EMG Activity of the Chewing Muscles during Adaptation of Dental Patients to Fixed Dentures

Abstract

Patterns of EMG activity of muscles involved in chewing movements (mostly of the mm. masseter and temporalis, M and T, respectively) were examined in 37 patients with defects of the dental rows treated with installation of fixed dentures (FDs) and in 10 control subjects with no above defects. It was found that, during 6-month-long adaptation to the FDs, the average period of chewing movements in the group of patients was mildly (by 5.5 to 7.9%) but significantly (P < 0.05) shorter than that in the control group, the structure of the chewing cycle in the M and T was modified due to significant (P< 0.05) shortening of the activity phase, and fractioning of the latter phase was manifested in many patients. The amplitudes of M and T EMG activities during the adaptation interval were significantly smaller than in the control and nearly completely recovered only in 6 months. Thus, the treatment of defects of the dental rows using the FDs, which results in changes of the afferent flow from the oral cavity, is related to noticeable modulation of the activity produced by the chewing brainstem central pattern generator, and the respective changes are smoothed only after a long-lasting (more than 6 months) adaptation period.