Cephalometric measurements and their impact on interlabial distance in individuals with and without anterior open bite: A comparative study.

Background: There has been limited research on the relationship between bone, dentoalveolar structures, and lip sealing, with no comparative studies on individuals with anterior open bite (AOB). This research aimed to evaluate the cephalometric measurements that modify interlabial distance in individuals with and without AOB. Material and Methods: This retrospective cross-sectional study included 110 cephalometric radiographs (55 with AOB and 55 matched controls). Eighteen cephalometric variables (9 angular and 9 linear) were measured using Blue Sky Plan 4 software (USA) by one trained and calibrated dentist. Data were analysed using SPSS version 26. Shapiro-Wilk test assessed normality; Student's t-test or Mann-Whitney test were applied accordingly. Multiple linear regression analyses were conducted to identify variables that modify interlabial distance (p<0.05). Results: In the control group, significant influences were identified for several factors: maxillomandibular divergence (B=0.03, p=0.019), upper lip height (B=0.06, p=0.032), upper lip to S-line distance (B=-0.05, p=0.024), and lower lip to S-line distance (B=0.05, p=0.047). In contrast, within the AOB group, only lower facial height had a significant influence (B=0.31, p=0.047). The final multiple linear regression analysis for the whole sample showed that AOB (B=0.703, p=0.009) and lower facial height (B=0.177, p=0.027) significantly affected the interlabial gap. Conclusions: The interlabial gap in individuals with AOB is mainly influenced by vertical facial dimension, while in controls, maxillomandibular divergence and lip-to-S-line distances play a greater role. Moreover, AOB and increased vertical facial dimension are the most influential factors affecting the interlabial gap, highlighting the need to address both during orthodontic diagnosis and treatment planning.