抄録
The ultimate aim of this study is to develop a quantitative and objective method for designing toothbrush handles for ease-of-grip by means of ergonomic procedures. It is reasonable to think that easy-to-grip handles would enable more effective removal of dental plaque. To this end, the present study considered a hypothesis that the upper and lower part of the handle would have different roles, and have different optimum diameters depending on the human hand sizes when the handle is palm-gripped. To examine the hypothesis, 24 test toothbrushes were prepared combining a cylindrical upper part of 4 different diameters with a cylindrical lower part of 6 different diameters. Eighteen subjects were divided into 3 groups by their hand sizes. Electromyogram (EMG) of 5 muscles in forearms and hands of the subjects were measured when brushing. The handle diameter which gave minimum muscle load (MML) was calculated by the quadratic regression analyses of the EMG data. The analysis has demonstrated that the diameters with MML for each handle part have been obtained depending on the hand size. In conclusion, our hypothesis was appropriate and this study has shown that ergonomic procedures by EMG measurements are potential tools for designing toothbrushes for ease-of-grip.
