关键词: 切牙, 阻生, 埋伏牙, 锥形束CT, 原位旋转术

Abstract: Objective    To construct a simulated in situ rotation model for the treatment of impacted anterior teeth in Beagle dogs and investigate the effects of in situ rotation on the dental body and periodontal supporting tissues in Beagle dogs. Methods    The study was conducted at the National Key Laboratory of Oral and Maxillofacial Reconstruction and Regeneration from January 2022 to October 2023. Twelve male Beagle dogs were randomly divided into the 1-month group，3-month group，and 6-month group based on the observation time after in situ rotation surgery（1，3，and 6 months postoperatively），with 4 dogs in each group. In one side of the oral cavity，in situ rotation surgery was performed on the corresponding incisor（6 teeth，study side），while on the contralateral side，a window was created without rotation（6 teeth，control side）. The probing pocket depth（PPD）was compared at 1，2，and 3 weeks and 1，3，and 6 months after tooth eruption in the 6-month group. Cone beam CT（CBCT）was used to measure and compare the root length，lingual alveolar bone thickness，labial alveolar bone thickness，and labial alveolar bone loss height on both sides in each group. Micro-computed tomography（MicroCT）was used to measure and compare the bone volume fraction（BV/TV），bone surface area to bone volume ratio（BS/BV），trabecular thickness（Tb.Th），trabecular separation（Tb.Sp），trabecular number（Tb.N），and periodontal membrane thickness on both sides in each group. The tooth strength（fracture load） was compared between the two sides in each group. HE and Masson staining were used to analyze the changes in dental body and periodontal tissues on both sides and calculate the collagen volume fraction（CVF）. Results    There was no significant difference in PPD measurements at different time points after tooth eruption between the study side and the control side in the 6-month group（all P > 0.05）. CBCT measurements showed no significant differences in root length，lingual alveolar bone thickness，labial alveolar bone thickness，or labial alveolar bone loss height between the study side and the control side in each time group（all P > 0.05）. MicroCT measurements showed that the BV/TV and BS/BV in the study side of the 1-month group were lower than those in the control side，and the differences were statistically significant（t values were 8.237 and 2.979，respectively，both P < 0.05）. There were on statistical differences in Tb.N，Tb.Th，Tb.Sp or periodontal membrane thickness between the two sides （all P > 0.05）. There were no significant differences in MicroCT measurements between the study side and the control side in the 3-month group and 6-month group（all P > 0.05）. There were no significant differences in fracture load in any time points between the two sides in each time group（all P > 0.05）. HE and Masson staining showed that there were more vascular differentiations in the pulp cavity near the root and thinner or partially disappeared periodontal ligament on the study side compared to the control side in the 1-month group，and the CVF on the study side was lower than that on the control side，the differences being statistically significant（t = 19.680，P < 0.001）. There were no significant differences between the study side and the control side in the 3-month group and 6-month group. Conclusion    In situ rotation surgery is effective in the treatment of impacted anterior teeth in Beagle dogs，and long-term observation results show that it does not have adverse effects on the dental body and periodontal tissues.

Key words: incisors, impacted, impacted tooth, cone beam CT, in situ rotation surgery