Frontal assessment of lip dimensions in individuals with different sagittal malocclusions and different lower face heights in the anteroposterior plane

Objective: The aim of this thesis is to comprehensively evaluate the distinct and shared effects of gender and skeletal malocclusions on lip morphology. Materials and Methods: This observational and cross-sectional study was conducted on 167 individuals aged between 18 and 30 years. Frontal photographs taken in the natural head position and at rest lip posture as well as data obtained from lateral cephalometric radiographs, were collected from participants who met the inclusion criteria.The sample was classified according to the anteroposterior direction using the ANB angle and according to the vertical dimension using the Lower Facial Height (LFH) (ANS–Xi–Pm) parameter. Results: Higher lip morphology values were observed in males. In the anteroposterior plane, most parameters were greater in Class III individuals. In the vertical plane, most linear lip measures were lower in individuals with decreased (AYY) than in the other groups. The interaction between anteroposterior and vertical dimensions was significant for lower and upper vermilion height, philtrum length, cutaneous lower lip and upper lip height, and for three ratios. Among individuals with increased LFH, upper lip height was highest in Class III, whereas upper vermilion height was greatest in Class I. In the normal LFH group, Class II showed lower values for cutaneous lower lip measurements and related ratios. Correlation analyses revealed that ANB was negatively correlated with lip and vermilion heights, but positively correlated with philtrum length and certain ratios. The LFH angle showed a positive correlation with linear lip measurements and a negative correlation with some ratios. Conclusion: The evaluation of lip dimensions became more informative when the combined effects of skeletal parameters in the anteroposterior and vertical directions were considered. In clinical assessment and treatment planning, simultaneous consideration of these two axes is essential for accurately managing individual morphological differences.