Statement of problem: The color stability of tooth-colored restorative materials for provisional restorations is of primary importance when provisional prostheses are worn long term. However, the effect of different polishing methods on the color difference of provisional restorative (PR) materials has not been completely clarified.
Purpose: The purpose of this study was to investigate the effect of different polishing methods on color stability of 2- and 3-component autopolymerized bis-acrylic composites, a light polymerized composite, and a methyl methacrylate-based PR material upon exposure to a staining agent. Material and methods Sixty cylindrical specimens (15 x 2 mm) were prepared for each of bis-acryl composites (Protemp II and Luxatemp), a light-polymerized composite (Revotek LC), and a methyl methacrylate-based (TemDent) PR material by using a brass mold. The specimens were divided into 6 groups (n=10), and different polishing procedures were used, including pumice (P), diamond polishing paste (Dpp), polishing discs (Pd), and combinations of these. Unpolished specimens served as the control. The specimens were stored for 48 hours at 37 degrees C in a coffee solution. The color of all specimens was measured with a colorimeter (Minolta CR-300) before and after exposure, and color changes (DeltaE) were calculated. The data were analyzed with a 2-way analysis of variance, and mean values were compared by the Tukey Honestly Significant Difference test (alpha=.05).
Results: The provisional materials, surface polishing procedures, and interaction were significant (P <.05). In the light-polymerized composite group, the lowest color difference (DeltaE) was observed in Group P-Dpp (4.9) and Group P (5.3), which were not significantly different from each other. In the autopolymerized bis-acryl composites and the methyl methacrylate-based provisional materials, the lowest color difference (DeltaE) was observed in Group P-Dpp. The largest color difference for the light-polymerized and autopolymerized composites was observed in Group Pd-Dpp and Group Pd, which were not significantly different from each other. In the methyl methacrylate-based material group, the largest color difference was observed in Group Pd. When comparing the 4 different PR materials, the methyl methacrylate-based material group demonstrated statistically significantly less color change than the other provisional material tested.
Conclusion: The methyl methacrylate-based PR material (TemDent) was found to be more color stable than the autopolymerized (Protemp II and Luxatemp) and light-polymerized (Revotek LC) composites tested. The use of diamond polishing paste after polishing with pumice significantly decreased the staining of methyl metacrylate and bis-acryl composites tested. The highest color-change values were obtained in the groups polished with polishing discs, which were found to be significantly different compared to values obtained with other polishing techniques.