10 Collaborative Techniques � Fall 2003

Selection of an appropriateframework will significantlyinfluence the definitive aes-

thetics of any crown or fixed partialdenture (FPD). With the prolifera-tion of precious metal copings andcomputer-assisted design/computer-aided manufacturing (CAD/CAM)materials, restorative options thatprovide both strength and appear-ance have increased. In this feature,considerations for selecting amongthe many framework and CAD/CAM options are reviewed andtheir characteristics compared.

CONSIDERATIONSAesthetics is a matter of opinion;a product is an extension of thefingertips of the operator, and anyproduct is only as good as theoperator. The product may or maynot be good, but the trick is toknow how and when to use it.Many products on the market todaypossess the desirable optical quali-ties of fluorescence and opalescence,but matching the product to therestorative environment is critical toits successful utilization. The goal ofthe ceramist is to create a lifelikeappearance and an illusion of real-ity, mimicking natural teeth. Copingmaterial and technology are amongseveral factors that influence theachievement of that goal. Choice ofthe most appropriate frameworkwill be determined by considerationof several factors.

Tooth MobilityAre the teeth mobile? Is there perio-dontal involvement? Do the teethneed to be splinted? If splinting isnecessary, all-ceramic restoration isnot an option. A porcelain-fused-to-metal (PFM) or gold (eg, Captek,Precious Chemicals, Altamonte, FL;Bio 2000, Argen Corporation, SanDiego, CA) framework is indicated.

Number of UnitsNonmetal copings have not yetdemonstrated the flexural strength

COPING MATERIALS FOR IMPROVED AESTHETICS:Combining Strength and AestheticsPinhas Adar, MDT, CDT*

necessary for restoration of longerspans. When a restoration of morethan three units is planned, PFM,gold, or another metal-ceramicframework is indicated.

Tooth PreparationEach proprietary coping materialrequires a preparation to meetmanufacturer specifications. This isespecially true with copings thatare machine-fabricated (eg, Procera,Nobel Biocare, Yorba Linda, CA;Lava, 3M ESPE, St. Paul, MN; Cercon,Dentsply Ceramco, Burlington, NJ).If the coping material has not beenselected prior to tooth preparation,and the tooth has not been pre-pared to the manufacturer’s speci-fications, framework selection willbe limited and many optionsforeclosed. The technician cannotcreate the magic of lifelike restora-

tions without sufficient reductionto layer the ceramic and a prepara-tion design appropriate to theintended framework. Clinicians whoprepare teeth as they always havefor PFM restorations will be limitedto placing PFM restorations.

Substrate ColorWhat is the substrate color? Is itdark? Nonvital? Is a post and corepresent? If so, what color is themetal of the post, (eg, gray, silver,gold) (Figure 1)? A single toothwithout root canals that has beenminimally prepared can be beauti-fully restored with a pressableceramic (eg, IPS Empress, IvoclarVivadent, Amherst, NY; Authentic,Microstar Corporation, Lawrence-ville, GA) in which the frameworkhas been encapsulated in therestoration (Figure 2). Because the

restoration’s color is a function ofthe natural tooth color, however,the porcelain, and the cement, analternative framework is indicatedwhen darkness in the natural toothis present and will be captured inthe pressed-ceramic restoration. Ifthree or fewer units are involvedand the teeth are not mobile, thissubstrate can be blocked with oneof the many CAD/CAM products(eg, Cercon, Dentsply Ceramco,Burlington, NJ; Lava, 3M ESPE,St. Paul, MN; Procera Zirconia,Nobel Biocare, Yorba Linda, CA)provided that sufficient space(1.5 mm or more) is available andthe ceramist is familiar with thematerial properties and limitationsof whichever product is selected(Figures 3 and 4). Accurate shade

FIGURE 2. Preoperative view of a fractured tooth. Minimaltooth preparation was performed to preserve as muchenamel as possible for better bonding strength.(Dentistry by David Garber, DMD.)

FIGURE 2. Postoperative appearance of the fracturedtooth restored with a single pressable all-ceramic crownrestoration. Notice the blend of the natural color in thetooth preparation bleeding through and creating aninvisible cervical margin with a healthy soft tissue color.(Dentistry by David Garber, DMD.)

FIGURE 3. Preoperative view demonstrates compromisedsubstructure preparation color in the anterior crown.Sufficiently reduced, the crown was replaced withan all-ceramic restoration.

FIGURE 4. Postoperative appearance 15 years later.Some of the natural tooth color from the preparationwas allowed to bleed through. (Dentistry by CathySchwartz, DDS.)

proceed to page 12

12 Collaborative Techniques � Fall 2003

COPINGMATERIALScontinued from page 10

match to the preparation as well asthe natural tooth is necessary withany of these technologies, a taskthat has been simplified with theadvent of shade guidance systems

such as the spectrophotometer(eg, SpectroShade, MHT Inter-national, Newton, PA; ShadeScan,Cynovad, Montreal, Canada) andthe colorimeter (eg, ShadeVision,X-Rite, Grandville, MI).

MATERIALSGold remains an excellent solutionfor all restorative cases. In recent

years, alloys and composite alloyswith very high gold content havecome to market that combine thecolor, burnishability, and biocom-patibility of pure gold but also dis-play the compromised strengthand oxidation associated with mosthigh-gold alloys. Laboratory tech-nicians have addressed these issueswith an internally reinforced and

strengthened network of high-fusing platinum, palladium, goldparticles (average 15 µm), givingthe restoration a “skeleton” thatdoes not melt and become distortedduring fabrication of the metal-work. Because oxide does not formon the surface during porcelain fir-ing, graying does not occur at themargins of the copings. A wide

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range of porcelains are compatiblewith the metal, allowing the use ofhigh-, medium-, and low-fusingporcelains for single-unit anterioror posterior crowns and fixedpartial dentures of up to six units

(Figures 5 through 9). The improvedlight-dispersing qualities of theresulting crown produce more nat-ural aesthetics than are typicallyassociated with PFM frameworkswith minimal tooth reduction.

Most CAD/CAM systems, onthe other hand, begin with innatelyaesthetic and biocompatible corematerials and endeavor to producenatural restorations with greaterstrength than existing all-ceramicalternatives (Table). CompetingCAD/CAM systems are distin-guished by their technical and pro-cedural characteristics, including:

� The type of scanner used tocapture the data (ie, laser,optical, or mechanical);

� If milling is performed, whetherthe outcome is a densely sin-tered (eg, Cercon, DentsplyCeramco, Burlington, NJ;Procera, Nobel Biocare, YorbaLinda, CA; Lava, 3M ESPE,St. Paul, MN) or infiltrated(eg, Cerec inLab, Sirona DentalSystems, Charlotte, NC; Wol-Ceram, Wol-Dent SDI, Miami,FL) product;

CAD/CAM systems canbe used to produce:

� Copings

� Bridges

� Abutments

� Single-unit crowns

� FPDs

� Laminate veneersLaminate veneermaterials include:

� Zirconia

� Zirconium-oxide

� Alumina

� Pure Polycrystalline oxides

� Titanium

� Densely sintered or infiltratedyttrium-stabilized zirconium-oxide

� Alumina-oxide

CONTEMPORARY

CAD/CAMAPPLICATIONS

Collaborative Techniques � Fall 2003 13

proceed to page 14

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FIGURE 5. The patient presented with mobility in teeth #8 and#9 that required splinting. A challenge was presented dueto the color differences between the two teeth. Two typesof restorations were fabricated for illustration and testingpurposes. (Dentistry by Henry Salama, DMD.)

FIGURE 6. The restorative options: two splinted Captek(Precious Chemicals, Altamonte, FL) units and two Procera(Nobel Biocare, Yorba Linda, CA) single-unit crowns.

FIGURE 7. The two single CAD/CAM crowns illustrate the abilityto conceal the dark tooth structure and achieve a harmoniousblend with the adjacent teeth. (Dentistry by Henry Salama, DMD.)

FIGURE 8.The splinted copings. Notice the nice warm color andvery sharp finish lines that were carried all the way tothe margin to block out the dark tooth structure.

� Whether the system can pro-duce multiunit or single-unitframeworks, or both.

CAD/CAM manufacturing maybe performed within the laboratoryor be outsourced to the system man-ufacturer. With an outsourced sys-tem, captured data are scanned withthe CAD/CAM three-dimensionalsoftware that allows for simplifiedvisualization of the die details.After the scanner operator hasdetermined the margin, the finaldata are precisely calculated andtransferred via Internet for fabrica-tion. After the mathematically con-trolled shrinkage behaviors of theceramic powder, the final productis densely sintered in a ceramiccoping that fits the original masterdie at the lab. The coping is thenreturned to the lab for the ordinaryporcelain buildup.

In-house systems equip the laboratory to perform all stages of fabrication on the laboratorypremises. Due to industrialrepeatability, CAD/CAM-generated

14 Collaborative Techniques � Fall 2003

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copings are believed to improveconsistency and reduce reliance onthe subjective skills of the techni-cian, which allows the laboratoryto focus more on the aesthetic

aspects of restoration (eg, porcelainbuildup). This focus on othervalue-added steps in the productioncycle, overall efficiency, and con-sistency in quality helps improvelab return on investment.

CONCLUSIONThe PFM restoration remains therestorative workhorse when teeth aremobile and require splinting, when

COPINGMATERIALScontinued from page 13

FIGURE 9. Postoperative appearance of the splinted restoration. The blend is harmo-nious with the adjacent tooth structure. While both restorations were acceptable tothe patient, the splinted gold substructure was selected due to tooth mobility.(Dentistry by Henry Salama, DMD.)

FIGURE 11. Postoperative appearance of the three-unit pressed-to-metal bridge. Notethe large porcelain finishing margin due to the pressable lost wax technique.

tooth color is so dark that a translu-cent restoration will be unaesthetic,and/or when fixed partial denturesin excess of six units are planned(Figures 10 through 13). When theseconditions are not present, the clini-cian and the laboratory may choosefrom a growing selection of frame-work materials that advance the goalof achieving a lifelike look. �

AcknowledgmentThe author wishes to acknowledge andthank Momo Vasilic of Nobel BiocareUS for technical information regard-ing CAD/CAM technology and LouAzzara of Captek Corporation for tech-nical information regarding theCaptek system.

*Owner, Adar International Inc,Atlanta, Georgia.

FIGURE 12. The three-unit bridge with a single porcelain veneer as viewed on thesolid soft tissue model.

FIGURE 13. Postoperative appearance following cementation. The pressed-to-metalbridge and the porcelain laminate veneer blend harmoniously. (Dentistry by AnitaTate, DMD.)

Collaborative Techniques � Fall 2003 15

CONTINUING EDUCATIONEXERCISE

The 10 multiple-choice questions for this Continuing Education (CE) exercise arebased on the article “Coping materials for improved aesthetics: Combining strengthand aesthetics,” by Pinhas Adar, CDT. This article is on Pages 000-000.

Upon reading this article and completing this exercise, the reader should:� Understand the role of treatment planning on appropriate framework

selection.� Recognize the clinical indications for various contemporary substruc-

tures and restorative options.

1. Which of the following factors will influence appropriate frameworkselection?a. The degree of tooth mobility.b. The number of units being restored.c. The degree of tooth preparation necessary.d. All of the above.

2. When evaluating tooth mobility, the clinician should notify thetechnician if:a. Periodontal involvement is evident.b. Nonmetal copings are required to provide predictable long span restoration.c. All-ceramic restoration is indicated to restore dentition that require

splint placement.d. CAD/CAM restoration is indicated due to the need for multi-unit

restoration (ie, more than 4 spaces).3. Contemporary CAD/CAM systems can be used to restore teeth if:

a. The dentition are not mobile.b. Three or fewer units are involved.c. Sufficient space (1.5 mm or more) is available.d. All of the above.

4. Accurate shade match to the preparation as well as the natural tooth isrequired for aesthetic restoration. This match can be achieved usingtraditional shade tabs and contemporary shade guidance systems.a. Both statements are true.b. Both statements are false.c. The first statement is true, the second statement is false.d. The first statement is false, the second statement is true.

5. What types of technical and procedural characteristics are used todistinguish amongst competing CAD/CAM systems?a. The type of scanner used to capture the data.b. Whether the system can produce multiunit or single-unit frameworks,

or both.c. If milling is performed, whether the outcome is a densely sintered

or infiltrated product.d. All of the above.

6. How has potentially compromised strength and oxidation associatedwith most high-gold alloys been addressed?a. Oxidation does not occur in high-gold alloys.b. By using porcelain substructures that do not suffer from oxidation during

firing, prior to the addition of gold.c. By using an internally reinforced network of high-fusing platinum,

palladium, and gold particles to provide a “skeleton” that does not meltand become distorted during fabrication.

d. None of the above.7. How does the color of the substrate influence the definitive aesthetics

of a prosthodontic restoration?a. The presence of a metal post and core may shine through the porcelain

and adhesive.b. The presence of a dark or nonvital substrate will influence the type of

framework used for the definitive restoration.c. Both a and b are correct.d. Neither a nor b are correct.

8. A single tooth without root canals that has been minimally preparedcan be predictably restored using:a. Metal-ceramic substrates.b. Pressable ceramic materials.c. Such teeth require extraction.d. Porcelain-fused-to-metal crowns only.

9. All-ceramic restorations are indicated when:a. The tooth’s color is extremely dark.b. Teeth are mobile and require splinting.c. When fixed partial dentures in excess of six units are planned.d. None of the above.

10. The restorative team’s primary goal should be to:a. Improve or restore the patient’s function.b. Create a lifelike appearance and an illusion of reality, mimicking

natural teeth.c. Both a and b are correct.d. Neither a nor b are correct.

CECONTINUING EDUCATION

FIGURE 10. Preoperative view of a patient’s smile showing unaesthetic PFM crowns.Tooth #8 required extraction. The treatment plan called for fabricating a three-unitbridge with one porcelain laminate veneer.