Muscle organization in individuals with and without pain and joint dysfunction

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 ≤ r2 ≤ 0.74). these computer-assisted models predicted muscle organization during static biting in humans with and without tmds. © 2012 international & american associations for dental research.