Effects of At-Home Bleaching Gel and Two Beverages on the Microhardness of an Aesthetic Composite Resin

Introduction: The purpose of this study was to investigate the effects of 15% carbamide peroxide, orange juice, and Cola on the microhardness of composite resin restoration material. Materials and Methods: In this in vitro study, forty disk-shaped composite samples were prepared and randomly classified into four groups (n=10); the artificial saliva (control), bleaching agent (15% carbamide peroxide), orange juice, and Cola. Vickers microhardness was measured on the surface of the samples before and after immersion for 6 and 48 hours. Results: The microhardness values of the 15 % carbamide peroxide, Orange juice and Cola groups were significantly lower after 48 hours compared to the artificial saliva group (P=0.003, P=0.002, P=0.001, respectively). However, these differences were not statistically significant after 6 hours of immersion (P=0.068). When comparing the microhardness values of these groups over time, as expected, these measures significantly decreased, except for the 15 % carbamide peroxide group in which the mean microhardness value did not significantly decrease from baseline after 6 hours immersion (P=0.106). However, there was a significant difference after 48 hours compared to baseline and 6 hours immersion (P=0.001, P=0.004). Conclusion: This suggests that 15 % carbamide peroxide gel can be employed as a bleaching agent in cases with composite restorations for a limited amount of time without significant deterioration of the microhardness.