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.
Relationships between the hand grasp force and occlusal pressure were investigated in young male adults during static teeth clenching and nonclenching. The hand grasp forces of left and right sides during static teeth clenching (L : 37.6±1.89 kg, R : 42.8±1.89 kg) were significantly greater than those during nonclenching (L : 35.7±1.16 kg, R : 40.5±1.06 kg). The findings indicated that the bite force influenced increase in hand grasp force.
The purpose of this study was to investigate in three dimensions the differences in face form between Filipino females, who belong to Sundadont, and Japanese females, who belongs to Sinodont, using moiré Topography. The Subjects were 70 adult Filipino females of ages 17-38 years and 70 Japanese females of ages 14-24 years. The width, height and depth of each facial part were measured and statistically compared. 1. The Japanese females had a broad and long middle face and a long nose, whether relatively or absolutely. The Filipino females had long mouths, broad noses, and large and protruding lips. These lip features are also identified in the Negroid, and are thought to be an adaptation to Southern migration. 2. Though a few items were large in the right face, the left face was relatively large in the Japanese female. In the Filipino female, no items were large in the right face and most were large in the left face. There seemed to be tendency for the left face to be large in general, although there was some difference between the groups.