Effects of root-cortex relationship, root shape, and impaction side on treatment duration and root resorption of impacted canines.

OBJECTIVES: This retrospective longitudinal study aimed to evaluate the factors that affect the orthodontic treatment duration (OTD) and external apical root resorption (EARR) of maxillary impacted canines (MIC) as root-cortex relationship, root shape, impaction side, and gender. MATERIAL AND METHOD: Thirty-eight patients (mean age 15.28 ± 1.48 years) who had unilateral MIC and undergone orthodontic treatment were included in this study. Root-cortex relationship, root-cortex intersection amount, root shape, impaction side, height, alpha angle, impaction zone, and length of the MIC were evaluated on cone-beam computed tomography images at the beginning of the treatment. Final assessments were performed on ortopantograms at the end of the treatment as canine angulation and tooth length. The sample was characterized by descriptive statistics; t-tests, Mann-Whitney U-test, ANOVA, and Kruskal-Wallis tests were used for the comparison of EARR and OTD values between the categorical groups. RESULTS: Root shape affected OTD, and the longest value was detected in MIC with bent root (P < 0.000). The presence of root-cortex relationship also prolonged OTD for approximately 3 months (P = 0.006). MIC with risk factors like positive root-cortex relationship and bent roots had higher EARR values than those with negative root-cortex relationship and normal roots (P = 0.042, P = 0.021, respectively). EARR of the palatal MIC was also higher than the buccal MIC (P = 0.009). OTD was significantly influenced by root-cortex intersection amount (P = 0.004). CONCLUSION: The presence of root-cortex relationship and abnormal root shape were risk factors for greater EARR of MIC along OTD, which was also significantly influenced by root shape and root-cortex relationship.