The effect of 10% carbamide peroxide bleaching material on microhardness of sound and demineralized enamel and dentin in situ

This in situ study evaluated the microhardness of sound and demineralized e namel and dentin submitted to treatment with 10% carbamide peroxide for thr ee weeks. A 10% carbamide peroxide bleaching agent-Opalescence/Ultradent (O PA)was evaluated against a placebo agent (PIA). Two hundred and forty denta l fragments-60 sound enamel fragments (SE), 60 demineralized enamel fragmen ts (DE), 60 sound dentin fragments (SD) and 60 demineralized dentin fragmen ts (DD)-were randomly fixed on the vestibular surface of the first superior molars and second superior premolars of 30 volunteers. The volunteers were divided into two groups that received bleaching or the placebo agent at di fferent sequences and periods at a double blind 2 x 2 crossover study with a wash-out period of two weeks. Microhardness tests were performed on the e namel and dentin surface. The SE and DE submitted to treatment with OPA sho wed lower microhardness values than the SE and DE submitted to treatment wi th PLA. There were no statistical differences in microhardness values for S D and DD submitted to the treatment with OPA and PLA. The results suggest t hat treatment with 10% carbamide peroxide bleaching material for three week s alters the enamel microhardness, although it does not seem to alter the d entin microhardness.