Investigation of effects of hybrid hyrax-mentoplate treatment in high-angle class III patients: A three-dimensional, retrospective study

Objective: This retrospective study evaluated three-dimensional effects of hybrid hyrax-mentoplate (HH-M) orthopaedic treat-ment in high-angle Class III individuals using Cone Beam Computed Tomography (CBCT) images.Materials and Methods: Pre-treatment (T0) and post-treatment (T1) CBCTs of 17 fully compliant high-angle Class III patients(7 males, 10 females, age: 11.7 ± 1.32 years, treatment duration: 12.62 ± 1.7 months) treated with HH-M were analysed. T0 andT1 CBCTs were superimposed from the cranial base using artificial intelligence-based AMASSS module of the 3D Slicer version5.8.1 software (www.slicer.org). Linear and angular changes were analysed in the sagittal, vertical and transverse planes, along-side three-dimensional landmark displacements and volumetric airway measurements. Significance level was set at p < 0.05.Results: Significant increases occurred in SNA, ANB and Occlusal Plane (OP) to Mandibular Plane (MP) angle (p < 0.001,p < 0.001, p = 0.001, respectively), while Sella-Nasion to OP and Palatal Plane (PP) to OP decreased (p = 0.008, p = 0.008, re-spectively). Vertical linear measurements remained stable (p > 0.05). All transverse linear measurements increased (p < 0.05).Upper Molar (UM) to PP, Upper Incisor to PP, Lower Incisor to MP and overjet have significantly increased (p < 0.001, p = 0.018,p = 0.048, p < 0.001, respectively). Overbite remained unchanged (p > 0.05). Nasopharynx (p = 0.008) and Middle Pharynx(p = 0.003) volumes significantly increased.Conclusion: Despite the significant alterations observed in OP and UM-PP, this technique effectively managed to maintain over-all vertical skeletal dimensions without inducing a significant change in other facial height parameters and enhanced the airwayvolume. Significant expansion occurred across maxillary, nasal and zygomatic levels. HH-M represents an effective orthopaedictreatment approach for high-angle Class III patients.