Radiographic assessment and orthodontic intervention effects on orthodontically induced root resorption: a systematic review and meta-analysis of clinical trials.
The relative contribution of radiographic methods and characteristics of the orthodontic intervention to orthodontically induced root resorption (OIRR) remains unknown. The aims of this systematic review and meta-analysis were to (1) estimate the pooled OIRR effect across orthodontic intervention versus comparator contrasts, (2) compare pooled estimates by radiographic method (2D [two-dimensional] vs. 3D/CBCT [three-dimensional/cone-beam computed tomography]), and (3) explore whether force mechanics (intrusive versus nonintrusive) modified OIRR magnitude. Seven randomized controlled trials and one prospective study (January 2010-October 2025) were included. Only OIRR was the outcome, reported as correlation coefficients (r). The primary analysis combined within-study intervention-versus-comparator estimates. Subgroup analysis of 2D versus 3D/CBCT imaging was prespecified, whereas post-hoc analysis of intrusive versus nonintrusive mechanics was performed. The pooled analysis for the primary outcome showed a small, nonsignificant OIRR effect (r = 0.07; 95% confidence interval [CI]: -0.12 to 0.27; p = 0.372) with high heterogeneity (I2 = 84.0%). Radiographic method did not change the pooled estimates significantly (p = 0.331). Force-mechanics analysis showed that intrusive mechanics was related to significantly higher root resorption than nonintrusive mechanics (r = 0.40; 95% CI = 0.15 to 0.65 versus r = -0.03; 95% CI = -0.16 to 0.10; p < 0.001). This accounted for 87.1% of the between-study variance. The average orthodontic intervention effect on OIRR was small and not significant; however, the OIRR magnitude was strongly affected by force mechanics, particularly by intrusive forces. There was no significant difference in pooled estimates by radiographic method; however, 3D/CBCT provides superior volumetric quantification and should be used judiciously according ALARA (as low as reasonably achievable) principles.