Influence of Vertical Facial Patterns on Dental Arch Parameters in Class III Malocclusions: A Cross-Sectional Study

Objective: To evaluate how vertical-patterns influence dental arch dimensions in class I (CI) and class III (CIII) malocclusions. Methods: Pretreatment patient files, lateral cephalometric parameters, and initial intraoral digital models of adult patients were retrieved from the archive in an academic setting. Skeletal and dental CI and CIII individuals were divided into three subgroups (n=20 for each group) according to frankfort-mandibular plane angle (FMA) values (angle between Frankfurt horizontal and mandibular planes): FMA <22° for low-angle (L), FMA=22-28° for normal-angle (N), and FMA >28° for high-angle (H) vertical patterns. Dental arch parameters were measured on digital models using 3D Slicer software (version 5.6.1; www.slicer.org). One-way analysis of variance, Kruskal-Wallis test, and Spearman correlation analysis were performed. The significance level was set at p<0.05. Results: A significant difference in maxillary intermolar width was found between CI-H and CIII-L groups (p=0.004). A significant difference in the maxillary intermolar angle was found between the CIII-N and CI-N groups and between the CIII-N and CI-L groups (p=0.003). A significant difference in intermolar mandibular width was observed between the CI-H and CI-L groups (p=0.002). Occlusal angle differed significantly between the CI-N and CIII-H groups and between the CI-N and CIII-L groups (p=0.002). No differences were observed in intercanine width, arch length, or arch depth. Conclusion: CIII-L group has a significantly greater intermolar width for both maxillary and mandibular arches. The clinical implications of this result can be particularly important when selecting prefabricated archwires. Therefore, it is recommended that this difference be taken into consideration in diagnosis and treatment planning to achieve effective and stable outcomes.