A prospective randomized controlled trial published in Clinical Oral Investigations included 60 male and female patients with a mean age of 19.87 ± 4.01 years who required bilateral maxillary first premolar extractions and maximum anchorage. Participants were randomly allocated to en-masse retraction (210 g/side) or two-step retraction (70 g canine retraction followed by 140 g incisor retraction). Cone-beam computed tomography scans were obtained before (T1) and after (T2) space closure.

Three-dimensional root models were reconstructed using Mimics software, and linear root length and volumetric changes were compared using the Mann–Whitney U test. Both groups showed statistically significant reductions (P<0.001) in root length (two-step: −0.56 ± 0.09 mm; en-masse: −0.57 ± 0.11 mm) and root volume (two-step: −8.88 ± 3.24 mm³; en-masse: −10.12 ± 4.49 mm³). No statistically significant…