Fractal Analysis-Based Comparison of Mandibular Bone Remodeling in Clear Aligner and Fixed Orthodontic Therapies

Background: To quantitatively compare treatment-related changes in mandibular trabecular bone between patients undergoing clear aligner therapy (CAT) and fixed orthodontic treatment (FOT) by means of fractal dimension analysis of panoramic radiographs. Methods: This retrospective investigation evaluated 76 patients who underwent orthodontic treatment with either clear aligner therapy (CAT; n = 34) or fixed orthodontic treatment (FOT; n = 42). Fractal dimension analysis was performed on panoramic radiographs obtained before treatment (T0) and after treatment completion (T1). Fractal dimension (FD) values were calculated for the mandibular molar, angulus, and condylar regions using ImageJ software based on the box-counting algorithm. Changes in FD were compared within and between groups using appropriate statistical tests, with statistical significance established at p < 0.05. Results: No statistically significant differences were observed between CAT and FOT groups regarding FD changes in the mandibular molar and angulus regions at T0 or T1 (p > 0.05). Within-group comparisons also revealed no significant FD changes in these regions following treatment in either group. In the condylar region, although FD values demonstrated a tendency toward change after treatment, intra-group differences were not statistically significant (p > 0.05). However, inter-group comparison revealed a statistically significant difference between CAT and FOT groups in condylar FD values (p ≤ 0.05), without evidence of destructive bone remodeling. Conclusions: CAT and FOT induce comparable adaptive responses in mandibular trabecular bone structure. FA findings suggest that both treatment modalities induce comparable adaptive remodeling patterns in mandibular trabecular bone without radiographic evidence of destructive bone changes, supporting the view that CAT could be considered a comparable alternative to FOT with respect to mandibular trabecular bone remodeling when appropriate patient selection and controlled force application are ensured.