[Effect of occlusal form in buccal cusps of molars on masticatory function and intraoral food flow].

PURPOSE: The degree of crushing and intraoral food flow was evaluated using peanuts by the occlusal forms of a removable bridge as indices to clarify the occlusal formative effect of maxillary molars on masticatory function. METHODS: The subject was a 29-year-old male without any gnathostomatic disorders and his removable bridge ([7] 6 [5]) was so made in interocclusal distance as to be 0.5, 1.0 or 1.5 mm from 0 mm standard having occlusal contact to antagonist. Then the subject was asked to chew 3 g of peanuts in a series of unilateral chewing schemes consisting of 5, 10, and 20 masticatory strokes each. The pool rate in the buccal oral vestibule and lingual proper oral cavity as an index of food flow was calculated as the weight of peanut particles accumulated in each side as a percentage of the total volume of recovered peanut particles. Also, the degree of crushing was calculated as the weight of peanut particles that passed through 10-mesh sieves as a percentage of the total weight in each side. RESULTS: As the interocclusal distance to the mandibular cusp increased with abrasion on the inside at maxillary buccal cusps, the pool rate of the buccal oral vestibule was significantly increased and correspondingly that of the lingual proper oral cavity was decreased. The degree of crushing indicated non-significances statistically among 0, 0.5, and 1.0 mm and significantly decreased in 1.5 mm as compared with 0 mm. CONCLUSION: As the interocclusal distance to mandibular cusps from the maxillary inside of buccal cusps was increased, the pool rate of the crushed peanuts in the buccal side increased and the pool rate of crushed peanuts in the lingual side decreased, and the particles showed a comparatively low degree of crushing. It is clear that maxillary buccal occlusion has an effect on the crushing function and food flow.