[Clinical study of enamel hypoplasia and its causes. 2. Permanent teeth]

A nation-wide field survey was carried out to investigate the etiology of enamel hypoplasia for permanent teeth in 286 subjects below 20 years of age with permanent dentition having enamel hypoplasia. Visual examination, photographic evaluation and questionnaire survey were used. The same questionnaire survey was also carried out in 111 subjects without hypoplastic teeth as controls. The following results were obtained. 1. The number of hypoplastic teeth ranged from 1 to 28 per subjects. 2. Upper central incisors were frequently involved, especially in subjects with few permanent teeth. Enamel hypoplasia in these teeth appeared symmetrically. 3. Only a few hypoplastic teeth seemed due to local causes. Hypoplastic teeth were not considered to be mottled teeth caused by fluoride. 4. Unbalanced diet (food liked and disliked) during pregnancy was not related to dental hypoplasia. 5. In subjects with many colored teeth, maternal diseases during embryogenesis and drugs administered for treatment were considered to be etiologically involved in the development of hypoplasia. 6. Viral infection during childhood seemed to be involved in the development of hypoplasia. 7. Many of the subjects with more than 7 hypoplastic teeth or colored teeth had contracted diseases during childhood. Moreover, the development of both viral infection and other disease was frequent. 8. The kind of teeth liable to damage, time of damage, sensitivity of individual subjects, multiple stimulation.