Objective This study aims to investigate the correlation between the rat masseter abnormal activity and the degree of pathological changes of temporomandibular joint disease under mental stress. Methods A total of 36 adult Wistar rats were randomly divided into three groups: three-week experimental, six-week experimental, and control groups(n=12 for each group). A predetermined stimulus was applied on the experimental groups to place the rats in a stress state. The three rat groups were then sacrificed. The rat temporomandibular joint and masseter muscle tissue were obtained and submitted to the joint pathological section for observation of the pathological changes of the joint organizational structure. The levels of lactate dehydrogenase(LDH) and creatine kinase(CK) were quantitatively determined in the masseter muscle tissue homogenates. Spearman correlation and multiple regression analyses were used for statistical analysis. Analysis of the CK and LDH contents in each specimen masseter muscle was carried out to determine their correlation to the severity of the temporomandibular joint. Results A positive correlation was observed between the LDH and CK contents in the masseter muscle of rats to the severity of the temporomandibular joint. The levels of LDH and CK in the masseters of stressed rats showed a reciprocal relationship to the extent of temporomandibular joint disease. Conclusion The masseter muscle abnormal activity under stress may be used as a reference indicator of the degree of pathological changes of the rat temporomandibular joint. The masseter muscle abnormal activity is possibly caused by a temporomandibular joint disease.
