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Six toothbrushing methods were evaluated using several kinds of toothbrushes. Two kinds of electric toothbrushes were tested also. Forty-two adults who had normal dentition and clinically healthy periodontal tissue, aged 20 to 34, 36 males and 6 females, voluntered for this study. The plaque score was calculated by the modified Volpe s method on which Suzuki et al. reported before. The scoring of the plaque was restricted to the six teeth (6/41|14/6). The average percentage of plaque removal from the total (labial and lingual) tooth surface by different toothbrushing methods was as follows: (1) 75.2± 9.9% by the Fones method with a hard brush, (2) 71.7 ± 11.1% by the Scrub method with a hard brush, (3) 67.4 ±12.5% by the modified Stillman’s method with a hard brush, (4) 64.7 ± 13.7% by the National electric toothbrush with a soft brush, (5) 62.9 ± 13.6% by the Roll method with a hard brush (6) 58.l ± 16.3% by the Charters method with a brush of a medium hardness, (7) 55.2 ± 10.2% by the Bass method with a brush of a medium hardness. A similar tendency was obtained independently on the labial, lingual and papillary tooth surface. The hard brush was the most effective for the plaque removal by all kinds of brushing methods.

This study was conducted to examine the effect of various dentifrices on the abrasion of acrylic resin and extracted human tooth. The influence of the difference in the hardness of the filament of the toothbrush on the abrasion was also studied, using three kinds of toothbrushes. The specimens (acrylic resin and extracted human tooth) were brushed 3.,000 times by the back­ and -forth stroke movement using a toothbrushing machine for two hours. The surface irregularities of the specimen were analyzed by the surface analyzer and observed by the scanning electron microscopy before and after the brushing procedure. Moreover, the weight loss of the test specimens of the acrylic resin materials was determined, weighing them by a microbalance before and after brushing. The abrasiveness of the dentifrices showed a wide range, but the abrasiveness of the toothbrush itself was not observed. All dentifrices except one which did not contain the abrasive materials had abrasive effects on both the acrylic resin and human tooth. There was a high correlation (r=0.96) between the weight loss and the surface irregularities in the case of acrylic resin.