Objective. A mathematical model of the temporomandibular joint was develope
d to study the magnitude and direction of the compressive loading experienc
ed at the temporomandibular joint during clenching.
Design. The model was based on the principles of static equilibrium in thre
Background Direct measurement of temporomandibular joint loading in humans
is extremely difficult. Animal models have provided an alternative in the p
ast. However, evidence suggests that primates are not the most accurate hum
an analogues for temporomandibular joint studies. A mathematical model was
used as an alternative to direct measurement.
Methods. The EMG activity of two masticatory muscles was combined with thei
r cross-sectional areas to calculate the force exerted by each muscle. Expe
rimentally determined forces were implemented into a quadratic programming
model to solve for the compressive forces on the joint. Two objective funct
ions were chosen and their ability to predict muscle and joint forces was e
Results. The maximum bite forces for normal men, normal women. and women wi
th temporomandibular joint disorders were 300 N (SD 102 N), 210 N (SD 57.7
N), and 120 N (SD 77.1 N). respectively, The calculated joint force for nor
mal males was 260 N (SD 84.1 N). Normal females and female temporomandibula
r joint disorder patients produced temporomandibular joint forces of 172 N
(SD 37.5 N) and 152 N (SD 44.2 N), respectively.