Toothbrushing Force Study

¹ Department of Periodontology, College of Dentistry, University of Iowa, Iowa City, Iowa, Department of Mechanical Engineering, West Virginia University School of Engineering, Morgantown, West Virginia, and Squibb Institute for Medical Research, New Brunswick, New Jersey

Altogether, 208 tests have been carried out with eight different types of toothbrushes to determine what forces are applied through the brushes to the surfaces of the teeth during toothbrushing procedures. The eight toothbrushes used in the tests were the cord-type, rotating-action toothbrush with four different types of bristles, namely, 0.006 nylon, 0.008 nylon, 0.006 polyamide plastic, and 0.008 polyamide plastic; the reciprocating-action, cordless brush with 0.011 nylon bristle; the rotary-action, batteryxs-powered brush with 0.006 nylon bristle; the multitufted, soft nylon manual brush with 0.008 nylon bristle; and the multitufted, nylon manual brush with 0.012 nylon bristle.

The torque (sweep) and normal (scrub) forces recorded during the tests varied widely from person to person, but test results indicated that the structure and the pattern of the bristle determined the brushing forces of each subject. The caliber arrangement and length of the bristles were found to be the most important factors. The maximum normal force (Gm.) with the various toothbrushes used in these tests ranged from 260 Gm. with the cord-type, rotating-action 0.006 polyamide plastic brush to 1,310 Gm. with the multitufted, soft nylon manual brush. The value of measured normal forces in all tests ranged from 182 with the cord-type, rotating-action 0.006 polyamide plastic brush to 1,153 Gm. with the multitufted, soft nylon manual brush.

The results of these tests indicate that the forces applied through the brushes to the surfaces of the teeth during toothbrushing vary to such a degree that any arbitrarily set hypothetical standards for such forces would be meaningless.

Results also suggest that abrasion studies using toothbrushing machines must use forces that vary during the brushing cycle.