The subjects of this study were 3,003 patients (1,410 boys and 1,593 girls) visited the pediatric dental clinic of the Tsurumi University Dental Hospital. The incidence of dens evaginatus (incisive tubercles of the anterior teeth and central cusps of the posterior teeth) of the permanent teeth was retrospectively surveyed by using the X-ray films and the oral examination records. The clinical management was suggested based on this survey. The results obtained were as follows:
1) Seven patients (0.23%) (2 boys and 5 girls) showed incisive tubercles. Eighty-eight patients (2.93%) (32 boys: 2.27% and 56 girls: 3.52%) showed central cusps. One patient showed both kinds of dens evaginatus.
2) Eight incisive tubercles were detected. Among them 2 cases were found in the upper central incisor and 6 cases were found in the upper lateral incisor.
3) Two hundreds and thirty-five central cusps were detected. Among them 234 cases were found in the premolar and one case was found in the molar. The numbers of central cusps observed among the premolars were respectively 96 lower second premolars (41%),71 lower first premolars (30%),37 upper second premolars (16%) and 30 upper first prmolars (13%).
4) The number of central cusps in the maxilla was 67 (28.6%) and in the mandible 167 (71.4%).
The incidence of central cusp in the latter was 2.5 times as much as in the former. The number of central cusps in the left side of the arches was 119 and the number in the right side of the arches was 115. Regarding the incidence of central cusps, no significant difference was observed between the left and right sides.
5) The average age of the patients having central cusps which were detected by means of oral examinations was 10 years and 5 months.
6) X-ray detection of central cusps was possible even prior to eruption of the premolars. The average age of such patients detected by the X-ray examination was 8 years and 5 months.