Changes in masticatory jaw movement and muscle activity following surgical orthodontic treatment of an adult skeletal Class III case.
This case report examines the masticatory jaw movements and electromyograph (EMG) recordings of anterior and posterior temporal and masseter muscles before and after surgical orthodontic treatment in an adult patient with incisor crossbite and skeletal Class III jaw base relationship. The prescribed treatment resulted in a good occlusion and skeletal and dental Class I relationship. The chopping type jaw movement pattern during gum chewing was transformed to more of a grinding motion after treatment. But this motion was not as broad as is normally seen. This observation is indicative of the difficulties associated with improving the masticatory jaw movements in an adult patient to a completely normal pattern even after retention. In this patient, the high frequency of silent periods on the EMG that were observed in the early intercuspal phase before treatment were decreased to normal low levels after treatment. A similar decrease was also seen in the mean duration of the chewing cycle. We conjecture that this patient unsuccessfully attempted to compensate for the silent periods by increasing the period of his chewing cycle.
Miyawaki
S
S
Department of Orthodontics, Okayama University Dental School, Japan; Department of Orthodontics, Faculty of Dentistry, Osaka University, Japan.
Yasuda
Y
Y
Yashiro
K
K
Takada
K
K