Microhardness change of enamel due to bleaching with in-office bleaching gels of different acidity

A selection of abstracts of clinically relevant papers from other journals. The abstracts on this page have been chosen and edited by John R. Radford.

Abstract

It is suggested that the pH of the bleaching gel may cause the 'enamel softening'.

Main

Magalhães JG, Marimoto ARK et al. Acta Odontol Scand 2012; 70: 122–126

The effect of three high concentration hydrogen peroxide gels (each ca. 35% hydrogen peroxide), on changes in Vickers microhardness of enamel, was investigated using a bovine incisor model. The bleaching regimens comprised three applications of the three gel products, each of 10 minute duration, in combination with light sources. Opalescence Xtra (Ultradent, South Jordan, UT) caused significantly more 'hardness loss' compared with Total Bleach (Clean Line, Taubaté, São Paulo, Brazil) and Whiteness HP, (FGM, Joinville, SC, Brazil). The pH of these gels were 4.30, 6.62 and 6.4 respectively, and it is this property that confers product stability. Although the investigators suggest that the pH of these gels cause the 'enamel softening', those bleaching agents whose pH were above the critical level for enamel demineralisation, were also associated with a reduction in enamel microhardness.