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The Factors that Influence the Dentist’s and Technician’s Choice of Restorative Materials

fault of a particular restorative material and moreof a cumulative effect of deficiencies in preparationand in a technician’s knowledge and experience.

The decision to use a specific type of crownshould be based upon the treatment expectations,strength, fabrication ease, and long-termpredictability. This is particularly important whenthe chosen restoration deviates from a standardthat has proven successful for many decades—theceramometal crown.1 Collaboration between thedentist and technician prior to patient treatmentenables the skilled ceramist to develop the hue,chroma, value and internal characterization foundin natural dentition regardless of the restorativematerial used.

Successfully fabricating and delivering full crownsin the esthetic zone requires diagnosis, caseselection, experience and close collaborationbetween the dentist and technician. Properpreparation design is an integral part of this process.Often, the technician encounters insufficientreduction, especially on the palatal or lingualsurfaces. Inadequate space leads to compromisesin porcelain layering, contour, emergence profile,and internal coloration. Dental manufacturershave introduced all-ceramic materials thatpurportedly address the dentist’s perception that ceramometal crowns lack optimal esthetics.There is a general assumption among dentists thatall-ceramic crowns have inherently superioresthetics that compensate for limitations in theceramometal system or technician skill. However,these perceived deficiencies are usually less the

Key Words:interdisciplinary

treatment,tooth

preparationdesign,

full crownporcelain

restorations,dental esthetics,

Creation™porcelain,

Authentic™pressableceramic,

Sinfony™,Captek ™,

comparativecrown strength,dental implant

crown

Today, manufacturers provide the dental technician and restorative dentist with amultitude of different materials for esthetic, full crown restorations for naturalteeth and dental implants. Over the past several years, there has been a generaltrend toward using all-ceramic crowns. One purported reason is an improvementin overall appearance due to increased light transmission and translucency. Deciding on the most appropriate crown for a specific restorative situationinvolves considering the strength and fracture resistance, fabrication ease, andlong-term predictability. A skilled ceramist can closely simulate the hue, chroma,value, and internal characterization found in natural dentition regardless of therestorative material employed. The dentist’s responsibility is to provide theproper tooth preparation needed to create the optimal crown. Proper toothreduction requirements and guidelines for choosing between ceramometal,pressed and layered all ceramic, and composite resin crowns are explained.Examples of clinical cases are also shown in this report.

Full Crowns in theEsthetic ZoneRichard P. Kinsel, D.D.S., Daniele Capoferri, CDT

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Figs. 1a and 1b. Diagram of the minimal tooth reduction for optimal esthetics of a full coverage crown restoration on a central incisor.Incisal reduction of 2.5 to 3 mm provides light transmission and translucency of the incisal edge. The gingival-axial reduction should beat least 1.2 mm (a). The facial and palatal reductions of 1.2 to 1.5 mm allow sufficient space for porcelain layering and proper palatalcontours (b).

Figs. 2a and 2b. The preoperative view of the demonstration typodont model. Tooth #9 will receive a ceramometal crown restoration using a preciousmetal alloy and a circumferential porcelain margin; tooth #10 will be restored with a self-curing acrylic resin core that is veneered with Sinfony™,and tooth #11 will have a pressable ceramic core veneered with layered porcelain (Authentic™).

PREPARING NATURAL ANTERIOR TEETH

Prior to initiating treatment, the dentist and thetechnician must review facebow mounteddiagnostic casts, the extra-oral and intra-oralphotographs of the teeth relative to generallyaccepted esthetic parameters, and have a thoroughunderstanding of the patient’s goals.2 The diagnosticwax up guides the dentist through the appropriatetooth reduction. With proper preparation providedon a master cast, the ceramist can fabricate a crownto simulate the natural tooth. Reduction between2.5 mm to 3.0 mm is important to develop atranslucent incisal edge. Facial and palatal reductionbetween 1.2 to 1.5 mm allows sufficient room forproper porcelain layering within the appropriatecontours (Fig. 1).

The following series demonstrates preparing teeth#9-11 for a ceramometal, composite resin, and all-ceramic crown restoration, respectively (Figs. 2through 7). The pretreatment situation is shownin Figure 2. A polyvinylsiloxane impression istaken (Lab-Putty, Coltène, Mahwah, New Jersey,USA) of either the pre-existing teeth or diagnosticwax up. The impression is sectioned to accuratelyrecord the facial and palatal contours (Figs. 3aand 3b). These matrices help the restorativedentist to determine adequate tooth reduction togive the technician room to produce an optimalesthetic result. The final preparations are shownin Figure 4. The facial and palatal guides verifythat sufficient tooth reduction occurs prior to thefinal impression. A shoulder preparation may besubstituted for the deep chamfer gingival margin.All line angles are rounded to eliminate acute

1a 1b

2a 2b

“The impressionis sectioned toaccuratelyrecord thefacial andpalatalcontours.”

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Figs. 4a and 4b. The final full crown preparations are completed. A shoulder gingival margin may be substituted for the deep chamfer. All line anglesare rounded.

Figs. 5a and 5b. The facial and palatal matrices are inserted to verify the proper reduction prior to the final impression.

Figs. 3a and 3b. Prior to tooth preparation, facial and palatal matrices of the diagnostic wax up serve as guides for the dentist.

copings (Figs. 6c through 6d). The definitivecrowns are shown in Figure 7. Regardless of therestorative material employed, the estheticappearance is the same. The minimum thicknessrequired for the crown contours are 1.5 mm facialand 1.2 mm palatal (Figs. 8a through 8c). Whenthe appearance of the definitive restorations iscomparable, the dentist’s decision on the type ofcrown restoration should be based on the strength,longevity, predictability, and fabrication ease.3-10

Often when a dentist requests an all-ceramiccrown it is because of the erroneous belief thatceramometal crowns cannot reproduce thetranslucency of the all-ceramic crown.

transitions that might complicate fabricating the metal coping or contribute to all ceramiccrown failures.

In this example, tooth #9 will be restored as aceramometal crown with a circumferential porcelainmargin, tooth #10 will have a self-curing acrylicresin core (SR Ivocron, Ivoclar AG, Schaan,Liechtenstein) that is veneered with a light-curedcomposite resin (Sinfony™, ESPE America, Inc,Norristown, PA), and a pressable ceramic copingwith layered porcelain (Authentic™, Microstar/Jensen Industries) will be fabricated for tooth #11 (Fig. 6).

The facial and incisal matrices confirm the propercontours for the metal and pressed ceramic

3a 3b

4a 4b

5a 5b

“Regardless ofthe restorative

materialemployed, the

estheticappearance is

the same.”

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Figs. 6a-d The working cast is fabricated in the normal manner (a). The precious metal coping and pressed-ceramic copings are verified with thematrices (b-d).

Figs. 7a-d. The definitive crown restorations are shown on the soft tissue cast (a,b) and on the typodont teeth (c,d). The hue,chroma, value, and texture of each are the same regardless of the type of restorative material that is used.

6a 6b

6c 6d

7a 7b

7c 7d

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Figs. 8a-c. The thickness of the facial and palatal surfacesaveraged 1.5 and 1.2 mm, respectively. These dimensions areimportant to simulate natural esthetics and contours with thedefinitive crowns.

Figs. 9a-l. A clinical example of the steps guiding the dentist in proper tooth reduction. The diagnostic wax up (a) is used to fabricate the facial andpalatal guides with a laboratory polyvinylsiloxane impression material (b,c). A soft tissue cast (d) is fabricated to transfer the contour of the softtissues for proper gingival contours (Gengisil, Techim Group, Milano, Italy). The facial and palatal matrices ensure that adequate tooth reduction ispresent (e,f). The definitive ceramometal crowns are shown on the soft tissue casts (g,h). The result closely simulates the initial wax up andincorporates the hue, intensity, translucency, and internal colors found in natural teeth (i-l).

8a

8b 8b

8c 8c

9a 9b

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9c 9d

9e 9f

9g 9h

9i

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Figs. 10a and 10b. Implant-supported ceramometal crowns in the esthetic zone often require using a long-term provisional restoration to developfavorable soft tissue contours (a). The Sinfony™ veneered acrylic core crown allows the technician to duplicate the natural tooth during gingivalmaturation (b). The acrylic core must be opaqued to prevent the gray influence of the titanium abutment.

the diagnostic wax up plays an integral role (Fig. 9a). The facial and palatal matrices providethe dentist with a guide for adequate toothreduction (Figs. 9b through 9f). With optimaltooth preparations and adequate impressionsincluding gingival contours, the skilled ceramistcan achieve a result that closely duplicates theinitial esthetic treatment goals (Figs. 9g through 9l).

Clinical cases are presented in Figures 10-14.Crown choice was based on the strength and long-term predictability combined with the individualpatient’s treatment goals. Although the decisionto restore anterior teeth with all-ceramic crowns is

The inherent challenges when fabricatingtranslucent ceramometal crowns tax the skills ofmany ceramists. Although the all-ceramic crownmay possibly compensate for the less skilledtechnician, the strength and longevity of thedefinitive restoration is compromised.4-7

Logically, the dentist’s decision regarding thecrown type should not be dependent upon theceramist’s limitations.

CLINICAL CASES

When multiple anterior restorations are a part ofthe overall rehabilitation of a patient’s dentition,

9j

9k 9l

10a 10b

“Logically, thedentist’sdecision

regarding thecrown type

should not bedependent upon

the ceramist’slimitations.”

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Figs. 11a - d. A full mouth rehabilitation with pressed ceramic, porcelain veneer anterior restorations and ceramometal crowns on the posteriorteeth. The three restoration types appear esthetically comparable while obtaining strength from metal substructures for areas with greaterfunctional forces.

11a 11b

11c 11d

certainly appropriate when the preparation designis ideal and the dentin color does not need to bemasked, the possible increased risk of fracture andfailure must also be considered. In the posteriorregion, because of the increased occlusal forces,the dentist must choose a crown design thatincorporates high strength7-9 with esthetics (Figs.11a through 11d). Implant-supported, all-ceramiccrowns (Figs. 12a through 12d) that are cementedon titanium abutments or crowns placed on teethrestored with cast posts and cores will not have anesthetic advantage over the ceramometal crown.Therefore, the ceramometal crown becomes aprudent design10 because eliminating the

influence of the metal color is required in eithercase and its increased strength has a decidedadvantage (Figs.13a and 13b). However, if alimited number of titanium posts are present,then all-ceramic anterior crowns combined withmetal ceramics is an acceptable alternative (Figs. 14a and 14b).

“The facial andpalatal matricesprovide thedentist with aguide foradequate toothreduction.”

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12b

12c

12d

Figs. 12a-d. Dental implant-supported porcelain crowns cemented on titanium abutments have no esthetic advantages if the definitive crown is eitherall ceramic or ceramometal since both restorations require an opaqued substructure prior to porcelain layering. Examples of ceramometal crownscemented on titanium abutments include an upper right central incisor (a), a lower right central incisor (b), an upper left central incisor (c), and aCaptek™ (Precious Chemicals, Inc, Altamonte Springs, FL) crown on a lower right cuspid implant (d).

12a

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Figs. 13a and 13b. The ceramometal crown has a distinct advantagewhen restorations are needed on teeth with cast posts or titaniumimplant abutments.

13a

14b

CONCLUSION

Collaboration between the dentist and the dentaltechnician is important when choosing theappropriate full porcelain crown restoration. Aclose relationship permits an open exchange ofideas to best address the patient’s needs andtreatment goals. Technicians frequently encounterinadequate space for an esthetic, properly contouredfull crown. This compromises the porcelain layeringtechniques that simulate natural dentition. Withproper preparations, the dental technician canuse various materials-full ceramic, composite,metal ceramic, pressed ceramic, or zirconium.

However, the predictability and longevity of theceramometal crown restoration should not bediscarded for all-ceramic crowns unless theadvantages outweigh the risks.

Dentistry is an evolving profession. This factstimulates the dentist and technician tocontinually improve their skills, knowledge, andexpertise. The best interests of the patient canonly be served when the dentist and technicianmake decisions based on well-established sciencerather than subjective preference based on amanufacturer’s marketing.

“Techniciansfrequentlyencounterinadequatespace for anesthetic,properlycontoured fullcrown.”

13b

14a

Figs. 14a and 14b A clinical case of ceramometal crowns on teeth #8 and 9with pressed ceramic and porcelain veneered on teeth #6, 7, 10, and 11.The harmony of appearance belies the material used.

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References

1. Christensen GJ. Porcelain-fused-to-metal vs. nonmetal crowns. JADA 1999; 130:409-411.

2. Kinsel RP, Capoferri D. Interdisciplinarycollaboration of the dental technician, restorative dentist, and periodontal surgeon. Dent Dialogue 2003; 3:176-190.

3. Wall JG, Cipra DL. Alternative crown systems. Is the mental-ceramic crown always the restorative of choice? Dent Clin North Am 1992; 36:765-782.

4. Miller A, Long J, Miller B, Cole J. Comparison of the fracture strengths of ceramometal crowns versus several all-ceramic crowns. J Prosthet Dent 1992; 68:38-41.

5. Smith TB, Kelly, JR, Tesk JA. In vitro fracture behavior of ceramic and metal-ceramic restorations. J Prosthodont 1994; 3:138-144.

6. Castellani D, Baccetti T, Giovannoni A,

Bernardini UD. Resistance to fracture of metal ceramic and all-ceramic crowns. Int J Prosthodont 1994; 2:149-154.

7. Blatz M. The faculty perspective. The clinical long-term success of ceramic restorations. Part II: Posterior full-coverage crowns. Pract Proced Aesthet Dent 2004; 16:702.

8. Josephson BA, Schulman A, Dunn, ZA, HurwitzW. A compressive strength study of complete ceramic crowns. Part II. J Prosthet Dent 1991; 65:388-391.

9. Pallis K, Griggs JA, Woody RD, Guillen GE, Miller AW. Fracture resistance of three all-ceramic restorative systems for posterior applications. J Prosthet Dent 2004; 91:561-569.

10.Erneklint C, Odman P, Ortengren U, Rasmusson L. Tolerance test of five different types of crowns on single-tooth implants. Int J Prosthodont 1998; 11:233-239.

Mr. Daniele Capoferri received his four-yeardental technician education from the ScuolaProfessionale Artigianale Industriale in Trevano,Switzerland in 1997. Following graduation, heworked closely with one of the finest mastertechnicians in Europe, Hans Peter Spielman, inthe office of Dr. Uli Grunder of Zurich. Mr.Capoferri emigrated to the U.S. in 2000 where hehas been an integral member of Dr. RichardKinsel’s restorative and implant treatment team inFoster City, California. Currently, he manages theSwiss Dental Design laboratory in Foster Cityemphasizing “natural esthetics” in ceramicrestorations and full mouth rehabilitations. Hehas lectured and published with Dr. Kinsel both inthe U.S. and internationally.

Assistant Clinical ProfessorDepartment of Restorative DentistryDivision of ProsthodonticsDirector, Implant Dentistry ProgramBuchanan Dental CenterUniversity of California, San FranciscoPrivate Practice

Dr. Richard Kinsel received his dental degree in1979 from the University of the Pacific School ofDentistry in San Francisco, California. He wasAssistant Professor for eight years in the Departmentof Fixed Prosthodontics at U.O.P. and is currentlyAssistant Clinical Professor in the Department ofRestorative Dentistry, Division of Prosthodontics at the University of California, San Francisco,School of Dentistry.

Dr. Kinsel is the Director of Implant Dentistryat the A.E.G.D. Post-Graduate Residency anddeveloped the program’s implant curriculum and syllabus. He is an active member of theAmerican Prosthodontic Society, Federation ofProsthodontic Organizations, the Academy ofOsseointegration, and an associate member of theAmerican Academy of Periodontology. He haspublished in various journals and presentednumerous seminars related to implant dentistryboth nationally and internationally. He maintainsa private practice in Foster City emphasizingimplant and periodontal prosthodontics.

Richard P. Kinsel, D.D.S.1291 East Hillsdale Blvd.Foster City, CA 94404650-573-8280 faxdrcycle@aol.com

Daniele Capoferri, CDTSwiss Dental Design1291 East Hillsdale Blvd.Suite 142Foster City, CA 94404650-572-9866swissdd@aol.com

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#1 Why has the general trend in dentistry been towardall-ceramic crowns?

a. They are cheapersb. They are strongerc. They have increased light transmissiond. All of the above

#2 What factors should be considered when choosing arestorative material?

a. Strength and fracture resistanceb. Ease of fabricationc. Long term predictabilityd. All of the above

#3 The proper tooth preparation is the…a. dentists responsibilityb. necessary for all ceramic crownsc. is rarely received in the laboratoryd. all of the above

#4 Inadequate space leads to compromises in…a. porcelain layeringb. contour and emergence profilec. internal colorationd. all of the above

#5 There is a general assumption amongst dentists thatall-ceramic crowns have better esthetics that compensatefor the…

a. limited skills of the technicianb. lack of space in the preparationc. limited esthetics of PFM restorationsd. both a and c

#6 Decisions to use a specific crown type should be basedupon…

a. strengthb. sase of fabricationc. long-term predictabilityd. all of the above

#7 How much incisal reduction is necessary to develop atranslucent incisal edge?

a. 1.0mm-2.0mmb. 1.5mm-2.5mmc. 2.5mm-3.0mmd. 3.0mm-3.5mm

#8 How much facial or palatal reduction is necessary forproper ceramic layering?

a. 0.5mm-0.7mmb. 0.8mm-1.0mmc. 1.0mm-1.2mmd. 1.2mm-1.5mm

#9 The all-ceramic crown may compensate for less skilledtechnicians…

a. but it costs too much for most dentistsb. but strength and longevity are compromised ceramicc. but proper space and margin preparation are difficult

to getd. all of the above

#10 The ceramists limitations should not dictate thedentists…

a. fee structureb. decisions regarding crown typec. turnaround timesd. all of the above

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