title: [EMG activities of the head, neck and upper trunk muscles with mandibular movements in healthy adults and mandibular asymmetry patients].
abstract: OBJECTIVE
  To study the activities of head, neck and upper trunk muscles during mandibular movements in healthy adults and mandibular asymmetry patients.
  
  
  METHODS
  Electromyographic integrogram was used to record and analyze the electromyographic activities of the anterior temporal (Ta), posterior temporal (Tp), sternocleidomastoid (SCM), and trapezius (TRAP) muscles in rest position and during mandibular movement among 10 normal adults and 10 mandibular asymmetry patients.
  
  
  RESULTS
  All the four muscles showed constant electromyographic activities when the mandible was in the rest position. The activities of Ta, Tp, and SCM muscles increased with protrusion of mandible, mouth opening, tapping, maximum clenching, and chewing. The activities of Ta and Tp muscles of the patients were 1.7 times greater than that of the normal adults during mandibular movement without occlusion, and were weaker by 50% during mandibular movement with occlusion. The difference between electromyographic activities during mandibular movement and in rest position was less among patients than among normal adults. The TRAP muscle of the patients showed constant electromyographic activities with the activity volume nearly 1.8 times that of the normal adults. The difference between the muscle and its namesake at the opposite side was greater among the patients (21%) than among the normal adults (8%).
  
  
  CONCLUSIONS
  All the four muscles participate in the maintenance of rest position of mandible and the realization of mandibular movements. The coordination of muscular activities among mandibular asymmetry patients is poorer than that among normal adults.
authors.affiliation: School of Stomatology, Peking University, Beijing 100081, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Jiang
authors.forename: Zhenkang
authors.initials: Z
authors.lastname: Zhang
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Yang
authors.forename: Biao
authors.initials: B
authors.lastname: Yi
authors.forename: Hailan
authors.initials: H
authors.lastname: Feng
authors.forename: Xing
authors.initials: X
authors.lastname: Wang
mesh_terms: D000328:Adult; D004576:Electromyography; D004594:Electrophysiology; D006257:Head / Q000503:physiopathology*; D006801:Humans; D008334:Mandible / Q000002:abnormalities*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D009333:Neck / Q000503:physiopathology*; D012782:Shoulder / Q000503:physiopathology*