Dentine hypersensitivity: the effects of brushing desensitizing toothpastes, their solid and liquid phases, and detergents on dentine and acrylic: studies in vitro

Dentine exhibiting symptoms of dentine hypersensitivity has tubules open at the dentine surface and patent to the pulp. The mechanisms whereby dentina l tubules are exposed is ill understood but probably involves a variety of abrasive and/or erosive agents. This study in vitro examined the quantitati ve and qualitative effects of toothpastes, their solid and liquid phases an d detergents on dentine and acrylic. Abrasion of dentine and acrylic were m easured by surfometry. Morphological changes to dentine were assessed by sc anning electron microscopy. Abrasion of dentine and acrylic by toothpastes increased with increasing brushstrokes with marked differences in the exten t of abrasion between different pastes. Brushing dentine with water or dete rgents produced progressive abrasion but which appeared to plateau around 2 mu m loss. Water and detergents produced minimal effects on acrylic. At 50 00 strokes dentine abrasion by solid phases was less than the parent toothp astes but the ranking order of abrasivity was the same as the parent toothp astes. Loss of dentine produced by liquid phases was minimal and in the ord er of 1-2 mu M Observationally, all toothpastes removed at least the dentin e smear layer to expose many tubules; with one desensitizing product leavin g a particulate deposit occluding most tubules. The solid phases of the too thpaste produced identical morphological changes to the parent paste. The l iquid phases and detergents all exposed dentinal tubules by 5000 strokes. W ater had little or no effect on the dentine smear layer. It is concluded th at toothpastes, solid phase, liquid phase and detergents have the potential to abrade or erode dentine to a variable degree and result in tubule expos ure. The effects of the liquid phases and detergents appear limited to the removal of the smear layer. Such detrimental effects seen in vitro could ha ve relevance to the aetiology and management of dentine hypersensitivity. T oothpaste formulations which despite exposing tubules have ingredients capa ble of occluding tubules may be an area of development for such products.