In This Issue:

in Dentistry

Vol. 2, No. 1, 2003

©2003. Medical World Business Press, Inc./An MWC Publication

Sponsored by 3M ESPEA Supplement to Contemporary Esthetics and Restorative Practice®

SynergyThe alliance between the dentist and lab technician

January 2003

The LavaTM All-Ceramic System: CAD/CAMZirconia Prosthodontics for the 21st Centuryby John A. Sorensen, DMD, PhD

An MWC Publication

2 Hours of CE Credit fromDental Learning Systems70-2009-3527-1

Achieving Clinical and Esthetic Successby Placing a Zirconia-Based All-Ceramic

Three-Unit Anterior Fixed Partial Dentureby Thomas K. Hedge, DDS

Dear Readers:Zirconia for all-ceramic single crowns and fixed partial

dentures (FPDs) has arrived. Once envisioned as a bridge toa distant future, zirconia is now touted as the present dayHoly Grail. For many years all-ceramic restorations havebeen gaining acceptance as technologies improve, to thepoint where clinical durability for single crowns for bothanterior and posterior restorations rivals metal-ceramicrestorations in published clinical studies. Concomitantly,porcelains and alternate metal substrates for metal-ceramicshave improved drastically in their esthetic potential in thelast few years, and, in the right ceramist’s hands, they canrival any all-ceramic restoration. The problem remains thatthe average ceramist has a difficult time dealing with theopaque metal substructure; relatively few ceramists havemastered this technique.

The ideal esthetic solution is to have a more translucentsubstrate that will have the long-term clinical durability ofmetal-ceramic restorations, especially for anterior crownsand FPDs. This appears to be the case for single-unitrestorations, as several clinical studies demonstrate clinicalsuccess for these types of restorations—especially ceramiccore systems that are generated by computer-assisteddesign/computer-assisted manufacture (CAD/CAM). Untilnow, no all-ceramic system demonstrated the physical prop-erties considered necessary for long-term clinical successfor posterior FPDs. Solid, sintered, monophase zirconia hasthe apparent physical properties necessary for use in poste-rior bridge applications where ideal connector dimensionscan be maintained. Clinical trials are being conducted atseveral universities; one published study from theUniversity of Zurich has been extremely promising, with nofailures to date. It is important to note that only 2-year datais available with these new systems and, while the early datais excellent, no long-term conclusions should be drawn.

As a long-awaited adjunct to conventional technologiesbecause it allows clinicans to automate some of the moremundane tasks and use industrial-quality ceramics thatcould not be used by conventional techniques, CAD/CAMis here to stay. Zirconia has unique properties in that it doesnot undergo corrosive weakening, as do many other ceram-ics, and it has a self-healing property against cracks. In thisissue of Synergy in Dentistry, both of these points areexplained elegantly by Dr. Sorensen. In addition, Dr. Hedgegives an excellent overview of some of the historical devel-opments in ceramics and demonstrates the use of the LavaTM

All-Ceramic system with a case report. Dental LearningSystems would like to thank 3M ESPE for sponsoring thisclinical series.

Sincerely,Edward A. McLaren, DDSDirector, Center for Esthetic DentistryDirector, School for Esthetic Dental DesignSchool of DentistryUniversity of California at Los AngelesLos Angeles, California

Jeff J. Brucia, DDS E. Steven Duke, DDSLee Culp, CDT

JANUARY 2003ADVISORY BOARD

This clinical series is sponsored by

in Dentistry

SynergyThe alliance between the dentist and lab technician

www.3MESPE.com

David Grin, CDT Gerard Kugel, DMD, MSDavid S. Hornbrook, DDS

Edward A. McLaren, DDS Matt RobertsMoshe Mizrachi, CDT

Dental Learning Systemsis an ADA CERP Recognized Provider

Academy of General DentistryApproved PACE Program Provider

FAGD/MAGD Credit 7/18/1990 to 12/31/2005

WARNING: Reading an article in Synergy in Dentistry does not necessarily qualifyyou to integrate new techniques or procedures into your practice. Dental LearningSystems expects its readers to rely on their judgment regarding their clinical expertiseand recommends further education when necessary before trying to implement anynew procedure.

The views and opinions expressed in the articles appearing in this publication arethose of the author(s) and do not necessarily reflect the views or opinions of the edi-tors, the editorial board, or the publisher. As a matter of policy, the editors, the edito-rial board, the publisher, and the university affiliate do not endorse any products, med-ical techniques, or diagnoses, and publication of any material in this journal should notbe construed as such an endorsement.

2 VOL. 2, NO. 1, 2003 SYNERGY IN DENTISTRY

John A. Sorensen, DMD, PhD Thomas F. Trinkner, DDSBruce Small, DMD

Learning ObjectivesAfter reading this article, the reader should be able to:• describe the “transformation toughening” mechanism

that strengthens zirconia ceramics.• compare zirconia ceramics to other metal-free

prosthodontic systems for posterior bridges.• describe the different methods for fabricating and

milling zirconia ceramic substructures.

The last decade has witnessed significant improve-ments in the strengths of ceramics and fabricationtechnologies for all-ceramic, fixed prosthodontic

systems. Although manufacturers have claimed thatceramic systems are strong enough to make fixed partialdentures (FPDs) to replace missing molars, to date clini-cal studies have not supported these claims. One studymeasuring the strength of all-ceramic systems found thatin three-point bend tests, the strongest material availableat the time was In-Ceram® Aluminaa at 450 MPa.1 A clin-ical trial using In-Ceram® Alumina demonstrated no fail-ures of anterior three-unit FPDs.2 However, a high failurerate of 11% for premolar pontic FPDs and 24% for molarpontic FPDs occurred. All of these FPD failures occurredin the connector between the retainer and the pontic.3

Similarly, the IPS Empress® 2b lithium disilicate all-ceramic system is primarily indicated for anterior single-tooth replacement and requires rather large occlusal–gin-gival connector heights for premolar pontic FPDs.4 Thisauthor is unaware of any significant clinical studies that

would support the systematic use of a fiber-reinforcedcomposite resin system to fabricate FPDs for replacingmolars. Until recently, no system has possessed sufficientphysical properties to make all-ceramic posterior FPDs.

Zirconia All-Ceramic SystemsA number of companies have recently developed zir-

conia all-ceramic systems. These zirconia polycrystallineceramics are a significant departure from earlier all-ceramic systems. One way of measuring the strength of aceramic material is through its fracture toughness.Fracture toughness is a measure of the material’s abilityto resist the propagation of cracks. Zirconia undergoes anunusual phenomena called transformation tougheningthat contributes to its remarkable strength. Zirconia canexist in three forms—monoclinic, tetragonal, and cubic.The addition of a stabilizing agent, such as 3% yttriumoxide, allows sintering of a fully tetragonal-phase ceram-

3SYNERGY IN DENTISTRY VOL. 2, NO. 1, 2003

ABSTRACTThe LavaTM All-Ceramic System (3M ESPE) uses

zirconia ceramic, which has the highest physicalproperties of any dental ceramic available today. Thetransformation toughening phenomena specific tozirconia ceramics and its resistance to degradation inwater make Lava zirconia the most promising all-ceramic posterior fixed partial denture material.Complete automation and standardization in the fab-rication of the frameworks is achieved with theCAD/CAM process, providing accurately fittingframeworks. The zirconia frameworks have an excel-lent esthetic potential because the desired shade canbe conferred to the framework, facilitating theachievement of natural shade and translucency withthe buildup of the veneering porcelain.

John A. Sorensen, DMD, PhD Oregon Dental Association Centennial Professor of Restorative DentistryDepartment of ProsthodonticsSchool of DentistryOregon Health Sciences UniversityPortland, Oregon

Table 1—Biaxial Disk Flexural Strength of Ceramics UnderDifferent Storage Conditions

Air Storage Water StorageMean SD Mean SD

Ceramic System Type of Ceramic (MPa) (MPa)

IPS Empress® 1 Leucite 147 26 114 23

IPS Empress® 2 Lithium disilicate 337 30 271 43

In-Ceram® Alumina 535 85 370 101

In-Ceram® 30% zirconia,70% alumina 704 93 663 99

LavaTM Zirconia 1,048 133 1,095 46

SD = Standard Deviationa Vita Zahnfabrik, Germany; distributed in US by VidentTM, Brea, CA 92621; 800-828-3839b Ivoclar Vivadent, Inc, Amherst, NY 14228; 716-691-0010

The LavaTM All-Ceramic System: CAD/CAMZirconia Prosthodontics for the 21st Century

ic known as partially stabilized zir-conia. When a crack attempts topropagate through the ceramic, thereis a high-energy stress state at theleading edge of the crack. This high-energy field in the area of the crackcauses the zirconia to transformfrom a tetragonal crystal configura-tion to a monoclinic configuration.Because the monoclinic crystal is3% to 5% larger, it places thisregion in compression (Figure 1).5

This is a perfect mechanism forstrengthening the ceramic becausethe transformation occurs exactly atthe location where the crack needsto be stopped, which helps to com-bat the crack propagation.

While many ceramic systems showfairly high strength, one major prob-lem with dental ceramics is that theirstrength can drop significantly whenstored in water. A study where theauthor and his colleagues storedceramic disks in water for only 1week demonstrated just how signifi-cantly this chemically assisted, slowcrack growth can reduce the strengthof ceramics.6 Table 1 demonstrateshow all of the ceramics except zirco-nia had significant strength reductionsafter only 1 week in water storage.The resistance to moisture-induceddegradation in strength makes zirco-nia ceramics especially appealing as aposterior FPD material.

Preliminary clinical studies on theCercon® Smart CeramicsTM Systemc

conducted at the University ofZurich, which used the same semi-sintered form of zirconia as theLavaTM All-Ceramic Systemd, lookquite promising for posterior three-and four-unit FPDs.7 The clinical

trial commenced with 183 units in 80patients. At 1 year, none of the three-and four-unit FPDs had fractured.

Two different strategies formilling and fabricating the zirconiasubstructure are currently used.One method completely sinters thezirconia with a process called hotisostatic pressure, which producesan extremely strong and densematerial. However, this material isquite difficult to mill, and itrequires a slower rate of millingwith water spray so cracks andflaws are not induced. The secondapproach is to use a semisinteredzirconia, which has the consistencyof chalk. This facilitates easy andvery rapid milling of the substruc-tures at a rate approximately fourtimes that of the zirconia sinteredwith hot isostatic pressure. Sub-sequently, the milled substructureis fired at a higher temperature tocomplete the sintering process.This sintering process has a shrink-age rate of about 20%. Therefore, ahigher level of sophistication isrequired in the computer-aideddesign (CAD) portion of the sys-tem to expand the virtual FPDdimensions by 20% to compensatefor the sintering shrinkage.

Unlike some of the other systemson the market that require waxing upthe substructure, the Lava system isa true CAD/computer-aided manu-facture (CAM) system (Figure 2A).The FPD dies (Figures 2B through2D) are scanned with a system thatthen allows for determination of thetooth preparation margins anddesign of the pontic and FPD con-nectors (Figure 3). The edentulousareas that were formed with an ovatepontic are also scanned for design ofthe antaglio surface of the frame-work (Figure 4). Additionally, theopposing bite registration can bescanned to design the lingualocclusal surface of the framework(Figure 5).

When designed, the appropriate

Figure 1—Transformation of zirconia fromtetragonal to monoclinic crystal configura-tion causes expansion of 3% to 5%.

Figure 2D—Trimmed dies for a four-unitanterior FPD.

Figure 2B—Trimmed dies for a four-unitanterior FPD.

Figure 2C—Trimmed dies for a four-unitanterior FPD.

Figure 2A—The Lava All-Ceramic System:Lava Form computer-aided milling machine.

c DENTSPLY® Ceramco, Burlington, NJ 08016; 800-487-0100

d 3M ESPE, St. Paul, MN 55144; 800-634-2249

4 VOL. 2, NO. 1, 2003 SYNERGY IN DENTISTRY

Zirconia undergoes an unusualphenomena called transforma-

tion toughening that contributes toits remarkable strength.

The LavaTM system is designedfor mass production.

The LavaTM system is a true CAD/CAM system.

zirconia block is selected, which hasa plastic holder labeled with a barcode (Figure 6A). The technicianregisters the unique design in theserver with this bar code (Figure6B), and then moves over to a sepa-rate milling machine. The Lava sys-tem is designed for mass produc-tion. As many as 20 zirconia blocksin plastic holders can be loaded inthe machine because the handling ofthe blocks is completely automatedfor the milling process. Because thezirconia block has a chalky consis-tency, carbide cutting burs can beused for milling. The cutting instru-ments experience very little wear,which contributes to the accuracy ofthe milling.

After the milling process is com-plete, the framework is separatedfrom the remaining holding portionof the zirconia block and fully sin-tered for approximately 7 hours(Figure 7). The framework has now

undergone the 20% sintering shrink-age, which was compensated for inthe CAD process. Figure 8 showsthe virtual framework design fromthe CAD process and the actual sin-tered framework. The frameworkhas been designed to take intoaccount soft tissue contours, theopposing occlusion, tooth prepara-tion design, and margins so thatminimal, if any, adjustment willhave to be made to the frameworkbefore applying the veneer porce-lain (Figure 9).

The LavaTM All-Ceramic Systemis unique because the appropriateshade can be inherently achieved inthe zirconia substructure (Figure10), whereas the Cercon® SmartCeramicsTM System zirconia is whiteand opaque, and therefore must bemodified with stain and dentin mod-ifiers. The CEREC® systeme forCAD/CAM fabrication of In-Ceram® zirconia substructuresallows for the infiltration glassprocess of conferring shade; howev-er, the substructure tends to beslightly gray or green in color. The

inherent natural shades of the Lavasubstructure help the ceramist toachieve a natural shade for thecrown or FPD. Lava Ceram veneer-ing porcelain is then artisticallyapplied to the zirconia substructure(Figures 11 through 14).

ConclusionThe LavaTM All-Ceramic System

uses zirconia ceramic, which hasthe best physical properties of anydental ceramic available today. Thetransformation toughening pheno-mena specific to zirconia ceramicsand its resistance to degradation inwater make Lava zirconia the mostpromising all-ceramic posteriorPFD material. Using the zirconia inthe semisintered state facilitates arapid milling process, while theCAD system allows for a virtualFPD design that is 20% larger thanthe actual FPD to compensate forthe sintering shrinkage and provide

Figure 3—CAD of anterior FPD frameworkwith pontics and connectors.

Figure 5—View of monitor with scannedopposing model for occlusion.

Figure 4—View of monitor with scanned softtissue contours.

e Sirona USA, Charlotte, NC 28273; 800-659-5977

Figure 6A—Lava Frame zirconia blocks forFPDs and crowns.

Figure 6B—Bar code scanning of zirconiablock holder.

5SYNERGY IN DENTISTRY VOL. 2, NO. 1, 2003

Figure 7—The Lava All-Ceramic System:LavaTM Therm sintering furnace.

Zirconia ceramic has the bestphysical properties of any dental

ceramic available today.

The shade of the framework canbe inherently achieved rather

than extrinsically modified.

highly accurate fitting frameworks.The zirconia frameworks areesthetic because the shade of theframework can be inherentlyachieved rather than extrinsicallymodified, as with a white andopaque ceramic. Therefore, theresulting shade of the veneeredFPD is enhanced by the appearanceof the zirconia substructure. TheLava system, a fully CAD/CAMzirconia system, is a major advancefor fixed prosthodontics in the 21stcentury.

AcknowledgmentsThe author wishes to thank Doug

Postlewaite of Esthetic OralDesign, Lake Oswego, Oregon, formaking the maxillary anterior FPD,and Opus One Dental Lab, AgouraHills, California, for making themandibular anterior crowns.

References1. Seghi RR, Sorensen JA. Relative flexural

strength of six new ceramic materials. Int JProsthodont. 1995;8(3):239-246.

2. Sorensen JA, Kang SK, Torres TJ, et al. In-Ceram® fixed partial dentures: three-yearclinical trial results. J Calif Dent Assoc.1998;26(3):207-214.

3. Kelly JR, Tesk J, Sorensen JA. Failure of all-ceramic fixed partial dentures in vitro and invivo: analysis and modeling. J Dent Res.1995;74(6):1253-1258.

4. Sorensen JA, Cruz M, Mito WT, et al. A clin-ical investigation on three-unit fixed partialdentures fabricated with a lithium disilicateglass-ceramic. Pract Periodontics AesthetDent. 1999;11(1):95-106.

5. Lawn B. Fracture of Brittle Solids. 2nd ed.Cambridge, England: Cambridge UniversityPress; 1993:321-330.

6. Sorensen JA, Berge HX, Edelhoff D. Effect ofstorage media and fatigue loading on ceramicstrength [abstract]. J Dent Res. 2000;79:271.Abstract 1017.

7. Sturznegger B, Luthy H, Filser F, et al.Klinische studie von zirkonoxid-brucken imseitenzahngebiet hergestellt mit dem DCM-System. Acta Med Dent Helv. 2000;5:131-139.

6 VOL. 2, NO. 1, 2003 SYNERGY IN DENTISTRY

Figure 14—Patient in full smile with theLava FPD.

Figure 13—Single Lava crowns on teethNos. 23 through 26.

Figure 11—A Lava four-unit anterior FPDon teeth Nos. 7 through 10, and 4 single Lavacrowns on teeth Nos. 23 through 26 in pro-trusive contact.

Figure 12—Ovate pontics on FPD teethNos. 7 through 10.

Figure 9—Milled and sintered Lava zirconiaFPD.

Figure 8—View of monitor with virtual FPDdesign and actual milled zirconia bridge.

Figure 10—Comparison of zirconia substruc-tures with A3.5 shade tab.

Dental Learning Systemsis an ADA CERP Recognized

Provider

Academy of General DentistryApproved

PACE Program ProviderFAGD/MAGD Credit

7/18/1990 to 12/31/2005

WARNING: Reading an article in Synergy in

Dentistry does not necessarily qualify you to inte-

grate new techniques or procedures into your prac-

tice. Dental Learning Systems expects its readers to

rely on their judgment regarding their clinical expert-

ise and recommends further education when neces-

sary before trying to implement any new procedure.

The views and opinions expressed in the articles

appearing in this publication are those of the

author(s) and do not necessarily reflect the views or

opinions of the editors, the editorial board, or the pub-

lisher. As a matter of policy, the editors, the editorial

board, the publisher, and the university affiliate do not

endorse any products, medical techniques, or diag-

noses, and publication of any material in this journal

should not be construed as such an endorsement.

Learning ObjectivesAfter reading this article, the reader should be able to:• discuss how the minimal survival rate that all-ceramic

systems must demonstrate was determined.• describe the ideal preparation for a three-unit fixed

partial denture using the Lava All-Ceramic System.• discuss the enhancements to all-ceramic systems that

have resulted from the need to provide patients with biocompatible, esthetic, and durable restorations.

Without question, porcelain restorations havebeen an essential component of dental care fordecades, even centuries. Successful attempts to

seat a porcelain tooth replacement date back to the 17thcentury.1 In the 19th century, Charles Henry Land devel-oped the porcelain jacket crown based on a feldspathiccomposition that is still used today, although in a modi-fied form. Years later, reinforcement of the jacket crownwas achieved with aluminum oxide-based ceramics.2

Further developments in ceramic restorations concen-trated on addressing the inadequate fracture resistance ofthe veneering ceramics and were based on increasing thematerial’s crystalline content with leucite (IPSEmpress®,a), mica (DICOR®,b), hydroxyapatite, or mixedglass-infiltrated oxides (In-Ceram®,c). Pure polycrys-talline oxide ceramics (Procera®,d) were introduced into

clinical practice about 10 years ago.Of these, pressed ceramics (such as IPS Empress®)

have been used successfully for anterior applications formore than a decade, and other porcelain systems havehad similar long-term success, but for posterior crownsand fixed partial dentures (FPDs), they have not. Giventhe success of porcelain-fused-to-metal (PFM) restora-tions during the last 30 years, all-ceramic systems mustdemonstrate comparable longevity; a minimum survivalrate of 85% after 10 years in vivo is required, even forposterior teeth.3

As a result of the need to provide patients with biocom-patible, esthetic, and durable restorations, furtherenhancements to all-ceramic systems have ensued. Today,all-ceramic restorations in the posterior region havebecome an increasingly important part of modern estheticrestorative dental care. However, truly fracture-resistantand esthetic ceramics for such indications or for commer-cially viable processing procedures have not been previ-ously available.4 Further, a strong, translucent FPD mate-rial has been previously an elusive goal in dentistry.

The quest to fabricate all-ceramic crowns and multiunitFPDs that demonstrate favorable clinical characteristicsand long-term stability in the posterior region has beenlimited by the mechanical properties of glass ceramicsand infiltrated ceramics. Further, requirements for accu-racy of fit and versatility (ie, can be reliably placed in allposterior as well as anterior situations) have been difficultto meet.

The polycrystalline ceramic frameworks fulfill thedemands placed on all-ceramic restorations, and it is zir-

7SYNERGY IN DENTISTRY VOL. 2, NO.1, 2003

Achieving Clinical and Esthetic Successby Placing a Zirconia-Based All-CeramicThree-Unit Anterior Fixed Partial Denture

ABSTRACTToday, all-ceramic restorations have become an

increasingly important part of modern estheticrestorative dental care. However, a strong, translu-cent, all-ceramic fixed partial denture (FPD) materi-al for anterior and posterior indications has been anelusive goal in dentistry. With the LavaTM All-Ceramic System (3M ESPE), all-ceramic FPDrestorations are now a reality. This article reviews thehistorical development of all-ceramic dental materi-als, highlights the clinical and material benefits of theLava All-Ceramic System, and presents a casedemonstrating the exceptional esthetics and match-ing capabilities of this long-awaited all-ceramicrestorative system.

Thomas K. Hedge, DDS Private PracticeThe Dental Health CenterWestchester, Ohio

a Ivoclar Vivadent®, Inc, Amherst, NY 14228; 800-533-6825b DENTSPLY® Trubyte, York, PA, 17405; 800-877-0020c Vita Zahnfabrik, Germany, distributed in US by VidentTM, Brea, CA 92621; 800-828-3839

d Nobel Biocare USA, Inc, Yorba Linda, CA 92887; 800-891-9191

conia oxide, in particular, that pro-vides suitability as the currentframework material of choice.Additionally, a computer-assisteddesign/computer-aided manufacture(CAD/CAM) system that does notrequire the laboratory technician ordentist to deviate from standardpreparation, impressioning, and con-ventional cementation protocol fur-ther enhances the prospects of zirco-nia-based all-ceramic restorations tosatisfy these multiple needs. To thisend, precise scanning and millingtechnologies, combined with thor-ough knowledge of zirconium oxideceramics, have resulted in the cre-ation of the LavaTM All-CeramicSysteme, which provides the dentist,laboratory, and patient with durable,versatile, and esthetic all-ceramicrestorations for a variety of anteriorand posterior indications.

The Lava SystemWith the Lava All-Ceramic

System, all-ceramic bridge restora-tions for anterior and posteriorregions have become a reality.4 Thesystem is based on machining

presintered zirconia, which is thensintered to a dense state. Because ofits outstanding mechanical proper-ties, biocompatibility, and excellentesthetics, Lava zirconia is an idealmaterial alternative for all-ceramicindications.4 Lava restorations areindicated for anterior and posteriorcrown-and-bridge applications.

Specifically, the system uses aCAD/CAM processing technique(scanning, CAD, and milling) forfabricating all-ceramic crowns andFPDs for anterior and posterior indi-cations. The zirconia framework isenhanced by a specially designedveneering ceramic. As a result, thesystem produces high-strength res-torations with excellent fit and supe-rior esthetics.

Zirconia—the cornerstone of theLava All-Ceramic System—is oneof only two polycrystalline ceramicssuitable for use in dentistry as a

framework material, able to with-stand high load-bearing stress inboth the anterior and posterior areas.For example, a veneered three-unitzirconium-dioxide posterior FPDdemonstrated high fracture resist-ance, even with an overall framethickness of 0.5 mm.5 Additionally,marginal gap studies have shownthat zirconia restorations demon-strate an exceptional accuracy of fit.6

They also provide the necessaryesthetic characteristics (eg, toothshade, opacity, translucency) andmaterial properties required of amodern esthetic restoration (Figures1 and 2).

The Lava frame and veneer ceram-ic have been specifically developed tocomplement each other and cannot becombined with other ceramic materi-als. The frameworks are available in 8 shades, and the veneering ceramic isavailable in 16 Vita®,c Classic shades.The color range consists of 7 shoul-der materials, 16 framework modi-fiers, 16 dentin materials,10 Magicintensive materials, 4 incisal materi-als, 2 enamel effect materials, and 4 Transpa-Opal materials. The sys-tem also includes 1 Transpa-Clearmaterial, 10 extrinsic colors, 1 glaze,and accompanying liquids to ensurethe ability of the technician to per-fectly match the clinician’s colormapping requirements.

Case PresentationA 45-year-old woman presented

with a variety of complicating andinterrelated health issues, includinglupus, chronic pain, allergies, asth-ma, a history of headaches, temporo-mandibular joint and facial pain, andclenching/bruxing. The patient alsohad neuromuscular pain. Her chiefconcern was the appearance of herteeth (Figure 1). Clinical examina-tion revealed numerous broken-down restorations resulting frombruxism. All of the porcelain hadbroken off one PFM crown. Further,

8 VOL. 2, NO. 1, 2003 SYNERGY IN DENTISTRY

Figure 1—Preoperative retracted view ofthe teeth to be restored.

Figure 3—Postoperative retracted maxillaryview of the Lava restorations in place.

Figure 4—Postoperative close-up retractedview of the Lava restorations in place.

Figure 2—Postoperative retracted full viewwith the Lava restorations in place.

e 3M ESPE, St. Paul, MN 55144; 800-634-2249

All-ceramic restorations in theposterior region have become

an increasingly important part ofmodern esthetic restorative dentalcare.

Zirconia is able to withstand highload-bearing stress in both the

anterior and posterior areas.

she presented with an old FPDreplacing tooth No. 10.

Treatment ConsiderationsBefore restorative treatment, the

patient underwent a series of scansthat included joint sonography, elec-tromyography, and computerizedmandibular scans. A comfortableneuromuscular position was identi-fied and an orthotic was fabricated.The patient was placed in this appli-ance, which she wears 24 hours aday and, since April 2002, remainspain-free.7

A number of esthetic restorativechallenges were presented with thiscase. First, to deliver to the patient the“dazzling” smile she desired, teethNos. 6 through 11 would have to berestored at a minimum, requiring themixing and matching of shades forone three-unit FPD and three porce-lain veneers. Traditionally, anteriorFPDs required some form of metalreinforcement, necessitating blockingout the metal and creating an opaquesituation. Although generally easy toprepare and cement, these restora-tions were rarely esthetic andrequired subgingival margins orporcelain butt-joints, adding addition-al challenges. Further, because offinancial constraints, treatmentoptions were limited.

The dentist and patient were ableto choose an esthetic shade becausethe six maxillary anterior teethwere to be covered with porcelain.The selected shade did not deviatesignificantly from the mandibularanterior teeth or the bicuspid regionof the maxillary teeth. TheShadeScanTM Systemf was used tomap translucency and color varia-tion of the mandibular naturalteeth.

Preparation and TemporizationThe patient was prepared to

receive one three-unit all-ceramicFPD and three pressed-ceramicveneers. The ideal preparation forthe Lava three-unit FPD is a shoul-der or chamfer preparation with a

circumferential step or chamferplaced at a more than 5-degreeangle horizontally. The verticalpreparation angle was 4 degrees ormore, and the inside angles wererounded. Provisional restorationswere fabricated with ProtempTM 3GarantTM,e temporization material,shade A1, using a polyvinyl silox-ane (PVS) putty matrix relinedwith light-body PVS wash over thewax-up.

Digital photographs were takenof the preoperative condition,preparations, and provisionalrestorations using a Canon EOSD60g, with a 100-mm macro lensand a Canon Macro Ring Lite MR-14EX ring flashg. Standard viewsas recommended in the author’stext, Digital Dentistry (publishedby tomhedge.com publications andavailable at The Las Vegas Instituteand Norman Camera), were used.

The color-mapping analysis andphotographic information were for-warded to the laboratory for use infabricating the final restorations.

Laboratory FabricationUsing impressions delivered

from the dentist, the laboratorytechnician created a workingmodel. The sectioned model wasthen positioned in the Lava Scan, aPC-based system for creating Lavarestorations. Individual prepara-tions and the ridge were recordedautomatically by the scanner anddisplayed on the monitor as a three-dimensional image, including gin-gival and occlusal records. The vir-tual design of the framework—including the insertion of the ponticand design/modeling of the con-nections—was completed using thecomputer keyboard and mouse.

The data were then transferred tothe Lava Form milling unit, fol-lowed by framework coloringaccording to the shade prescribed.The framework was sintered andthen prepared for application andlayering of the veneering ceramicand, ultimately, finished and fired.

9SYNERGY IN DENTISTRY VOL. 2, NO. 1, 2003

Figure 7—Postoperative view of patient innatural smile.

Figure 8—Close-up retracted view of thefinal Lava restorations in place.

f CYNOVAD, Saint-Laurent, Quebec, Canada; 514-337-1444

Figure 5—Preoperative full smile view. Noteacrylic placed over a broken-down, nonrestor-able tooth No. 10 but not finished, contoured,or polished by previous dentist.

Figure 6—Preoperative retracted view ofteeth to be restored.

Marginal gap studies haveshown that zirconia restora-

tions demonstrate an exceptionalaccuracy of fit.

g Canon USA, Inc, Lake Success, NY 11042; 516-328-5000

CementationAt the seating appointment, the

patient’s provisional restorationswere removed, the preparations wereproperly cleansed, and the three-unitLava restoration and the pressedceramic veneers were readied forplacement. In this case, the three-unit FPD was cemented into placeusing a self-adhering cement(RelyXTM Uniceme), and the veneerrestorations were placed with anadhesive bonding cement (RelyXTM

ARCe). The Lava FPD restorationrequired no finishing after cementa-tion (Figures 2 through 4).

Traditional cementation with glassionomer cements (KetacTM-Ceme orRelyXTM Luting Cemente) is alsorecommended for cementing crownsand FPDs fabricated from the Lavasystem material, regardless of loca-tion or type of restoration. The use ofphosphate cements is contraindicat-ed for Lava restorations because of

esthetic considerations. Figures 5 through 10 show a sec-

ond case that was prepared,impressioned, fabricated, andcemented in the same manner usingthe Lava system.

ConclusionAs with all indirect restorations,

preparation and laboratory fabrica-tion techniques added to the successof this case, in addition to the labo-ratory technician’s ability to matchthe new Lava ceramic material shadeto the traditional pressed-ceramicveneers. Colorable frameworks ofthe ideal translucency, and thin coat-ing thickness to which color can beapplied, ensured the natural appear-ance and harmonious blending of theFPD with the patient’s adjacent nat-ural dentition as well as the pressed-ceramic veneer restorations.

As a result of the remarkablestrength and stability of zirconia, a

three-unit Lava bridge restorationcan be confidently placed in eitherthe anterior or posterior region.Preparation can be achieved conser-vatively, and cementation can becompleted using conventional meth-ods. Additionally, Lava restorationsdeliver exceptional physical proper-ties, including fracture toughnessand transformation toughening toprevent crack propagation, andhighly accurate-fitting frameworks.Further, the esthetic capability andbiocompatibility of Lava restora-tions represent the optimum in all-ceramic systems.

References1. Kelly JR et al. Ceramics in dentistry: histor-

ical roots and current perspectives.J Prosthet Dent. 1996;75(1):18-32.

2. Eicher K, Kappert HF. ZahnarztlicheWerkstoffe und ihre Verarbeitung [Dental mate-rials and their uses.] Huthig Verlag. 1996; 328.

3. Probster L. In: Vollkeramik, Werkstoffekunde—Zahntechnik—Klinische Erfahrung [AllCeramic, Material Science—Lab Technique—Clinical Experiences]. Hrsg Kappert HF.Berlin: Quintessenz Verlag-GmbH. 1996; 114.

4. Suttor D, Bunke K, Hoescheler S, et al.LAVA—the system for all-ceramic ZrO2crown and bridge frameworks. Int J ComputDent. 2001;4(3):195-206.

5. Tinschert J, Natt G, Doose B, et al. Posteriorbridges made from high-strength structuralceramic. DZZ. 1999;54(9):545-550.

6. Hertlein G, Hoscheler S, Frank S, et al.Marginal fit of CAD/CAM manufacturedall-ceramic zirconia prostheses [abstract].J Dent Res. 2001;80(Special Issue).Abstract #49.

7. Jankelson RR. Comparison of muscle activi-ty between conventional and neuromuscularsplints. J Prosthet Dent. 1994;71(3):329-330.

Figure 9—Postoperative retracted maxillaryview of the final Lava restorations in place.

Figure 10—Postoperative view of patient innatural smile.

10 VOL. 2, NO. 1, 2003 SYNERGY IN DENTISTRY

Dental Learning Systemsis an ADA CERP Recognized Provider

Academy of General DentistryApproved PACE Program Provider

FAGD/MAGD Credit 7/18/1990 to 12/31/2005

QuizDental Learning Systems provides 2 hours of Continuing Education credit for those who wish to

document their continuing education endeavors. Participants are urged to contact their state registryboards for special CE requirements. To receive credit, complete the enclosed answer sheet and mail it,along with a check for $20, to Dental Learning Systems, 405 Glenn Drive, Suite 4, Sterling, VA20164-4432, for processing. You may also phone your answers in to 888-596-4605, or fax them to 703-404-1801. Participants with a score of at least 70% will receive a certificate documenting completionof the course. For more information, call 800-926-7636, ext 180.

Program #: D481

Dr. Sorensen

1. Which of the following is ameasure of a material’s abilityto resist the propagation ofcracks?a. fracture transformationb. aspect ratioc. fracture toughnessd. stoichiometric value

2. Zirconia undergoes what unusu-al phenomenon that contributesto its remarkable strength?a. transformation tougheningb. yttrium perfusionc. hydrogen uptaked. crystal precipitation

3. When a crack attempts to prop-agate through the ceramic, thereis a high-energy stress state:a. in the middle of the crack.b. at both ends of the crack.c. at the leading edge of the crack.d. at the trailing edge of the crack.

4. One major problem with dentalceramics is that their strengthcan drop significantly when

stored in:a. saline.b. water.c. oil.d. room temperature air.

5. Semisintered zirconia has theconsistency of:a. chalk.b. putty.c. gelatin.d. dough.

Dr. Hedge

6. All-ceramic systems mustdemonstrate a minimum sur-vival rate of:a. 75% after 10 years.b. 75% after 15 years.c. 85% after 10 years.d. 85% after 15 years.

7. The frameworks are available inhow many shades?a. 3b. 5c. 8d. 9

8. Veneering ceramic is available inhow many Vita® shades?a. 16b. 24c. 28d. 32

9. The ideal preparation for theLava three-unit FPD is a shoul-der or chamfer preparation witha circumferential step or cham-fer placed at more than whatdegree angle horizontally?a. 4 degreesb. 5 degreesc. 6 degreesd. 7 degrees

10. The use of which cement is con-traindicated for Lava restora-tions because of esthetic consid-erations?a. glass ionomerb. phosphatec. self-etchingd. self-curing

This Supplement to Contemporary Esthetics and Restorative Practice® was made possible through anunrestricted educational grant from 3M ESPE. To order additional copies, call 800-926-7636, x180. D481

11SYNERGY IN DENTISTRY VOL. 2, NO. 1, 2003

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