External root resorption in root-filled and vital teeth after extraction and non-extraction orthodontic treatments: a split-mouth retrospective study.

Objective: This study aimed to compare the amounts of external root resorption (ERR) during different modalities of orthodontic treatment (OT) in root-filled teeth (RFT) and their contralateral teeth with vital pulp (VPT) in the same patient.
Material and Methods: The study sample consisted of 69 patients in two groups: 35 patients in the non-extraction group (18 female, 17 male; 18.16 ± 3.79 years), and 34 patients in the extraction group (19 female, 15 male; 17.72 ± 2.78 years). Digital panoramic radiographs of each patient taken before and after OT were used to measure the tooth length and root surface area. The amounts of ERR in RFT and contralateral VPT were evaluated pre- and post-OT in mandibular molars. The data were statistically analyzed with the paired t -test, independent t -test, and analysis of covariance (ANCOVA) ( p  < .05).
Results: A statistically significant difference was observed in both the orthodontic treatment groups when RFT and VPT were compared in terms of ERR ( p  < .05). A significant difference was observed between RFT and VPT in extraction treatments when the reduction in the root area between the two sides in the groups was compared ( p  < .05).
Conclusions: RFT are more resistant to ERR than VPT. The ERR in RFT may not be a significant matter for the planning of OT.