Dentine hypersensitivity--the effect of toothbrushing and dietary compounds on dentine in vitro: an SEM study.

Dentine hypersensitivity occurs when dentinal tubules are open on the dentine surface and patent to a vital pulp. There has been limited interest in the aetiology of dentine hypersensitivity. In particular, little is known about agents that remove the dentine smear layer to expose tubules. Toothbrushing certainly may expose dentine, but whether a toothbrush per se has the effect of opening tubules has not been established. The aim of this study in vitro was to determine whether a toothbrush could remove or create a smear layer. In addition, the combined effects of toothbrushing with dietary fluids on dentine was assessed. Toothbrushing was observed, by scanning electron microscopy, both to remove and to recreate a smear layer on dentine specimens. However, the processes took a considerable time, and under conditions of normal toothbrushing it is unlikely that the latter plays a direct aetiological role in opening tubules. Indeed, together with toothpaste it is more likely that brushing has a therapeutic action by mechanically forming a smear layer. Conversely, and importantly, toothbrushing in the presence of dietary acids enhanced smear layer removal. This finding raises the question of whether the dental profession should be advising that teeth be brushed before meals rather than after, as is often the case.