Effect of different peroxide bleaching regimens and subsequent fluoridation on the hardness of human enamel and dentin

Effect of Different Fluoridation Regimes on the Microhardness of Bleached Enamel

“…This finding is in accordance with a number of previous studies that also showed a decrease in microhardness during bleaching treatment. 7,9,13,[19][20] However, other studies reported that 10% carbamide peroxide gel did not affect enamel surface hardness. [21][22][23] These contradictory findings among different studies might be due to differences in method, such as frequency and time of bleaching treatment, storage media or the use of human or bovine teeth.…”

“…Also, frequency and duration of toothpaste and gel fluoridation of the samples were adjusted to the recommendations for regular oral hygiene measures. In contrast to a study by Lewinstein and others, 7 who also analyzed fluoridation effects on the hardness of bleached enamel, the samples were immersed in artificial saliva, instead of distilled water. Artificial saliva was used as the calcium and phosphate source for the remineralization of bleached enamel.…”

“…[5][6] The application of carbamide peroxide gels has been reported to affect calcium and phosphate content and, as a result, might also decrease the surface microhardness of the enamel layer. [7][8][9] Thereby, the loss of surface microhardness is not limited to the outermost enamel but can also be detected in the subsurface enamel layer. 10 Despite the protective and remineralizing potential of human saliva, when bleaching is performed for six to eight hours daily for two to three weeks, microhardness loss is sometimes evident under in situ conditions.…”

“…Fluoride might also contribute to the repair of the microstructural defects of bleached enamel. Attin and others 14 and Lewinstein and others 7 showed that the loss of microhardness could be reversed by a post-bleaching period in which fluoride gels or rinses were administered. Thereby, fluoridation with a pure amine fluoride gel was shown to be more effective in increasing the microhardness of bleached enamel than when bleaching was performed using a fluoridated carbamide peroxide gel.…”

“…Thereby, fluoridation with a pure amine fluoride gel was shown to be more effective in increasing the microhardness of bleached enamel than when bleaching was performed using a fluoridated carbamide peroxide gel. 15 Generally, the fluoridation of bleached enamel is frequently recommended for improving microhardness 7,14 and, thus, increasing the abrasion resistance of softened enamel. [16][17] However, there is no general agreement on the optimal time point of fluoridation during the bleaching regime.…”