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The purpose of this study was to determine whether enamel that has been bleached by hydrogen peroxide gel (HPG) is at increased risk of acid erosion than un-bleached enamel. Human incisors/canines were selected, roots removed and the enamel gently pumiced. Each enamel specimen was mounted in acrylic, covered with varnish save for an exposed window, and randomly assigned to one of 4 groups: (a) 10% HPG, b) 16% HPG, c) 22% HPG (all by Southern Dental Industries GmbH) and d) 10% Urea Peroxide Gel (Biocosmetics, SA). Each specimen was moistened with saliva and the appropriate formulation placed for 2 h. The teeth were rinsed and gently brushed for 2 min in an automatic tooth-brushing machine. This procedure was repeated for 20 cycles. In order to ensure that bleaching had taken place, tooth shades were monitored using digital photographs and the Shade-Eye device. Whitening effects were noted in all teeth. Following the bleaching process, the varnish was removed from the enamel and refreshed leaving a window exposing both bleached and non-bleached enamel. Each specimen was then subjected to a total of 4 h of erosive challenge (0.1% citric acid, pH 2.74)) with gentle agitation and examined hourly using QLF. At the completion of the erosive challenge a final QLF image was taken and samples sectioned for analysis using TMR. Erosion was detected in all samples (.Q 126 ± 23.4), in both bleached and non-bleached areas. There was no statistical difference (at the 95% level) between the bleached and non-bleached areas, either within the treatment groups or between them, when measured by QLF or TMR. These results suggest that tooth bleaching with hydrogen peroxide does not increase the susceptibility of enamel to acid erosion. |