| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2005: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2004: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 2003: ¥2,900,000 (Direct Cost: ¥2,900,000)
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| Research Abstract |
In order to elucidate the effect of osseous ankylosis of immature permanent teeth on tooth eruption, we conducted a replantation experiment on the right upper first and second incisors of 10 juvenile dogs. The experimental teeth were removed, and after detaching the periodontal ligament from the entire circumference, they were immersed in 2% acidulated phosphate sodium fluoride solution for 20 min. After removing the pulp, ankylosis was experimentally induced in the immature teeth by applying calcium hydroxide to the root canal and replanting the teeth, and the teeth were compared with the healthy opposite side.
The clinical evaluation revealed infraversion and attrition of the experimental teeth, and they were more marked in the second incisor, whose root is immature, than in the first incisor. It was possible to rate the bony ankylosis on standardized X-ray films beginning 6 weeks after replantation. From 6 weeks after replantation onward the mobility of the experimental teeth was les
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s than that of the control teeth, and a metallic sound was confirmed by percussion.
We confirmed the development of osseous ankylosis in all of the experimental teeth by histopathological evaluation, and the coursing of the periodontal ligament collagen fibers seen on the opposite side was absent. The osseous ankylosis was confirmed to consist of a type in which the root dentin is resorbed and which rapidly progresses, and a type in which ankylosis is observed but is not accompanied by rapid root resorption. The alveolar crest was lower in the experimental teeth than in the control teeth, and the alveolar bone in the vicinity of the necks of the experimental teeth on the labial side was more concave than on the control side. The septum interalveolare widened as a result of progression of the ankylosis, and the central trabecula had rarified. On the experimental side the fluorescence extraction region, which indicates bone formation, was wider than on the control side, and relative fluorescence intensity was higher. This change was more marked in the first 3 weeks after replantation, and the relative fluorescence intensity values were higher on the tooth neck side, but at 12 weeks after replantation a tendency to approach the control side was observed. The median palatine suture was interposed, and bony ankylosis of the experimental teeth seldom affected the opposite side.
The above findings suggested that osseous ankylosis that occurs in the developmental period inhibits tooth eruption because of the lack of a periodontal ligament and that it inhibits development of the jaw in the labial and vertical direction. Less
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