EffectofTwo Bleaching Regimens onThe Surface Roughness andHardness ofTooth Colored Restorativies

Objectives: The purpose of this invitro study was to evaluate the effects of 10% carbamide peroxide (Vivastyle/ Vivadent) and 6.5% hydrogen peroxide strip bands (Crest Professional Whitestrips/ Procter & Gamble) on the surface roughness and hardness of the five different tooth colored restoratives; Ormocer (Definite/ Degussa), compomer (Dyract AP/ Dentsply De Tray), packable composite (Filtek P60/ 3M), flowable composite (Filtek Flow/ 3M) and hybrid composite (Filtek Z250/ 3M). Methods: A total of 48 samples (10 mm in diameter and 2mm thick) of each materials were fabricated against a myler surface. After polished with Sof-Lex discs they were randomly divided into three groups of 16 and treated as follows: Group I, stored in distilled water at 37¢ªC for two weeks (control); Group II, treated with Vivastyle for two hours per day for two weeks; Group III, treated with Whitestrips for 30 minutes twice daily for two weeks. For groups II and III, specimens were stored in distilled water at 37¢ªC during the hiatus period. At the end of the test period, the specimens were first subjected to surface roughness (Mitutoyo Surftest-4, JAPAN) then to micro hardness (Frank/ Prufent-Messen, GERMANY) tests. The data were analyzed by Kruskall-Wallis and Mann-Whitney U tests. Results: Both bleaching regimens increased the roughness of the materials (p<0.05), but Whitestrips significantly increased the roughness of materials than Vivastyle (p<0.05). Both bleaching regimens decreased significantly the hardness of tested materials except Filtek P60 (p<0.05). Conclusion: Bleaching agents may effect the surface of existing restorations, therefore not be used indiscriminately when tooth colored restorations are present.