Comparative in vitro evaluation of two provisional restorative materials

Comparative in vitro evaluation of two provisional restorative materials Henry M. Young, DDS,a Charles T. Smith, DDS, MS,b and Dean Morton, BDS, MSc College of Dentistry, University of Florida, Gainesville, Fla., and College of Dentistry, University of Tennessee, Memphis, Tenn. Statement of problem. Provisional crowns traditionally have been associated with problems such as poor occlusion, contour, fit, and finish. Fabrication procedures should be uncomplicated and predictable within a realistic time frame. Purpose. The purpose of this study was to compare the quality of provisional restorations fabricated by dental students from 2 different materials (bis-acryl composite resin and PMMA) and identify the advantages and disadvantages associated with each material. Material and methods. This study evaluated the occlusion, contour, marginal adaptation, and finish of 222 provisional crowns fabricated by 2 groups (A and B) of dental students. One bis-acryl composite resin material (Integrity) and 2 PMMA resins (C&B Resin and Snap) were evaluated. Results. For group A, Integrity was statistically superior (P<.05) to C&B Resin in all 4 categories for anterior provisional crowns. For posterior provisional crowns, Integrity proved superior in the categories of contour and marginal adaptation, but no significant differences were established for occlusion and finish. For group B, Integrity was statistically superior to Snap in the categories of occlusion, contour, and marginal adaptation, whereas there was no statistical difference in finish. When all 4 categories were analyzed, Integrity was found to be statistically superior. Conclusion. Bis-acryl composite resin (Integrity) was significantly superior to PMMA (C&B Resin and Snap) as a provisional restorative material. (J Prosthet Dent 2001;85:129-32.)

CLINICAL IMPLICATIONS Within the scope of this study, bis-acryl composite resin proved to be a predictable material for the efficient fabrication of provisional restorations.

A

utopolymerizing PMMA resins have been used to fabricate provisional restorations with direct and indirect methods. In recent years, light-initiated PMMA and composite resins have gained popularity.1,2 Although improvements have been made in the physical properties of provisional materials, none has proved ideal.3,4 Autopolymerizing PMMA resins have several deficiencies. Previous studies have reported polymerization shrinkage and marginal discrepancies with these materials.4-8 The danger of pulpal damage because of exothermic reaction of polymerization has been equally well documented,9-15 as has sensitivity of the periodontium to the contour and fit of provisional restorations.16-18 However, these probaAssociate

Professor, Department of Operative Dentistry, College of Dentistry, University of Florida. bAssociate Professor, Division of Fixed Prosthodontics, College of Dentistry, University of Tennessee. cAssistant Professor, Center for Implant Dentistry, Department of Prosthodontics, College of Dentistry, University of Florida. FEBRUARY 2001

lems are associated primarily with direct methods of fabrication. It is beneficial to fabricate provisional restorations indirectly on casts made from impressions of prepared teeth. The indirect technique has been associated with superior fit and pulpal protection,6,7 but time constraints and inadequate laboratory support have led to the continued use of the direct technique.3,4 From a biomaterial and clinical perspective, the fabrication of direct provisional restorations with adequate quality to ensure a healthy, functional, and esthetic dentition is a challenging task, even for the most experienced dentist. Dental students and professionals alike need a restorative material that is cost-effective and applicable to the general practice of prosthodontics. This study compared the performance of bis-acryl composite resin and PMMA resin when used by dental students to fabricate custom provisional crown restorations.

MATERIAL AND METHODS This study evaluated 222 provisional crown restorations fabricated by 17 senior dental students (group A) THE JOURNAL OF PROSTHETIC DENTISTRY 129

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Table I. Group A: Anterior results Occlusion

Mean SD T stat P value Significant

Contour

Margin

Finish

C&B Resin

Integrity

C&B Resin

Integrity

C&B Resin

Integrity

C&B Resin

Integrity

3.94 1.60

4.94 0.24

2.82 1.47

4.53 0.72

2.29 1.69

4.47 0.44

3.35 1.46

4.76 0.43

–2.54 .0216 YES

–4.47 .0004 YES

–4.96 .0001 YES

–3.29 .0046 YES

Contour

Margin

Finish

Total

–4.49 .0004 YES

n=17

Table II. Group A: Posterior results Occlusion

Mean SD T stat P value Significant

C&B Resin

Integrity

C&B Resin

Integrity

C&B Resin

Integrity

C&B Resin

4.24 1.30

4.88 0.49

3.88 1.27

4.53 0.62

1.82 1.51

3.06 1.20

4.00 1.12

–1.95 .0686 NO

–2.18 .0442 YES

–4.24 .0006 YES

Integrity

Total

4.47 0.51 –1.46 .1635 NO

–3.35 .0041 YES

n=17

and 77 sophomore dental students (group B). Integrity (L. D. Caulk, Dentsply Int, Milford, Del.) was the bis-acryl composite resin material chosen for evaluation. C&B Resin (L. D. Caulk, Dentsply Int) and Snap (Parkell, Farmingdale, N.Y.) were the PMMA resins chosen for evaluation; C&B Resin was evaluated by group A and Snap by group B. Two faculty members evaluated all provisional crown restorations. Grading criteria were based on 4 categories: occlusion, contour, marginal adaptation, and finish. Each category was scored on a 1-to-5 scale (with 5 representing the highest quality) for a potential maximum score of 20 points per restoration. Statistical analysis of data was performed with Student t test with statistically significant (P<.05) results. The 17 senior dental students in group A had used autopolymerizing PMMA resin for 2 years during their preclinical and clinical education. However, they had no prior experience with Integrity. Therefore, before fabrication of test provisional crowns, group A received the following: (1) a 45minute lecture on the properties and use of Integrity, (2) a 15-minute demonstration of the fabrication of an individual provisional crown with Integrity on a standardized ivorine tooth preparation with vinyl polysiloxane putty matrix, and (3) a 15-minute period to practice fabricating an individual provisional crown with the prescribed technique. Group A students then were required to fabricate 2 provisional crowns, one with Integrity and the other with C&B Resin, on a standardized anterior ivorine tooth preparation. Each restoration was fabricated with a vinyl

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polysiloxane putty matrix within 15 minutes. This process was repeated by using a standardized posterior ivorine tooth preparation. The 77 sophomore students in group B were given instructions on the fabrication of provisional crowns with both Snap and Integrity. These instructions included a 45-minute lecture on the biomaterial properties and manipulation of each material and 4 hours of laboratory instruction on the fabrication of anterior and posterior crowns with each material. Each student in group B was provided with a standardized anterior ivorine tooth preparation and instructed to fabricate 2 provisional crowns, one with Snap and the other with Integrity. Each restoration was fabricated with the assistance of a vinyl polysiloxane putty matrix. Group B students were allowed 30 minutes to fabricate each provisional restoration.

RESULTS Data in each of the 4 grading categories were gathered and statistically analyzed, and an overall score was determined for each type of restoration in each group. For anterior provisional restorations fabricated by group A, Integrity was statistically superior (P<.05) to C&B Resin in all individual categories and in the overall evaluation (Table I). For posterior provisional crowns fabricated by group A, Integrity was statistically superior in contour and marginal adaptation as well as in the overall evaluation; no significant differences were reported in the individual categories of occlusion and finish (Table II). When the data were combined for anterior and posterior provisional restorations,

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Table III. Group A: Anterior and posterior results combined Occlusion

Contour

Margin

Finish

C&B Resin

Integrity

C&B Resin

Integrity

C&B Resin

Integrity

C&B Resin

Integrity

4.09 1.11

4.91 0.26

3.35 1.09

4.53 0.48

2.06 1.34

3.76 0.73

3.68 0.97

4.62 0.28

Mean SD T stat P value Significant

–2.90 .0105 YES

–4.05 .0009 YES

–5.36 .0001 YES

–3.77 .0017 YES

Contour

Margin

Finish

Total

–5.15 .0001 YES

n=17

Table IV. Group B: Results Occlusion

Mean SD T stat P value Significant

Snap

Integrity

Snap

Integrity

Snap

Integrity

Snap

Integrity

4.55 0.55

4.95 0.22

4.03 0.87

4.56 0.68

3.94 1.20

4.52 0.87

4.52 0.85

4.60 0.77

–6.22 .0001 YES

–4.27 .0001 YES

–3.88 .0002 YES

–0.68 .5005 NO

Total

–5.16 .0001 YES

n=17

Integrity was statistically superior in all 4 categories (Table III). Identical statistical tests were applied to data obtained from group B. Integrity was statistically superior to Snap in the categories of occlusion, contour, and marginal adaptation; there was no statistical difference in the finish category. When the total of the 4 categories was analyzed, Integrity was statistically superior (Table IV).

DISCUSSION Dental students were expected to construct provisional crowns with acceptable occlusion, contour, marginal adaptation, and finish. The materials selected for this study have substantial advantages and disadvantages. PMMA resin possesses satisfactory overall physical properties, including marginal finish and the potential to impart and maintain polish. However, polymerization shrinkage, exothermic setting reaction, and the irritation associated with monomer are among the material’s disadvantages,9 and relatively lower levels of finish and fine marginal adaptation have been reported.3-6 Moreover, the working and resultant biophysical properties of set autopolymerizing PMMA can be influenced by the monomer-powder ratio, which can vary from mix to mix and from dentist to dentist. Composite resin has gained popularity because of its ease of manipulation, reported low polymerization shrinkage, and lack of exothermic reaction. However, the material appears to suffer from inherent brittleness, which makes finishing and polishing difficult. Although

FEBRUARY 2001

the manufacturer claims that Integrity generates less heat than autopolymerizing methyl methacrylates during setting reactions, it was not within the scope of this study to evaluate this feature. One attractive aspect of Integrity is its convenient, cartridge-based dispensing system, which should result in a more accurately proportioned and consistent mix. This innovative approach may have contributed to the superior results credited to Integrity. It should be noted that the dento-form arches used in this study were not equilibrated. This reduced the necessity for occlusal equilibration and subsequent polishing. Because Integrity has a naturally shiny, smooth surface, it may be more appropriate to analyze the categories of marginal adaptation and contour (rather than finish). When the totals for these 2 categories were compared, Integrity was statistically superior to C&B Resin and Snap. Although group A had used C&B Resin for 2 years (both in preclinic laboratory and clinic), they were able to fabricate statistically superior restorations with Integrity, which they had been familiar with for less than 2 hours. Group B had only preclinical experience with provisional restorations and received equal training in the manipulation of both materials. This group also fabricated statistically superior restorations with Integrity. These results were attributed to the method of delivery and properties of Integrity. The time provided was not sufficient to allow a reline of the PMMA crowns to adversely affect fit.

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Time constraints may have influenced these results. Conventional acrylic resins should be hand mixed and allowed to reach the desired consistency before placement on a tooth preparation. Removal of the provisional restoration at the appropriate time to limit distortion and allow it to cure completely before adjustment was crucial for success in all categories. Integrity was placed immediately after dispension in the matrix and removed 1 to 2 minutes later; it was completely set in 5 minutes.

CONCLUSIONS The bis-acryl composite resin material Integrity was statistically superior to the autopolymerizing PMMA resins evaluated in this study. The results were consistent at both levels of dental student experience and for anterior and posterior restorations. REFERENCES 1. Bell TA Jr. Light-cured composite veneers for provisional crowns and fixed partial dentures. J Prosthet Dent 1989;61:266-7. 2. Wood M, Halpern FG, Lamb MF. Visible light-cured composite resins: an alternative for anterior provisional restorations. J Prosthet Dent 1984;51:192-4. 3. Wang RL, Moore BK, Goodacre CJ, Swartz ML, Andres CJ. A comparison of resins for fabricating provisional fixed restorations. Int J Prosthodont 1989;2:173-84. 4. Robinson FB, Hovijitra S. Marginal integrity of direct temporary crowns. J Prosthet Dent 1982;47:390-2. 5. Barghi N, Simmons EW Jr. The marginal fit of the temporary acrylic resin crown. J Prosthet Dent 1976;36:274-7. 6. Crispin BJ, Watson JF, Caputo AA. The marginal accuracy of treatment restorations: a comparative analysis. J Prosthet Dent 1980;44:283-90. 7. Monday JJ, Blais D. Marginal adaptation of provisional acrylic resin crowns. J Prosthet Dent 1985;54:194-7.

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8. Tjan AH, Tjan AH, Grant BE. Marginal accuracy of temporary composite crowns. J Prosthet Dent 1987;58:417-21. 9. 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. 10. Wolcott RB, Paffenbarger GC, Schoonover IC. Direct resinous filling materials: temperature rise during polymerization. J Am Dent Assoc 1951;42:253. 11. Kramer IRH, McLean JW. The response of the pulp to self-polymerizing acrylic restorations. Part I. Br Dent J 1952;92:255-61. 12. Kramer IRH, McLean JW. The response of the pulp to self-polymerizing acrylic restorations. Part II. Br Dent J 1952;92:281-7. 13. Kramer IRH, McLean JW. The response of the pulp to self-polymerizing acrylic restorations. Part III. Br Dent J 1952;92:311-5. 14. Langeland K, Langeland LK. Pulp reactions to crown preparations, impressions, temporary crown fixation and permanent cementation. J Prosthet Dent 1965;15:129-43. 15. Suarez CL, Stanley HR, Gilmore HW. Histopathologic response of the human dental pulp to restorative resins. J Am Dent Assoc 1970;80:793. 16. Donaldson D. Gingival recession associated with temporary crowns. J Prosthet Dent 1973;44:691. 17. Palomo F, Peden J. Periodontal considerations of restorative procedures. J Prosthet Dent 1976;36:387. 18. Richter WA, Ueno H. Relationship of crown margin placement to gingival inflammation. J Prosthet Dent 1973;30:156. Reprint requests to: DR HENRY M. YOUNG COLLEGE OF DENTISTRY UNIVERSITY OF FLORIDA PO BOX 100415 GAINESVILLE, FL 32610 FAX: (352)846-1643 E-MAIL: [email protected] Copyright © 2001 by The Editorial Council of The Journal of Prosthetic Dentistry. 0022-3913/2001/$35.00 + 0. 10/1/112797 doi:10.1067/mpr.2001.112797

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