Developmental disturbances in permanent teeth after exarticulation of their primary predecessors.

The frequency and type of developmental disturbances in the permanent teeth in relation to the patient's age at the time of injury were examined in 77 patients with 85 exarticulated primary incisors. The central incisors are the most frequently affected teeth and injuries occur more often to teeth on the right than on the left side. The frequency of disturbed normal development of the permanent teeth was 74.1% for the total material. From 0-2 years the frequency is 94.5% and after the age of 5 years the frequency is only 18.2%. External enamel hypoplasia is the more common result in patients whose trauma occurred when they were less than 3 years old, whereas internal enamel hypoplasia is the unsual result of traumas occurring after the age of 3 years.