Abstract
Since the percent of plaque removal is in proportion to the product of the brushing force and the number of strokes, a conscious increase of one or both of these factors increases the plaque removal effect. But the larger the number of brushing strokes per twenty seconds becomes, the smaller the brushing force becomes; and the number of brushing strokes has a tendency to decrease when the brushing force becomes stronger than 400g or 600g.
In this study, the brushing force was specified during observation of each brushing force wave with a cathode-ray tube oscillograph, and the number of brushing strokes was specified by synchronization with the sounds of a metronome.
It was concluded that a larger percentage of plaque removal was obtained by brushing with a force of 800g and 30 strokes per twenty seconds than by brushing with a force of 600g and 40 strokes, or with 1, 000g and 24 strokes per twenty seconds, even though the product of the brushing force and number of strokes is the same (24, 000). Also six days of instruction in tooth brushing resulted in a greater degree of plaque removal than lesser amounts of instruction time (Tables 1-4 and Figs 5-8).
