Thirty-five percent carbamide peroxide application causes in vitro demineralization of enamel

Objectives The objective of this in vitro study was to investigate whether a high concentration ‘in-office’ bleaching agent affected the mineral content of enamel and dentin. Methods A commercially available 35% carbamide peroxide bleaching agent was applied for 2 h to sectioned teeth (n = 11). Specimens were then immersed in artificial saliva at 37 °C for a further 24 h to simulate the oral environment. Tomographic images of these sections were obtained (micro-CT 80, Scanco, Switzerland) prior to and post-bleach application. Eight three-dimensional regions of interest (ROI), starting from the enamel surface extending to the dentinoenamel junction, were selected for each section. The hydroxyapatite equivalent mineral concentrations (g/cm3) of the ROIs were calculated. Any changes in mineral content as a consequence of the bleaching procedure were calculated in relation to each ROI. Results There was a significant reduction in the mineral content of enamel specimens post-bleach application extending to a depth of 250 μm (paired t-test, p < 0.05); this reduction in mineral content was greatest in the ROIʹs closest to the tooth surface. There was, however, no significant difference in the mineral content of dentin as a consequence of bleaching. Significance This in vitro study has shown that significant demineralization of enamel occurred following bleaching with 35% carbamide peroxide. The concept that ‘in-office’ bleaching is a non-destructive cosmetic procedure should be reconsidered.