The purpose of this study was to clarify the difference in mastication efficiency between adult Japanese and Chinese with difference dieatary habits. The subjects were a total of 110 adult Japanese and Chinese males and females. A dental prescale 30H series was used. According to the tooth types of the permanent molars in the maxilla and mandible, the mean occlusal pressure, occlusal contact area, and occlusal force were compared between the Japanese and Chinese subjects. The following results were obtained.
1. The mean occlusal pressure was larger on the premolars than on the molars in both the Japanese and Chinese males and females. In both the maxilla and mandible, the mean occlusal pressure was significantly higher on the first premolars than on the second premolars among the Chinese males and on the first molars than on the second molars among the Japanese males. Comparison between the Japanese and Chinese showed a higher occlusal pressure in the maxilla and mandible among the Japanese than among the Chinese in both male and female; significant differences were observed on the first molars among the males and on the first and second molars among the females.
2. The occlusal contact area and occlusal force showed similar results, which were inversely related to the occlusal pressure. Higher values were observed on the molars than on the premolars, according to the occlusal contact area and occlusal force. On the premolars, the second premolars showed higher values than the first premolars. On the molars, the first molars showed higher values than the second molars in the maxilla, and the second molars showed higher values than the first molars in the mandible. However, only Japanese males showed higher values on the second molars in the maxilla and mandible. When the Japanese and Chinese were compared, the occlusal contact area and occlusal force of molars in both maxilla and mandible among the Chinese males and females showed twice the values of the Japanese males and females. These differences were more marked among the adults.