Lip Position Differences Across Skeletal ClassesUsing Steiner’s and Ricketts’line : A CephalometricStudy

Objective: To compare sagittal upper and lower lip positions across skeletal Classes I, II, and III using Steiner’s( S) Line and Ricketts’ (E) Line , and to determine whether these two reference lines can reliably differentiate sagittal soft-tissue variations.Methods: A retrospective analysis was conducted on 120 normodivergent Yemeni adults (18–35 years) with equal distribution across skeletal Classes I, II, and III (n=40 each). Skeletal classification was determined by ANB angle and confirmed by Wits appraisal. The perpendicular distances from the upper and lower lip landmarks to Steiner’s (S) Line and Ricketts’ (E) Line were measured and compared across the skeletal classes using EzDenti cephalometric software. Statistical analysis included descriptive statistics, independent t-tests, ANOVA, Tukey post-hoc tests, and Pearson correlations (p < 0.05).Results: Class II subjects showed the most anterior lip positions relative to both S and E Lines, while Class III subjects demonstrated marked retrusion. Class I individuals exhibited mild protrusion to S Line but moderate retrusion to E Line, representing a balanced soft-tissue profile. ANOVA revealed significant interclass differences for all S and E Line measurements (p < 0.01). Gender had no significant influence except for mild E Line variation in Class I (p < 0.05). Correlation analysis showed positive association between ANB and lip protrusion on S Line, and negative association on E Line.Conclusion: Significant differences in lip position were found among the skeletal classes when assessed using Steiner’s (S) Line and Ricketts’ (E) Line. Both reference lines demonstrated significant differences in sagittal lip position among skeletal classes and may serve as complementary reference lines for soft-tissue assessment during orthodontic diagnosis. The differences observed between the Yemeni population and the widely used Caucasian norms highlight the importance of using population-specific cephalometric reference values to support individualized orthodontic diagnosis and treatment planning.