¿que sistema totalmente cerámico es optimo para restauraciones anteriores?

8/6/2019 Que sistema totalmente cermico es optimo para restauraciones anteriores?

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Background. As ceramic materials for dentistry evolveand patients demand for esthetic restorations increases, prac-titioners must keep up with the science as well as the demand.

The authors offer guidance to the practitioner in selecting theappropriate all-ceramic systems for crowns when faced withdifferent esthetic demands.Conclusions. Clinicians should reserve dental ceramicswith high translucency for clinical applications in which high-level esthetics are required and the restoration can be bondedto tooth structure. Ceramics with high strength tend to bemore opaque and pose a challenge when trying to matchnatural tooth color, but they can mask discoloration whenpresent.Practice Implications. Knowledge of the opticalproperties of available ceramic systems enable the clinicianto make appropriate choices when faced with various esthetic

challenges.Key Words. All-ceramics; esthetics; crowns; veneers;restorative materials.

JADA 2008:139(9 suppl):19S-24S.

Dentistry has undergone arevolution in the last 30years, not only with regardto the introduction of newmaterials and techniques,

but also with regard to the scientificevidence supporting their clinical appli-cations. Land 1 introduced all-ceramiccrowns in 1903, but the material wasweak, the fabrication technique compli-cated and the choice of luting agentslimited.

EVOLUTION OF ALL-CERAMICMATERIALS

McLean 2 introduced alumina-reinforcedporcelain jacket crowns in the mid-1960s. About 10 years later, researchbegan to be published documenting the

successor lack thereofof all-ceramiccrowns. 3 By the mid-1980s, the litera-ture showed that anterior porcelain

jacket crowns had a 25 percent chanceof failing in vivo by 11 years; the failurerate was even higher in the posteriorregions. 4 Fortunately, significantadvances in materials and techniqueshave occurred in the last 30 years that

justify the routine use of all-ceramic

A B S T R A C T

Dr. Spear is a founder and director, Seattle Institute for Advanced Dental Education, Seattle.Dr. Holloway is an associate professor and associate director of the advanced prosthodonticsgraduate education program, The Ohio State University College of Dentistry, 305 W. 12th Ave.,Room 3005-U, Columbus, Ohio 43210, e-mail [email protected]. Address r eprint requeststo Dr. Holloway.

Which all-ceramic system is optimalfor anterior esthetics?Frank Spear, DDS, MSD; Julie Holloway, DDS, MS

JADA, Vol. 139 http://jada.ada.org September 2008 19SCopyright 2008 American Dental Association. All rights reserved.


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restorations in dentistry today.One of the most significant of these changes

occurred in 1983 when Horn 5 and Simonsen andCalamia 6,7 independently introduced acid-etchedceramics to create the bonded porcelain veneer,one of the most successful restorations whenbonded primarily to enamel. With the advent of dentin adhesives in the early 1990s, porcelainrestorations with significantly higher bondstrengths than those that had been available pre-viously became possible. 8,9 This prompted manypractitioners to forego metal-ceramics and usebonded ceramics in clinical situations in whichthey had never before been usedsometimes suc-cessfully and sometimes unsuccessfully. A chal-lenge still exists in that the dentin/adhesive bondis not as durable or predictable as the enamel/ adhesive bond. 10

Major strides in technology permitting routineuse of all-ceramic restorations are the improve-ment and scientific innovations in the ceramicmaterials themselves. High-strength corematerials containing alumina, zirconia, zirconia-toughened alumina, magnesium aluminate spineland lithium disilicate have been introduced andclinically tested. Laboratory technicians(ceramists) then apply esthetic veneering

ceramics over these core materials to create afinal, esthetic restoration.The other change that has occurred in the use

of all-ceramic restorations has been societal atti-tudes concerning esthetics. Before the early1980s, people in the entertainment industry wereprimarily the only patients who requested elec-tive esthetic dental procedures. With the onlytreatment option being full-mouth rehabilitationinvolving the use of complete-coverage crown

preparations with sub-gingival margins, thesepatients were faced withthe potential risks of recession, exposure of

the margin, discoloredgingivae and pulpalinvolvement. Theseclassic metal-ceramicrestorations requirednot only extensive toothreduction, but a highlyskilled master techni-cian to achieve excellentesthetics.

MATERIALS OPTIONS

Modern all-ceramic systems can be categorizedbroadly into two groups: those that are translu-cent and those that consist of an opaque, high-strength core onto which esthetic layeringceramic must be applied to achieve a naturalappearance (Figure 1). Examples of translucentmaterials are conventional sintered feldspathicporcelain fabricated on refractory dies or plat-inum foil, pressable ceramics (for example, IPSEmpress Esthetic, Ivoclar Vivadent, Amherst,N.Y.) and some of the in-office machinableceramics made via computer-aided design/ computer-aided manufacturing (for example,

Vitablocs Mark II, Vita Zahnfabrik, BadSckingen, Germany). Examples of opaque lay-ered materials are nonmetallic restorations madewith alumina, zirconia or lithium disilicate usedas high-strength core materials (for example, IPSe.max, Ivoclar Vivadent; Procera, Nobel Biocare,Gteborg, Sweden; In-Ceram, Vita Zahnfabrik;Lava, 3M ESPE, St. Paul, Minn.; and Cercon,Dentsply Ceramco, York, Pa.).

Properties. As a general rule, the two groupsof all-ceramic systems have distinctly differentproperties in several areas. With regard to toothreduction, clinicians can use the translucent

materials with more conservative tooth prepara-tions compared with the opaque, layered systems.Optically, the translucent materials usually aremore esthetic than the layered materials. Mosttranslucent restorations must be bonded toimprove their predictability, while layered resto-rations do not have this sensitivity to choice of luting agent. 11

Because of these differences, dentists can usemost opaque layered materials for traditional

20S JADA, Vol. 139 http://jada.ada.org September 2008

Figure 1. All-ceramic and metal-ceramic crowns. Translucent unlayered (left to right): Dicor (Dentsply,York, Pa.; no longer on the market), IPS Empress Esthetic (Ivoclar Vivadent, Amherst, N.Y.), OPC (Pen-tron Ceramics, Somerset, N.J.). Opaque layered: In-Ceram Alumina (Vita Zahnfabrik, Bad Sckingen,Germany), In-Ceram Spinel (Vita Zahnfabrik), Procera Zirconia (Nobel Biocare, Gteborg, Sweden).Metal-ceramic crown with porcelain labial margin and conventional metal-ceramic crown.

Copyright 2008 American Dental Association. All ri ghts reserved.


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crown or bridge restorations, while they can usetranslucent materials for full-coverage or moreconservative partial-coverage bonded restora-tions. We can best summarize these differences asesthetic but weaker versus stronger but moreopaque, a dichotomy that drives the process of selecting all-ceramic materials. 12

Restorative needs. Dentists should basetheir choice of material on the requirements of the tooth being restored. For purposes of sim-plicity, we can group restorations into four majorcategories: porcelain laminate veneer restorationsthat replace primarily enamel, partial-coveragerestorations that replace enamel and dentin, con-ventional complete crowns that cover acceptablycolored dentin, and complete crowns that coverdiscolored dentin or metal posts that must bemasked.

PARTIAL ENAMEL REPLACEMENTThe most conservative of all indirect restorationsessentially replace enamel with minimal, if any,preparation into dentin. These restorations areuseful when the overall tooth color is pleasingand the restorative goal is to place a new, morepleasing external surface on the tooth withoutchanging the tooth color significantly. 13,14 Becausethe enamel thickness of a natural tooth variesfrom 0.4 millimeters on the facial aspect in thecervical one-third to 0.8 to 1.0 mm on the facialaspect in the incisal one-third, true enamel

replacement restorations typically are 0.3 to0.5 mm thick and require minimal preparation. 15

In general, some tooth preparation is desirable toallow for ideal cervical emergence contours. 16,17

Because of the ceramic thickness needed forenamel replacement restorations, dentists shoulduse only translucent unlayered materials.

In addition to the low possibility of pulpal irri-tation, margin placement is another advantage of enamel replacement restorations. The ultrathin,

highly translucent ceramic that makes changingcolor difficult with these restorations also allowsthem to have invisible supragingival margins. 15,18

This allows conservative margin preparationshort of the proximal contact or incisal edge andhelps maintain gingival health.

DENTIN AND ENAMEL REPLACEMENT

As desirable as the conservative nature of enamelreplacement restorations may be, many teethsimply cannot be treated minimally. Situationsinvolving large interproximal restorations, toothmalposition, tooth discoloration, wear or fracturesmay require a restoration that involves theremoval of more tooth structure but does notnecessitate a conventional complete-coveragecrown. When the clinician must replace bothdentin and enamel but will not alter the occlusionor color, translucent ceramics still are thematerials of choice, because of their excellentenamellike appearance and ability to be bonded tonatural tooth structure.

COMPLETE CROWN AND ACCEPTABLY COLORED DENTIN

In general, the reasons to use an all-ceramic,complete-coverage crown for an anterior toothinclude replacement of an existing crown; thetooth structurally requires that the lingual sur-face be prepared; the occlusion requires a signifi-cant change so that lingual coverage is needed;

and large proximal areas of decay are present orthe patient has pre-existing restorations. This isthe one restoration for which clinicians may findit difficult to decide whether to use translucentmaterials or opaque, layered materials, becauseboth may work equally well. In general, the deci-sion will be based on the need for high strengthowing to the lack of anterior guidance or the pres-ence of parafunctional habits, the amount of toothreduction required, the laboratorys preference

JADA, Vol. 139 http://jada.ada.org September 2008 21S

Figure 2. A. A central incisor fractured in an automobile accident without any pulpal involvement. B. The remaining tooth preparationis between 2 and 3 millimeters in height. C. The final restoration is a translucent unlayered (pressed ceramic) crown bonded to achieveacceptable retention.

B A C



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and whether the clinician wishes to cement oradhesively bond the restoration.

For teeth with normally colored preparations,

translucent materials enable clinicians to reduceless tooth structure (typically 1.0 mm), createesthetic margins when they are supragingival orequigingival, and achieve a predictable bond tothe restoration itself, because sintered feldspathicceramics and pressable ceramics are etchedeasily. This can be a particular advantage whenan anterior tooth is fractured, because a toothwith a traditional cemented restoration might nothave adequate resistance and retention form to

retain the restoration. Bychoosing an adhesivelybonded, translucentceramic, the dentistmight be able to use as

little as 2 mm of verticalpreparation heightwithout the need for addi-tional foundation restora-tions 19,20 (Figure 2).

COMPLETE CROWN AND DISCOLOREDDENTIN OR METALLICPOST

A highly discolored ante-rior tooth presents anesthetic challenge. Insuch cases, the dentistwill need to use a restora-tive technique capable of re-creating the naturalcolor of dentin and thenoverlay the tooth prepara-tion with a more translu-cent material to achievean esthetic finalappearance.

To achieve this,authors have advocatedseveral approaches. 21-24

One method 21 advocatesthat clinicians use rela-tively translucentceramics, which have thegreatest potential to beaffected adversely by thecolor of the dark prepara-tion, but also use anopaque cement to mask

the discoloration. This technique can be suc-cessful, but often it is the least predictable solu-tion, because there is no way for the dentist to see

the final color until the restoration is luted. Thisbecomes difficult for the technician, who mustestimate the impact that the tooth preparationcolor and cement will have on the final restora-tion color (Figure 3).

A far more predictable approach is to use acrown with a more opaque core that is lessaffected by the preparation color. 25,26 The layeredceramic systems with more opaque cores are well-suited for the treatment of discolored teeth. The

22S JADA, Vol. 139 http://jada.ada.org September 2008

Figure 3. A. A discolored central incisor crown preparation. B. A translucent unlayered restorationat try-in. Note that even though the technician thought it had been opaqued adequately, the darkcolor of the tooth structure shows through.

A

A

D

B

C

B

Figure 4. A. A patient needing veneer restorations to restore the worn lateral incisors and caninesand crowns to replace the central incisor crowns. B. The cervical portion of the tooth preparation hasbeen prepared an additional 0.3 millimeters to allow for opaque composite to be placed. C. Eventhough an opaque layered zirconia crown is used, opaqueing the cervical portion prevents the darkpreparation from showing through. D. The final restorations are sintered feldspathic veneers onteeth nos. 6, 7, 10 and 11 and layered zirconia-based crowns on teeth nos. 8 and 9.



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technician can see thefinal restoration colorduring fabrication,because preparationcolor has little impact

on the seated restora-tion. When usingthese restorations fordiscolored teeth, theclinician must ensurea reduction of 1.2 to1.4 mm on the facialaspect, and he or sheshould use subgin-gival margins to avoidan unesthetic cervicalappearance. Clini-cians also should usethese materials whenthe need arises tocover a metal post andcore that cannot beremoved 27 (Figure 4).

CONCLUSION

We have described the possible types of anteriorrestorations and the ceramic materials of choicefor them. It is clear that the requirements foroptical properties, tooth reduction, margin place-ment, strength and method of placement (bondedversus cemented) vary for different clinical situa-tions. Is there a single material that can be usedin all situations? The closest are the translucentsystems, either sintered feldspathic or pressedceramics, owing to their ability to be bonded totooth structure, as well as to their translucency.How do dentists choose the material to use, par-ticularly in the anterior region? First, we recom-mend that they take into consideration the labo-ratorys experience and expertise. Second, weadvise them to refer to the table to best addressthe clinical situations encountered.

Disclosure. Drs. Spear and Holloway did not report any disclosures.

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17. Gurel G. The Science and Art of Porcelain Laminate Veneers.Chicago: Quintessence; 2003.

18. Garber DA. Porcelain laminate veneers: to prepare or not to pre-pare? Compendium 1991;12(3):178-182.

19. el-Mowafy OM, Fenton AH, Forrester N, Milenkovic M. Retentionof metal ceramic crowns cemented with resin cements: effects of prepa-ration taper and height. J Prosthet Dent 1996;76(5):524-529.

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JADA, Vol. 139 http://jada.ada.org September 2008 23S

TABLE

Clinical situations. VARIABLE PARTIAL

COVERAGEENAMEL

REPLACEMENTONLY

PARTIALCOVERAGE

ENAMEL

AND DENTINREPLACEMENT

COMPLETECROWN

COVERING

ACCEPTABLY COLORED DENTIN

COMPLETE CROWNCOVERING

DISCOLORED

DENTIN ORMETALLIC POST

Amountof ToothReduction

Minimal(0.3-0.5 mm*),in enamelonly

As needed;does notinvolve lingualsurface

Circumferential,1.0-mm chamfer

Circumferential,1.2- to 1.4-mmchamfer

MarginPlacement

Supragingival Supragingivalor equigingival

Supragingival orequigingival

Subgingival

StrengthRequirements

None, noocclusal forcesencountered

Low, fewocclusal forcesencountered

Depends onpresence of ante-rior guidance,parafunctionalhabits

Depends onpresence of anterior guid-ance, parafunc-tional habits

All-CeramicMaterial of Choice

Requirestranslucentceramic

Requirestranslucentceramic

Translucent orchoose opaqueceramic if

greater strengthneeded

Requires opaqueceramic

Cementation Adhesiveresinnecessary

Adhesive resinnecessary

Adhesive resinor conventionalluting agent

Adhesive resinor conventionalluting agent

* mm: Millimeters.



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sence Int 1991;22(12):929-933.24. Barath VS, Faber FJ, Westland S, Niedermeier W. Spectrophoto-

metric analysis of all-ceramic materials and their i nteraction withluting agents and different backgrounds. Adv Dent Res 2003;17:55-60.

25. Rasetto FH, Driscoll CF, Prestipino V, Masri R, von FraunhoferJA. Light transmission through all-ceramic dental materials: a pilotstudy. J Prosthet Dent 2004;91(5):441-446.

26. Heffernan MJ, Aquilino SA, Diaz-Arnold AM, Haselton DR,Stanford CM, Vargas MA. Relative translucency of six all-ceramic sys-tems, part II: core and veneer materials. J Prosthet Dent 2002;88(1):10-15.

27. Vichi A, Ferrari M, Davidson C. Influence of ceramic and cementthickness on the masking of various types of opaque posts. J P rosthetDent 2000;83(4):412-417.

24S JADA, Vol. 139 http://jada.ada.org September 2008Copyright 2008 American Dental Association. All ri ghts reserved.

¿que sistema totalmente cerámico es optimo para restauraciones anteriores?

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