FPDsANDPERIODONTALLYCOMPROMISEDTEETH
26. Lindhe J. Textbook of clinical periodontology. Copenhagen, Denmark: Munksgaard Publishing Co, 1984. 27. Langeland K, Rodriques H, Dowden W. Periodontal disease bacteria and pulpal histopathology. Oral Surg 1974;37:257-70.
19. Dykems RW, Goodacre CJ, Phillips RW. Johnston’s modern practice in fixed prosthodontics. 4th ed. Philadelphia: WB Saunders Co, 1986. 20. Miller SC. Textbook in periodontia. Philadelphia: Blakiston Division/ McGraw-Hill Book Co, 1950. 21. Lindhe J, Nyman S, Westfelt E. Critical probing depths in periodontal therapy. J Clin Periodontol 1982;9:323-36. 22. Silneas J, L6e H. Periodontal disease in pregnancy. II. Correlation between oral hygiene and periodontal condition. Acta Odontol Stand 1964;22:121-35. 23. L6e H, Silness J. Periodontal disease in pregnancy. I. Prevalence and severity. Acta Odontol Stand 1963;21:532-51. 24. Ramfjord SP. Indices for prevalence and incidence of periodontal disease. J Periodontol 1959;30:51-9. 25. Smith LW, Suomi JD, Greene JC, et al. A study of intra-examiner variation in scoring oral hygiene status, gingivai infiammation and epithelial attachment level. J Periodontol 1970;41:671-4.
Effect of metal characteristics Donald M. Belles, E. S. Duke, D.D.S., University
of Texas
Reprint requeststo: DR. MARTIN
A. FREILICH SCHOOL OF DENTAL. MEDICINE UNIVERSITY OF CONNECTICUT FARMINGTON, CT 06032
HEALTH
CENTER
Contributing author Ralph V. Katz, D.M.D., Ph.D., Associate Professor, Behavioral Sciences and Community Health, University of Connecticut, School of Dental Medicine, Farmington, Conn.
design and technique on the marginal of the collarless metal ceramic restoration D.D.S., M.S.,* M.S.D.***
Health
Science
Center,
Robert Dental
J. Cronin, School,
Jr., D.D.S.,**
San Antonio,
and
Tex.
This investigation examined the marginal characteristics of the collarless metal ceramic restoration made with two commonly used direct-lift techniques: (1) a porcelain/wax paste and (2) a porcelain/liquid slurry. The metal copings touched the shoulder in half of the groups and were left 0.6 mm short in the other half to comprise the four experimental groups. Marginal seal was evaluated at facial and lingual surfaces on embedded and sectioned specimens for each group. Photo negatives were made of each specimen and projected at a constant magnillcation so that tracings could be made of the space between the die shoulder and corresponding porcelain. Composite surface measurements were made for each sample with a Zeiss Interactive Digital Analysis System instrument to evaluate porcelain adaptation to the shoulder. The porcelainfliquid groups demonstrated significantly smaller (p 5 0.05) facial marginal openings than the porcelain/wax groups. The group made with the porcelain/liquid technique with the metal on the die shoulder produced the most consistent overall results. The porcelain/liquid group with the metal off the shoulder had a statistically larger (p 5 0.05) mean marginal opening from the external margin to a point 0.75 mm to the interior than both techniques with the metal on the shoulder. Lingual marginal adaptation did not vary with each of the four experimental groups. (J PROSTHET DENT 1991;65:61 l-9.)
The opinions contained in this article are those of the authors end are not to be construed as official or as reflecting the views of the United States Air Force or the Department of Defense. Based on a thesis submitted to the graduate faculty, University of Texas, Graduate School of Biomedical Sciences, San Antonio, Tex., in partial fulfillment of the requirements for the Master of
Science degree. Third place, American College of Prosthodontists, John J. Sharry Research Award Competition, Charleston, SC. *Lieutenant Colonel, U.S. Air Force, DC; Assistant Director, Area Dental Laboratory, USAF Clinic Kadene/SGDL, APO San
Francisco. **Colonel, U.S. Air Force, DC; Chairman, Department of Prosthodontics, Wilford Hell Medical Center, San Antonio, Tex. ***Associate Professor, Department of Restorative Dentistry.
10/l/27304
THEJOURNALOFPROSTHETICDENTISTRY
T
he esthetic demand in the region of the labial margin combined with the strength of conventional metal ceramic restorations may explain the increasing popularity of the collarless metal ceramic restoration.’ To simplify these restorations, several techniques have evolved over the years.2-5 A technique introduced by Prince et a1.6 used wax as a binder for the porcelain powder. The use of a wax suspension allows a more consistent separation of condensed porcelain from the die material. It also enhances flowing wax and porcelain into the small marginal gap that results from shrinkage in the original firing. Shrader et al.’ found 11.4% less shrinkage with the porcelain/wax method than with the conventional porcelain/
611
BELLES,
Fig. 1. Plexiglas master die.
Fig. 2. Feeler gauge establishing and rotating template.
distance between die
liquid technique. Gordnersdemonstrated that the decrease in porcelain shrinkage attained with the wax technique is due to an increase in porosity. As the ratio of porcelain to wax increases, the shrinkage percentage, apparent specific gravity, and transverse rupture strength decreases. He recommended the use of a porcelain/wax technique only in limited situations and then with a ratio of 6:l by weight. When comparing porcelain/wax, direct-lift, and platinum foil techniques, Cooney et al9 found that those produced by the porcelain/wax technique yielded the poorest marginal adaptation.
612
CRONIN,
AND
DUKE
Fig. 3. Sculptured wax coping.
Metal substructure design for the collarless metal ceramic restoration using a direct-lift technique consists of three distinct configurations. Feathering the metal short of the external finish line1°-12 allows the shrinkage of the porcelain shoulder to be reduced to a minimum, However, it may introduce problems with metal distortion and esthetics. By far the most popular technique is to bring the metal to the junction of the axial wall and shoulder floor.13-l5 This procedure is a direct modification of the platinum foil and refractory die techniques and is recommended because it results in improved color as a result of the increased porcelain thickness at the gingival margin. The concept of leaving the metal short of the shoulder was developed to avoid the darkening effect of metal on the adjacent tooth structure.i6p I7 There have been no investigations of the effect of metal substructure design on porcelain adaptation to the shoulder. This investigation (1) compares the marginal character of the porcelain/wax technique with that of the porcelain/ liquid; (2) examines the metal design for influence on margin characteristics; (3) compares marginal adaptations of the porcelain/wax technique and the porcelain/liquid technique; and (4) examines the influence of technique on lingual margin fit.
METHODS
AND
MATERIAL
A master die having a 2.5 degree axial wall taper, a 1.5 mm gingival shoulder, a crown height of 7 mm, and an occlusal diameter of 6.1 mm was machined in Plexiglas acrylic plastic (Fig. 1). Twenty impressions were made of the master die with an addition reaction silicon material (President, Coltene Inc., Hudson, Mass.). Three working dies were made from each impression in a refractory investment
MAY
1991
VOLUME
65
NUMBER
6
EFFECT
OF METAL
DESIGN
AND
TECHNIQUE
Fig. 5. Second template sculpturing
lingual surface.
Fig. 4. Silicon putty matrix for forming lingual wall.
stone (DVP, Whip-Mix Corp., Louisville, Ky.) providing a total of 60 specimens. To ensure uniform wax application for each die, a sculpturing device previously described18 was used. A 0.4 mm feeler gauge was used to establish the distance between each die and a movable template that was attached to a ball bearing race (Fig. 2). The angle of the axial wall of the die and template remained constant at 2.5 degrees. A hard inlay wax (Maves Co., Cleveland, Ohio) was applied and the template was revolved symmetrically around the die sculpturing the wax (Fig. 3). To aid in the casting of the specimens and to provide a control surface, a lingual wall of wax was added. A silicon putty matrix allowed for standardization of the bulk wax buildup (Fig. 4), and a second movable template at 1.5 mm from the die allowed for uniform sculpturing (Fig. 5). The wax/refractory die systems were sprued in groups of three (Fig. 6) and invested in a phosphate-bonded material (Ceramigold, Whip-Mix Corp.). Castings were then made in Olympia metal (J.F. Jelenko and Co., New Rochelle, N.Y.) by use of a centrifugal casting machine following the recommended procedures for the alloy. The metal samples were divested, cleaned, and cut from their sprues. The shoulder of each casting was carefully finished to a smooth flat surface by successive abrasion on No. 240 through 600 grit silicon carbide strips (Buehler Ltd., Lake Bluff, Ill.). A small notch was then placed on the internal aspect of the shoulder at the midpoint of each casting buccolingually to provide an alignment guide.
(Reliance Dental Manufacturing Co., Worth, Ill.) was used in each casting by a previously described technique,21 and a brass dowel pin was then inserted vertically with slight hand vibration (Fig. 7). To allow for the use of the sculpturing device during porcelain application, bases were made for each die by inserting the resin die into one of the initial silicon impressions of the master die and pouring a stone base (Die-Keen, Columbus Dental, St. Louis, MO.) (Fig. 8). The casting-die systems were randomly divided into two groups and the metal at the margins was altered to conform to the two types of metal configurations under investigation. The first design allowed metal to remain at the junction of the axial wall and shoulder floor and the second design left the metal 0.5 mm short of the shoulder (Fig. 9). Each group was then randomly divided, providing four experimental groups of 15.
Fabrication
Porcelain
of custom
dies
To make working dies, a method similar to that described by McCunelg and Gavelis et a1.20was used. Duralay resin
THE
JOURNAL
OF
PROSTHETIC
DENTISTRY
Fig. 6. Sprued wax copings.
fabrication
To make the results of this investigation as clinically relevant as possible, the porcelain fabrication was con613
BELLES,
CRONIN,
AND
DUKE
Fig. 7. Trimmed resin die and cast coping.
Fig. 10. Rotating template sculpturing
porcelain.
Fig. 8. Resin die in original impression to allow stone base to be made.
Fig. 11. Restoration resin.
Fig. 9. Shoulder metal designs: Left, Metal to shoulder; Right, metal 0.5 mm short of shoulder.
ducted in a manner closely approximating the porcelain’s actual clinical use and laboratory fabrication. Two layers of VMK-68 opaque (Vident, Baldwin Park, Calif.) were applied and fired on all 60 specimens as described in the Vita technique manua1.22 The porcelain used to establish the shoulder was a commercially available high-fusing, 614
ready for embedding in polyester
low-shrinkage material (594X, Vident). VMK-68 modeling liquid (Vident) was used as the medium for 30 of the samples, and margin fabrication was based on a technique previously described.23 A pilot investigation revealed that the initial marginal buildup could not be made with a porcelain/wax mixture because of the excessive slumping that occurred when the mixture was allowed to volatilize beneath the muffle of the porcelain oven. To establish the initial margin buildup, the same technique as that used for the porcelain/liquid specimens was used. All additional correctional firings for the 30 specimens were completed with a porcelain/wax mixture following a previously described technique6 with a 61 ratio of shoulder porcelain (Vident) to wax (Plastodent U, Degussa, Long Island, N.Y.) by weight. MAY
lSB1
VOLUME
66
NUMBER
6
EFFECT
OF METAL
DESIGN
AND
TECHNIQUE
12. Representative margins from porcelain/liquid technique. A, Specimen with metal to shoulder; B, specimenwith metal off shoulder. Fig.
A specially designedsculpturing device was usedto ensure uniform thickness of the porcelain walls. A feeler gaugeestablisheda 1.5 mm distance between the die and secondtemplate (Fig. 10). Two porcelain applications were completed on eachsample.A final marginal correction was done on every samplewith the sametechnique used prior to a final glaze.
removed and the restorations were then individually embeddedin a pourablepolyester resin (ChemcoResinCrafts, Dubin, Calif.) (Fig. 11). The embedded specimenswere sectionedocclusal-gingivally at the faciolingual midpoint. The sectioned crowns were then metallographically polished by successiveabrasion on No. 240 through 600 grit silicon carbide strips (Buehler Ltd.).
Specimen
Measurement
preparation
The finished restorations were seatedon their respective dies and weighted on their occlusalsurfaceswith a static 2 lb load. A thin Iayer of alpha-cyanoacrylate cement (Vigor Company, New York, N.Y.) was painted on the external margin surfaceand allowed to dry. The baseof the die was THE
JOURNAL
OF PROSTHETIC
DENTISTRY
analysis
The facial and lingual margin openingswere measured on each of the 60 sampleswith a travelling microscope (Gaertner Scientific Corp., Chicago, Ill.) by following the protocol describedby Faull et a1.24 The marginsproduced as a result of the porcelain/liquid technique were consis615
BELLES,
CRONIN,
AND
DUKE
13. Representative marginsfrom porcelain/wax technique. A, Specimenwith metal to shoulder; B, specimenwith metal off shoulder. Fig.
tently sharp and easily read (Fig. 12). However, thosemade with the porcelain/wax mixture were difficult to read becauseof the rounding that occurred (Fig. 13). To standardize the measurementof these margins, 10 samples were examined and it was found that the rounding was limited to the external 100pm of the porcelain. A composite marginal opening was produced for all the porcelain/ wax margins by making three measurements(external margin and internally at 40 wrn and 100 pm). The technique usedto measureporcelain adaptation to the shoulder was describedby Brukl and Philp.s5 Thirtyfive millimeter photonegatives of each of the sectioned60 sampleswere madeand projected at a constant magnification. The space between the porcelain and the die was 616
traced over a surface 0.75 mm from the external margin, and the surfaceof eachwascalculatedwith the aid of a Zeiss Interactive Digital Analysis System (Carl ZeissInc., Thurnwood, N.Y.) instrument (Fig. 14). Data were collected and organized into three main categories: (1) facial margins, (2) lingual margins, and (3) averagemeanmarginal openingfrom a distanceof 0 to 0.75 mm on the shoulder. Means were determined for each of the four experimental groupsin eachcategory. To evaluate the variation between each grouping, the standard deviation was calculated. A one-way analysis of variance (ANOVA) was used to examine variation between the groups.A two-way ANOVA wasusedto determine whether there wasany interaction between facial and lingual mar-
MAY
1991
VOLUME
65
NUMBER
6
EFFECT
OF METAL
DESIGN
AND
Fig.
TECHNIQUE
14. Stylus for tracing with ZIDAS (Zeissinteractive digital analysis system).
gins. A post-hoc Duncan multiple comparison test was performed to identify significant differences and to rank the group meansat a p 5 0.05 level of significance.
RESULTS The marginal openingsfor the facial margins are presented in Table I. Significant differences were found between the porcelain/liquid groups A and C (27.48 and 25.17pm openings)and the porcelain/wax groupsB and D (49.31and 59.14pm openings)at the p 5 0.05 level. When lingual margins of the four groups were compared (Table II), no significant differences were found (p 5 0.05). Comparisonsof the porcelain adaptation from the external margin to 0.75 mm internally (Table III) revealed a significant difference 0, i .0025). Analysis demonstrated that the porcelain/liquid group (C) with the metal off the shoulderwas significantly (p 5 0.05) larger in the average marginal gap than both groups (A and B) with the metal on the shoulder. There was no statistical difference between groups C and D.
DISCUSSION A major concernin the fabrication of the porcelain facial margin is the expressingof a small amount of porcelain slurry beneath the metal coping during vibration and condensation. This material can causethe restoration to tip lingually or can prevent its complete seating.Although the material can be removed after firing, it can result in an improved fit of the facial margin and a diminished fit of the lingual margin. Statistical analysisrevealed no significant differences between any of the four groups under investigation. This confirmed a previous investigation,26which found that clinically acceptable adaptation of the metal
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
Table
I. External facial margins Mean N
A
15
27.48
13.73
15
49.31
10.97
15
25.17
8.36
15
59.14
17.60
(Porcelain/liquid) (Metal to shoulder) B (Porcelain/wax) (Metal to shoulder) C (Porcelain/liquid) (Metal off shoulder) D (Porcelain/wax) (Metal off shoulder)
(microns)
Standard deviation
Group
coping margin can be preserved during fabricatian of the all-porcelain labial margin. Statistical analysisrevealed that the marginal openings of the porcelain/liquid groups were significantly smaller ‘than thoseof the porcelain/wax groups. Only one previous investigationlo compared the fit of porcelain/liquid with that of porcelain/wax. Under the conditions of that study, no significant differences were found. A possibleexplanation of this was their use of body porcelain instead of shoulder porcelain, which causedrounding of the external margin. Microscopic observation of the four groupsin this investigation revealed that those madewith the porcelain/ liquid technique maintained their sharp integrity during firing. Those made by useof the porcelain/wax technique were rounded at the outer 100Hrn of the margin. The sig-
617
BELLES,
Table
II. External lingual margins Group
A (Porcelain/liquid) (Metal to shoulder) B (Porcelain/wax) (Metal to shoulder) C (Porcelain/liquid) (Metal off shoulder) D (Porcelain/wax) (Metal off shoulder)
N
15
15
15
15
Mean (microns)
10.72
15.52
17.31
12.93
Standard deviation
that is resistant
7.31
6.04
5.44
to pyroplaetic
flow. In certain instances, such as margin surfaces that contain undercuts, fixed partial dentures with multiple splinted abutments, or small final corrective procedures, the porcelain/wax technique may be the one of choice.
CONCLUSIONS Basedon the findings of this investigation, the following conclusionscan be drawn: 1. The porcelain/liquid groups demonstrated significantly smallerfacial marginal gapsthan the porcelain/wax groups. 2. The porcelain/liquid technique demonstrated sharp and distinct external margins, whereas those made with the 618
AND
DUKE
Table III. Average marginal opening from 0 to 0.75 mm on shoulder Mean (microns)
Standard deviation
Group
N
A (Porcelain/liquid) (Metal to shoulder) B (Porcelain/wax) (Metal to shoulder) C (Porcelainiliquid) (Metal off shoulder) D (Porcelain/wax) (Metal off shoulder)
15
34.88
14.67
15
36.91
9.59
15
55.85
23.25
15
44.40
12.42
4.26
nificance of this external margin is important. The change in emergenceprofile may produce a stagnant region that allowsfood debris and bacteria to accumulate, causingadverse effects on the gingival tissue. One of the main advantagesof the porcelain/wax technique is its relative simplicity.27To investigate whether the porcelain/wax technique allowed better adaptation of the sintered porcelain to the die shoulder, the meanmarginal opening was computed with the aid of a Zeissinteractive digital analysis system (ZIDAS). Considering the overall margin from the external surface to 0.75 mm internally, there was a significant difference between the two techniques: (1) with the metal touching the shoulder,the opening was34.88and 36.91pm and (2) with the porcelain/liquid technique with the metal 0.5 mm off the shoulder, the opening was 55.85 pm. If the internal fit of porcelain is consideredimportant, the lifting of the metal coping off the margin may not be a viable alternative when the porcelain/ liquid technique is used. Examining the results regarding both the external marginal fit and the internal margin adaptation, the technique with porcelain/liquid with the metal brought down to the shoulder was superior to the other techniques. Although the porcelain/wax technique wassimpler to use,the excessive rounding of the external surface reduced the effectiveness of using a porcelain
CRONIN,
porcelain/wax technique were rounded over a 100 pm distance. 3. The group made with the porcelain/liquid technique with metal to the shoulder produced the most consistent overall resulta. 4. Lingual marginal adaptation did not vary with any of the experimental groups. REFERENCES 1. Prince J, Donovan TE. The esthetic metal-ceramic margin: a comparison of techniques. J PROS= DENT 19&33;50:185-92. 2. Jeffrey T. Construction of combined porcelain to foil and porcelain jacket. NACDL J 1969;16:17-8. 3. Vickery RC, Badinelli LA, Waltke RW. The direct fabrication of restorations without foil on a refractory die. J PROSY DENT 1969;21:22734. 4. Goodacre CJ, Van Roekel NB, Dykema RW, Ullman RB. The collarless metal-ceramic crown. J PROSTHET DENT 1977;38:615-22. 5. Vryonis P. A simplified approach to the complete porcelain margin. J PROSTHS~
DENT
6. Prince J, Donovan for ceramo-metal
1979;42:592-3.
TE, Presswood RG. The all-porcelain labial margin restorations: a new concept. J PROSTHET DENT
1983;50:793-6.
7. Schrader JA, Duke ES, Haney SJ, Herbold ET. Volumetric shrinkage of a porcelain suspended in wax technique. J PROS= DENT 1986; 55302-4. 8. Gordner WH. Properties of dental porcelain fabricated by the porcelain/war technique [Thesis]. University of Texas HSC at San Antonio, 1986. 9. Cooney JP, Richter WA, MacEntee MI. Evaluation of ceramic margins for metal-ceramic restorations. J PR~WHET DENT 1985;54:1-5. 10. Toogood GD, Archibald JF. Technique for establishing porcelain margina. J PR~STHJST DENT 1978;40:464-6. 11. Hunt JL, Cruickshanks-Boyd DW, Davies EH. The marginal characteristics of collarless bonded procelain crowns produced using a separating medium technique. Quintessence Dent Technol 1978;2:21-6. 12. Scharer P. A clinician’s view of porcelain reconstructions. In: Proceedings of the First International Symposium on Ceramics. Chicago: Qulntessence Publishing Co, Inc. 1983301. 13. LaHoste LH. The porcelain butt margin. Quintessence Dent Technol 1981;2:149-51. 14. Zalkind M. A labial porcelain butt-joint ln ceramco-metal restorations. Quintessence Int 1984;11:1117-20. 15. Howard JB. A new procedure for all porcelain labial margins. Trends Techniques 1985;22-5. MAY
1991
VOLUME
65
NUMBER
5
EFFECT
OF METAL
DESIGN
AND
TECHNIQUE
24. Faull TW, Hesby RA, Pelleu GB, Eastwood GW. Marginal opening of single and twin platinum foil-bonded aluminous porcelain crowns. J
16. Behrend DA. Ceramometal restorations with supragingival margins. J PROSTHET DENT 1982;47:625-32. 17. Chiche G, Radiquet J, Pinault A, Genini P. Improved esthetics for the ceramometal crown. Int J Periodont Restor Dent 1986;1:77-87. 18. Philp GK, Brukl CE. Compressive strengths of conventional, twin foil, and all-ceramic crowns. J PROSTHEFT DENT 1984;52:215-20. 19. McCune RJ. The effect of occlusal venting and film thickness on cementation of full cast crowns [Thesis]. Indianapolis: Indiana University, School of Dentistry, 1968. 20. Gavelis JR, Morency JD, Riley ED, Sozio RB. The effect of various finished line preparations on the marginal seal and occlusal seat of full crown preparations. J PROSTHET DENT 1981;45:138-45. 21. Thomas GD, Baylis MA. Immediate, abrade-resistant, fine removable dies. Quintessence Dent Technol 1986;10:17-21. 22. Vita Zahnfabrik. The Vita VMK technique: working instructions. Bad Sackingen, Germany 198827-8. 23. Kessler JC, Brooks TD, Keenan MP. The direct lift-off technique for constructing porcelain margins. Quintessence Dent Technol 1986; l&145-50.
Predictability enhancement Herbert Medical
DENT
1985$3:29-33.
56527-30. Reprint
requests
to:
DR. DONALD M. BELLES USAF CLINIC KADENAISGDL APO SAN FRANCISCO 96239
of color matching and the possibilities of ceramic laminate veneers
Victor University
PROSTHET
25. Brukl CE, Philp GK. The fit of Cerestore, twin foil, and conventional ceramic crowns [Abstract]. J Dent Res 1985;362. 26. Wanserski DJ, Sobcsak KP, Monaco JG, McGivney GP. An analysis of margin adaptation of all-porcelain facial margin ceramometal crowns. J PROWHET DENT 1986;56:289-92. 27. Wiley MG, Huff TL, Trebilcock C, Girvan TB. Esthetic porcelain margins: a modified porcelain-wax technique. J PROSTHET DENT 1986;
Exner, B.Ch.D., M.Sc.Dent.Sc., of Southern
Africa,
Dental
Faculty,
for
D.H.A.*
Medunsa,
South
Africa
This study investigated the predictability of color (Hue, Value, and Chroma) on three illustrated surfaces of ceramic veneers and the extent to which laminates may be shade-adapted by use of tints and opaquers on the fitting surface. Significant discrepancies were found in the flnal color match. The dentist should opt for a lighter, more translucent shade, which can be modified before final cementation. (J PROSTHET DENT 1991;68:619-22.)
I
nlaid ceramic laminates or veneers are the most conservative method of esthetically altering the appearance of anterior teeth, but they should be used judiciously.1-3These restorations pose a unique challenge in shadeselection in that they differ from the metal ceramic and porcelainjacket crownsin thickness (asthin as0.5 mm) of material usedand becausethe underlying dentin may or may not affect the final color.4The interproximal surfaces of the tooth are left intact, and this eliminates the unnatural interproximal translucence encountered in porcelain jacket crowns.When a clear bonding resin is usedto bond the restoration, incident light and specularand diffuse reflection may affect the overall shadeand color.5-7 This study determinespredictability of the final product and the extent to which the operator may have control over color and shadesof the final ceramic veneers.
MATERIAL
AND
METHODS
Extracted human anterior teeth were mounted in plaster and prepared in a systematic sequenceto receive the *Associate Professor, sion Undergraduate
Department Teaching
of Prosthodontics; and Training.
10/l/24173 TRE
JOURNAL
OF PROSTHETIC
DENTISTRY
Head,
Divi-
finished product. In the caseof the castableglasses(Dicer, Dentsply, York, Pa.), the actual teeth were usedasdies to prepare the final wax models (Fig. 1). Conventional ceramic restorations were prepared on refractory dies. The final shade and color were achieved through the application of tints below the glaze layer. The rest of the restoration was translucent porcelain or cast glass.One Vita (Bad Siickingen, Germany) shadeguide was usedby the dentist and the technicians who prepared the finished product. The finished veneerswere compared with the relevant shade-guide tooth and then, through parallel windows, with the samplesplaced on a black velvet backing and with a collimated light sourcefalling at the sameanglefor each sample. Each sample was also observed on its relevant tooth and the shade-guidetooth to determine the effect of the color of the underlying dentin (Figs. 2 and 3). Three separatesurfaceson each samplewere observed. In the second part of the experiment, the veneers were tinted with translucent tints applied with a fine camel-hair brush (Fig. 3). Blue tint wasapplied to the incisal edgesand combinations of brown/orange and/or red were usednear the margins. In someinstances,white tint wasusedon the body section.Each tooth wasindividually characterized by 619
26. Lindhe J. Textbook of clinical periodontology. Copenhagen, Denmark: Munksgaard Publishing Co, 1984. 27. Langeland K, Rodriques H, Dowden W. Periodontal disease bacteria and pulpal histopathology. Oral Surg 1974;37:257-70.
19. Dykems RW, Goodacre CJ, Phillips RW. Johnston’s modern practice in fixed prosthodontics. 4th ed. Philadelphia: WB Saunders Co, 1986. 20. Miller SC. Textbook in periodontia. Philadelphia: Blakiston Division/ McGraw-Hill Book Co, 1950. 21. Lindhe J, Nyman S, Westfelt E. Critical probing depths in periodontal therapy. J Clin Periodontol 1982;9:323-36. 22. Silneas J, L6e H. Periodontal disease in pregnancy. II. Correlation between oral hygiene and periodontal condition. Acta Odontol Stand 1964;22:121-35. 23. L6e H, Silness J. Periodontal disease in pregnancy. I. Prevalence and severity. Acta Odontol Stand 1963;21:532-51. 24. Ramfjord SP. Indices for prevalence and incidence of periodontal disease. J Periodontol 1959;30:51-9. 25. Smith LW, Suomi JD, Greene JC, et al. A study of intra-examiner variation in scoring oral hygiene status, gingivai infiammation and epithelial attachment level. J Periodontol 1970;41:671-4.
Effect of metal characteristics Donald M. Belles, E. S. Duke, D.D.S., University
of Texas
Reprint requeststo: DR. MARTIN
A. FREILICH SCHOOL OF DENTAL. MEDICINE UNIVERSITY OF CONNECTICUT FARMINGTON, CT 06032
HEALTH
CENTER
Contributing author Ralph V. Katz, D.M.D., Ph.D., Associate Professor, Behavioral Sciences and Community Health, University of Connecticut, School of Dental Medicine, Farmington, Conn.
design and technique on the marginal of the collarless metal ceramic restoration D.D.S., M.S.,* M.S.D.***
Health
Science
Center,
Robert Dental
J. Cronin, School,
Jr., D.D.S.,**
San Antonio,
and
Tex.
This investigation examined the marginal characteristics of the collarless metal ceramic restoration made with two commonly used direct-lift techniques: (1) a porcelain/wax paste and (2) a porcelain/liquid slurry. The metal copings touched the shoulder in half of the groups and were left 0.6 mm short in the other half to comprise the four experimental groups. Marginal seal was evaluated at facial and lingual surfaces on embedded and sectioned specimens for each group. Photo negatives were made of each specimen and projected at a constant magnillcation so that tracings could be made of the space between the die shoulder and corresponding porcelain. Composite surface measurements were made for each sample with a Zeiss Interactive Digital Analysis System instrument to evaluate porcelain adaptation to the shoulder. The porcelainfliquid groups demonstrated significantly smaller (p 5 0.05) facial marginal openings than the porcelain/wax groups. The group made with the porcelain/liquid technique with the metal on the die shoulder produced the most consistent overall results. The porcelain/liquid group with the metal off the shoulder had a statistically larger (p 5 0.05) mean marginal opening from the external margin to a point 0.75 mm to the interior than both techniques with the metal on the shoulder. Lingual marginal adaptation did not vary with each of the four experimental groups. (J PROSTHET DENT 1991;65:61 l-9.)
The opinions contained in this article are those of the authors end are not to be construed as official or as reflecting the views of the United States Air Force or the Department of Defense. Based on a thesis submitted to the graduate faculty, University of Texas, Graduate School of Biomedical Sciences, San Antonio, Tex., in partial fulfillment of the requirements for the Master of
Science degree. Third place, American College of Prosthodontists, John J. Sharry Research Award Competition, Charleston, SC. *Lieutenant Colonel, U.S. Air Force, DC; Assistant Director, Area Dental Laboratory, USAF Clinic Kadene/SGDL, APO San
Francisco. **Colonel, U.S. Air Force, DC; Chairman, Department of Prosthodontics, Wilford Hell Medical Center, San Antonio, Tex. ***Associate Professor, Department of Restorative Dentistry.
10/l/27304
THEJOURNALOFPROSTHETICDENTISTRY
T
he esthetic demand in the region of the labial margin combined with the strength of conventional metal ceramic restorations may explain the increasing popularity of the collarless metal ceramic restoration.’ To simplify these restorations, several techniques have evolved over the years.2-5 A technique introduced by Prince et a1.6 used wax as a binder for the porcelain powder. The use of a wax suspension allows a more consistent separation of condensed porcelain from the die material. It also enhances flowing wax and porcelain into the small marginal gap that results from shrinkage in the original firing. Shrader et al.’ found 11.4% less shrinkage with the porcelain/wax method than with the conventional porcelain/
611
BELLES,
Fig. 1. Plexiglas master die.
Fig. 2. Feeler gauge establishing and rotating template.
distance between die
liquid technique. Gordnersdemonstrated that the decrease in porcelain shrinkage attained with the wax technique is due to an increase in porosity. As the ratio of porcelain to wax increases, the shrinkage percentage, apparent specific gravity, and transverse rupture strength decreases. He recommended the use of a porcelain/wax technique only in limited situations and then with a ratio of 6:l by weight. When comparing porcelain/wax, direct-lift, and platinum foil techniques, Cooney et al9 found that those produced by the porcelain/wax technique yielded the poorest marginal adaptation.
612
CRONIN,
AND
DUKE
Fig. 3. Sculptured wax coping.
Metal substructure design for the collarless metal ceramic restoration using a direct-lift technique consists of three distinct configurations. Feathering the metal short of the external finish line1°-12 allows the shrinkage of the porcelain shoulder to be reduced to a minimum, However, it may introduce problems with metal distortion and esthetics. By far the most popular technique is to bring the metal to the junction of the axial wall and shoulder floor.13-l5 This procedure is a direct modification of the platinum foil and refractory die techniques and is recommended because it results in improved color as a result of the increased porcelain thickness at the gingival margin. The concept of leaving the metal short of the shoulder was developed to avoid the darkening effect of metal on the adjacent tooth structure.i6p I7 There have been no investigations of the effect of metal substructure design on porcelain adaptation to the shoulder. This investigation (1) compares the marginal character of the porcelain/wax technique with that of the porcelain/ liquid; (2) examines the metal design for influence on margin characteristics; (3) compares marginal adaptations of the porcelain/wax technique and the porcelain/liquid technique; and (4) examines the influence of technique on lingual margin fit.
METHODS
AND
MATERIAL
A master die having a 2.5 degree axial wall taper, a 1.5 mm gingival shoulder, a crown height of 7 mm, and an occlusal diameter of 6.1 mm was machined in Plexiglas acrylic plastic (Fig. 1). Twenty impressions were made of the master die with an addition reaction silicon material (President, Coltene Inc., Hudson, Mass.). Three working dies were made from each impression in a refractory investment
MAY
1991
VOLUME
65
NUMBER
6
EFFECT
OF METAL
DESIGN
AND
TECHNIQUE
Fig. 5. Second template sculpturing
lingual surface.
Fig. 4. Silicon putty matrix for forming lingual wall.
stone (DVP, Whip-Mix Corp., Louisville, Ky.) providing a total of 60 specimens. To ensure uniform wax application for each die, a sculpturing device previously described18 was used. A 0.4 mm feeler gauge was used to establish the distance between each die and a movable template that was attached to a ball bearing race (Fig. 2). The angle of the axial wall of the die and template remained constant at 2.5 degrees. A hard inlay wax (Maves Co., Cleveland, Ohio) was applied and the template was revolved symmetrically around the die sculpturing the wax (Fig. 3). To aid in the casting of the specimens and to provide a control surface, a lingual wall of wax was added. A silicon putty matrix allowed for standardization of the bulk wax buildup (Fig. 4), and a second movable template at 1.5 mm from the die allowed for uniform sculpturing (Fig. 5). The wax/refractory die systems were sprued in groups of three (Fig. 6) and invested in a phosphate-bonded material (Ceramigold, Whip-Mix Corp.). Castings were then made in Olympia metal (J.F. Jelenko and Co., New Rochelle, N.Y.) by use of a centrifugal casting machine following the recommended procedures for the alloy. The metal samples were divested, cleaned, and cut from their sprues. The shoulder of each casting was carefully finished to a smooth flat surface by successive abrasion on No. 240 through 600 grit silicon carbide strips (Buehler Ltd., Lake Bluff, Ill.). A small notch was then placed on the internal aspect of the shoulder at the midpoint of each casting buccolingually to provide an alignment guide.
(Reliance Dental Manufacturing Co., Worth, Ill.) was used in each casting by a previously described technique,21 and a brass dowel pin was then inserted vertically with slight hand vibration (Fig. 7). To allow for the use of the sculpturing device during porcelain application, bases were made for each die by inserting the resin die into one of the initial silicon impressions of the master die and pouring a stone base (Die-Keen, Columbus Dental, St. Louis, MO.) (Fig. 8). The casting-die systems were randomly divided into two groups and the metal at the margins was altered to conform to the two types of metal configurations under investigation. The first design allowed metal to remain at the junction of the axial wall and shoulder floor and the second design left the metal 0.5 mm short of the shoulder (Fig. 9). Each group was then randomly divided, providing four experimental groups of 15.
Fabrication
Porcelain
of custom
dies
To make working dies, a method similar to that described by McCunelg and Gavelis et a1.20was used. Duralay resin
THE
JOURNAL
OF
PROSTHETIC
DENTISTRY
Fig. 6. Sprued wax copings.
fabrication
To make the results of this investigation as clinically relevant as possible, the porcelain fabrication was con613
BELLES,
CRONIN,
AND
DUKE
Fig. 7. Trimmed resin die and cast coping.
Fig. 10. Rotating template sculpturing
porcelain.
Fig. 8. Resin die in original impression to allow stone base to be made.
Fig. 11. Restoration resin.
Fig. 9. Shoulder metal designs: Left, Metal to shoulder; Right, metal 0.5 mm short of shoulder.
ducted in a manner closely approximating the porcelain’s actual clinical use and laboratory fabrication. Two layers of VMK-68 opaque (Vident, Baldwin Park, Calif.) were applied and fired on all 60 specimens as described in the Vita technique manua1.22 The porcelain used to establish the shoulder was a commercially available high-fusing, 614
ready for embedding in polyester
low-shrinkage material (594X, Vident). VMK-68 modeling liquid (Vident) was used as the medium for 30 of the samples, and margin fabrication was based on a technique previously described.23 A pilot investigation revealed that the initial marginal buildup could not be made with a porcelain/wax mixture because of the excessive slumping that occurred when the mixture was allowed to volatilize beneath the muffle of the porcelain oven. To establish the initial margin buildup, the same technique as that used for the porcelain/liquid specimens was used. All additional correctional firings for the 30 specimens were completed with a porcelain/wax mixture following a previously described technique6 with a 61 ratio of shoulder porcelain (Vident) to wax (Plastodent U, Degussa, Long Island, N.Y.) by weight. MAY
lSB1
VOLUME
66
NUMBER
6
EFFECT
OF METAL
DESIGN
AND
TECHNIQUE
12. Representative margins from porcelain/liquid technique. A, Specimen with metal to shoulder; B, specimenwith metal off shoulder. Fig.
A specially designedsculpturing device was usedto ensure uniform thickness of the porcelain walls. A feeler gaugeestablisheda 1.5 mm distance between the die and secondtemplate (Fig. 10). Two porcelain applications were completed on eachsample.A final marginal correction was done on every samplewith the sametechnique used prior to a final glaze.
removed and the restorations were then individually embeddedin a pourablepolyester resin (ChemcoResinCrafts, Dubin, Calif.) (Fig. 11). The embedded specimenswere sectionedocclusal-gingivally at the faciolingual midpoint. The sectioned crowns were then metallographically polished by successiveabrasion on No. 240 through 600 grit silicon carbide strips (Buehler Ltd.).
Specimen
Measurement
preparation
The finished restorations were seatedon their respective dies and weighted on their occlusalsurfaceswith a static 2 lb load. A thin Iayer of alpha-cyanoacrylate cement (Vigor Company, New York, N.Y.) was painted on the external margin surfaceand allowed to dry. The baseof the die was THE
JOURNAL
OF PROSTHETIC
DENTISTRY
analysis
The facial and lingual margin openingswere measured on each of the 60 sampleswith a travelling microscope (Gaertner Scientific Corp., Chicago, Ill.) by following the protocol describedby Faull et a1.24 The marginsproduced as a result of the porcelain/liquid technique were consis615
BELLES,
CRONIN,
AND
DUKE
13. Representative marginsfrom porcelain/wax technique. A, Specimenwith metal to shoulder; B, specimenwith metal off shoulder. Fig.
tently sharp and easily read (Fig. 12). However, thosemade with the porcelain/wax mixture were difficult to read becauseof the rounding that occurred (Fig. 13). To standardize the measurementof these margins, 10 samples were examined and it was found that the rounding was limited to the external 100pm of the porcelain. A composite marginal opening was produced for all the porcelain/ wax margins by making three measurements(external margin and internally at 40 wrn and 100 pm). The technique usedto measureporcelain adaptation to the shoulder was describedby Brukl and Philp.s5 Thirtyfive millimeter photonegatives of each of the sectioned60 sampleswere madeand projected at a constant magnification. The space between the porcelain and the die was 616
traced over a surface 0.75 mm from the external margin, and the surfaceof eachwascalculatedwith the aid of a Zeiss Interactive Digital Analysis System (Carl ZeissInc., Thurnwood, N.Y.) instrument (Fig. 14). Data were collected and organized into three main categories: (1) facial margins, (2) lingual margins, and (3) averagemeanmarginal openingfrom a distanceof 0 to 0.75 mm on the shoulder. Means were determined for each of the four experimental groupsin eachcategory. To evaluate the variation between each grouping, the standard deviation was calculated. A one-way analysis of variance (ANOVA) was used to examine variation between the groups.A two-way ANOVA wasusedto determine whether there wasany interaction between facial and lingual mar-
MAY
1991
VOLUME
65
NUMBER
6
EFFECT
OF METAL
DESIGN
AND
Fig.
TECHNIQUE
14. Stylus for tracing with ZIDAS (Zeissinteractive digital analysis system).
gins. A post-hoc Duncan multiple comparison test was performed to identify significant differences and to rank the group meansat a p 5 0.05 level of significance.
RESULTS The marginal openingsfor the facial margins are presented in Table I. Significant differences were found between the porcelain/liquid groups A and C (27.48 and 25.17pm openings)and the porcelain/wax groupsB and D (49.31and 59.14pm openings)at the p 5 0.05 level. When lingual margins of the four groups were compared (Table II), no significant differences were found (p 5 0.05). Comparisonsof the porcelain adaptation from the external margin to 0.75 mm internally (Table III) revealed a significant difference 0, i .0025). Analysis demonstrated that the porcelain/liquid group (C) with the metal off the shoulderwas significantly (p 5 0.05) larger in the average marginal gap than both groups (A and B) with the metal on the shoulder. There was no statistical difference between groups C and D.
DISCUSSION A major concernin the fabrication of the porcelain facial margin is the expressingof a small amount of porcelain slurry beneath the metal coping during vibration and condensation. This material can causethe restoration to tip lingually or can prevent its complete seating.Although the material can be removed after firing, it can result in an improved fit of the facial margin and a diminished fit of the lingual margin. Statistical analysisrevealed no significant differences between any of the four groups under investigation. This confirmed a previous investigation,26which found that clinically acceptable adaptation of the metal
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
Table
I. External facial margins Mean N
A
15
27.48
13.73
15
49.31
10.97
15
25.17
8.36
15
59.14
17.60
(Porcelain/liquid) (Metal to shoulder) B (Porcelain/wax) (Metal to shoulder) C (Porcelain/liquid) (Metal off shoulder) D (Porcelain/wax) (Metal off shoulder)
(microns)
Standard deviation
Group
coping margin can be preserved during fabricatian of the all-porcelain labial margin. Statistical analysisrevealed that the marginal openings of the porcelain/liquid groups were significantly smaller ‘than thoseof the porcelain/wax groups. Only one previous investigationlo compared the fit of porcelain/liquid with that of porcelain/wax. Under the conditions of that study, no significant differences were found. A possibleexplanation of this was their use of body porcelain instead of shoulder porcelain, which causedrounding of the external margin. Microscopic observation of the four groupsin this investigation revealed that those madewith the porcelain/ liquid technique maintained their sharp integrity during firing. Those made by useof the porcelain/wax technique were rounded at the outer 100Hrn of the margin. The sig-
617
BELLES,
Table
II. External lingual margins Group
A (Porcelain/liquid) (Metal to shoulder) B (Porcelain/wax) (Metal to shoulder) C (Porcelain/liquid) (Metal off shoulder) D (Porcelain/wax) (Metal off shoulder)
N
15
15
15
15
Mean (microns)
10.72
15.52
17.31
12.93
Standard deviation
that is resistant
7.31
6.04
5.44
to pyroplaetic
flow. In certain instances, such as margin surfaces that contain undercuts, fixed partial dentures with multiple splinted abutments, or small final corrective procedures, the porcelain/wax technique may be the one of choice.
CONCLUSIONS Basedon the findings of this investigation, the following conclusionscan be drawn: 1. The porcelain/liquid groups demonstrated significantly smallerfacial marginal gapsthan the porcelain/wax groups. 2. The porcelain/liquid technique demonstrated sharp and distinct external margins, whereas those made with the 618
AND
DUKE
Table III. Average marginal opening from 0 to 0.75 mm on shoulder Mean (microns)
Standard deviation
Group
N
A (Porcelain/liquid) (Metal to shoulder) B (Porcelain/wax) (Metal to shoulder) C (Porcelainiliquid) (Metal off shoulder) D (Porcelain/wax) (Metal off shoulder)
15
34.88
14.67
15
36.91
9.59
15
55.85
23.25
15
44.40
12.42
4.26
nificance of this external margin is important. The change in emergenceprofile may produce a stagnant region that allowsfood debris and bacteria to accumulate, causingadverse effects on the gingival tissue. One of the main advantagesof the porcelain/wax technique is its relative simplicity.27To investigate whether the porcelain/wax technique allowed better adaptation of the sintered porcelain to the die shoulder, the meanmarginal opening was computed with the aid of a Zeissinteractive digital analysis system (ZIDAS). Considering the overall margin from the external surface to 0.75 mm internally, there was a significant difference between the two techniques: (1) with the metal touching the shoulder,the opening was34.88and 36.91pm and (2) with the porcelain/liquid technique with the metal 0.5 mm off the shoulder, the opening was 55.85 pm. If the internal fit of porcelain is consideredimportant, the lifting of the metal coping off the margin may not be a viable alternative when the porcelain/ liquid technique is used. Examining the results regarding both the external marginal fit and the internal margin adaptation, the technique with porcelain/liquid with the metal brought down to the shoulder was superior to the other techniques. Although the porcelain/wax technique wassimpler to use,the excessive rounding of the external surface reduced the effectiveness of using a porcelain
CRONIN,
porcelain/wax technique were rounded over a 100 pm distance. 3. The group made with the porcelain/liquid technique with metal to the shoulder produced the most consistent overall resulta. 4. Lingual marginal adaptation did not vary with any of the experimental groups. REFERENCES 1. Prince J, Donovan TE. The esthetic metal-ceramic margin: a comparison of techniques. J PROS= DENT 19&33;50:185-92. 2. Jeffrey T. Construction of combined porcelain to foil and porcelain jacket. NACDL J 1969;16:17-8. 3. Vickery RC, Badinelli LA, Waltke RW. The direct fabrication of restorations without foil on a refractory die. J PROSY DENT 1969;21:22734. 4. Goodacre CJ, Van Roekel NB, Dykema RW, Ullman RB. The collarless metal-ceramic crown. J PROSTHET DENT 1977;38:615-22. 5. Vryonis P. A simplified approach to the complete porcelain margin. J PROSTHS~
DENT
6. Prince J, Donovan for ceramo-metal
1979;42:592-3.
TE, Presswood RG. The all-porcelain labial margin restorations: a new concept. J PROSTHET DENT
1983;50:793-6.
7. Schrader JA, Duke ES, Haney SJ, Herbold ET. Volumetric shrinkage of a porcelain suspended in wax technique. J PROS= DENT 1986; 55302-4. 8. Gordner WH. Properties of dental porcelain fabricated by the porcelain/war technique [Thesis]. University of Texas HSC at San Antonio, 1986. 9. Cooney JP, Richter WA, MacEntee MI. Evaluation of ceramic margins for metal-ceramic restorations. J PR~WHET DENT 1985;54:1-5. 10. Toogood GD, Archibald JF. Technique for establishing porcelain margina. J PR~STHJST DENT 1978;40:464-6. 11. Hunt JL, Cruickshanks-Boyd DW, Davies EH. The marginal characteristics of collarless bonded procelain crowns produced using a separating medium technique. Quintessence Dent Technol 1978;2:21-6. 12. Scharer P. A clinician’s view of porcelain reconstructions. In: Proceedings of the First International Symposium on Ceramics. Chicago: Qulntessence Publishing Co, Inc. 1983301. 13. LaHoste LH. The porcelain butt margin. Quintessence Dent Technol 1981;2:149-51. 14. Zalkind M. A labial porcelain butt-joint ln ceramco-metal restorations. Quintessence Int 1984;11:1117-20. 15. Howard JB. A new procedure for all porcelain labial margins. Trends Techniques 1985;22-5. MAY
1991
VOLUME
65
NUMBER
5
EFFECT
OF METAL
DESIGN
AND
TECHNIQUE
24. Faull TW, Hesby RA, Pelleu GB, Eastwood GW. Marginal opening of single and twin platinum foil-bonded aluminous porcelain crowns. J
16. Behrend DA. Ceramometal restorations with supragingival margins. J PROSTHET DENT 1982;47:625-32. 17. Chiche G, Radiquet J, Pinault A, Genini P. Improved esthetics for the ceramometal crown. Int J Periodont Restor Dent 1986;1:77-87. 18. Philp GK, Brukl CE. Compressive strengths of conventional, twin foil, and all-ceramic crowns. J PROSTHEFT DENT 1984;52:215-20. 19. McCune RJ. The effect of occlusal venting and film thickness on cementation of full cast crowns [Thesis]. Indianapolis: Indiana University, School of Dentistry, 1968. 20. Gavelis JR, Morency JD, Riley ED, Sozio RB. The effect of various finished line preparations on the marginal seal and occlusal seat of full crown preparations. J PROSTHET DENT 1981;45:138-45. 21. Thomas GD, Baylis MA. Immediate, abrade-resistant, fine removable dies. Quintessence Dent Technol 1986;10:17-21. 22. Vita Zahnfabrik. The Vita VMK technique: working instructions. Bad Sackingen, Germany 198827-8. 23. Kessler JC, Brooks TD, Keenan MP. The direct lift-off technique for constructing porcelain margins. Quintessence Dent Technol 1986; l&145-50.
Predictability enhancement Herbert Medical
DENT
1985$3:29-33.
56527-30. Reprint
requests
to:
DR. DONALD M. BELLES USAF CLINIC KADENAISGDL APO SAN FRANCISCO 96239
of color matching and the possibilities of ceramic laminate veneers
Victor University
PROSTHET
25. Brukl CE, Philp GK. The fit of Cerestore, twin foil, and conventional ceramic crowns [Abstract]. J Dent Res 1985;362. 26. Wanserski DJ, Sobcsak KP, Monaco JG, McGivney GP. An analysis of margin adaptation of all-porcelain facial margin ceramometal crowns. J PROWHET DENT 1986;56:289-92. 27. Wiley MG, Huff TL, Trebilcock C, Girvan TB. Esthetic porcelain margins: a modified porcelain-wax technique. J PROSTHET DENT 1986;
Exner, B.Ch.D., M.Sc.Dent.Sc., of Southern
Africa,
Dental
Faculty,
for
D.H.A.*
Medunsa,
South
Africa
This study investigated the predictability of color (Hue, Value, and Chroma) on three illustrated surfaces of ceramic veneers and the extent to which laminates may be shade-adapted by use of tints and opaquers on the fitting surface. Significant discrepancies were found in the flnal color match. The dentist should opt for a lighter, more translucent shade, which can be modified before final cementation. (J PROSTHET DENT 1991;68:619-22.)
I
nlaid ceramic laminates or veneers are the most conservative method of esthetically altering the appearance of anterior teeth, but they should be used judiciously.1-3These restorations pose a unique challenge in shadeselection in that they differ from the metal ceramic and porcelainjacket crownsin thickness (asthin as0.5 mm) of material usedand becausethe underlying dentin may or may not affect the final color.4The interproximal surfaces of the tooth are left intact, and this eliminates the unnatural interproximal translucence encountered in porcelain jacket crowns.When a clear bonding resin is usedto bond the restoration, incident light and specularand diffuse reflection may affect the overall shadeand color.5-7 This study determinespredictability of the final product and the extent to which the operator may have control over color and shadesof the final ceramic veneers.
MATERIAL
AND
METHODS
Extracted human anterior teeth were mounted in plaster and prepared in a systematic sequenceto receive the *Associate Professor, sion Undergraduate
Department Teaching
of Prosthodontics; and Training.
10/l/24173 TRE
JOURNAL
OF PROSTHETIC
DENTISTRY
Head,
Divi-
finished product. In the caseof the castableglasses(Dicer, Dentsply, York, Pa.), the actual teeth were usedasdies to prepare the final wax models (Fig. 1). Conventional ceramic restorations were prepared on refractory dies. The final shade and color were achieved through the application of tints below the glaze layer. The rest of the restoration was translucent porcelain or cast glass.One Vita (Bad Siickingen, Germany) shadeguide was usedby the dentist and the technicians who prepared the finished product. The finished veneerswere compared with the relevant shade-guide tooth and then, through parallel windows, with the samplesplaced on a black velvet backing and with a collimated light sourcefalling at the sameanglefor each sample. Each sample was also observed on its relevant tooth and the shade-guidetooth to determine the effect of the color of the underlying dentin (Figs. 2 and 3). Three separatesurfaceson each samplewere observed. In the second part of the experiment, the veneers were tinted with translucent tints applied with a fine camel-hair brush (Fig. 3). Blue tint wasapplied to the incisal edgesand combinations of brown/orange and/or red were usednear the margins. In someinstances,white tint wasusedon the body section.Each tooth wasindividually characterized by 619
