Surface EMG activity of the masseter muscle in denture wearers during chewing of hard and soft food.

Previous studies mainly on dentate subjects, have clearly shown that food texture affects the various chewing parameters. The purpose of this investigation was to study the influence of food texture on the surface electromyographic (EMG) activity of the masseter muscle in a sample of denture wearers. Nine experienced denture wearers (mean age of 68.7 years) with clinically satisfactory dentures consented to participate in this study. Carrots and peeled apples cut into equally sized pieces were chosen as representing a hard and a soft food respectively. The parameters studied from the raw and integrated EMG recordings were: chewing rate, mean peak RMS activity, chewing cycle and chewing burst duration and relative contraction period. The findings were in line with those earlier reported on dentate subjects, in that harder foods require higher chewing rates, higher electrical activity of the masseter muscle and higher relative contraction periods, accompanied by shorter cycle durations. Most of these differences were statistically significant (P< 0.05) as tested by paired t-test. Moreover a strong inverse correlation was found between chewing rate and cycle duration (r = -0.92, P < 0.05). We concluded that the texture of food has an obvious effect on all the studied parameters of EMG activity, and that those adjustments to food consistency are probably due to a combined powerful peripheral input mediated through receptors, other than the periodontal ones.