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-induc ed 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 abras ives and strontium chloride hexahydrate as an active ingredient. Thirty den tin 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 dentif rice was performed 1 min per day, respectively. Brushing with the dentifric e gradually decreased the mean average of occluded tubules from about 91 to 77% during 2 to 8 weeks, although there were no significant differences am ong the individual values. However, the mean abrasive loss of the dentin su rfaces brushed with dentifrice significantly increased from about 52 to 143 mum in depth. The brushed surfaces of the dentin showed a rough topography with numerous toothbrush scratches but no organic pellicle was found. On t he 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 denti n surfaces at 8 weeks were entirely covered with organic pellicle containin g fine mineral granules derived from saliva, and the abrasive loss was abou t 1.4 mum 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.