title: Muscle organization in individuals with and without pain and joint dysfunction.
abstract: Central nervous system organization of masticatory muscles determines the magnitude of joint and muscle forces. Validated computer-assisted models of neuromuscular organization during biting were used to determine organization in individuals with and without temporomandibular disorders (TMD). Ninety-one individuals (47 women, 44 men) were assigned to one of four diagnostic groups based on the presence (+) or absence (-) of pain (P) and bilateral temporomandibular joint disc displacement (DD). Electromyography and bite-forces were measured during right and left incisor and molar biting. Two three-dimensional models employing neuromuscular objectives of minimization of joint loads (MJL) or muscle effort (MME) simulated biting tasks. Evaluations of diagnostic group and gender effects on choice of best-fit model were by analysis of variance (ANOVA) and Tukey-Kramer post hoc tests, evaluations of right-left symmetry were by Chi-square and Fisher's exact statistics, and evaluations of model accuracy were by within-subject linear regressions. MME was the best-fit during left molar biting in +DD individuals and incisor biting in men (all p < 0.03). Incisor biting symmetry in muscle organization was significantly higher (p < 0.03) in healthy individuals compared with those with TMD. Within-subject regressions showed that best-fit model errors were similar among groups: 8 to 15% (0.68 ≤ R(2) ≤ 0.74). These computer-assisted models predicted muscle organization during static biting in humans with and without TMDs.
authors.affiliation: University of Missouri-Kansas City, School of Dentistry, Department of Orthodontics & Dentofacial Orthopedics, Kansas City, MO 64108, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Nickel
authors.forename: Y M
authors.initials: YM
authors.lastname: Gonzalez
authors.forename: W D
authors.initials: WD
authors.lastname: McCall
authors.forename: R
authors.initials: R
authors.lastname: Ohrbach
authors.forename: D B
authors.initials: DB
authors.lastname: Marx
authors.forename: H
authors.initials: H
authors.lastname: Liu
authors.forename: L R
authors.initials: LR
authors.lastname: Iwasaki
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D001732:Bite Force; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D003198:Computer Simulation; D003799:Dental Stress Analysis; D004576:Electromyography; D005157:Facial Pain / Q000503:physiopathology*; D005260:Female; D006801:Humans; D004204:Joint Dislocations; D016014:Linear Models; D008297:Male; D008410:Masticatory Muscles / Q000502:physiology / Q000503:physiopathology*; D008875:Middle Aged; D008954:Models, Biological; D013705:Temporomandibular Joint Disorders / Q000503:physiopathology*; D055815:Young Adult