The study of the effect of dental arch form on chewing movement

As the dental arch form is the curve connecting the cusp tip of each tooth, it is one of the important factors of occlusal reconstruction. Many studies about dental arch form have been reported but it is unclear to infer the position of the teeth in dental arch form, and to evaluate the effect of the horizontal dental arch form on chewing movement. The purpose of this study is to elucidate the effect of dental arch form on chewing movement. 100 subjects with individual normal occlusion were evaluated. By multiple regression analysis on the basis of the relation of position of the canine and the first molar, the positions of teeth in dental arch were inferred. According to buccolingual relationship of maxillary to mandibular posterior teeth, the dental arch forms were classified into five groups. Using Sirognathograph Analyzing System i, the patterns of chewing movement were analyzed by Maruyama's classification. According to the classification of dental arch form and the analysis of patterns of chewing movement, the patterns of chewing movement in each group were evaluated and compared with those of the normal group. Results were summarized as follows; 1.Objective criteria to infer the positions of the first premolar, the second premolar, and the second molar in dental arch were established. 2. Opening path in chewing movement The group in which the maxillary second molar's position is on the buccal side, the chewing patterns which have the vertical guide openings in frontal plane, the posterior guide openings in horizontal plane were observed. The group in which the maxillary premolar's position is on the lingual side, the chewing patterns which have the protrusive shift openings in horizontal plane and sagittal plane were observed. 3. Closing path in chewing movement In each group except for the normal group, the chewing patterns which have the concave closings in frontal plane and in horizontal plane were observed. The group in which the maxillary premolar's position is on the buccal side, the chewing patterns which have the lateral guide closings in frontal plane and in horizontal plane, the vertical guide closing in sagittal plane were observed. From the results, the close relationships were found between dental arch form and chewing movement. It is suggested that the evaluation of dental arch form is effective in the diagnosis of function of stomatognathic system.