Abstract
The purpose of this study was to assest periodontitis at an early stage in children who are growing and developing, by understanding well the change of normal alveolar bone.
We used radiographs of 40 patients who had normal periodontal tissue shown by clinical examination and taking caries treatment and prevention every year. We observed the height of the interproximal alveolar bone crest, the form of the interalveolar septum and the prosperity and decline of lamina dura of molars in the mandibulla. The height of the interproximal alveolar bone crest of the deciduous molars changed little except for the medial of the first parmanent molar. We obtained the change of the height according to the replacement of the teeth. In the distal of the deciduous first molar (the first premolar), and the mesial and distal of the deciduous second molar (the second premolar), the height of alveolar crest decreased according to the replacement of the tooth. Until 1-2 years after the complete eruption of the second premolar, the height increased, and after that, it became stable.
In the mesial of the first molar, the height of the alveolar crest became higher year after year, but it is not little effected by the replacement of a tooth. The change of height continues for 5 years after complete eruption of the second premolar. We classified the following 5 types according to the pattern of the form of the interalveolar septum, the Flat type, the Gentle slope type, the Steep slope type, the Cup shape type, and the Roof type.
The deciduous dentition had almost all Flat type and Gentle slope types. Corresponding to the replacement of a tooth, the pattern of form became various. Finally, in all cases, the form of the interalveolar septum became the flat type.
Lamina dura was not clear until 5 years of age. After 5 years of age, it became clear gradually. Corresponding to the replacement of a tooth, the lamina dura became indistinct again, but after 3-5 years, after the complete eruption of second premolar, it became clear again.
