An orthopantomographic study of hypodontia in permanent teeth of Japanese pediatric patients

Hypodontia of permanent teeth was evaluated from orthopantomograms of 2072 apparently healthy pediatric patients at The Hospital of Nihon University School of Dentistry at Matsudo. The prevalence of congenitally missing teeth (CMT) was 8.7% in boys and 10.8% in girls, and 9.4% for both sexes combined. Most cases (67.8%) involved either one or two missing teeth. There were in total 574 CMT, and on average 2.8 teeth were missing per child. The most commonly absent tooth was the mandibular second premolar. On the other hand, no first molars were missing in any case. A high frequency of CMT mandibular incisors (18.82%) was observed, and this seems to be a characteristic peculiar to individuals of Asian ethnicity. Oligodontia (6 or more CMT excluding the third molar) ranged from 6 to 14 teeth, with a prevalence of 1.4% in general: 1.8% for girls and 0.9% for boys. Symmetry of CMT was predominant: 214 pairs for bilateral symmetry and 107 pairs for symmetry between two antagonistic quadrants. The distribution of CMT between maxillary and mandibular hypodontia in the right and left quadrants for boys and girls no had significant association (P < 0.05).