Dentoskeletal Effects and Mandibular Trabecular Bone Changes Following Clear Aligner Mandibular Advancement and Twin Block Therapy: A Fractal Dimension and Lacunarity Analysis

Background/Objectives: Clear aligner mandibular advancement (MA) is an aesthetic alternative to conventional functional appliances in growing patients with skeletal Class II malocclusion. This study compared dentoskeletal changes and mandibular trabecular bone texture after clear aligner MA and Twin Block therapy using fractal dimension (FD) and lacunarity analyses. Methods: This retrospective study included 54 growing patients divided into Twin Block, MA, and untreated control groups (n = 18 each). Pretreatment and posttreatment panoramic radiographs were evaluated in all groups; lateral cephalometric radiographs were available only for treated patients. Standard cephalometric and Pancherz sagittal analyses assessed dentoskeletal changes. FD was calculated using box counting, and lacunarity was assessed in standardized mandibular regions. Exploratory regional comparisons were adjusted using the Benjamini–Hochberg false discovery rate (FDR) procedure. Results: Both treatment groups showed significant increases in sella–nasion–point B (SNB) and decreases in point A–nasion–point B (ANB), overjet, and overbite (p < 0.05). Pancherz analysis identified significant intergroup differences in molar relationship, condylar head position, and maxillary molar movement, but not mandibular base position, mandibular length, overjet, or incisor-related changes. Baseline molar relationship also differed between treatment groups (p = 0.046), warranting caution when interpreting molar correction. In unadjusted analyses, right mandibular corpus FD (p = 0.043) and right condylar lacunarity (p = 0.029) increased in the Twin Block group; neither remained significant after FDR correction. No significant intergroup differences were observed in FD or lacunarity changes. Conclusions: Both therapies improved sagittal relationships, but neither produced consistent treatment-specific changes in mandibular trabecular complexity or spatial heterogeneity during the approximately one-year observation period. Isolated regional findings were not robust after multiple-comparison correction.