Correlation between the atlas morphology and the maxillo-mandibular divergence pattern

Objective: To evaluate the correlation between atlas morphology and maxillo-mandibular divergence. Study Design: Cross-sectional, analytic study. Place and Duration of Study:Dental Clinics, The Aga Khan University Hospital, Karachi, Pakistan from February to August 2017. Methodology: Pretreatment lateral cephalograms of 208 subjects, aged 18 to 25 years, were evaluated. The atlas parameters were categorized into atlas dorsum, anteroposterior and ventrum, and measured on View Pro-X software. Various maxillary (FPPP, SNPP and FHPP angles) and mandibular (SNGoGn, saddle, articulare, gonial, sum of posterior and Y-axis angles) parameters were used to evaluate the divergence pattern of the individuals. Mann-Whitney U-test was used to compare atlas and maxillo-mandibular parameters between genders. Spearman correlation was used to correlate atlas and maxillo-mandibular parameters across genders. A p-value ≤ 0.05 was considered as statistically significant. Results: Statistically significant differences were found between various atlas and maxillo-mandibular parameters between genders. With atlas dorsum, the saddle angle (r = -0.3) in males; whereas gonial (r = -0.2), Y-axis (r = 0.1) and SNPP (r = -0.2) angles in females showed significant weak correlation. With atlas anteroposterior, saddle (r = -0.2), articulare (r = 0.2), SNPP (r = -0.2) and FHPP (r = -0.3) angles in males showed significant weak correlation. However, only the SNPP angle (r = -0.2) in females showed a significant weak correlation with atlas ventrum. Conclusion: A weak correlation was found between atlas parameters and various maxillo-mandibular angular parameters in both genders. Therefore, atlas morphology cannot be regarded as a good predictor of future maxillo-mandibular divergence pattern.