A 3-month study in monkeys of occlusal dysfunction and stress.

A dysfunctional occlusal relationship was produced in six Macaca irus monkeys by insertion of occlusal splints in the maxilla which raised the vertical dimension of occlusion by 3-4 mm and incorporated interferences into the occlusion (test side). Cortisol levels of plasma and urine were measured by competitive protein binding analysis. At week 1 and week 3 after insertion of the splints there was a significant increase of 24 h urinary cortisol excretion rate and plasma cortisol concentration, indicating emotional stress. Furthermore, there was evidence of acute trauma from occlusion of the mandibular teeth of the test side, including a significant increase of tooth mobility and GI; radiographically there were signs of breakdown of margial and interradicular alveolar bone. One animal developed periodontal pockets of 4-5 mm adjacent to the teeth of the test side. At week 6 and week 12 urinary and plasma cortisol levels had declined to basal values whereas tooth mobility, GI and PI remained elevated. There was no clinical or radiographic evidence of further loss of bone or increase of pocket depth adjacent to the teeth of the test side during the latter part of the experimental period. The results suggest that emotional stress may be involved in periodontal reactions associated with acute trauma from occlusion.