Application of the environmental SEM in human dentin bleached with hydrogen peroxide in vitro

The environmental SEM (E-SEM) can be used unfixed biological samples under a low vacuum and wet condition. In this study, the fractured dentin of unfixed human teeth was treated with a 30% hydrogen peroxide solution (H2O2) for the examination of tooth-bleaching prior to the E-SEM and a conventional SEM. The peritubular matrix (PM) always showed a few cracks along the long axis of a dentinal tubule, and the ends of fine fibrils rose to the smoothly changed surface of the intertubular matrix (IM). The E-SEM with non-fixation and the conventional SEM following fixation indicated that the hydrogen peroxide solution easily permeated the PM and dissolved the non-fibrillar substance including the cracks of the PM by the constriction. In the IM, the solution may partially dissolve the organic parts within mineralized fibrils as well as non-fibrillar substance between the fibrils, although these remnants might precipitate again there.