Dentine hypersensitivity: uptake of toothpastes onto dentine and effects of brushing, washing and dietary acid--SEM in vitro study.

Toothpastes are commonly used in the treatment of dentine hypersensitivity. One mode of action could be to block patent dentinal tubules with toothpaste ingredients or by abrasion to form a smear layer. Studies in vitro have shown that toothpaste abrasives have variable affinity for the dentine surface but retention may be limited. This SEM study extended previous work and determined the uptake in vitro of toothpaste ingredients onto the dentine surface and their retention when challenged by washing with water or orange juice. All products were seen to leave variable residues on the surface of etched or unetched dentine specimens, furthermore brush application produced some smearing with closure of previously open tubules. Washing with water and more particularly orange juice removed most residues and orange juice etched the dentine to open previously closed tubules. One product with an artificial silica abrasive was relatively resistant to both water and orange juice washings and in a pilot experiment showed some penetration into tubules not seen with another desensitizing product. These findings suggest that some abrasives may be usefully employed in desensitizing products, but without consideration of erosive factors in the aetiology of dentine hypersensitivity recurrences of the condition will be common.