Marginal accuracy of temporary composite crowns

Marginal accuracy of temporary composite crowns Anthony H. L. Tjan, Dr.Dent., D.D.S.,* Albert H. Tjan, D.D.S.,** and Ben E. Grant, D.M.D.*** Loma Linda University, School of Dentistry, Dentistry, Los Angeles, Calif.

Loma Linda,

Calif.,

and University

of Southern

California,

School of

A

ccurate marginal fit and proper contour and surface finish of a temporary crown is needed to maintain healthy contiguous gingiva before placing the final restorations.‘-4 Such a well-adapted temporary crown also assures good protection of the freshly prepared dentin from physical, thermal, bacterial, and chemical irritants, with less postoperative sensitivity. In addition, it provides optimal esthetics because of a minimum of gingival recession. Many techniques for making temporary restorations are described in the literature.5-9 A direct clinical procedure that may involve either complete or partial curing of the resin on the preparation seems to be favored.” This study compared quantitatively the marginal adaptation of temporary crowns made from the recently introduced Bis-GMA composite (Protemp, ESPE-Premier Corp., Norristown, Pa.) with those made from epimine plastic (Scutan, ESPE-Premier Corp.), ethylmethacrylate (Provisional, Cadco Dental Products Inc., Los Angeles, Calif.), and vinylethylmethacrylate (Trim, Harry J. Bosworth Co., Skokie, Ill.).

MATERIAL Fabrication

AND METHODS

A direct technique was used in which temporary complete crowns were made on prepared typodont teeth by using an impression as a matrix. Five artificial mandibular molar teeth (Ivorine teeth, Colombia Dentoform Corp., New York, N.Y.) were prepared for complete crown restorations with 1 mm shoulder finish lines 7 mm high with a taper of approximately 5 degrees. The root portions were then lubricated with petrolatum and mounted in a dental stone block that was furnished with a plastic base used to secure each prepared tooth (master die) with a screw (Fig. 1). This was to allow their removal, which was necessary for measuring the marginal discrepancy of the *Professor and Director of Biomaterials Research, Department of Restorative Dentistry, Loma Linda University, School of Dentist‘Y. **Clinical Instructor, Department of Restorative Dentistry, University of Southern California, School of Dentistry. ***Associate Professor and Coordinator of Dental Materials, Department of Restorative Dentistry, Loma Linda University, School of Dentistry. THE JOURNAL

Fig. 1. Master dies mounted in a dental stone block.

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DENTISTRY

Fig. 2. Impression used as matrix for making temporary crowns. temporary crowns. V-grooves were cut on both ends of the stone block to orient the matrix impression when seating it. Wax patterns with flat occlusal surfaces were made on the preparations with type II blue inlay wax (Sybron/ Kerr, Romulus, Mich.). Impressions were then made with an addition silicone of heavy viscosity (Permagum, ESPE-Premier Corp.) by using perforated acrylic custom trays and adhesive. These impressions served as the matrix for making the temporary crowns (Fig. 2). 417

TJAN, TJAN, AND GRANT

TEMPORARY

CROWN

DISCREPANCY

MASTER

Fig.

3. Spring-loading

temporary

holding device crown during mounting.

Table I. Temporary

restorative

Material

used to secure

materials

DIE

Fig. 4. Marginal discrepancy is determined by measuring discrepancy (space between arrows) at six reference points.

tested

Brand

Batch No.

Bis-GMA composite

Protemp

L349MD121484

Epimine

Scutan

K209MD101783

Ethylmethacrylate

Provisional

5028

Vinylethylmethacrylate

Trim

101182942

Manufacturer/distributor

EWE-Premier Corp. Norristown, Pa. ESPE-Premier Corp. Norristown, Pa. Cadco Dental Products Inc. Los Angeles, Calif. Harry J. Bosworth Co. Skokie, Ill.

and the time of removal. The resin-filled impressions were adapted on the lubricated master dies and secured firmly with rubber bands. They were then placed in a water bath at 37” C. The temporary crowns were removed and reseated once during the elastic phase of polymerization. The excess material was used to indicate the proper time to remove the temporary crowns. Excess flash was trimmed from the crown margins with scissors. The crowns were reseated on the preparation and allowed to set completely in the waterbath at 37” C. After curing was completed the gingival margins of the temporary crowns were trimmed under a x20 binocular microscope (Anchor Optical Co., Haddon Height, N. J.).

load during measuring (Fig. 3). A centrally located hole at the base of the tooth engaged the pointer-rod incorporated in the device. The marginal discrepancy of the temporary crown was measured by using a measuring microscope with a micrometer eyepiece attachment calibrated to one thousandth (0.001) of a millimeter at original magnification Xl00 (Toolmakers’ Microscope, Mitutoyo, Japan). The marginal discrepancy was determined by measuring the space (marginal opening) between the margin of the crown and the finish line of the preparation (Fig. 4). For each crown and preparation assembly, measurements were made at six reference points previously marked at random around the circumference of the finish line of the preparation. The marginal discrepancy value was the arithmetic mean of these six measurements. A one-way analysis of variance (ANOVA) and Duncan’s new multiple range test were used to establish the statistical significance among the means of the groups.

Measuring of the marginal discrepancy

RESULTS

A spring-loaded holding device was used to secure the temporary crown on its preparation under a uniform

Table II shows the data, mean, and standard deviation of the marginal discrepancy of temporary crowns made

Four temporary restorative materials (self-curing resins) were studied (Table I). From each of these materials 10 temporary crowns were made according to the manufacturers’ manipulation,

418

directions proportioning,

with

respect

to

mixing,

OCTOBER

1987

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NUMBER

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MARGINAL

ACCURACY

OF TEMPORARY

COMPOSITE

PROTEMP

CROWNS

SCUTAN

TRIM

PROVISIONAL

Fig. 5. Graph indicating means and standard deviations of marginal discrepancies from the four temporary restorative materials studied. Protemp material produced a marginal accuracy comparable to those made from Provisional and Trim materials. Temporary crowns made from Scutan material had the largest marginal discrepancy at p < .Ol (Figs. 5 and 6).

Table II. Data, means, and standard deviation

of marginal discrepancies of temporary crowns in microns (10m3mm)

DISCUSSION Inasmuch as all procedures were standardized, the observed marginal discrepancy of crowns made from Scutan material may have been caused by polymerization shrinkage. However, Robinson and Hovijitra” reported much higher values for Trim and Scutan materials with a direct technique. This discrepancy may be attributed to a minor difference in the procedure whereby the resins were allowed to set rigidly on the master dies. Removing the temporary crown from the prepared tooth before complete curing is claimed to cause the most distortions.” The technique used in this study, a direct technique involving resin completely cured on the preparation, is similar to that suggested by Kaiser.* Indirect temporary techniques have been reported to produce temporary restorations with better marginal fit than those made by using a direct technique.‘2s’3 This is likely to be true only when the resin is partially cured on the tooth preparation, as was demonstrated in this study. Some dentists do not want their temporary restorations to fully set on the tooth preparations because (1) the polymerization of resins usually used produces heat that could injure the pulp,‘O (2) uncured resin may also THE JOURNAL

OF PROSTHETIC

DENTISTRY

Mean SD

Protemp

Scutan

Provisional

53.3 55.6 25.2 28.0 42.7 56.3 44.3 32.3 31.0 32.7 40.1 11.87

94.4 141.0 210.0 102.0 121.0 52.2 68.5 139.0 198.5 64.7 119.2 53.97

51.5 35.8 39.0 41.5 38.7 12.8 27.3 11.8 12.0 11.5 28.2 15.10

Trim 20.6 27.5 33.5 28.2 24.5 20.0 29.5 29.3 11.2 12.2 23.6 7.51

injure the pul~,‘~aI5 and (3) preparation undercuts may be a problem. It has been reported that temporary acrylic resin crowns may be fully cured directly on prepared teeth with external cooling without undue heating of the pulp.” External heat dissipation may be enhanced either by cooling with a water spray’) lo or by curing the crowns in silicone impressions that have a high heat capacity and sufficient thermal conductivity.” A thin insulating layer may also be applied to protect dentin from chemical or thermal injury from the resins. The use of a lubricant not only facilitates the removal of a set resin but also protects the pulp and gingiva.16 It is recommended to relubricate the teeth when reseating the temporary crowns for complete setting, especially when 419

TJAN,

TJAN,

AND

GRANT

Fig. 6. Temporary crowns seated on master dies. A, Protemp; B, Provisional; C, Trim; D, Scutan.

Protemp composite is used, because crowns made from it are generally difficult to remove. A release agent such as Rubber-Sep (George Taub Products, Jersey City, N. J.) may be useful to ease the removal of a temporary crown and at the same time create a cement space. SUMMARY

REFERENCES

2.

420

4. 5.

AND CONCLUSIONS

An in vitro study was conducted to quantitatively compare the marginal adaptation of temporary crowns made from Protemp material with those made from Scutan, Provisional, and Trim materials. A direct technique ‘was used to make temporary restorations on prepared teeth with an impression as a matrix. Protem, Trim, and Provisional materials produced temporary crowns of comparable accuracy. Crowns made from Scutan material had open margins.

1.

3.

Donaldson D. Gingival recession associated with temporary coverage. J Periodontol 1973;44:691-6. Donaldson D. The etiology of gingival recession associated with temporary crowns. J Periodontol 1974;45:468.

6.

7. 8. 9.

Segat L. Protection of prepared abutments between appointments in crown and bridge prosthodontics. J Mich Dent Assoc 1962;44:32-5. Waerhaug J. Temporary restorations: advantages and disadvantages. Dent Clin North Am 1980;24:305-16. Sotera AJ. A direct technique for fabricating acrylic resin temporary crowns using Omnivac. J PR~~THET DENT 1973; 29:577-80. Greenberg JR. The metal band-acrylic provisional restoration featuring ultra thin stainless steel bands. Compend Contin Educ Dent 1981;2:7-11. Barghi N, Simmons EW. The marginal integrity of the temporary acrylic resin crown. J PR~~THET DENT 1976;36:274-7. Kaiser DA. Accurate acrylic resin temporary restorations. J PROSTHET DENT 1978;39:158-61. Federick DR. The provisional fixed partial denture. J PROSTHET DENT 1975;34:520-6.

10. Grajower R, Shaharbani S, Kaufman E. Temperature rise in pulp chamber during fabrication of temporary self-curing resin crowns. J PROSTHET DENT 1979;41:535-40. 11. Robinson FB, Hovijitra SH. Marginal fit of direct temporary crowns. J PROSTHET DENT 1982;47:390-2. 12. Crispin BJ, Watson JF, Caputo AA. The marginal accuracy of treatment restorations: a comparative analysis. J PROSTHET DENT 1980;44:283-90.

13.

Monday JJL, Blais D. Marginal adaptation of provisional acrylic resin crowns. J PROSTHET DENT 1985;54:194-7. OCTOBER

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OF TEMPORARY

COMPOSITE

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14.

Langeland K, Langeland KL. Pulp reactions to crown preparations, impression, temporary crown fixation and permanent cementation. J PROSTHETDENT 1965;15:129-43. 15. Seltzer S, Bender IB. The dental pulp. 2nd ed. Philadelphia: JB Lippincott Co, 1975;219. 16. Suarez CL, Stanley HR, Gilmore HW. Histopathologic response of the human dental pulp to restorative resins. J Am Dent Assoc 1970;80:793-800.

Repint requests to: DR. ANTHONY H. L. TJAN LOMA LINDA UNIVERSITY SCHOLLOF DENTISTRY LOMA LINDA, CA 92350

A new chemical method for etching metal frameworks of the acid-etched prosthesis Asterios Doukoudakis, D.D.S., M.S.,* Bernard Cohen, D.D.S.,** and Andreas Tsoutsos, D.D.S.*** Case Western Reserve University, Dentistry, Athens, Greece

School of Dentistry,

Cleveland,

Ohio, and University

of Athens, School of

M

ethods of attaching metal retainers on enamel surfaces of teeth with a self-polymerizing composite have been introduced to several disciplines of clinical dentistry. Rochette’ was the first to describe a technique of bonding a metal framework on the lingual surfaces of anterior abutment teeth, and many authors have reported improvements in the technique and clinical application.2-6 Most improvements were made in framework design. The initial design included retainers with perforations that provided the mechanical retention of the framework.’ The introduction of internally etched retainers through an electrolytic process improved appearance and retention.“” However, there are problems that limit the technique as an alternative to the conventional methods of fixed prosthodontics. The technique is sensitive and success lies in the selection of patients and disciplined methodology. One of the main problems is that the framework requires etching by a commercial laboratory and the etching procedures vary according to the metal alloy used. Moreover, the etched surfaces can be easily contaminated, resulting in a weak mechanical bond between the composite and the metal framework. Because it is impossible to assessthe quality of etching on the framework without a microscope, dentists rely totally on the commercial laboratories. Traditionally,

*Associate Professor, Department of Fixed Prosthodontics, Case Western Reserve University, School of Dentistry. **Assistant Professor, Department of Fixed Prosthodontics, Case Western Reserve University, School of Dentistry. ***Associate Professor, Department of Prosthodontics, University of Athens, School of Dentistry. THE JOURNAL

OF PROSTHETIC

DENTISTRY

Fig. 1. Met-Etch gel applied to metal framework,

Fig. 2. Etched metal framework ready for bonding. internally etched retainers require three appointments for completion to accommodate a try-in appointment for the framework.’ Recently, a gel (Met-Etch Gresco Products Inc., Stafford, Tex.) was introduced that is capable of chemically etching metal retainers without an electrolytic procedure. The product is an aqua regia solution 421