実験的歯周炎に供した臼歯の歯根吸収に及ぼす矯正力の影響

Effect of orthodontic forces on root resorption in molars submitted to experimental periodontitis.

抄録

今回の実験的研究では、第一大臼歯の歯頸部に綿の結紮具を48時間装着し、51gまたは75gの歯列矯正力と歯周病の誘発を行ったラットの大臼歯における歯根吸収部の発生と大きさについて検討した。結紮器を外した直後、または48時間後に歯列矯正装置を装着した。装置は2本のスチールバンドで構成されていた。口蓋側に力を加えるヘリコイドバネのアームが、バンドに溶接された口蓋チューブを通過していた。中心根のレベルで得られた頬側-口蓋側切片を用いて、歯根吸収領域の歯根破砕細胞の数と割合を組織形態学的に測定した。その結果、歯周炎を誘発したラットの臼歯に矯正力を加えると、歯根吸収領域が増加することが示された。矯正力の大きさは、歯根吸収領域の大きさおよび歯根破折細胞の数に比例した。これらのエンドポイントはいずれも、炎症反応が沈静化した後に力を加えた場合に小さい値を示した。本研究により，矯正治療を受ける歯周病患者において，より軽い力を加え，炎症徴候が落ち着くまで治療を遅らせた方が，歯根吸収領域の発生リスクが低くなることが示された．

The present experimental study addresses the issue of the development and size of root resorption areas in molars of rats submitted to orthodontic forces of 51 or 75 g and the induction of periodontal disease by placing a cotton ligature around the cervix of the first upper molars for 48 hours. Immediately on removal of the ligature or 48 hs later we put an orthodontic device in place. The device comprised two steel bands. The arms of a helicoidal spring that exerted force towards palatine passed through the palatine tubes welded to the bands. The number of odontoclasts and the percentage of root resorption areas were determined histomorphometrically on bucco-palatine sections obtained at the level of the central roots. The data showed an increase in root resorption areas when the orthodontic forces were applied to molars of rats following the induction of periodontitis. The magnitude of the force was proportional to the size of the resorption areas and to the number of odontoclasts. Both these end-points exhibited smaller values when the forces were applied once the inflammatory reaction had subsided. The present study shows that the risk of development of root resorption areas in patients with periodontal disease submitted to orthodontic treatment would be lower if lighter forces were applied and treatment were delayed until the inflammatory signs have subsided.