Three-dimensional volumetric evaluation of root resorption in maxillary anteriors following en-masse retraction with varying force vectors - a randomized control trial.

Background: Root resorption in orthodontics is associated with direction and magnitude of force application as primary etiological factors. Well-controlled trials that utilize three-dimensional segmentation to detect volumetric changes in tooth structure are required to assess the quantitative nature of root resorption.

Objective: To assess the severity of root resorption (RR) during retraction of maxillary anteriors with three different force vectors (with and without skeletal anchorage) via cone-beam computed tomography (CBCT) superimpositions.

Trial Design: Three-arm parallel randomized clinical trial (RCT).

Materials And Methods: Forty-two (16 males, 26 females) patients, (17-28 years), in permanent dentition with bimaxillary protrusion were randomly allocated to three groups of 14 patients each using block randomization (1:1:1 ratio) and allocation concealment. En-masse anterior retraction post first premolar extractions was carried out with modified force vectors in the three groups based on anchorage type [Molar, Mini-implant and Infrazygomatic crest (IZC) bone screws]. Volumetric root loss and linear dimensional changes were blindly assessed on initial (T0) and final (T1, end of space closure) CBCT scans. Normality distribution of values was done using Shapiro-Wilk's test. ANOVA and Post-hoc Tukey HSD test were done to compare measurements between groups at significance levels (P < .05).

Results: Forty patients were analysed (14, 14, and 12 in three groups). Significant volumetric loss was noted in all groups. Central incisors demonstrated a significant reduction in IZC group (81.5 ± 21.1 mm ) compared to conventional (50.1 ± 26.5 mm ) and mini-implant groups (76.1 ± 27.6 mm ). Canines demonstrated a significant reduction in mini-implant group (108.9 ± 33.9 mm ) compared to conventional (68.8 ± 42.5 mm ) and IZC groups (103.1 ± 29.1 mm ). Regarding linear parameters, central incisors and canines revealed significant root length reduction in both skeletal anchorage groups. Lateral incisors showed no significant changes between groups.

Conclusions: Intrusive force vectors generated during skeletally anchored retraction can predispose anteriors to an increased risk of resorption. Greater loss of root volume was noted in the centrals and canines when retracted with skeletal anchorage.

Limitations: Small sample size and variations during CBCT acquisition.

Harms: Low-dose CBCT scans were taken at T0 and T1 treatment intervals.