Abstract: BACKGROUND: During orthodontic treatment of impacted canines, the site, angle, and force value of bonded orthodontic attachments have a large impact on the traction effect as well as periodontics, but there are fewer studies related to the appropriate traction site, angle, and magnitude of traction force values.
OBJECTIVE: To analysis the periodontal stress distribution of maxillary impacted canines under different traction forces during orthodontic treatment by the three-dimensional finite element method.
METHODS: Cone-beam CT scan data of a patient diagnosed with a maxillary impacted canine was selected, from which a three-dimensional finite element model including the impacted canine, maxilla, and its supporting structures was created. In the three-mentioned model, traction forces (30, 60, and 90 g) at angles of 60°, 90°, and 120° to the long axis of the tooth were applied to the incisal 1/3, middle 1/3, and cervical 1/3 of the labial surface of the crown. Von Mises stress distribution in the periodontium of the impacted canine was analyzed.
RESULTS AND CONCLUSION: (1) There was similar periodontal stress distribution of the maxillary impacted canine under different working conditions. When the force was applied in the incisal 1/3 of the canine, the Von Mises stress of the periodontium near the cervical part of the model was smaller, and the Von Mises stress of the periodontium near the cervical part of the lingual surface was larger; when the force was applied in the middle 1/3 of the canine, the Von Mises stress of the periodontium near the cervical part of the model was smaller, and the Von Mises stress of the periodontium near the cervical part of the labial surface was larger; and when the force was applied in the cervical 1/3 of the canine, the Von Mises stress of the periodontium near the cervical part of the model was smaller, and the Von Mises stress of the periodontium near the middle part of the labial surface was larger. (2) When the force was applied at the same site and angle, the maximum Von Mises stress of the periodontium tended to increase with the increase of the applied force; when the same amount of force was applied at the same angle, the maximum Von Mises stress of the periodontium at the incisal 1/3, mesial 1/3, and cervical 1/3 sites showed a decreasing trend. When the same amount of force was applied to the incisal 1/3, the maximum and minimum Von Mises stresses of the periodontium tended to decrease with the increase in the angle of the force. When the same amount of force was applied to the cervical 1/3, the maximum Von Mises stresses of the periodontium tended to increase with the increase in the angle of the force. To conclude, traction of the maxillary impacted canine should try to bond the brackets as close as possible to the cervical region. The direction of traction is associated with the site of traction. The traction force of the maxillary impacted canine is generally between 30-60 g.

中国组织工程研究杂志出版内容重点：组织构建；骨细胞；软骨细胞；细胞培养；成纤维细胞；血管内皮细胞；骨质疏松；组织工程

Key words: orthodontic treatment, maxillary impacted canine, three-dimensional finite element, periodontal stress, impacted tooth