Comparison of the marginal fit of various ceramic crown systems

SECTIONEDITORS

ison of the marginal Matty Willis

F. Abbate, D.D.S.,* M. Fox, D.D.S.*

Anthony

fit of various

H. L. Tjan,

Dr. Dent.,

ceramic

D.D.S.,**

crown

and

LomaLinda University, Schoolof Dentistry, LomaLinda, Calif. This ceramic facial

study

evaluated crowns

margin,

marginal

the

with (3)

Cerestore

adaptation

were

video-enhanced

microscope

high

television

yielded

resolution comparable

marginal

a metal

(2)

crowns, with

(4)

from digital

the

crown

ceramic

Dicor

and

fit.

that

cus of various investigations.l-l1 The fit and distortion of metal ceramiccrowns,including the effectsof repeatedfiring and various marginal designs, have been intensely scrutinized.3p*+9,lo, 12-15A well-fitting crown reduces the chancefor recurrent cariesand periodontal disease,whereas the spacebetweena poorly-fitting artificial crown and tooth preparation enables accumulation of bacterial plaque. Waerhaug16and Loe17reported that plaque accumulatedin this spaceis responsiblefor inflammation of the periodontal tissues. All-ceramic crowns have been developed recently in responseto specificand demandingesthetic expectations.Two .of the more popular are the Cerestorecrown with a shrinkfree aluminum ceramic core (Johnson & Johnson, East Windsor, N.J.) and the Dicer crown, made from castable glass ceramic (Dentsply International, York, Pa.). The appearanceof the newceramiccrownsis greatly enhancedby elimination of metal substructure and they are stronger and better fitting than feldspathic porcelain jacket crowns. Becauseof the predictable dimensionalstability of aluminumoxide core materials, the marginal adaptation of the Cerestore crown was reported as similiar to metal ceramic crowns.2Lugassyet al.l8 also noted that Dicer crowns have excellent marginal fit. This study comparedthe marginal fit of (1) metal ceramic crowns with a metal-butt facial margin, (2) metal ceramic crowns with a porcelain-butt facial margin, (3) Cerestore crowns, and (4) Dicer crowns. Presentedat the annualmeetingof the A.mericanAcademyof RestorativeDentistry, Chicago,Ill. Supportedby Johnson& Johnsonand LomaLinda University. *AssistantProfessor, Departmentof RestorativeDentistry. **Professor Restorative THE JOURNAL

and Director Dentistry. OF

PROSTHETIC

Biomaterials

DENTISTRY

Research,

Department

image all

four

(J PROSTHET

T he marginal fit of artificial crownshasbeenthe fo-

of

(1)

with

metal

a porcelain

Measurements lingual

and

indicate

marginal

systems,

crowns

crowns.

facial

micrometer

Results

acceptable

ceramic

metal

and

recorded screen.

and

fit of four

margin,

of the

margins

by

using

intensification crown DENT

MATERIAL

a

in a

systems 1989;61:527-31.)

AND

METHODS

Tooth preparations. Two tooth-preparations were designed;one for the metal ceramiccrownsand another for the all-ceramic Cerestoreand Dicer crowns.The tooth preparation for the metal ceramiccrownswasdesignedwith a 1.3mm slanted margin with approximately 120-degreeslope and a lingual chamfer. The margins for the all-ceramic crowns were a 120-degreeshoulderwith rounded axio-gingival-line angleapproximately 1.3 mm in width. The preparations had an axial taper of 5 degreesand were 5 mm high. Master preparations were madefrom compositeresin tooth analogs (Ivorine teeth, Viade Corp., Camarillo, Calif.) and replicated by the manufacturer (Fig. 1). Forty tooth-preparation analogs,20 for eachpreparation, were divided into experimental groups,of 10 as follows. Group 1: Metal ceramic crowns with a metal-butt facial margin Group 2: Metal ceramic crowns with a porcelain-butt facial margin Group 3: Cerestorecrowns Group 4: Dicer crowns Diepreparation. Groups of four tooth-preparation analogs,two for metal ceramic crowns and two for all-ceramic crowns,weremounted on a jig. Customimpressiontrays with a 2 mm relief were madefrom autopolymerizing acrylic resin (Blue Tray, Bosworth Co., Skokie, Ill.). Impressionswere made with an addition-type silicone material (Permagum, ESPE Premier SalesCorp., Norristown, Pa.) and poured 1 hour after setting. Groups 1,2, and 4 werepoured in die stone (Superstone, Sybron/Kerr, Romulus, Mich.). For group 3, the Cerestorecrowns,the impressionswere poured in epoxy die material (Johnson& Johnson).A Dicer die spacer(batch No. 052085,Dentsply International) was used to coat the stone dies of groups 1, 2, and 4. For group 3 the die spacer provided by the manufacturer (Johnson& Johnson)wasapplied according to instructions. 527

ABBATE,

TJAN,

AND

FOX

Fig. 1. A, Tooth preparation for metal ceramic crown (left) and preparation for all-ceramic crown (right). B, Proximal views of four ceramic crowns seated on their preparations: (A) metal ceramic crown with metal-butt facial margin; (B) metal ceramic crown with porcelain-butt margin; (C) Cerestore crown; (0) Dicer crown.

Crown fabrication. The metal ceramic crowns for groups 1 and 2 were made with type III ceramic gold (Williams Gold, Buffalo, N.Y.) and Vita porcelain (Vita Zahnfabrik, Sackingen, Germany). The facial porcelain-butt margin in group 2 was made by using a lift-off technique described by Vyronis.ig The Cerestore and Dicer crowns were made in accordance with manufacturer’s specifications. Cementation of crowns. The 40 crowns were cemented on their respective composite resin analog preparations with a zinc-phosphate cement (batch No. AN121085, Ames, Teledyne-Getz, Elk Grove, Ill.). A controlled technique was used to standardize the cement mixtures at a ratio of 1.3 gm powder to 0.5 ml liquid. A precision scale was used to proportion the cement powder, and a 1 ml tuberculin-test syringe for dispensing the liquid. Each mixture was spatulated for 40 seconds. The internal surface of the crown was 528

coated evenly with the cement mix, seated on the composite resin tooth analog with finger pressure, and sustained under a static load of 5 kgf for 10 minutes. i%feasurement of the mbrginal opening. The cemented crowns were embedded individually in phenolic rings with epoxy resin (Buehler Ltd., Lake Bluff, Ill.) and sectionedbuccolingually into three slices.Both of the cuts were made approximately 1 mm from the midplane, producing a center slice 2 mm thick (Fig. 2) that was not used further in the study. The cut surfacesof the outer two sections were sequentially finished by using silicone-carbide abrasive papers 320 to 600 grit size on a Handimet grinder (Buehler Ltd.). The cement thicknessesat the marginal openings were measuredby using a video-enhancedmeasuringmicroscope with digital micrometer and imageintensification on a highMAY

1989

VOLUME

61

NUMBER

5

COMPARISON

OF MARGINAL

FIT

Fig. 2. Cemented crowns sectioned buccolingually

near midplane.

FACIAL

LINGUAL .- ‘-CEMENTED /

CROWN

\

CEMENT

.

+

TOOTH

Fig. 3. Measurement sites 100, 200, and 300 pm from finished margin.

resolution television screen(Mitutoyo, Tokyo, Japan). The measurementswere recorded from the facial and lingual margins of the two finished surfacesof each sectionedspecimen at three predetermined reference points 100,200, and 300pm from the actual finish margin (Fig. 3). Thesepoints were selected to avoid magnifying the marginal discrepancies resulting from an occasionaldefect at the margin. Discrepancy values were computed as averages of the measurementsobtained. The discrepancy value of the facial margin for eachtooth wasthe averageof six measurements from two facial locations of the sectioned specimen.The discrepancy value of the lingual margin for each tooth was the averageof six measurementsfrom two lingual locations. The overall discrepancy value of a crown was the mean of TEfE

JOURNAL

OF PROSTHETIC

DENTISTRY

both facial and lingual marginal discrepancies.The marginal discrepancy values of the 10 teeth in each group were averaged for a marginal discrepancy value of the entire group. The data were analyzed with a one-way analysis of variance.

RESULTS The four crown systemsyielded comparablemarginal fit. They demonstrated marginal openingsin the range of 56 to 81 pm. Cerestorecrownshad the lowest marginal discrepanciesand Dicer crownshad the greatest. However, statistical analysis indicated no significant difference in marginal fit among the four crown systems. The raw data, arithmetic means,and standard deviations of the marginal discrepancy 529

ABBATE,

FACIAL

TJAN,

AND

FOX

q

LINGUAL OVERALL0

PFM-P

PFM

Fig.

4.

CERESTORE

DICOR

Fa ciaII, lingual, and overall marginal discrepancies.

I. Raw data, mean, and standard deviation of marginal discrepancy in Mm (10e3 mm)

Table

Table

II.

Analysis of variance sum

Mean SD

1

2

3

4

44 52 41 33 59 127 69 47 69 65 60.6 26.4

35 95 103 52 67 33 43 43 52 41 57.0 24.2

39 76 40 45 45 35 42 34 47 38 44.1 12.0

47 80 60 66 14 89 57 30 71 79 65.3 17.5

Group 1, Metal ceramic crowns with metal-butt margins; group 2, metal ceramic crowns with porcelain-butt margins; group 3, &restore crowns; group 4, Dicer crowns.

values are listed in Table I. The facial, lingual, and overall marginal discrepancies are illustrated graphically in Fig. 4. One-way analysis of variance of the data is presented in Table II.

DISCUSSION The discrepancy values, derived from averages of multiple measurements made at locations slightly removed from the actual margin, are considered representations of the various groups. Cerestore crowns produced the lowest marginal opening and Dicer crowns the greatest, but the differences were not statistically significant. McLean and Von Fraunhofer,20 in their clinical study of 530

squares

DF

Variance estimate

18043.5 2480.1 15563.4

39 3 36

826.1 432.32

of

Group

Total Between groups Within groups

Critical region is F 2 2.86 for 5% significance Difference between groups is not significant.

F

1.91

P

>0.05

level.

1000 restorations over a 5-year period, concluded that 120 Mm represented the maximum clinically acceptable marginal opening. Our data indicated that all four ceramic crown systems were acceptable. Cracks were observed in the all-ceramic crowns in this study. A crescent-shaped fracture was noted on three of the Dicer crowns during cementation with a static load of 5 kgf. This followed a specific pattern and occurred at the lingual surface with thinner ceramic. It was continuous, involving both medial and distal transitional line angles joined by a horizontal occluso-axial crack. In a few Cerestore crowns, incomplete longitudinal cracks were observed at the margins. In clinical conditions, a complete breakage of cracked allceramic crowns can occur after a short period because of the stress imposed during mastication. The cracks may occur in obscure proximal or lingual surfaces and remain undetected. Because of the potential for cracks noted under laboratory conditons, gentle application of a low load is mandatory clinically in cementing all-ceramic crowns. Incorporation of an internal escape channel as described by Tjan et a1.21-24or increasing the convergence angle of the preparation would facilitate the flow of cement. This would MAY

1989

VOLUME

61

NUMBER

5

COMPARISONOFMARGINALFIT

10. Eden GT, Franklin OM, Powel JM, Ohta Y, Dickson G. Fit of porcelainfused-to-metal crown and bridge castings. J Dent Res 1979;58:2360-79. 11. Hunt JL, Cruikshanks-Boyd DW, Davies EH. The marginal characteristics of collarless bonded porcelain crowns produced using a separating medium technique. Quintessence Dent Technol1978;9:21. 12. DeHoff PH. Anusavice HJ, Boyce RJ. Analysis of thermally induced stresses in porcelain metal systems. J Dent Res 1983;62:593-7. 13. Bridger DV, Nicholls JI. Distortion of ceramometal fixed partial dentures during the firing cycle. J PROSTHET DENT 1961;45:507-14. 14. Buchanan WT, Svare CW, Turner KA. The effect of repeated firings and strength on marginal distortion in two ceramometal systems. J PROWHET

diminish the seating pressure and reduce the possibility of fracture. Rounding of all line angles is suggested to prevent the concentration of stress noted by Walton and Leven25 in photoelastic studies.

SUMMARY

AND

CONCLUSIONS

This study evaluated the marginal fit of four ceramic crown systems, (1) metal ceramic crown with a metal-butt facial margin, (2) metal ceramic crown with a porcelain facial margin, (3) Cerestore crown, and (4) Dicer crown. The results indicated that all four crown systems yielded comparable and acceptable marginal fit. The all-ceramic crowns exhibited various cracks under laboratory conditions. Suggestions were made for avoiding clinical fractures.

DENT 1981;45:502-6. 15. Shillingburg HT, Hobo

distortion 1973;29:276-64.

1. Faull TW, Hesby RA, Pelleu GB Jr, Eastwood GW. Marginal opening of single and twin platinum foil-bonded aluminous porcelain crowns. J PROSTHET DENT 1985;53:29-33. 2. Ghan C, Haraszthy G, Jurgen G, Heiner W. The marginal fit of Cerestore full ceramic crowns: a preliminary report. Quintessence Int 1985;16:399402. 3. Belser US, MacEntee MI, Richter WA. Fit of three porcelain-fusedto-metal marginal designs in viva: a scanning electron microscope study. J PRIXJTHET DENT X%$53:24-9. Van Rensburg F, Strating H. Evaluation of the marginal integrity of ceramometal restorations: part II. J PRWTHET DENT 1984;52:210-4. Crispin BJ, Watson JF, Frawley JF. Silver plated dies. part III: marginal accuracy of cast restorations. J PROS= DENT 1984;51:768-73. Kawamura RM, Swartx ML, Phiiips RW, Dykema RW, Davis WH. Marginal seal of cast full crowns: an in vitro study. Gen Dent 1983;31:292-4. Antonson DE, Fischlschweiger W. Scanning electron microscopy in clinical dental research: observation of die-spaced and non-die-spaced cast gold margins before and after cementation. Fla Dent J 1983;54:15-8. a. Pascoe DF. An evaluation of the marginal adaptation of extracoronal restorations during cementation. J PROSTH~T DENT 1983;49:657-62. 9. Faucher RR, Nicholls JI. Distortion related to margin design in porcelainfused-to-metal restorations. J PROS= DENT 1980,43:149-55.

S. I. Vitsentzos, University

to directly

design and margin J PROSTHET DENT

16. Waerhaug J. Histologic considerations which govern where the margins of restorations should be located in relation to the gingiva. Dent Clin North Am 1960,March:161-76. 17. Lo+ H. Reaction of marginal periodontal tissues to restorative procedures. Int Dent J 196&l&759-78. 18. Lugassy AA, Moffa JP, Ellison JA. Cast glass ceramic crowns: a one-year clinical study. Calif Dent Assoc J 1986;14:72-7. 19. Vyronis P. A simplified approach to the complete porcelain margin. J PROSTHET DENT 1979;42:592-3. 20. McLean JW, Von Fraunhofer JA. The estimation of cement film thickness by an in viva technique. Brit Dent J 1971;131:107-11. 21. Tjan AHL, Miller GD, Sarkissian R. Internal escape channel to improve the seating of full crowns with various marginal configurations: a followup study. J PROSTHET DENT 1985;53:759-63. 22. Tjan AHL, Sarkissian R. The effectiveness of an internal escape channel’s role in crown cementation with various dental cements. Gen Dent 1985;33:209-11. 23. Tjan AHL, Sarkissian R. Comparison of internal escape channels with die spacing and occlusal venting. J PR~~THET DENT 1985;53:613-7. 24. Tjan AHL, Sarkissian R. Internal escape channel: an alternative to venting complete crowns. J PR~~THET DENT 1984,52:50-6. 25. Walton CB, Leven MM. A preliminary report of photoelastic tests of strain patterns within jacket crowns. J Am Dent Assoc 1955;50:44-8.

REFERENCES

A new device teeth

S, Fisher DW. Preparation in porcelain-fused-to-metal restorations.

Reprint requests to: DR. MATTY P. &BATE LOMA LINDA UNIVEFWT~ SCHOOL OF DENTISTRY LOMA LINDA, CA 92350

examine

parallelism

of abutment

D.D.S., Dr. Dent.*

of Thesaaloniki,

School

of Dentistry,

Thessaloniki,

Greece

The path of insertion is essential for the successful seating of ftxed partial dentures. A new device is described that directly examines the parallelism of the axial walls of the abutment teeth. It can also be used to create guiding planes for abutment teeth of removable partial dentures and determine the path of insertion of a Maryland Bridge fixed partial denture. The various parts of this device, its principle of operation, the results of its use, and advantages in relation to similar devices are presented. (J PROSTRET DENT 1989$1:691-4.)

T

he parallelism of the axial walls of abutment teeth is fundamental for the accurate placement of a fixed partial denture (FPD). The path of insertion of an FPD is expressed

‘Assistant

Professor,

Department

THEJOURNALOFPROSTHETICDENTISTRY

of Fixed

Prosthesis.

by the anglebetweenthe horizontal plane through the teeth and the plane tangent to the axial wall of the abutment teeth. When the abutment teeth do not have a particular inclination, the path of insertion of the FPD is approximately 90 degrees. When an abutment tooth is inclined mesially, removal of an inordinate amount of tooth substance can 531