Abstract
1. The first experiment was an in vivo study made using weekly observations of the interrelationship between the wear of toothbrush bristles and toothbrushing force.
The results obtained were as follows:
1) The toothbrushing forces employed by the subjects tended to increase slightly as the bristles became worn.
2) The toothbrush bristles spread out very little regardless of toothbrushing forces.
3) Scanning electron microscopic observations showed no wear in the tip of the bristles themselves after 2 weeks when weak toothbrushing forces were used. However, at 4 weeks the tip of the bristles were observed to overspread slightly.
However, when stronger brushing forces were used, wear of the tip of the bristles was clearly observed at 2 weeks, and at 4 weeks the round cut off tip of the bristles was observed to overspread considerably.
4) Hardness of the toothbrush bristles was observed to decrease with the use of the toothbrush.
2. The second experiment was an in vitro study observing the interrelationship between the wear of the toothbrush bristles and their plaque removing effect.
The results obtained were as follows
1) The actual scratching area was found to decrease for used toothbrushes for all values of brushing force.
2) Quantitative measurement showed that less gold coating was removed by used toothbrushes for all values of brushing force.
3) Hardness of the toothbrush bristles was observed to decrease with the number of brushing trokes.
