Effects of toothbrushing on eroded dentine.

It is an established assumption that eroded dental hard tissues are particularly prone to toothbrush abrasion. Only a few studies have aimed to show this for dentine and, if so, disregarded the complex histological structure of this tissue. Therefore, the present study sought (i) to investigate the effects of toothbrushing on eroded dentine and (ii) to analyze how the organic matrix influences the outcome of established methods for quantifying dental hard tissue loss. The effects of brushing were investigated by optical (P-O) and mechanical (P-M) profilometry, by longitudinal microradiography (LMR), and by scanning electron microscopy (SEM). The SEM images showed that a demineralized organic layer had developed, which was unaffected by brushing. For substance loss, there was no significant difference between eroded and eroded/abraded samples. Considerable differences occurred, however, when results from the different methods were compared. P-O yielded the lowest (7.0 +/- 3.4 microm) and LMR the highest (109.8 +/- 10.7 microm) substance loss values. When the organic material was removed enzymatically, all methods gave comparable results. The results of this study do not lend support to the notion that brushing increases substance loss of eroded dentine. Profilometry was not suitable for measuring mineral loss, unless the organic material was removed.