Assessment of External Apical Root Resorption Following Fixed Orthodontic Treatment in Adolescents: A Retrospective Radiographic Study

Abstract

Background: External apical root resorption (EARR) is a recognized adverse effect of orthodontic tooth movement, with its severity potentially influenced by patient- and treatment-related factors. This study evaluated factors associated with the extent of EARR following fixed orthodontic treatment. Materials and Methods:  A clinical observational study was conducted among patients who underwent fixed orthodontic treatment. EARR was assessed and compared according to sex, extraction status, treatment duration, incisor intrusion, and malocclusion type. Correlation analysis was performed to evaluate associations between EARR and age, treatment duration, and apical displacement. Multivariable logistic regression was used to identify independent predictors of clinically significant EARR. Results: Female patients had a mean EARR of 0.84 ± 0.63 mm compared with 0.79 ± 0.61 mm in males probability (p=0.651). Mean EARR was significantly greater among patients treated with extractions than among those treated without extractions (1.02 ± 0.68 vs. 0.64 ± 0.52 mm; p=0.004). Patients treated for >24 months also demonstrated higher EARR than those treated for ≤24 months (1.12 ± 0.72 vs. 0.68 ± 0.53 mm; p=0.002). Incisor intrusion was associated with greater EARR (1.08 ± 0.70 vs. 0.70 ± 0.53 mm; p=0.001). EARR differed significantly across malocclusion groups (p=0.006), with the highest mean observed in Class II malocclusion (0.98 ± 0.67 mm). Apical displacement (r=0.48, p<0.001) and treatment duration (r=0.36, p<0.001) showed significant positive correlations with EARR, whereas age did not (r=0.12, p=0.191). In multivariable analysis, extraction treatment (adjusted odds ratio OR=2.31, p=0.047), treatment duration >24 months (adjusted OR=2.87, p=0.019), incisor intrusion (adjusted OR=2.64, p=0.032), and apical displacement (adjusted OR=1.76 per 1-mm increase, p=0.003) were independently associated with clinically significant EARR. Conclusion: EARR was significantly associated with extraction treatment, prolonged orthodontic treatment, incisor intrusion, and greater apical displacement. These findings support careful treatment planning and radiographic monitoring in patients undergoing fixed orthodontic treatment.