Background: Labially impacted maxillary canines may lack periodontal tissue after orthodontic traction. This study evaluated the periodontal status of labially impacted maxillary canines after the closed eruption technique followed by orthodontic traction and investigated pretreatment variables affecting periodontal changes. Methods: Patients with one labially impacted maxillary canine (impaction group) and one contralateral normal canine (control group) were selected retrospectively. Maxillary canine pretreatment variables (angle, depth, sector, and Nolla stage) were determined from initial panoramic radiography. Periodontal outcomes including sulcus probing depth, bone probing depth, keratinized gingiva width (KGW), attached gingiva width (AGW), clinical crown length (CCL), cemento-enamel junction to alveolar crest (CEJ-AC) distance, root length, and bone support were measured from radiographic and clinical examinations after treatment and compared between the two groups. Pretreatment variables affecting the periodontal outcomes were determined using linear regression analyses. Results: Fifty-four patients (21 males and 33 females; mean age, 12.85 years) were enrolled. The KGW, AGW, and root length were shorter; the CCL and CEJ-AC distance were longer; and the bone support on the interproximal sides was less in the impaction group than in the control group (P < 0.05). The root length was shorter with higher Nolla stages and the distal alveolar crest was lower with deep and mesially angulated impaction (P < 0.01). Conclusions: After the closed eruption technique, impacted canines exhibited slight but clinically insignificant periodontal recession compared with the contralateral normal tooth. The root developmental stage and pretreatment depth and angle may influence periodontal recession.
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