Occlusal dysfunction and stress. An experimental study in macaque monkeys.

A dysfunctional occlusal relationship was produced in six macaca irus monkeys by insertion of occlusal splints which raised the vertical dimension of occlusion by 3--4 mm and incorporated interferences into the occlusion. Cortisol levels of plasma and 24 h urine samples were measured by competitive protein-binding analysis. After insertion of the splints there was an immediate, approximately two-fold rise of the mean 24 h urinary cortisol excretion rate and a significant decrease of urinary volume and body weight. The plasma cortisol level did not rise significantly. During the 3 weeks experimental period the teeth showed increasing mobility and occlusal wear facets developed on the splints. Urinary cortisol excretion rates were significantly elevated throughout the experimental period. Urinary cortisol levels declined to basal values when the splints were removed. This animal model produces experimental evidence in support of the hypothesis that a dysfunctional occlusal relationship may result in bruxism associated with emotional stress.