Dentine hypersensitivity: the effects of brushing toothpaste on etched and unetched dentine in vitro.

Although many people have exposed dentine, only a percentage exhibit symptoms of dentine hypersensitivity. This has been ascribed to opening and closing of the dentinal tubules by for example, smear layer changes or tubular occlusion. The aims of this study were to examine the surface morphological changes of etched and unetched dentine in vitro, attributed to the effects of toothbrushing with and without toothpastes designed for the alleviation of dentine hypersensitivity. A total of 96 etched and 96 unetched human dentine specimens were brushed with various toothpastes and water for 1, 2, 5 or 10-min periods in a toothbrushing machine and subsequently examined under scanning electron microscopy for surface changes. Analyses of brushed etched specimens demonstrated that time and treatment were significant variables (P < 0.05) for tubule occlusion. Further, the interaction between time and treatment was significant (P < 0.05). The artificial silica based paste was significantly better for all time intervals at occluding the dentine tubules. All toothpastes investigated caused dynamic changes to the smear layer of the unetched dentine, opening tubules. However, the artificial silica based paste resulted in occluded rather than patent tubules. All of the pastes evaluated had the capacity to remove the smear layer but some could then occlude tubules through the contained abrasives.