ceramic adhesive restorations and biomimetic dentistry: tissue … · 2014. 8. 15. · and...

CLINICAL RESEARCH

354THE INTERNATIONAL JOURNAL OF ESTHETIC DENTISTRY

Correspondence to: Gil Tirlet

234 Boulevard Raspail, 75014 Paris, France. Tel : +33 43204130: E-mail: [email protected]

Ceramic adhesive restorations

and biomimetic dentistry:

tissue preservation and adhesion

Gil TirletSenior Lecturer, Department of Prosthetic Dentistry, Faculty of Dental Surgery,

Paris Descartes University, Paris, France

Private Practice Specializing in Esthetic Dentistry, Paris, France

Hélène CrescenzoCeramic Dental Technician, Espace Diamant, Cogolin, France

Dider CrescenzoCeramic Dental Technician, Espace Diamant, Cogolin, France

Panaghiotis Bazos, DDS

Emulation, Athens, Greece

TIRLET ET AL


Abstract

Thanks to sophisticated adhesive tech-

niques in contemporary dentistry, and the

development of composite and ceramic

materials, it is possible to reproduce a

biomimetic match between substitution

materials and natural teeth substrates.

Biomimetics or bio-emulation allows for

the association of two fundamental par-

ameters at the heart of current therapeu-

tic treatments: tissue preservation and

adhesion. This contemporary concept

makes the retention of the integrity of

the maximum amount of dental tissue

possible, while offering exceptional clin-

ical longevity, and maximum esthetic

results. It permits the conservation of

the biological, esthetic, biomechanic-

al and functional properties of enamel

and dentin. Today, it is clearly possible

to develop preparations allowing for the

conservation of the enamel and dentin in

order to bond partial restorations in the

anterior and posterior sectors therefore

limiting, as Professor Urs Belser from

Geneva indicates, “the replacement of

previous deficient crowns and devital-

ized teeth whose conservation are justi-

fied but whose residual structural state

are insufficient for reliable bonding.”1

This article not only addresses ceramic

adhesive restoration in the anterior area,

the ambassadors of biomimetic dentist-

ry, but also highlights the possibility of

occasionally integrating one or two res-

torations at the heart of the smile as a

complement to extensive rehabilitations

that require more invasive treatment.

(Int J Esthet Dent 2014;9:354–369)


CLINICAL RESEARCH


Introduction

Biomimetics is the reproduction or copy

of a model or a standard.2,3 More pre-

cisely, the notion of biomimetics consists

of reproducing and artificially imitating

natural systems in living organisms.

Biomimetics is an emerging interdisci-

plinary field in materials science, engi-

neering, and biology, in which lessons

learned from a biological standard form

the basis for novel technological ma-

terial innovation. It involves the inves-

tigation of both structures and physi-

cal functions of biological composites

of engineering interest, with the goal of

designing and synthesizing new and

improved materials.

The term bio-emulation was intro-

duced as a new expression for the dis-

cipline of dentistry, corresponding to

the reproduction of the natural model

via spatial, structural and optical histo-

anatomic emulation.4 In contemporary

dentistry, the concept of biomimetics

is a true synonym for natural integra-

tion,3 meaning biological, biomechan-

ical, functional and esthetic integration,

which closely mimicks the physiological

behavior of the natural tooth.3,5

Because of sophisticated adhesive

techniques and the progress that has

been made in ceramic adhesives, today

it is possible to produce a biomimetic

match between esthetic substitution ma-

terials and the anatomical substrates of

the natural tooth.

Biomimetics associates two funda-

mental attributes at the core of modern

care: tissue preservation and adhesion.

It Is undisputable that this concept has

had the most profound effects on the

paradigms of modern restorative den-

tistry. As Pascal Magne points out,3 the

concept of modern biomimetics can

be summarized into three distinct, but

closely linked, categories:

Observation of nature, biology, its

role, its mechanical behavior, and

its optical characteristics

Respect of nature in preparing a

minimal dental tissue

Reproduction of nature using

adhesion and modern biomaterials

(composites and ceramics)

Reference model:

the natural tooth

Natural teeth are the physiological result

of a subtle association between enam-

el, rigid and breakable, and the dentin,

resilient and flexible. From a functional

point of view, dentin cannot exist if an

enamel shell does not cover it.3 These

two tissues are associated and joined

together by an incredibly rich anatom-

ical interface called the dentoenamel

junction (DEJ). It is capable, through

the intermediary of large fasces of col-

lagen fibers to deflect and to impede the

spreading of crevices in the enamel due

to plastic deformation.3

Thus, due to its role as a buffer and

stress absorber, it is a reference model

for adhesive systems and polymer adhe-

sives used for reinforcing the biomech-

anical integrity of dental crowns5 (Fig 1).

Substitution model: adhe-

sive ceramic restorations

The replacement of the enamel shell with

a soft material, such as composites, only

TIRLET ET AL


allows for a partial restitution of the rigid-

ity of the dental crown. From this point of

view, the choice of ceramics allows for a

faithful restitution of this rigidity.2,3

Furthermore, aging is synonymous

with the volumetric reduction of the

enamel layer, and thus, an increase in

the flexibility of the tooth due to its de-

creasing rigidity.

The restitution of the original volume

of the enamel thus represents an esthet-

ic as well as a biomechanical approach.

Adhesive bonding technology and ce-

ramics have the ability to reverse and

resist the effects of aging on teeth.3 For

the aforementioned reasons, a rational

selection of restorative materials proves

to be essential.

Another essential point is the mater-

ial to combination ratio. The CER/COMP

ratio should ideally be superior to 3. This

is of great importance, due to the con-

tracting of polymers in the bonding com-

posite, and the differences in thermal

expansion between the two materials.

Thus, for an average bonded joint den-

sity of 100 mm, the ideal density of the

veneer should be a minimum of 300 mm.

A ratio inferior to the critical level of 3 will

have important consequences in terms

of potential failure rates of the restoration

(fissures and cracks in the ceramic ad-

hesive restoration).3

Therefore, the changing of paradigms

must be accompanied by the progres-

sive passage from full coverage ce-

ramic restorations to partial coverage

ceramic restorations.6 The latter may

take the form of inlays, onlays, overlays,

veneerlays in the posterior sector and

in veneers, half veneers or chips in the

anterior sector.6 The scope of this article

aims to address the various partial cov-

erage ceramic adhesive restorations in

the anterior sector.

The recognition of the importance of

the integrity of dental tissue is the focus

of biomimetics. An analysis of these last

points is critical following the removal of

a prior restoration, trauma, or the elimi-

nation of a decayed lesion, in order to

economize hard tissue removal.

This analysis must be conducted in

conjunction with the occlusion scheme

at hand, with emphasis on the presence

or absence of horizontal and/or oblique

stress, the latter being the most detri-

mental for teeth (eg, supraocclusion,

dental wear, parafunctions, poor align-

ment).

Composites – in part due to their in-

herent low elastic modulus – appear to

be challenged by mechanical stresses,

both masticatory and occlusal, when

replacing large anterior coronal defi-

ciencies.7 In conjunction, the thermal

conduction mismatches them, and hy-

groscopic expansion renders them even

Fig 1 View of the natural incisors photographed

in transmission, allowing for the observation of dif-

ference in thickness between the enamel (of the cer-

vical on the edge of the incisor) and the dentin, as

well as the amelodentin junction.

CLINICAL RESEARCH


more vulnerable over time.7 Additionally,

composites require relatively frequent,

meticulous clinical maintenance in or-

der for them to reach their approximate

10-year life expectancy. Swift, with a pan-

el of experts, concluded that the more

complex the restoration, the shorter the

longevity.8 This statement partially con-

firms the deficiency in stiffness attain-

ment by composite, in order to recover

the original rigidity – that of enamel.

Thus today, in our clinical approach,

the stratification of anterior composites

may increasingly give way to partial cov-

erage ceramic adhesive restorations in

cases of large anterior coronal deficien-

cies, which are most often required in

adults in situations where stable high

esthetic requirements and longevity are

demanded.9-11 These types of restor-

ations embody the conservative doc-

trine, undisputedly placing them as the

therapeutic ambassador for modern

biomimetic dentistry.

This article will illustrate four clinical

cases, three of which deal with vital teeth

and one with a non-vital tooth. The clinic-

al situations have been chosen in order

to demonstrate that beyond the biomi-

metic approach (the chosen path for al-

most 20 years of “French” conservative

and esthetic dentistry, today considered

to be modern), the practitioner must de-

ploy all modern therapeutic possibilities

in order to not only treat the damaged

tooth or teeth but also take into consider-

ation the targeted esthetic requirements

of their patients, particularly in regards

to the therapeutic gradient.12

Case studies

Case 1

A 65-year-old woman, concerned about

her central upper incisors, presented for

an esthetic consultation. Her chief com-

Fig 2 Initial situation. Fig 3 Clinical view of preparation with post and

core (POM, Ivoclar/Vivadent on 12) and Partial

preparations with conservation of maximum enamel

on 11 and 21. The thickness of the preparation was

between 0.4 and 0.6 mm thus creating an optimal

enamel surface for bonding.

TIRLET ET AL


Fig 4 Preparation

after curing of the ad-

hesive system on 11.

Fig 6 Final result at 1-week follow-up. Note the

biological and morphological appearance. This

view perfectly illustrates the biomimetic concept

using the “enamel substitution,” allowing the total

recovery of the intrinsic strength of the teeth.

Fig 5 View of the

ceramic adhesive

restoration at bond-

ing. The adhesive

used was Optibond

Solo plus (Kerr).

Fig 7 One-month follow-up with contrastor.

plaint was that she disliked the shape

and the position of 21 and 11 (Fig 2).

The following treatment plan was pro-

posed to the patient: the rehabilitation of

her smile by a new crown on 12 (she pre-

sented gingival inflammation induced

by the actual prosthesis’ overcontour),

as well as two resin-bonded partial-cov-

erage ceramic restorations. Tooth 22

dictated the esthetic outcome and guid-

ed this minimally invasive rehabilitation

(Figs 3 to 7). No crown lengthening in or-

der to correct the gingival margin archi-

tecture was performed since the patient

preferred to avoid additional surgery.

Although a lack of symmetry among the

anterior teeth can be observed, the pa-

tient’s smile is still harmonious and natu-

ral (Figs 8 to 11).

CLINICAL RESEARCH


Case 2

A 17-year-old patient consulted in or-

der to re-evaluate previous endodontic

work on tooth 21 that was completed 3

years previously following a trauma – it

was discolored due to a root canal. The

therapeutic choice in this case only took

into consideration the biological, bio-

mechanical and esthetic rehabilitation

of tooth 21 per the patient’s esthetic re-

quest (Fig 12).

The composite restoration was fixed

with a stainless steel post and core,

which characterizes conventional den-

tistry based on mechanical concepts

(Fig 13). An initial radiograph was taken,

which displayed the high quality of the

endodontics (Fig 14). The composite

restoration and the stainless steel post

and core were removed (Fig 15).

A dental dam was applied. The crown

presented very good residual tissue. After

sandblasting, etching and the placing of

Fig 8 One-year follow-up (with two lateral softbox).

At this time, we can notice a little gingival injury (me-

sial side on 12) caused by severe tooth brushing.

Fig 10 One-year follow-up: left lateral view of the

smile. The asymmetry in the shape and the dental

composition remains the principal key to the smile’s

expression.13

Fig 9 One-year follow-up. Image taken with con-

trastor (with two lateral soft boxes).

Fig 11 One-year follow-up: right lateral view of

the smile.

TIRLET ET AL


the adhesive system, flow micro hybrid

composite was applied at the base of

pulpal chamber preceding the placement

of the restoration composite (UD2, Enamel

HRi, Mycerium). A post was not necessary

in this situation due to the important ferrule

effect – the result of the conservation of

residual tissue (Fig 16).

The ceramic adhesive restoration

(e.max MO1, Ivoclar Vivadent) on the

buccal side was prepared, increasing

the enamel surface. A metallic matrix was

Fig 13 The composite restoration is fixed with a

stainless steel post and core.

Fig 15 Clinical view following the removal of the

composite restoration and prior to the removal of the

stainless steel post and core.

Fig 12 Initial clinical situation.

Fig 14 An initial radio-

graph exhibits the high

quality of the endodontics.

Fig 16 Clinical view of 21 with dental dam.

CLINICAL RESEARCH


Fig 17 Preparation of the ceramic

adhesive restoration on the buccal

side.

Fig 19 Final occlusal view with the palatal exten-

sion going beyond the cingulum.

Fig 21 View of the

ceramic adhesive res-

toration at the moment

of bonding. The adhe-

sive used was Optibo-

nd Solo plus.

Fig 18 Completion of the buccal

preparation with an Acteon/Satelec

insert.

Fig 20 View of the Emax MO1 ce-

ramic adhesive restoration.

Fig 22 Radiograph fol-

lowing bonding that dem-

onstrates the perfect fit

and seal of the restoration.

TIRLET ET AL


connected to a plastic corner (Fender

wedge, Pred), which protected the ad-

jacent teeth. The buccal preparation

was completed with an Acteon/Satelec

insert for finishing two diamond grits: 76

microns and 46 microns to perfectly fin-

ish the margins (Figs 17 to 19). The ce-

ramic adhesive restoration was bonded

(Figs 20 and 21) and a radiograph at-

tested for a good adaptation (Fig 23).

Figures 23 to 26 show the final result and

biomimetic integration after bonding.

Figure 27 shows the clinical result at the

3-year follow-up.

Fig 24 Black and white picture to appreciate

brightness of the single restoration.

Fig 26 Smile integration.

Fig 23 Clinical view one week after bonding.

Fig 25 One-week follow-up (with contrastor).

Fig 27 Three-year follow-up.

CLINICAL RESEARCH


Case 3

A 34-year-old man had a large compos-

ite on the left central incisor (21). The

patient refused proposed orthodontic

treatment. He preferred to find another

esthetic solution to restore his tooth. The

suggested treatment consisted of re-

placing the composite restoration with

a ceramic bonded partial restoration

(Fig 28).

Fig 28 Initial situation.

Fig 29 The clinical view of the preparation for the

ceramic half veneer. Excellent tissue preservation

can be observed.

Fig 31 The preparation following placement of

the dam before bonding.

Fig 30 The final step in preparation with diamond

ultrasonic insert.

Fig 32 Ceramic half-veneer

restoration before bonding.

TIRLET ET AL


When the preparation for the ceramic

half veneer was carried out, excellent

tissue preservation could be observed.

The tooth was then prepared with a di-

amond ultrasonic insert (Fig 29 to 31).

A rubber dam was applied before the

bonding of the ceramic half-veneer

(Figs 31 and 32). Figure 33 and 34

(1 year and 6 months follow-up with two

lateral soft boxes) shows the final biomi-

metic results.

Case 4

A 35-year-old woman came to our prac-

tice because of a bike trauma (Fig 35).

We diagnosed crown fractures from me-

dium to severe on teeth 11, 21 and 22

and also had to plan endodontic treat-

ment. A temporary composite build

up was performed on the three teeth.

Preparations were guided by mock-ups

(Figs 36 to 38). Figures 39 to 43 show

the biomimetic results. Figure 44 shows

a radiograph to control apical healing

Fig 33 Final biomimetic result.

Fig 35 Initial situation: emergency.

Fig 34 Final situation (with two lateral soft box).

Fig 36 Preparation driven by mock-up.3,14 The

wax-up permitted the creation of a mock-up with

a silicone index use during the preparation stage.

CLINICAL RESEARCH


Fig 39 Final view: one-week follow-up after

bonding.

Fig 41 Polarized view with Polar_eyes (Emulation).

Fig 38 View of four preparation for ceramic ad-

hesive restorations. No post or crown in this case

even on non-vital teeth and preservation of maximal

enamel.

Fig 37 Mock-up just after preparation. (Luxatemp

Star, DMG)

Fig 40 Black and white picture to appreciate

brightness of the four restorations.

Fig 42 Lateral view of smile: right side.

TIRLET ET AL


Fig 45 Buccal view at one-year follow-up. Note

the biomimetic integration and especially the bio-

logical integration with the gum.

Fig 44 Radiograph with complete apical healing

on four anterior teeth.

Fig 43 Intra buccal view: right side.

Fig 46 Buccal view at two-year follow-up (with

two lateral soft boxes).

and demonstrates a lack of Post and

core (Endodontic treatment: Dr Anne

Laure Simon, Paris). Figures 45 and 46

show the results at a two-year follow up

with two lateral soft boxes).

Conclusion

In choosing partial coverage ceramic

adhesive restorations, biomimetics per-

mits the imitation of the biological, es-

thetic, biomechanical and functional

properties of enamel and dentin.

Provided there is diligent implemen-

tation and management of modern

dental technology, dental adhesive sys-

tems have proven to be reliable over

time, thus imparting a secure bond

between the tooth and the restoration.

Nonetheless, deep knowledge of bio-

mechanical principles and techniques

of conservative tooth preparation are

essential to create optimal conditions

CLINICAL RESEARCH


for the implementation of a favorable

oral restitution.

The timelessness, the ideal surface

characteristics and biomechanical inter-

action that are ensured by a high per-

formance dynamic bond to the tooth as

a whole, classify ceramics as the ideal

restorative materials and the best choice

in terms of esthetic satisfaction. Optimal

rigidity in delicate areas, excellent chew-

ing capacity, biocompatibility with peri-

odontal tissues, combined with excel-

lent continuity between the material and

enamel after bonding, bestows them

with the ability to act as a true enamel

replacement. It is important, however,

to be attentive in order to conserve the

maximum amount of enamel by imple-

menting contemporary protocols, such

as preliminary wax-ups, mock-ups and

volumetric driven matrix guided reduc-

tions.

Partial coverage ceramic adhesive

restorations can be utilized as the re-

storative treatment modality in a variety

of clinical cases, vital and/or non-vital

teeth provided that fundamental bond-

ing requirements can be met.

The goal of this article is not only to

showcase the said restorative modality

in the anterior dentition, as a strong pro-

ponent of biomimetic dentistry, but also

to highlight the possibility of achieving

a seamless integration of restorations at

the heart of the smile as a contrast to ex-

tensive and invasive rehabilitations that

would require more invasive treatment.

Today the possibility exists to estheti-

cally reconstruct teeth while preserving

tissue. It is important to take this major

evolution of biomimetics into considera-

tion in our respective practices.

In conclusion, Pascal Magne at the

Brussels Conference, December 2011,

perfectly illustrated this concept: “Get

bonded, stay bonded.”15

Acknowledgments

I would like express my most sincere

gratitude to my advisor Professor Michel

Degrange for all that he has taught me,

both clinically and scientifically, and

to express my utmost admiration for

all that he has contributed to adhesive

dentistry throughout his career and life. I

would also like to warmly thank my other

mentor Dr Pascal Magne for all that he

has brought me over the past 20 years

through his clinical and scientific work.

His place at the summit of contemporary

dentistry remains for me an absolute ex-

ample and reference.

I would also like thank to my “brother”,

Dr JP Attal for sharing in this exceptional

human and professional adventure at

the university and the hospital, as well

as through GRF’s biomimetic workshops

over the past seven years.

I also extend my warmest thanks to

my new professional “family,” the Bio-

Emulation Group, through whose daily,

challenging exchanges I continue to

progress ever more.

I finally thank Maris Harrington for her

invaluable help in the writing and editing

of this article.

TIRLET ET AL


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British Dental Journal volume

213 no. 4 aug 25. 2012.

ceramic adhesive restorations and biomimetic dentistry: tissue … · 2014. 8. 15. · and...

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