Effects of sample hardness on human chewing force: a model study using silicone rubber.

This study aims to clarify the effects of sample hardness on chewing force of humans. Silicone rubber was chosen as a food model, and three silicone rubber samples of varying hardness were chewed between the upper and lower incisors or molars in a natural way. Chewing force, contact area between a specimen and teeth, and pressure applied into the specimen were dynamically measured with a multiple-point sheet sensor. The multiple-point measurement revealed that a harder sample evoked higher peak force, longer duration, higher impulse, and higher active pressure values, whereas the chewing cycle and time to peak were not affected by sample hardness. The contact area between the sample and teeth decreased for the harder sample during incisor chewing. The peak force and force-related parameters, contact area, time to peak and bite force duration showed higher values for molar bites than for incisor bites, while the chewing cycle was similar in both cases. The measurement with the sheet sensor system clearly indicated that sample hardness modified chewing force of humans. We hypothesise that the effect of sample hardness is mainly mediated by mechanoreceptors in the periodontal ligament.