교정용 미니스크류 제거후 치조골의 치유 양상

Abstract

Temporary anchorage devices (TADs) such as miniscrews are frequently used for contemporary orthodontic treatment. However, visible scarring is noted at the removal sites and the bone healing process after the removal of TADs is still unknown. Therefore, the purpose of the study is to evaluate the course of alveolar bone healing after the removal of orthodontic miniscrews.

Total of 40 orthodontic miniscrews (1.4mm in diameter) were inserted in the interdental bone of both maxilla and the mandible in two beagle dogs. The miniscrews were serially removed with the systemic injection of calcein, tetracycline, xylonol orange, arlizarin red to evaluate the removal site after the healing period of 3,5,7,10 and 13weeks. Micro CTs were taken and bone volume(BV)/tissue volume(TV) of the miniscrew removal sites were measured and compared to the neighboring interdental bone(control) followed by histologic evaluation using undecalcified histological sections.

The removal of the miniscrew resulted in a distinct radiolucent region in the shape of the removed miniscrew in the alveolar bone with a discontinuous cortical coverage. However, the removal site morphologically became similar to the adjacent alveolar bone after 7weeks. BV/TV of the removal sites was significantly reduced compared to the control interdental bone up to 5weeks(p<0.05). However, BV/TV increased and reached similar levels with the adjacent bone after 7weeks. Histologically, active mineral apposition was noted at the removal site from 2 weeks after removal. However, the removal site was filled with woven bone, which was distinguished from the adjacent lamellar bone even after 7 weeks of healing.

Many clinicians expect complete healing after the removal of TADs. However, the removal of TADs leaves a transit full thickness defect penetrating the oral cavity, soft tissue and the underlying alveolar bone. Fortunately, BV/TV reached similar levels to the adjacent bone after the period of 7 weeks indicating natural healing of the alveolar bone. However, the quality of the bone per se was distinct from the adjacent bone even after 7 weeks, suggesting the need for long term monitoring of healing after the removal of TAD in the clinical setting.