1997 年 17 巻 4 号 p. 341-350
Structural changes of human dentin by brushing with several kinds of commercial dentifrices in vitro were observed with scanning electron and scanning laser microscopes. Their gel, fluid, and paste-type dentifrices for gingivitis, sound enamel, or sensitive teeth contained no abrasives, crystallized sodium chloride (NaCl) which has not been noted as abrasive, abrasive silica, or several abrasives containing silica. Automatic toothbrushing rotated two-dimensionally was performed on the tangential ground surfaces of the cervical sound dentin for 10 min. The brushing with dentifrice containing abrasive silica or silica-containing abrasives caused dentin abrasion although the abrasivity of dentifrice containing NaCl and fluid-type dentifrices containing silica was weakened, while most of their dentinal tubules were occluded. Similar data have been obtained in our previous study using paste-type abrasive dentifrices for sensitive teeth or nicotine removal. Under brushing with a gel-type dentifrice containing no abrasives for gingivitis, the abrasivity was significantly lower than that of abrasive dentifrices. However, the dentifrice caused all the dentinal tubules to open following the erosion of the peritubular matrix because the pH range was 5 to 6. Such a patency of the tubules will cause dentin hypersensitivity in a case of in situ. Therefore, one must be cautious about the abrasivity of NaCl as well as abrasive silica and also the pH range in dentifrice even if dentifrice has no abrasives, when the cervical regions of teeth exposed to the oral cavity are brushed with commercial dentifrice.