Aesthtetic Inlays Desarrollo

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Operative Dentistry

Aesthetic inlaysin the dental practice

AbstractMany of the studies conducted in the field of RestorativeDentistry aim to obtaining an ideal filling material. Amalgam alloystill remains the most widely used material for restoration of pos-terior teeth, but this pattern of practice is changing as a result ofmaterials and techniques developed in recent years. There hasbeen an increased demand for aesthetic restoration and also agrowing concern about biocompatibility, raising questions regard-ing the safety of mercury in amalgam, both for the dentist and thepatient.Aesthetic inlays are a valid alternative to direct restorations in the

case of large defects in posterior teeth. The purpose of this paperis to provide the practicing dentist with a panoramic view and asystematic step by step technique for the adhesive luting of suchkind of restorations.

Dr. G. Goracci1 - Dr. M. Andreasi Bassi2

DENTAL NEWS, VolumeVI, Number 2, 1999. 11Aestheticinlaysinthedental practice

Correspondence address:

Guido Goracci. Via Tagliamento,50, 00198 Rome, Italy.

Tel.: 396+ 8548260Fax: 396+ 8414218

INTRODUCTION

1- MSD, DDS, Professor and Director, Department of Operative Dentistry,University of Rome La Sapienza, Italy.

2- DDS, Ph. D., Department of Operative Dentistry, University of RomeLa Sapienza, Italy.

Aesthetic considerations are becomingalways more important in OperativeDentistry even for the restoration of pos-terior teeth. Aesthetic inlays (AI) repre-sent an heterogeneous family of toothcolored restorations for the permanentrestoration of posterior teeth and joinedby the presence of a composite cementinterposed between the restoration andthe tooth cavity. AI are the most suitable

solution for restoration of large defects.Their advantage is that most of the com-posite used is displaced by an inertbody. Thus, the amount of compositepolymerized in the oral cavity is mini-mal1. This reduces the problem of thepolymerization shrinkage to insignificantlevels. AI require a particular uppercutcavity preparation with a 10-15 taperwithout beveled enamel margins7,17. Theyalso require a meticulous use of anadhesive technique which produces amicromechanical and chemical bondbetween both, luting composite and

tooth cavity as well as between com-posite and inlay. Therefore inlays insert-ed with adhesive techniques always

show an excellent margin behaviour andno marginal openings13. Normally, whenthe cavities do not interest the cusps, itis correct to speak of inlays, while whenthe cavity preparation involves one ormore cusps, such restorations are calledonlays7. Depending on the material used

AI can be initially divided into twogroups: Ceramic inlays and Compositeinlays.


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DENTAL NEWS, VolumeVI, Number 2, 1999.12 Aestheticinlaysinthedental practice

Operative Dentistry

Ceramic Inlays

Since their introduction, in 1839 by

J ohn Murphy12

, numerous techniqueshave been adopted both to increase theaccuracy of fit of these restorations andto improve and simplify their methods ofproduction. Ceramic materials havemany excellent properties, particularlyin terms of biocompatibility, chemicaldurability, and optical and aestheticproperties. Ceramic inlays, however,have never been adopted for routineand large use because of the complexi-ty of the technique, time-consumingmethods and consequential costs offabrication12.

According to their method of construc-tion they can be classificated as: plaitedceramic inlays; preshaped ceramicinlays; fired feldspathic ceramic inlays;glass-ceramic inlays.

Plaited ceramic inlays are performedusing blocks of ceramic material whichare plaited in the correct shape bymeans of a particular plaiting-machine.

Two systems are available: Cerec 2(Siemens) and Celay (Mikrona). TheCerec 2 system uses CAD/CAM tech-nique to produce the inlay. After cavity

preparation an optical imprint of thecavity is taken by means of a small videocamera. The cavity must be previouslycoated with a thin layer of titanium diox-ide to eliminate light reflections. Thenthe inlay is plaited with a computerassisted plaiting-machine in 5-10 min-utes13,14. The Celay system uses a partic-ular copy plaiting-machine13. A remov-able dark blue composite inlay (pro-inlay) is made directly in the patientsmouth or indirectly in the dental labora-tory. This inlay is then manually tracedwith a stylus. The stylus reads the sur-face of the pro-inlay and has a fixed rela-tion to a turbine which plaits the inlayout of a ceramic bloc. Both Cerec 2 andCelay systems plait the ceramic blockswith diamond burs, producing initiallyrough surfaces which have to be pol-ished by the dentist with abrasives (alu-minum dioxide and diamond particles)and rotary instruments (flexible discs,felt cones and abrasive silicon points) toavoid the wear of opposite teeth13, 16.

Preshaped ceramic inlays are stan-dardized ceramic inserts performed bythe manufacturer to fill tooth cavities cutwith especially made diamond burswhich have the same dimension of the

Fig. 1: The amalgam restoration oftooth 36 will be replaced by a firedfeldspathic ceramic inlay.

Fig. 2: The rubber dam is placed.

Fig. 3: The tooth after cavity prepara-tion.

Fig. 4: Silicon impression of the tooth.

inserts. The commercial system iscalled Cerafill (Komet). The limit of thistechnique is that often the caries is larg-er or smaller than the inserts and the

corresponding diamond burs; for thisreason, in smaller caries a sacrifice ofhealthy tissue is required and in biggerlesions a larger quantity of compositemust be polymerized in the oral cavity,which limits their beneficial effect1,13.

Fired feldspathic ceramic inlays arepreferred by dental technicians,because they may be performed usingconventional porcelain furnaces. Theseinlays are fired on phosphate-bonded-investment-replicas of the mastermodel. This is possible because modern

ceramics have a lower sintering temper-ature and because the thermal expan-sion of both refractory die and ceramicmaterial are very near. However, refittingthe fired inlay on the master model isoften difficult and time consuming andthe fit of such restorations is highlydependent on the patience and the skillof the dental technician. Anyway, theesthetic result is excellent because thedental technician can layer the ceramicmaterial with different opacities/translu-cencies and colors to match theanatomical form of the tooth13.

Fig. 5: The tooth temporarily filled.

Fig. 6: Master model of the preparedtooth.


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Composite Inlays

Glass ceramic inlays are performed bymeans of the well known lost waxmethod; they are called also castableceramic inlays. The commercially avail-able materials are Dicor (Dentsply

International) and Empress (Ivoclar). TheDicor inlays are cast from special glassingots. In a second process, the glassinlay is partially recrystallized to form aglass ceramic. During this thermalprocess mica crystals grow within theglass phase conferring the Dicor ceram-ic high strength. Dicor was initially pro-duced as a crown material. However,problems arose with the staining tech-nique, because the material is uncol-ored have induced dental technicians to

Fig. 7: The ceramic inlay.

Fig. 8: The inner surface of the inlay isetched with hydrofluoric acid.

use it as a core material only. Therefore,the Dicor system in some way fadedout, also due to the high costs of equip-ment. Only few dental technicians are

still offering this material13

. The Empresssystem has proved to be a better way toproduce full ceramic restorations,because the technique is quite simpleand the necessary equipment is inex-pensive and the process requires onlyone step. After the casting, the ceramicis subjected to a heat procedure by con-trolled cooling of the furnace. In thisphase leucite crystals grow within theceramic, producing its high strength13.

Fig. 9: The inner surface of the inlay issilanized.

Composite inlays have been proposedfor the first time in 1982 with the aim toresolve the problem of excessive shrink-age of direct composite fillings. The ideawas to compensate the polymerizationshrinkage and the consequent gap for-mation by means of a compositecementum interposed between restora-tion and cavity. Polymerization shrinkageoccurs during the performance of theinlay, and any subsequent shrinkage canoccur only during the setting of the lut-

ing agent. Such a kind of restoration hasbetter mechanical properties and wearresistance than direct compositerestoration due to its complete polymer-ization performed in suitable fur-naces2,3,7,9,18. Composite inlays may beclassified according to their performingtechnique in: direct inlays; indirectinlays; direct/indirect inlays.

Direct composite inlays: the tooth cav-ity is isolated with glycerin and filled witha posterior composite resin which isthen lightcured. In class II cavities metal,matrixes and wedges are required for aproper performing of proximal contacts.A plastic pin is then bonded to thechewing surface of the inlay for itsremoval. The restoration is then extra-orally completely cured (postcuring)before being adhesively luted in thetooth cavity11,13. Examples of this tech-nique are the Brillant Aesthetic Lineinlay/onlay system (Coltene) where theinlays are postcured in high light intensi-ty at up to 120C for 7 minutes and the

Indirect composite inlays: in this casethe dental technician performs the inlaywith posterior composite resin based onan impression taken by the dentist6,7,13,15.An example of this technique is the SR-Isosit inlay/onlay system (Ivoclar) wherethe inlays are cured at 120 C at 6 bar ofpressure in watery environment. Theesthetic result with indirect compositeinlays are excellent because the dentaltechnician can layer the composite mate-rial copying the nat ural aspect of thetooth in the same manner of fired felds-pathic ceramic inlays13.

Kulzer inlay system (Kulzer), in which theinlays are secondary cured in highintensity light in an enclosed light-acti-vating unit attachment with internal mir-

rored surfaces7,13

.

Fig. 10: Acid etching of the tooth cavity.

Fig. 11: Ceramic inlay immediatelyafter insertion.

Fig. 12: The restored tooth after rub-ber dam removal.


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DENTAL NEWS, VolumeVI, Number 2, 1999.14 Aestheticinlaysinthedental practice

Operative Dentistry

Independently from the material or thetechnique of performance adopted, theAI inlays can be adhesively luted to cav-ities by means of the same technique.First of all the rubber dam is placed.After a preliminary control of the correctinlay fitting into the cavity and checkingthe proximal contacts with dental floss,the inner surface of inlay and tooth cav-ity can be prepared for the adhesive lut-ing. The preparation of the tooth cavityincludes total etching, with phosphoric

acid gel (37 %) for 15 seconds, produc-ing microporosities on both enamel anddentin surfaces. Acid etching alsoinvolves exposition of collagen fibers onthe dentin and consequently creates aresin impregnated hybrid layer when theresin primer is applied on it. In order toobtain an optimal bond between resinprimer and collagen fibers, the cavitymust not be dried completely after acidremoval by water, in order to avoid thecollapse of such fibers, warranting in thisway a complete penetration of theprimer into the collagen network5. As to

Direct/ indirect composite inlays: thistechnique is basically an indirect tech-nique; however the single steps are sofast and simple that may be done chair-

side, while the patient is waiting for therestoration to be made. An example ofthis technique is the EOS system(Vivadent) not anymore in commerce dueto the low quality of the inlays performedwith this system as compared with indi-rect composite inlays (7,8). However, thistechnique has been recently reviewedand improved and presently allows toobtain composite inlays with a bettermarginal adaptation and the same aes-thetic and mechanical properties as indi-rect composite inlays4.

Fig. 13: The composite restoration oftooth 16 will be replaced by an indi-

rect composite inlay.

Fig. 14: The rubber dam is placed.

Fig. 15: The tooth after cavity prepara-tion.

Operative techniquefor adhesive luting of

aesthetic inlays

Fig. 16: Silicon impression of the tooth.

Fig. 17: The tooth temporarily filled.

the inner surface of the inlay, the follow-ing procedure is recommended:

Ceramic inlays: 1- degrease with ace-

tone; 2- etch with hydrofluoric acid(10%) for 120 seconds; 3- rinse for 60seconds; 4- dry with air; 5- applicationof silane for 30 seconds; 6- dry gentlywith air blast or, if possible, apply hot air(ca. 100 C) for 30 seconds13.

Composite inlays: 1- sand blasting withaluminum dioxide; 2- silane applicationfor 30 seconds; 3- dry gently with the airblast or, if possible, apply hot air (ca.100 C) for 30 seconds5,10,13.

Tooth and inlay are coated with a thinlayer of bonding resin. The luting com-

posite is mixed and applied into the cav-ity. The inlay is positioned and insertedinto the cavity. Then the excess of com-posite material must be removed fromthe interproximal areas, first by anexplorer and then by a dental floss.Occlusally the composite excess is bestremoved by a spatula, followed by anylon paintbrush. To avoid oxygen poly-merization-inhibition on the surfacelayer, the composite is covered withglycerin gel. For a complete hardening,composite is then lightcured for 60 sec-onds for each surfaces5,13. The rubber

dam is now removed. Occlusion ischecked in centric relation and ineccentric movements. Finishing is donewith fine grit diamond burs on theocclusal surface and with aluminumdioxide-coated discs for the interproxi-mal regions. The inlay is then polishedwith abrasives (aluminum dioxide anddiamond particles) and rotary instru-ments (flexible discs, felt cones andabrasive silicon points)16.

Fig. 18: Composite inlays performedon plaster model immediately beforeof its postcuring.


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Fig. 24: The restored tooth after rub-ber dam removal.

References1- BAUSH J .R., DE LONG K., DAVIDSON C.L.:

Clinical significance of polimerization shrink-age of composite resins. J . Prosth. Dent.; 48:59-67; 1982.

2- BIANCHI S., PAROLI R., RIVA R.: Intarsi inresina composita: caratteristiche fisiche.Dental Cadmos, 10: 56-82; 1994.

3- BURKE F.J .T., WATTS D. C., WILSON N.H.F.,WILSON M.A.: Current status and rationale forcomposite inlays and onlays . Brit. Dent. J ., 6:269-273; 1996.

4- CITO C., ANDREASI BASSI M:, MORI G.,GORACCI G.: Evaluation of a photo-activationtechnique in indirect composite inlays using atransparent silicon model J. Dent. Res. 77(5):1262 Abstr. no. 443; 1998.

5- GORACCI G., MORI G.: La cementazione ade-siva. In: CAROSSA S., PERA M.: Ricostruzionicoronali parziali. Ed. Masson, Milano; 1997.

6- FERRARI M., MASON P.M.: Adaptability andmicroleakage of indirect resin inlays: an in vivo

investigation. Quint. Int.; 12: 861-865; 1993.7- GORACCI G., E. ACCARISI, M. CORIGLIANO:Otturazioni estetiche nei quadranti posteriori:intarsi in composito. In Tema di Odontoiatria eCultura; 1: 29-44; 1991.

8- GORACCI G., M. CORIGLIANO: Nuova metod-ica per la realizzazione di intarsi in composito.In Tema di Odontoiatria e Cultura; 5: 19-31;1992.

9- KREJCI I., GLAUSER R., SAGESSER M., HICKELR.: Marginale adaptation und verschleissfes-tigkeit eines feinhybridkomposit-inlays in vitro.Schwez Monatsschr. Zahnmed.; 103: 973-978;1993.

10- LATTA M. A., BARKMEIER W.W.: Bond strengthof a resin cement to a cured composite inlaymaterial. J . of Prost. Dent., 72(2): 189-193;1994.

11- LEUNG R., FAN P., JOHNSON W.: Post irradia-tion polymerization of visible light-activatedcomposite resin. J . Dent. Res.; 62: 363-65;1983.

12- QUALTRHOUGH A., WILSON N., SMITH G.:The porcelain inlay: a historical view. Oper.Dent., 15: 61-70; 1990.

13- ROULET J F.: Esthetic posterior restorarions.In: DONDI DALLOROLOGIO G., FUZZI M.,PRATI C.: Adhesion in restorative dentistrypp.27-47. Ed. Valbonesi, Forl; 1996.

14- SCHMALZ G., FEDERLIN M., REICH E.: Effectof dimension of luting space and luting com-posite on marginal adaptation of class II ceram-ic inlay. J . Prosthet Dent.; 73: 392-9; 1995.

15- VAN DIJ KEN J .V.W.: A 6-year evalutation of adirect composite resin inlay/onlay system andglass ionomer cement-composite resin sand-wich restorations . Acta Odontol. Scand., 52:368-376; 1994.

16- VANINI L., DEVOTO W.: Rifinitura e lucidaturadei restauri in composito. Il Dentista Moderno,5: 5-13; 1997.

17- WASSEL R.W., Mc CABE J .F., MURRAY J.J .:Cavity convergence angles for direct compos-ite inlays. J . Dent.; 20(5): 294-7; 1992.

18- WENDT S.L.: Effetti del calore come fontesecondaria di polimerizzazione sulle proprietfisiche di tre compositi. I Parte: resistenzadiametrale alla trazione, resistenza alla com-pressione e stabilit dimensionale marginale.Quintessence Inter., 5: 395-403; 1987.

Fig. 19: The inner surface of the inlayis silanized.

Fig. 20: Acid etching of the tooth cavity.

Fig. 21: The adhesive is applied to thecavity.

Fig. 22: Composite inlay immediatelyafter insertion.

Fig. 23: The composite excess isremoved by a nylon paintbrush.

The increasing demand by patients foraesthetic restorations and the search forsubstitutes of metal restorations (amal-gam and gold) focused the attention ofthe researcher and the dental manufac-turers on new operative techniques andmaterials. Aesthetic inlays are the out-come of this endeavor. However, thiskind of restoration has only limited appli-

Conclusions

cations and their placement is moretime consuming compared to directrestorations. They also require muchmore effort and skill on dentists part

and the assistance of a dental techni-cian is often involved. For this reasonthey are more expensive than directrestorations and less used in daily prac-tice12,13. However, their use is very satis-fying for the dentist and the patients,due to the high aesthetic results whichare possible to obtain with them.

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Aesthtetic Inlays Desarrollo