Depth of Curve of Spee in Relation to Craniofacial and Dental Morphology.

Objectives: To quantify the depth of the Curve of Spee (CoS) in untreated orthodontic patients, evaluate its variations across Angle classifications, and identify its skeletal and dental morphological correlates. Materials and Methods: This retrospective study analyzed digital intraoral scans and lateral cephalograms of 240 untreated orthodontic patients (age range: 13-17 years). Subjects were categorized into four groups: Angle Class I, Class II/1, Class II/2, and Class III. CoS depth was measured using OrthoCAD, while skeletal and dental variables were assessed via AX.Ceph software. Statistical significance was determined using one-way ANOVA with Tukey's post-hoc tests, Pearson's correlation coefficients, and multiple linear regression analysis to identify primary predictors of CoS depth. Results: The mean CoS depth was 2.18 mm. Significant intergroup differences were observed, with the greatest depth recorded in Class II/2 (2.49 mm) and the shallowest in Class III (1.82 mm). CoS depth demonstrated significant positive correlations with overbite, overjet, ANB angle and Wits appraisal. Conversely, an inverse relationship was found with vertical skeletal parameters. A multivariate regression analysis identified overbite and sagittal skeletal indicators as the most relevant predictors of CoS depth. Conclusion: The depth of the CoS is critically influenced by sagittal skeletal discrepancies and incisal relationship (overbite), with vertical craniofacial morphology playing a secondary role. These findings highlight its relevance in orthodontic diagnosis and treatment planning. And the need for the individualized mechanics for CoS leveling based on the patient's specific skeletal and dental phenotype.