This study was designed to determine the relationship between the congenital anodontism and jaw size. Of 3,981 patients seen at the Department of Orthdontics, Iwate Medical University, 245 with congenital anodontism were examined. The relationship between congenital anodontism and jaw size was studied by longitudinal X-ray cephalometric analysis. Statistical analysis was carried out by Neyman’s method. The patients were divided into 3 groups by the magnitude of ANB angle. A large number of teeth were obviously missing in the maxilla in the ANB≦0°group. No difference was found in the number of missing teeth between the maxilla and mandible in the 0°<ANB≦4°group. There was obviously a large number of missing teeth in the mandible in the 4°<ANB group. In the group with a smaller mandibular size, teeth were missing mainly in the lower incisors area. These findings suggested that congenital anodontism was related to jaw size.
