title: Electromyographic activity of the jaw-closing muscles during jaw opening--comparison of cases of masseter muscle contracture and TMJ closed lock.
abstract: Contracture of jaw-closing muscles is one of the causes of limitations of jaw opening. In contracture patients who have no history of trauma or infection, it is not easy to distinguish contracture from temporomandibular joint (TMJ) closed lock (TCL). The purpose of this study was to clarify whether there is any difference between electromyographic (EMG) activities of jaw muscles during jaw opening in patients with TCL and patients with masseter muscle contracture (MMC). The MMC-patient group consisted of one male and 11 females with no history of trauma or infection. The TCL-patient group consisted of one male and 11 females. Ten of the MMC patients showed certain types of EMG activities in masseter muscles (and eight in temporal muscles) during jaw opening. However, particular EMG activities were not observed in most of the TCL patients. The integral values in masseter muscles and in temporal muscles at the maximum opening position were significantly higher in the MMC-patient group than those in the TCL-patient group. These findings demonstrate that the EMG pattern of MMC patients without a history of trauma or infection is different from that of TCL patients. Therefore, EMG analysis of jaw-closing muscles during jaw opening is expected to be useful for differential diagnosis between MMC and TCL.
authors.affiliation: Special Clinic for Specific Disorders, School of Dentistry, Hokkaido University, Sapporo, Japan. taihiko@den.hokudai.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Yamaguchi
authors.forename: K
authors.initials: K
authors.lastname: Satoh
authors.forename: K
authors.initials: K
authors.lastname: Komatsu
authors.forename: K
authors.initials: K
authors.lastname: Kojima
authors.forename: N
authors.initials: N
authors.lastname: Inoue
authors.forename: K
authors.initials: K
authors.lastname: Minowa
authors.forename: Y
authors.initials: Y
authors.lastname: Totsuka
mesh_terms: D000293:Adolescent; D000328:Adult; D003196:Computer Graphics; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008406:Masseter Muscle / Q000503:physiopathology*; D008875:Middle Aged; D009119:Muscle Contraction; D018709:Statistics, Nonparametric; D013704:Temporomandibular Joint / Q000503:physiopathology*; D013705:Temporomandibular Joint Disorders / Q000503:physiopathology*; D014313:Trismus / Q000503:physiopathology*