The incidence of unerupted permanent teeth and related clinical cases.

The impacted or mal-erupted tooth and its associated pathosis provide great diagnostic challenges to the dentist. The frequency of occurrence of impaction was found to be over 10,000 in 5,000 Army recruits. The type and position of impaction are summarized in tables. The incidence of impactions was higher than previously reported and may reflect some sampling bias. The incidence of impacted second and fourth molars is higher than expected. Impactions or mal-eruptions were seen to involve every permanent tooth except the mandibular incisors and first molars. Impactions can occur because of malpositioning of the tooth bud or obstruction in the path of eruption. However, the exact mechanism is still unknown. Six unusual cases of impacted permanent teeth are described to illustrate the importance of panoramic radiographs in the discovery of some anomalously located impactions.