Alveolar bone and maxillary canine root changes after micro-osteoperforation-assisted retraction: a secondary analysis of a split-mouth randomized controlled trial

Micro-osteoperforations (MOPs) may increase bone remodeling during orthodontic tooth movement, but their effects on the maxillary canine root and alveolar bone remain unclear. This study compared CBCT changes between MOP-assisted and conventional canine retraction. This was a secondary analysis of prespecified CBCT safety outcomes from a single-centre, assessor-blinded, split-mouth randomized controlled trial. Forty participants aged 16–25 years with Angle Class I malocclusion requiring bilateral maxillary first-premolar extraction received three MOPs on one allocated side; the contralateral side served as control. Both canines were retracted with miniscrew anchorage and 150-g nickel–titanium closed-coil springs. CBCT measurements at week 4 (T1) and week 16 (T4) included root length, buccal and palatal cementoenamel-junction-to-alveolar-crest distances, canine long-axis angle to the palatal plane, and cross-sectional alveolar bone area at the cervical, middle, and apical thirds. Paired t tests or Wilcoxon signed-rank tests were used as appropriate. The parent trial was powered for canine-retraction rate, not for these CBCT outcomes. All 40 participants completed follow-up. Root shortening was greater on the MOP side than on the control side (paired difference − 0.18 mm, 95% CI − 0.24 to − 0.12; P < 0.001). Buccal and palatal CEJ-to-crest increases were also greater on the MOP side (0.23 mm, 95% CI 0.19 to 0.27; and 0.22 mm, 95% CI 0.18 to 0.26; both P < 0.001). The canine-to-palatal-plane angle decreased by an additional 3.06° on the MOP side (95% CI − 3.52 to − 2.60; P < 0.001). Cross-sectional bone area increased buccally and decreased palatally on both sides; however, no statistically significant between-side difference in the T1-to-T4 change was detected at any measured level ( P = 0.116–0.989). MOP-assisted retraction produced small additional changes in root length and vertical alveolar-crest level, together with greater canine tipping. No statistically significant between-side differences were detected in T1-to-T4 changes in cross-sectional alveolar bone area. Because these were multiple secondary outcomes and the trial was not powered for CBCT differences, the findings should be considered exploratory. ClinicalTrials.gov NCT07155018 (retrospectively registered first submitted on 27 August 2025 first posted on 4 September 2025).