Effects of brushing with a dentifrice for sensitive teeth on tubule occlusion and abrasion of dentin.

By using a dentifrice or toothpaste for sensitive teeth, the brushing-induced effects on dentinal tubule occlusion and abrasion of human sound dentin were investigated with a scanning electron microscope and a scanning laser microscope. The dentifrice contained diatomaceous earth and silica as abrasives and strontium chloride hexahydrate as an active ingredient. Thirty dentin pieces of human premolar teeth with an average of 20% occluded dentinal tubules were attached to resin plates and exposed to the oral cavities of five adult subjects for 2, 4, and 8 weeks. Brushing with and without dentifrice was performed 1 min per day, respectively. Brushing with the dentifrice gradually decreased the mean average of occluded tubules from about 91 to 77% during 2 to 8 weeks, although there were no significant differences among the individual values. However, the mean abrasive loss of the dentin surfaces brushed with dentifrice significantly increased from about 52 to 143 microm in depth. The brushed surfaces of the dentin showed a rough topography with numerous toothbrush scratches but no organic pellicle was found. On the other hand, brushing without dentifrice caused about 99% of the dentinal tubules to occlude in 2 and 4 weeks and 100% in 8 weeks. The brushed dentin surfaces at 8 weeks were entirely covered with organic pellicle containing fine mineral granules derived from saliva, and the abrasive loss was about 1.4 microm in mean depth. Such results indicate that brushing with abrasive dentifrices for sensitive teeth remarkably erodes dentin, and suggest that the brushing should cause the dentinal tubules to open again for a certain period of time.