Effects of 10% Carbamide Peroxide on Fracture Toughness and Microhardness of Human dentin In Situ

There have been some reported negative effects on dental hard tissues associated with tooth bleaching. This in situ study evaluated the effect of 10% carbamide peroxide dental bleach on the dentin fracture toughness and microhardness. Compact tension fracture toughness dentin specimens, were prepared from extracted molars, irradiated and fitted into custom-made bleaching trays. The bleaching trays were loaded with either bleach (10% Carbamide Peroxide gel, Opalescence, Ultradent, n=34) or placebo gel (control group, n=31) and worn overnight for approximately 14 nights. Dentin specimens were tested 24-48 hrs after the end of treatment. The mean values for dentin fracture toughness were: 2.22 +/- 0.71 & 2.26 +/- 0.86 (MPa m ½) and for microhardness were: 66.80 +/- 40.14 & 53.35+/- 42.52 (KHN) for bleaching and control respectively. Independent t-test showed no significant difference in dentin fracture toughness and microhardness after 14 days of in situ bleaching using 10% carbamide peroxide.