Comparative evaluation of apical root resorption in adult patients treated with clear aligners and fixed orthodontic appliances using CBCT

BACKGROUND: Orthodontically induced external apical root resorption is a common iatrogenic effect of tooth movement. With the increasing use of clear aligner therapy, it is important to evaluate whether its biomechanics reduce root resorption compared with fixed orthodontic appliances. AIM: To compare apical root resorption in patients treated with clear aligners and fixed appliances using cone-beam computed tomography (CBCT). METHODOLOGY: A retrospective comparative CBCT-based analysis was conducted on 120 orthodontic patients. Root volumes and lengths were measured from the cementoenamel junction to the apex using pre- and post-treatment CBCT scans. Apical root resorption was quantified as percentage volume loss and absolute root length reduction. Primary analyses employed linear mixed-effects models adjusted for clustering of teeth within patients and for tooth type, arch, extraction status, and treatment duration. RESULTS: Clear aligner therapy was associated with significantly lower apical root resorption than fixed appliances. Mean percentage root volume loss was lower in the aligner group (6.1 ± 4.8%) than in the fixed appliance group (8.4 ± 6.1%) (p = 0.004). Mean root length reduction was also smaller with aligners (p = 0.001). Clinically significant root resorption occurred less frequently in the aligner group (p = 0.048). Longer treatment duration increased resorption risk. CONCLUSION: Clear aligner therapy is associated with less apical root resorption than fixed orthodontic treatment, while treatment duration remains an independent risk factor.