging effect of

spreaders used during the filling procedure, excessive pressure during post

cementation, excessive post space preparation and excessive dentin removal by

instrumentation have been proposed as contributing to vertical root fractures.

Endodontic procedures during the biomechanical preparation induce craze

lines and cracks on the canal walls which become areas of high stress concentration.

Discussion

49

These cracks may spread slowly over a period of time to the surface eventually

resulting in a vertical root fracture. (Yoldas O., et al in 2012107) The cracks usually

begin at the apex of the root and propagate cervically. Judicious use of

instrumentation procedures either hand or rotary and selection of a optimal irrigation

system for customized for the tooth will minimize the incidence of such craze lines

and cracks and avoid incidence of fractures later. The change in the mechanical

properties of dentin with age and the loss of hydration after endodontic therapy has

also been a reason for the reduced tolerance of teeth to fractures. This has lead to

various researchers looking to reinforce the structure of the crown and the root after

the completion of the biomechanical preparation.

Optical coherence tomography has been suggested as a potential tool for

identification and localizing the vertical root fractures. This was introduced in 1991

and allows micrometer scale imaging of the tissues using infrared light waves which

reflect off the internal microstructure of the tissues. It has a resolution of ten

micrometers and has been suggested as a valuable tool to identify perforations, intra

canal anatomy and canal cleanliness. The sensitivity of this tool is better than that of

computerized tomography in identification of vertical root fractures (Shemesh H.,

et al in 200886)

The prognosis for teeth with transverse or horizontal root fractures is usually

good. It is very important to differentiate between the kind of fracture which has

happened, either vertical or horizontal fractures. There is a poor prognosis in

conditions with vertical type of fractures which split roots along their long axis .

Horizontal root fractures are the most common type and occur mainly in the anterior

region of the maxilla, owing to a frontal impact. They are common in the middle-

Discussion

50

third and rarely occur in the apical and coronal third of the root. Successful

management of a tooth that has sustained a transverse root fracture depends on the

fracture line position, the mobility of the coronal segment, and the status of the

radicular and coronal pulp.

The position and relationship of the fracture line to the gingival crevice are

the most important factors affecting the long term prognosis. Coronal third and

middle third type of root fractures has shown to have a unfavorable prognosis than

apical third type of root fractures. As long as the fracture is infrabony with no

communication to the gingival sulcus and the patient practices meticulous oral

hygiene, appropriate treatment options can result in successful outcome of therapy.

Fractures in the apical third of the root can be viewed in occlusal radiographs,

whereas periapical radiographic views are better for visualizing coronally located

root fractures. Verified pulp necrosis has been reported with a percentage of

incidence of 43.7% in horizontal root fractures. Treatment of transverse or

horizontal root fractures depends on the position of the tooth after it has been

fractured, the mobility of the coronal segment, the status of the pulp, and the

position of the fracture line. Repair and healing of the injury to the coronal and

apical segments occurs either by hard tissue union, which is the most desirable, bony

ingrowth across the fracture, fibrous healing, or ingrowth of granulation tissue.

Fractures as a result of fatigue have been reported in teeth which are vitan and have

been subjected to repetitive occlusal forces.

The biologic dentin post system demonstrated the highest fracture resistance

when a unidirectional force was applied and was repairable in an in vitro setting.

The masticatory forces are multi-directional in a clinical situation. Development of

Discussion

51

tooth banks have been suggested for ready availability of these dentin biologic posts.

(Kurthukoti A J., et al in 201543

)

The process of retreatment has been shown to increase further amounts of

dentin from within the canal space rendering these retreated teeth more susceptible

to fracture. The rotary files used for gutta percha removal during the retreatment

procedure have been shown to remove the surface dentin, as well as further

enlargement of the apical thirds to achieve better cleansing which contributes to a

reduced fracture resistance of the root. There has been a positive corelation between

the removal of dentin during retreatment procedures and reduction of fracture

resistance. (Ganesh A, et al in 201429)

This has lead to various researchers looking to reinforce the structure of both

the crown and the root after the completion of endodontic treatment. The commonly

used root canal filling material is gutta percha in combination with a sealer. The low

elastic modulus of gutta percha presents little or no capacity to reinforce roots after

completion of endodontic therapy. (Ribero F.C., et al in 2008)64 Thus, there is a

compelling need to develop materials and techniques to overcome the shortcomings

of current endodontic obturation materials and post endodontic restorations to

reinforce root structure post therapy.

Swartz D B., et al in 198395 stated that failure rate of endodontically treated

teeth was almost double in cases without the process of adequate post endodontic

restoration. Newer generation of materials tend to improve the bond between

radicular dentin and the sealer and the sealer-core interface which helps to increase

the fracture resistance and reduces ingress pathways. To reinforce the roots the

modulus of elasticity of the root filling material should approximate that of the

Discussion

52

dentin. (Williams C., et al in 2006105). This presents the concept of a monoblock,

which aims at creating mechanically sound homologous units with radicular dentin.

They can be classified into primary, secondary and tertiary monoblocks based on the

number of interfaces present between the bonding material and the core material. A

primary monoblock has only one interface between the material and the canal wall.

A secondary monoblock has two circumferential interfaces between the core

material and the canal walls. When a third substrate is introduced between the

bonding substrate and the abutment material it forms a tertiary monoblock. This is

easier said than done as the complexity of the canal system, difficulties in access and

cleansing present difficulties in predictably achieving the target monoblock unit.

Priming the radicular dentinal surface and creating a bond between the sealer and

dentin, sealer and core material would effectively achieve this. A number of sealer

and core materials have been formulated with the aim of achieving this. The

modulus of elasticity of the post, the filling material and the sealer has to match that

of radicular dentin so that the load stresses are evenly distributed and borne by the

components of the monoblock. (Tay F.R., et al in 200796).

Intra orifice barrier is an efficient alternative method to decrease coronal

leakage after endodontic treatment. (Yavari H R., et al in 2012)106. This procedure

involves placing additional material into the canal orifices immediately after

removal of the coronal portion of gutta-percha and sealer. This also improves the

fracture resistance of the root structure. (Roghanizad N., et al in 1996)109.

Materials like resin modified glass ionomers, flowable composites, and bonded

amalgam can ideally be used as intra-orifice barriers.

Discussion

53

A new breed of restorative materials for use as endodontic filling materials

have been introduced in conjunction with adhesive sealers and modified core

materials with a aim of increasing the fracture resistance of the endodontically

treated teeth by formation of effective bonds at the interfaces, hydrophilic and

which effectively bond to dentin. Glass fiber posts and carbon fiber posts with

different properties have been formulated. Glass fiber posts have been used to

restore endodontically treated teeth, mainly because they are aesthetic, faster to

execute and have an elastic modulus near that of tooth structure (30-50 GPa). (Scotti

R et al in 2003)45 In the present study we have use a glass fiber post and a carbon

fiber post system for evaluation.

The cast post and core method of post endodontic reconstruction has been

traditionally used and can be considered as gold standard. This technique has its own

limitations. There is a greater removal of radicular dentinal structure, need for

multiple clinical leading to more turnover time and has a elastic modulus which is

high compared to tooth structure (200 Gpa) which can lead to fractures. (Sarkis-

Onofre R et al in 2014)85

For post preparations survival rates ranging from 71 to 100% for fiber posts

and 50 to 97.1% for metal posts have been reported. No difference in the survival

among different kinds of metallic posts were reported. No differences were reported

between fiber and metal posts by most studies conducted. Two studies also showed

that remaining dentine height, number of walls and ferrule increased the longevity of

the restored teeth. Post loss of retention was the reason for failure fiber posts.

Metallic post failures were mostly related to root fracture, post fracture or crown

Discussion

54

or post retention loss. Studies with longer follow up are needed. (Scotti R et al in

2003)45

Irrigant solutions have been traditionally used for removal of smear which

consists of organic and inorganic components consisting of blood, microbes,

necrotic pulp, saliva, and debris which is generated during the process of

biomechanical preparation. They have also been used for lubrication during

instrumentation, flushing out of debris from the canal, anti-bacterial property, and

removal of smear. This process of cleansing affects the intra radicular dentinal

structure which is composed of organic and inorganic components. Therefore the use

of these solutions has to be done in a way that it achieves its targeted role without

affecting the structure or the mechanical properties of the tooth. A ideal irrigant

solution should not affect the structural integrity of the tooth structure but should

contribute to it yet at the same time achieving the objective of a clean canal system.

Hence the parameters of volume, the concentration of the irrigant, time of exposure

and mode of delivery should be ideally be matched to the particular nature of the

irrigant and its properties. No single irrigant is effective against all the constituents

of the canal space. They have thus been used in combinations as multiple rinses to

achieve the target of a clean canal system which is a prerequisite for three

dimensional obturation of the root canal system. Irrigant solutions have been shown

to have an effect on the resistance to fracture of endodontically treated teeth. The

concentration and time of exposure of the irrigant play a role in the reduction of

fracture resistance of the tooth. A number of irrigant solutions been successfully

formulated for clinical use. Sodium hypochlorite in a concentration of 5% has been

used to remove the organic debris, and chelating agents like ethylene diamine

tetraacetic acid, citric acid, have been used to remove the inorganic components in

Discussion

55

varying concentrations. Endodontic irrigation thus leads to an alteration of the

chemical composition of intra radicular dentin due to the changes effected to the

organic and inorganic phases. This change alters the properties of microhardness,

permeability and solubility of the dentinal structure which leads to changes in the

ability of the teeth to resist fracture under varying loads.

Ethylene diamine tetraacetic acid widely used irrigant has been shown

previously to affect the fracture resistance of the tooth structure depending on the

exposure time and concentration. (Uzunoglu E, et al in 2012101) Citric acid a

chelating agent with good properties of stability, anti-microbial and smear removal

capacity is also being used widely as a root canal irrigant in different concentrations.

It has been suitably modified and is available for use as a final rinse solution

(MTAD and Tetraclean). The effects of citric acid on the fracture resistance of teeth

have been evaluated for different time exposures and concentrations and has been

found not to significantly change the fracture resistance of the tooth. (Arslan H.,

et al in 201412)

Sealers have evolved as a important interface in the root canal obturation

procedures. Their role in contributing to improving the fracture strength of the roots

has been evaluated by different researchers. (Bhat S S, et al in 201215) New

research methodologies have resulted in materials that facilitate more of adhesion to

the root canal walls which increases the mechanical interlocking and reduces the risk

of fracture. (Jhamb S, et al in 200937). The adhesion of the sealer to both interfaces

of the canal wall and that of the core material results in a more effective tertiary

monoblock which resists fracture when forces are applied.

Discussion

56

Selection of the obturation material and technique is very important as it

plays a role in reinforcing the root structure. As discussed previously the bio-

mechanical preparation of the root weakens the structure and using the right

obturation technique in strengthening the root. Various authors have evaluated

different obturation techniques and their effect on fracture resistance and observed

that a correctly done procedure of canal obturation improves the resistance of the

root to fracture. The use of gutta percha along with adhesive resin sealers have also

been reported to improve the fracture resistance of roots. (Sandickci T, et al in

201472) Technologies which incorporate a adhesive ionomer coating on the gutta-

percha for a thickness of two microns to which a adhesive ceramic sealer could be

bonded to form a tertiary monoblock have also been developed and evaluated. The

authors observe that all the materials used enhanced the fracture resistance of the

root. (Celikten B, et al in 201517)

Gutta percha with a resin based sealer has been used a gold standard for a

obturation procedure. There are several advantages of this system but the

hydrophobic nature and inability to sufficiently reinforce the root canal remain its

drawback. This has led to the development of hydrophilic materials which utilize the

moisture in the dentinal walls which allows the material to bond to the root canal

wall and core which reinforces the structure of the root by formation of a

monoblock. The increase in fracture resistance is also attributed to the penetration of

the dentinal tubules to varying depths and subsequent bonding due to incorporation

of nanoparticles in sealer also contributes to increased resistance to fracture. The

polymerization shrinkage of the resin based sealers that may be due to high C-factor

associated with the root canal also leads to contraction of the sealer post filling

Discussion

57

leading to a weakening of the bond between the sealer and the canal wall leading to

reduced resistance to fracture. A novel sealer C-point system has been introduced

which has got the property of sealer expansion due to its self expanding and

hydrophilic composition which significantly increased the resistance to fracture.

(Hegde V., et al in 201532)

The fracture which occurs in the root can be looked upon as a

communication which extends from root canal all the way to the external surface of

the root. There are also existence of external cracks or craze lines which extend from

the external surface into dentin which do not reach the root canal. The structural

defects in the structure of the root has been investigated and found to cause more

fractures, the reason being the amplification of induced stresses at these formed

microcracks. (Gudoutos E E, et al in 200530)

Microcracks are formed as a result of the rotational forces that are being

applied to the canal walls during the process of bio-mechanical preparation. The

procedures of endodontic therapy have contributed to the intiation and formation of

these microcracks. The formation of these microcracks may also be influenced by

the anatomy and the morphology of the root. The increased incidence of these

microcracks have been reported with the use of rotary instruments for canal

preparation. The amount of microcracks which are formed may be related to the

design features of rotary instruments like the tip size, geometry of cross-section, the

pitch which can be constant or variable, the taper which can be constant or

progressive and flute form (Yoldas O, et al in 2012107) The hand instruments

produce a lesser number of dentinal defects compared to rotary instruments. (Shori

D D.,et al in 201588)

Discussion

58

The introduction of reciprocating instruments and the self adjusting file

system for the canal preparation has drastically changes the way in which the canal

is prepared. The reciprocating file systems have been shown to produce significant

amount of incomplete dentinal cracks in the apical third of the canal system when

compared to a full sequence rotary files (Burklien S, et al in 201310) The creation of

a glide path has no significant effecting the formation of dentinal defects in

reciprocation instruments. (Saber S E, et al in 201571) The reciprocating

instruments for the canal preparation namely Reciproc and Waveone produced

defects in the roots which were not statistically significant. They caused more

defects in the apical parts of the canal compared to hand instruments which caused

more defects in the coronal and middle thirds. Both hand and reciprocating

instruments induced formation of dentinal defects during the canal preparation

(Helvacioglu-Yigit, et al in 201433)

There has been a positive correlation between the microcrack formation and

the incidence of root fractures. Investigations have revealed that the event of a root

fracture is not an instant event but a gradual propagation of craze lines and

microcracks in radicular root structure.

External craze lines and cracks are often found more commonly and were

found not to connect with the canal space. They were also in places which where in

places away from the direct contact of the rotary instruments. One possible reason is

that the stress generated during the instrumentation of the canals is transmitted to the

external surface of the teeth where it overcomes the bonds in dentin to form these

craze lines, micro cracks and eventually resulting in fractures. (Shemesh H, et al in

200986) The role of the obturation technique in formation of these defects has also

Discussion

59

been considered. The excessive forces generated during the process result in stresses

causing these defects in root dentin. Dentinal defects have been observed in root

filled with gutta percha and AH26 using lateral compaction and continuous wave

techniques. (Shemesh H, et al in 201087)

This study was to evaluate the fracture strength was done on extracted

maxillary central incisor teeth in an in vitro setting. Due to the large amount of

variations in the volume and weight of the roots among the samples selected,

sufficient protocols were followed for standardization of the controllable factors.

The anatomical variations inherent in the root structure with regard to size and

volume, the time of extraction, age of the patient, storage conditions, level of

hydration and degree of calcification would have an effect on the results of this

study. The normality testing of these variables was assessed statistically and the

distributions were found to be normal at 5% level of significance.(Table: 6,7)

For mechanical testing of the teeth structure standardization of the samples is

very important as fracture strength of the samples was being evaluated in each

experimental group prepared for a different post and core system. The mesiodistal

and buccolingual diameters at the cemento enamel junction level were recorded. To

eliminate the variations and standardize the samples the roots were distributed to the

various experimental groups equally based on their buccolingual and mesiodistal

diameters as well as their weights. (Table: 5) The teeth were mounted on the bases at

an angle of thirty three degrees to create the similar conditions as in the oral cavity.

For testing the fracture strength the forces were to the prepared samples using a

specially designed stainless steel tip with a diameter of three millimeters using in

universal testing machine with a cross head speed of 1millimeter /min. The point of

Discussion

60

seating of the stainless steel tip was also in the zone where the lower incisor would

normally occlude. The maximum load at fracture was recorded.

After the fracture testing procedure with a universal testing machine the

fractured samples and fragments were collected in separate pouches for each sample

and were further analysed for the types of root fracture encountered during the

testing procedure. They were assessed by two different operators and the results

compared, tabulated and analysed. (Table: 2 Chart: I) The result of the fracture

testing which was recorded on the universal testing machine was tabulated and

analysed statistically. (Table: 3,4 Chart: II) There was statistically significant

difference between the experimental groups in load values of root fracture.

(Table: 10)

Fracture strength testing is a method of evaluating the likelihood of the

treated root to fracture when a component of force is applied to the tooth in a

specific direction till fracture occurs. Though these values are generally indicative of

the ability of the root to resist fracture, in a clinical situation the type of forces

involved and that to which the root is subjected to is different. Also the fracture of

the tooth could be because of the creation of microcracks in radicular dentin which

serve as areas where increased concentration of stresses in the root occur. When

forces are applied to the root it leads to propagation of these cracks and eventually

results in a fracture. A statistical comparison of the metallic and non-metallic post

and core groups used in this study found a significant difference with the

combination of Groups I-IV comparatively better fracture resistance values than the

combination of Groups V-VI.

SUMMARY

Summary

61

Seventy two freshly extracted maxillary central incisors were collected

cleaned and stored in bottles containing 1% thymol in normal saline at 30 degree

Celsius. They were investigated for the presence of intact root morphology with a

patent canal free of any anomalies, gross destruction and restorations.

The weight of the tooth, the buccolingual and mesiodistal diameters were

calculated and samples evenly distributed based on their weights across the

experimental and control groups (n=8), rinsed with distilled water and stored in

normal saline at 4°C in separate glass bottles. The working lengths were calculated

the canals were prepared with hand files. The prepared samples were then obturated

and allowed to set for 48 hours, the access cavities restored. Subsequently post space

preparation was done. Based on the experimental group either wax patterns for

metallic post and core or protocols for luting a fibre post system followed by a core

preparation was followed. They were then mounted on to resin bases with the aid of

a base former. The cast post and core preparations were luted on to the teeth. They

were subjected to a fracture test under vertical loading applied with a 3mm stainless

steel tip in a universal testing machine and the load at fracture data recorded. After

the fracture testing process, type of fracture was analysed. The results tabulated and

statistically analysed.

CONCLUSION

Conclusion

62

On conclusion of the study, on the analysis of the fracture strength of roots

instrumented different post and core systems, the following conclusions are made:

Overall the Mesiodistal type of fracture was the most common among the

experimental groups with a percentage of incidence of 60.50%[Table 2 Chart I]

The communited type of fracture was the next commonest with a percentage of

incidence of 18.7% [Table 2 chart I].The incidence of buccolingual, transverse and

other type of fracture was not common and had a percentage of incidence of

12.50%, 4.15% and 4.15% respectively [Table 2 chart I].

Amongst the experimental groups in the metallic cast post and core groups

(Groups I-IV) all types of fractures were seen with the highest incidence being

mesiodistal with a incidence of 75%. The other type of fractures encountered were

communited, bucco-lingual, transverse and other group fractures with a incidence of

18.13 %, 3.13 %, 6.25% and 6.25% respectively. [Table 3]

On a statistical analysis of groups I –VI, Group III was found to have a

statistically siginificant difference with other groups. (p < 0.05)[Chart III Table10].

Within the limitations and standardization protocols used in this study, it can

be concluded that the resistance to fracture of the roots prepared with metallic cast

post and core [Groups I-V] was better than the non-metallic post and core

groups [V-VI]. There was a statistically significant difference between the metallic

and non-metallic groups in load values of root fracture (p < 0.05) [Chart III

Table 7]. Further evaluation of these different post and core systems and assessment

in a clinical setting is recommended.

BIBLIOGRAPHY

Bibliography

1. Alkhatri R, Saleh ARM, Kheder W. Evaluating Fracture Resistance And

Failure Modes Of Root Filled Teeth Restored With CAD/CAM-Fabricated Post

And Core. Clin Cosmet Investig Dent. 2019 Nov 14;11:349-355.

2. Artopoulou II, O'Keefe KL. Materials used in prefabricated post and core

systems. A review of the literature. Tex Dent J. 2006 Apr;123(4):358-63. Review.

3. Bacchi A, Caldas RA, Schmidt D, Detoni M, Matheus Albino Souza, Cecchin D,

Farina AP. Fracture Strength and Stress Distribution in Premolars Restored with

Cast Post-and-Cores or Glass-Fiber Posts Considering the Influence of Ferule.

Biomed Res Int. 2019 Jan 3;2019:2196519.

4. Bakirtzoglou E, Kamalakidis SN, Pissiotis AL, Michalakis K. In vitro

assessment of retention and resistance failure loads of complete coverage

restorations made for anterior maxillary teeth restored with two different cast

post and core designs. J Clin Exp Dent. 2019 Mar 1;11(3):e225-e230.

5. Bane K, Faye B, Sarr M, Niang S O, Ndiaye D, Machtou P Root canal shaping

by single file systems and rotary instruments: A laboratory study Iranian

Endodontic Journal 2015; 10(2): 135-139.

6. Bolla M, Muller-Bolla M, Borg C, Lupi-Pegurier L, Laplanche O, Leforestier E.

WITHDRAWN: Root canal posts for the restoration of root filled teeth.

Cochrane Database Syst Rev. 2016 Nov 28;11:CD004623. Review.

7. Brignardello-Petersen R. Preformed-metal posts seem to have a lower cost than

and similar effectiveness as cast-metal, glass-fiber, and carbon-fiber posts. J Am

Dent Assoc. 2017 Aug;148(8):e108.

Bibliography

8. Broch J, Marchionatti AM, Bergoli CD, Valandro LF, Kaizer OB. Fracture

resistance of weakened roots restored with different intracanal retainers. Gen

Dent. 2015 May-Jun;63(3):58-63.

9. Bromberg CR, Alves CB, Stona D, Spohr AM, Rodrigues-Junior SA, Melara R,

Burnett LH Jr. Fracture resistance of endodontically treated molars restored with

horizontal fiberglass posts or indirect techniques. J Am Dent Assoc. 2016

Dec;147(12):952-958.

10. Bürklein S, Tsotsis P, Schafer E. Incidence of dentinal defects after root canal

preparation: reciprocating versus rotary instrumentation. J Endod. 2013 Apr;

39(4):501-4.

11. Byakova SF, Novozhilova NE, Makeeva IM, Grachev VI, Kasatkina IV. The

detection of vertical root fractures in post-core restored teeth with cone-beam

CT: in vivo and ex vivo. Dentomaxillofac Radiol. 2019 Sep;48(6):20180327

12. Capar ID, Saygili G, Ergun H, Gok T, Arslan H, Ertas H. Effects of root canal

preparation, various filling techniques and retreatment after filling on vertical

root fracture and crack formation. Dent Traumatol. 2015 Aug; 31(4):302-7.

13. Capar ID, Arslan H, Akcay M, Uysal B. Effects of Protaper Universal, Protaper

Next, and HyFlex instruments on crack formation in dentin. J Endod. 2014. Sep;

40(9):1482-4.

14. Carvalho MA, Lazari PC, Gresnigt M, Del Bel Cury AA, Magne P. Current

options concerning the endodontically-treated teeth restoration with the adhesive

approach. Braz Oral Res. 2018 Oct 18;32(suppl 1):e74.

Bibliography



approach. Braz Oral Res. 2018 Oct 18;32(suppl 1):e74. doi:10.1590/1807-

3107bor-2018.vol32.0074. Review.



approach. Braz Oral Res. 2018 Oct 18;32(suppl 1):e74.5.

17. Celikten B, Uzuntas CF, Gulsahi K. Resistance to fracture of dental roots

obturated with different materials. Biomed Res Int. 2015 Feb:1-5

18. Chisnoiu A, Picos A, Lascu L, Negucioiu M, Chisnoiu R, Kui A. Dentists'

perspectives on the reconstruction possibilities of a non-vital tooth. Med Pharm

Rep. 2019 Oct;92(4):387-392.

19. Cloet E, Debels E, Naert I. Controlled Clinical Trial on the Outcome of Glass

Fiber Composite Cores Versus Wrought Posts and Cast Cores for the Restoration

of Endodontically Treated Teeth: A 5-Year Follow-up Study. Int J Prosthodont.

2017 Jan/Feb;30(1):71-79.

20. Comut A, Foran D, Cunningham RP. A technique to salvage endodontically

compromised maxillary anterior tooth. N Y State Dent J. 2014 Jan;80(1):33-7.

21. De Moraes AP, Poletto Neto V, Boscato N, Pereira-Cenci T. Randomized clinical

trial of the influence of impression technique on the fabrication of cast metal

posts. J Prosthet Dent. 2016 Jul;116(1):47-51.

Bibliography

22. Campanella V, Carosi P, Casella S, Pinto A, Di Girolamo M. Clinical fitting of a

cast metal post and core obtained by means of an intraoral optical scanning

(IOS) and digital workflow. J Biol Regul Homeost Agents. 2019 May-Jun;33(3

Suppl. 1):43-50.

23. Dhingra A, Ruhal N, Miglani A. Evaluation of Single File Systems Reciproc,

Oneshape, and WaveOne using Cone Beam Computed Tomography -An In Vitro

Study. J Clin Diagn Res. 2015 Apr; 9(4):ZC30-4.

24. Elavarasu P, Karumaran CS, Indira R, Anilkumar R, Mani R, Natarajan R. An In

Vitro Evaluation of Fracture Resistance of Endodontically Treated Maxillary

Central Incisor Restored with Custom-Made Cast Post and Core with Uniform

and Nonuniform Core Ferrule Heights. J Pharm Bioallied Sci. 2019

May;11(Suppl 2):S407-S412.

25. . Ertas H, Sagsen B, Arslan H, Ertas E.T. Effects of physical and morphological

properties of roots on fracture resistance. Eur J Dent 2014; 8(26):1-4.

26. Fokkinga WA, Kreulen CM, Vallittu PK, Creugers NH. A structured analysis of

In vitro failure loads and failure modes of fiber, metal, and ceramic post-and-

core systems. Int J Prosthodont. 2004 Jul-Aug;17(4):476-82.

27. Fontana PE, Bohrer TC, Wandscher VF, Valandro LF, Limberger IF, Kaizer OB.

Effect of Ferrule Thickness on Fracture Resistance of Teeth Restored With a

Glass Fiber Post or Cast Post. Oper Dent. 2019 Nov/Dec;44(6):E299-E308.

28. Fuss Z, Lustig J, Tamse A. Prevalence of vertical root fractures in extracted

endodontically treated teeth. Int Endod J. 1999; 32(4):283-86.

Bibliography

29. Ganesh A, Venkatesh Babu N, John A, Deenadhayalan G, Kandaswamy D A.

comparative assessment of fracture resistance of endodontically treated and

retreated teeth: An in-vitro study. Jour of Cons Dent 2014;17(1):61-65.

30. Gudoutos EE, Fracture Mechanics: An introduction 2nd edition, Dordrecht,

Netherland: Springer Publishers, 2005: 79-94.

31. Haralur SB, Al Ahmari MA, AlQarni SA, Althobati MK. The Effect of

Intraradicular Multiple Fiber and Cast Posts on the Fracture Resistance of

Endodontically Treated Teeth with Wide Root Canals. Biomed Res Int. 2018

Aug 15;2018:1671498.

32. Hegde V, Arora S. Fracture resistance of roots obturated with novel hydrophilic

obturation systems. J Conserv Dent. 2015 May-Jun;18(3):261-4.

33. Helvacioglu-Yigit D, Aydemir S, Yilmaz A. Evaluation of dentinal defect

formation after root canal preparation with two reciprocating systems and hand

instruments: An in-vitro study. Biotechnol Equip. 2015 Mar 4; 29(2):368-373.

34. Hendi AR, Moharrami M, Siadat H, Hajmiragha H, Alikhasi M. The effect of

conventional, half-digital, and full-digital fabrication techniques on the retention

and apical gap of post and core restorations. J Prosthet Dent. 2019

Feb;121(2):364.e1-364.e6.

35. Hof R, Perevalov V, Eltanani M, Zary R, Metzger Z. The self-adjusting file

(SAF) Part 2: Mechanical analysis. J Endod 2010;36(4):691-702.

36. Isidor F, Odman P, Brøndum K. Intermittent loading of teeth restored using

prefabricated carbon fiber posts. Int J Prosthodont. 1996 Mar-Apr;9(2):131-6.

Bibliography

37. Jhamb S, Nikhil V , Singh V. Effect of sealers on fracture resistance of

endodontically treated teeth with and without smear layer removal- An in vitro

study. J Conserv Dent 2009 july-sep;12( 3):114-17

38. Johnson M. E., Stewart G. P., Nielsen C. J., and Hatton J. F. Evaluation of root

reinforcement of endodontically treated teeth, Oral Surgery, Oral Medicine, Oral

Pathology, Oral Radiology, and Endodontics. 2000:90(3): 360-64.

39. Kar S, Tripathi A, Trivedi C. Effect of Different Ferrule Length on Fracture

Resistance of Endodontically Treated Teeth: An In vitro Study. J Clin Diagn Res.

2017 Apr;11(4):ZC49-ZC52.

40. Karteva EG, Manchorova NA, Vladimirov SB, Keskinova DA. Clinical

Assessment of Endodontically Treated Teeth, Restored with or without Radicular

Posts. Folia Med (Plovdiv). 2018 Jun 1;60(2):291-299.

41. Khiavi HA, Habibzadeh S, Safaeian S, Eftekhar M. Fracture Strength of

Endodontically treated Maxillary Central Incisors restored with Nickel

Chromium and Nonprecious Gold Alloy Casting Post and Cores. J Contemp

Dent Pract. 2018 May 1;19(5):560-567.

42. Kim HC, Lee MH, Yum J, Versluis A, Lee CJ, Kim BM. Potential relationship

between design of nickel-titanium rotary instruments and vertical root fracture. J

Endod. 2010 Jul; 36(7):1195-9.

Bibliography

43. Kurthukoti AJ, Paul J, Gandhi K, Rao DB. Fracture resistance of endodontically

treated permanent anterior teeth restored with three different esthetic post

systems: An in vitro study. J Indian Soc Pedod Prev Dent 2015 0ct-Dec; 33(4);

296-301.

44. Lertchirakarn V, Timyam A, Messer HH. Effects of root canal sealers on vertical

root fracture resistance of endodontically treated teeth. J Endod 2002;28:217-19.

45. Malferrari S, Monaco C, Scotti R. Clinical evaluation of teeth restored with

quartz fiber-reinforced epoxy resin posts. Int J Prosthodont. 2003 Jan-

Feb;16(1):39-44.

46. Mankar S, Kumar NS, Karunakaran JV, Kumar SS. Fracture resistance of teeth

restored with cast post and core: An in vitro study. J Pharm Bioallied Sci. 2012

Aug;4(Suppl 2):S197-202.

47. Marchionatti AME, Wandscher VF, Rippe MP, Kaizer OB, Valandro LF. Clinical

performance and failure modes of pulpless teeth restored with posts: a

systematic review. Braz Oral Res. 2017 Jul 3;31:e64.

48. Martino N, Truong C, Clark AE, O'Neill E, Hsu SM, Neal D, Esquivel-Upshaw

JF. Retrospective analysis of survival rates of post-and-cores in a dental school

setting. J Prosthet Dent. 2019 Jul 26. pii: S0022-3913(18)30702-9.

49. Meister F Jr., Lommel T. J., and Gerstein H. Diagnosis and possible causes of

vertical root fractures. Oral Surgery Oral Medicine and Oral Pathology 1980:

49(3): 243-253.

Bibliography

50. Metzger Z, Teperovich E, Zary R, Cohen R The self adjusting file(SAF) Part 1:

Respecting the root canal anatomy- A new concept of endodontic files and its

implementation J Endod 2010; 36(4): 679-690.

51. Mohajerfar M, Nadizadeh K, Hooshmand T, Beyabanaki E, Neshandar Asli H,

Sabour S. Coronal Microleakage of Teeth Restored with Cast Posts and Cores

Cemented with Four Different Luting Agents after Thermocycling. J

Prosthodont. 2019 Jan;28(1):e332-e336.

52. Munaga S, Das A, Kaur T, Yaqoob A, Mokashi R, Ismail PM. Comparative

Clinical Evaluation of Composite Overcast Gold Post and Core Buildups in

Endodontically Treated Teeth. J Contemp Dent Pract. 2018 Oct 1;19(10):1273-

1277.

53. Muttlib NA, Azman AN, Seng YT, Alawi R, Ariffin Z. Intracanal Adaptation of a

Fiber Reinforced Post System as Compared to a Cast Post-and-Core. Acta

Stomatol Croat. 2016 Dec;50(4):329-336.

54. Naumann M, Schmitter M, Frankenberger R, Krastl G. "Ferrule Comes First.

Post Is Second!" Fake News and Alternative Facts? A Systematic Review. J

Endod. 2018 Feb;44(2):212-219.

55. Naumann M, Schmitter M, Krastl G. Postendodontic Restoration: Endodontic

Post-and-Core or No Post At All? J Adhes Dent. 2018;20(1):19-24.

Bibliography

56. Nokar S, Bahrami M, Mostafavi AS. Comparative Evaluation of the Effect of

Different Post and Core Materials on Stress Distribution in Radicular Dentin by

Three-Dimensional Finite Element Analysis. J Dent (Tehran). 2018

Mar;15(2):69-78.

57. Nur BG, Ok E, Altunsoy M, Tanriver M, Capar ID. Fracture strength of roots

instrumented with three different single file systems in curved root canals. Eur J

Dent. 2015 Apr-Jun;9(2):189-93.

58. Öztürk C, Polat S, Tunçdemir M, Gönüldaş F, Şeker E. Evaluation of the fracture

resistance of root filled thin walled teeth restored with different post systems.

Biomed J. 2019 Feb;42(1):53-58.

59. Pereira JR, do Valle AL, Shiratori FK, Ghizoni JS, Bonfante EA. The effect of

post material on the characteristic strength of fatigued endodontically treated

teeth. J Prosthet Dent. 2014 Nov;112(5):1225-30.

60. Peters OA, Paque F. Current developments in root canal instrument technology

and clinical use: A review. Quintessence Int 2010 June; 41(6):479-88.

61. Ravi N, Mahima G, Shalini S .Comparison Of Fracture Resistance in roots of

endodontically treated teeth using different root filling materials: An in Vitro

Study. Indian Journal of Dental Sciences. September 2012; 3 (4): 7-8.

62. Rayyan MR, Aldossari RA, Alsadun SF, Hijazy FR. Accuracy of cast posts

fabricated by the direct and the indirect techniques. J Prosthet Dent. 2016

Sep;116(3):411-5.

Bibliography

63. Rezaei Dastjerdi M, Amirian Chaijan K, Tavanafar S. Fracture resistance of

upper central incisors restored with different posts and cores. Restor Dent

Endod. 2015 Aug;40(3):229-35.

64. Ribeiro F. C., Souza-Gabriel A. E., Marchesan M. A., Alfredo E., Silva-Sousa Y.

T. C, and Sousa-Neto M. D., “Influence of different endodontic filling materials

on root fracture susceptibility,” Journal of Dentistry 2008: 36(1): 69-73.

65. Rippe MP, Santini MF, Bier CA, Baldissara P, Valandro LF. Effect of root canal

preparation, type of endodontic post and mechanical cycling on root fracture

strength. J Appl Oral Sci. 2014 Jun;22(3):165-73.

66. Rippe MP, Santini MF, Bier CA, Borges AL, Valandro LF. Root canal filling:

fracture strength of fiber-reinforced composite-restored roots and finite element

analysis. Braz Dent J. 2013 Nov-Dec;24(6):619-25.

67. Roane JB, Sabala CL, Duncanson MG. The “balanced force” concept for

instrumentation of curved canals. J Endod. 1985; 11: 203-211.

68. Robbins JW. Restoration of the endodontically treated tooth. Dent Clin North

Am. 2002 Apr;46(2):367-84. Review.

69. Rodrigues JL, Seraidarian PI, Oliveira DD, Jansen WC, Alves KP, Faria-e-Silva

AL. Effect of increased post length due to the presence of the remaining coronal

structure on the fracture strength of post-retained restorations. Eur J Prosthodont

Restor Dent. 2014 Sep;22(3):132-5.

70. Roghanizad N, Jones JJ. Evaluation of coronal microleakage after endodontic

treatment. J Endod. 1996; 22(9):471-73.

Bibliography

71. Saber SE, Schäfer E. Incidence of dentinal defects after preparation of severely

curved root canals using the Reciproc single-file system with and without prior

creation of a glide path. Int Endod J. 2015 Oct 1.

72. Sandikci T, Kaptan R F. Comparative evaluation of the fracture resistances of

endodontically treated teeth filled using five different root canal filling systems.

Nigerian Journal of Clinical practice 2014;17(6):667-672.

73. Santos Pantaleón D, Morrow BR, Cagna DR, Pameijer CH, Garcia-Godoy F.

Influence of remaining coronal tooth structure on fracture resistance and failure

mode of restored endodontically treated maxillary incisors. J Prosthet Dent. 2018

Mar;119(3):390-396.

74. Santos-Filho PC, Veríssimo C, Soares PV, Saltarelo RC, Soares CJ, Marcondes

Martins LR. Influence of ferrule, post system, and length on biomechanical

behavior of endodontically treated anterior teeth. J Endod. 2014 Jan;40(1):119-

23.

75. Saritha MK, Paul U, Keswani K, Jhamb A, Mhatre SH, Sahoo PK. Comparative

Evaluation of Fracture Resistance of Different Post Systems. J Int Soc Prev

Community Dent. 2017 Nov-Dec;7(6):356-359.

76. Sary S B, Samah M S, Walid A AZ. Effect of restoration technique on resistance

to fracture of endodontically treated anterior teeth with flared root canals. J

Biomed Res. 2019 Apr 22;33(2):131-138.

Bibliography

77. Savychuk A, Manda M, Galanis C, Provatidis C, Koidis P. Stress generation in

mandibular anterior teeth restored with different types of post-and-core at

various levels of ferrule. J Prosthet Dent. 2018 Jun;119(6):965-974.

78. Schwendicke F, Stolpe M. Cost-effectiveness of Different Post-retained

Restorations. J Endod. 2017 May;43(5):709-714.

79. Schwindling FS, Tasaka A, Hilgenfeld T, Rammelsberg P, Zenthöfer A. Three-

dimensional-guided removal and preparation of dental root posts-concept and

feasibility. J Prosthodont Res. 2019 May 16. pii: S1883-1958(18)30403-1.

80. Sedgley CM, Messer HH. Are endodontically treated teeth more brittle? J

Endod. 1992 Jul;18(7):332-5.

81. Shamseddine L, Chaaban F. Impact of a Core Ferrule Design on Fracture

Resistance of Teeth Restored with Cast Post and Core. Adv Med.

2016;2016:5073459.

82. Shetty RR, Nayak M, Thomas J. Fracture Resistance of endodontically treated

roots filled with Resilon and Guttapercha - A comparative in Vitro Study. J of

ICDRO 2009; 1(3): 37-48.

83. Singh S, Thareja P. Fracture resistance of endodontically treated maxillary

central incisors with varying ferrule heights and configurations: In vitro study. J

Conserv Dent. 2014 Mar;17(2):115-8

84. Skupien JA, Cenci MS, Pereira-Cenci T. Although Cast Post and Cores Present

Acceptable Survival, Patient-related Factors May Influence Survival. J Evid

Based Dent Pract. 2016 Mar;16(1):62-3.

Bibliography

85. Skupien JA, Sarkis-Onofre R, Cenci MS, Moraes RR, Pereira-Cenci T. A

systematic review of factors associated with the retention of glass fiber posts.

Braz Oral Res. 2015;29.

86. Shemesh H, van Soest G, Wu MK, Wesselink PR. Diagnosis of vertical root

fractures with optical coherence tomography. J Endod. 2008 Jun; 34(6):739-42.

87. Shemesh H, Wesselink PR, Wu MK. Incidence of dentinal defects after root

canal filling procedures. Int Endod J. 2010 Nov; 43(11):995-1000.

88. Shori DD, Shenoi PR, Baig AR, Kubde R, Makade C, Pandey S.

Stereomicroscopic evaluation of dentinal defects induced by new rotary system:

"ProTaper NEXT". J Conserv Dent. 2015 May-Jun;18(3):210-3.

89. Solomon CS, Osman YI. In vitro comparison of endodontic posts in structurally

compromised roots of maxillary incisors. SADJ. 2011 Jun;66(5):220-3.

90. Sonkesriya S, Olekar ST, Saravanan V, Somasunderam P, Chauhan RS,

Chaurasia VR. An in vitro comparative evaluation of fracture resistance of

custom made, metal, glass fiber reinforced and carbon reinforced posts in

endodontically treated teeth. J Int Oral Health. 2015 May;7(5):53-5.

91. Sornkul E, Stannard JG. Strength of roots before and after endodontic treatment

and restoration. J Endod 1992; 18:440-3.

92. Sreedevi S, Sanjeev R, Raghavan R, Abraham A, Rajamani T, Govind GK. An In

Vitro Study on the Effects of Post-Core Design and Ferrule on the Fracture

Resistance of Endodontically Treated Maxillary Central Incisors. J Int Oral

Health. 2015 Aug;7(8):37-41.

Bibliography

93. Stankiewicz NR, Wilson PR. The ferrule effect: a literature review. Int Endod J.

2002 Jul;35(7):575-81. Review.

94. Stavridakis M, Brokos Y, Krejci I. Is the glass half empty or half full? A novel

"philosophical" approach to the "mystery" of the so-called ferrule effect. Med

Hypotheses. 2018 Jun;115:35-41.

95. Swartz DB, Skidmore AE, Griffin JA. Twenty years of Endodontic success and

Failures. Journal of Endodntics. 1983; 9(5):198-202.

96. Tay FR, Pashley DH. Monoblocks in root canals: A hypothetical or a tangible

goal. J Endod 2007; 33:391-8.

97. Tsintsadze N, Juloski J, Carrabba M, Tricarico M, Goracci C, Vichi A, Ferrari M,

Grandini S. Performance of CAD/CAM fabricated fiber posts in oval-shaped

root canals: An in vitro study. Am J Dent. 2017 Oct;30(5):248-254.

98. Tsintsadze N, Juloski J, Carrabba M, Tricarico M, Goracci C, Vichi A, Ferrari M,

Grandini S. Performance of CAD/CAM fabricated fiber posts in oval-shaped

root canals: An in vitro study. Am J Dent. 2017 Oct;30(5):248-254.

99. Türker SA, Özçelik B, Yilmaz Z. Evaluation of the Bond Strength and Fracture

Resistance of Different Post Systems. J Contemp Dent Pract. 2015 Oct

1;16(10):788-93.

100. Upadhyaya V, Bhargava A, Parkash H, Chittaranjan B, Kumar V. A finite

element study of teeth restored with post and core: Effect of design, material,

and ferrule. Dent Res J (Isfahan). 2016 May-Jun;13(3):233-8.

Bibliography

101. Uzunoglu.E, Aktemur S, Uyanik M O, Durmas V, Nagas E Effect of

ethylenediaminotetracetic acid on root fracture with respect to concentration at

different time exposures J Endod 2012; 38: 1110-1113.

102. Vadavadagi SV, Dhananjaya KM, Yadahalli RP, Lahari M, Shetty SR,

Bhavana BL. Comparison of Different Post Systems for Fracture Resistance:

An in vitro Study. J Contemp Dent Pract. 2017 Mar 1;18(3):205-208.

103. Vallabhaneni S, More GR, Gogineni R. Single file endodontics. Indian J Dent

2012; 4(2): 822-826.

104. Wang CH, Du JK, Li HY, Chang HC, Chen KK. Factorial analysis of variables

influencing mechanical characteristics of a post used to restore a root filled

premolar using the finite element stress analysis combined with the Taguchi

method. Int Endod J. 2016 Jul;49(7):690-9.

105. Williams C, Loushine RJ, Weller RN, Pashley DH, Tay FR. A comparison of

cohesive strength and stiffness of Resilon and gutta-percha. J Endod

2006;32:553-555.

106. Yavari HR, Samiei M, Shahi S, Aghazadeh M, Jafari M, Abdolrahimi M, et al.

Microleakage comparison of four dental materials as intra-orifice barriers in

endodontically treated teeth. Iran Endod J. 2012; 7(1):25-30.

107. Yoldas O, Yilmas S, Atakan G, Knudsen C, Kasan Z Dentinal microcrack

formation during root canal preparations by different rotary niti instruments

and the self-adjusting file J. Endod 2012;38:232-5.

“fracture resistance of endodontically treated …

Documents