Abstract
In the development of normal permanent dentition, it is a necessary condition that deciduous teeth and succedaneous permanent teeth change places at a regular period and in normal sequence. However, some succedaneous permanent teeth develop a delay in the eruption period or impact clinically due to various causes.
With Orthopantomographs of ambulatory patients as the material used in the study, the frequency by tooth group of impacted teeth and the crown-root formative status of the delayed eruption of teeth were discussed using a total of 66 subjects in whom impaction was observed 2 SD later or longer than the reference value for the eruption period of Japanese children, and the following conclusions were obtained:
1. The incidence of the delayed eruption of teeth showed no difference based on sex.
2. One tooth was largest in the number of delayed eruptions of teeth per child patient. In the maxilla, the delayed eruption of teeth most often occurred among the central incisors, followed by the canines, lateral incisors. The number was extremely low in the lower jaw compared with the upper jaws.
3. The crown-root formative status was apt to lag behind in the delayed side.
4. Abnormal erupting direction and lack of erupting space caused impaction in many cases.
