Bruxism and trauma from occlusion. An experimental model in Macaca monkeys.

The present study describes an experimental approach for inducing bruxism and trauma from occlusion in animals. Gold occlusal cap splints overlaying the maxillary premolar and molar teeth were inserted in eight Macaca irus monkeys. The cap splints were designed to raise the vertical dimension of occlusion by 3--4 mm and were adjusted to a balanced occlusion with the mandible in an unstrained retruded position. The splint on the right side (test side) was given a tight occlusion with the opposing mandibular teeth, whereas the splint on the left side (reference side) had only small occlusal contact areas. Before insertion of the splints, the monkeys had slight gingivitis but no alveolar bone loss. The cap splints were in situ for 4 weeks. During this period the monkeys showed distinct signs of bruxism. The mandibular teeth on the test side showed increased mobility and there was radiographic evidence of breakdown of marginal and interradicular alveolar bone. Mean GI increased significantly on the test side and in two animals gingival abscesses developed. Deep intrabony pockets persisted adjacent to these teeth. Only slight gingival and radiographic changes were seen adjacent to the teeth on the control side. From the present experimental study there was no overall clinical or histological evidence that bruxism had caused a progression of gingivitis to destructive, chronic marginal periodontitis.