Effect of premolar extraction on lip strain, lip length, and lip fall in normal and short lip length patients

Aim: To study and quantify the effect of premolar extractions on the lip strain, lip length, and lip fall in normal and short lip length patients. Materials and Methods: This retrospective study included patients aged 18 and older with an overjet >5 mm who required first premolar extractions and had normal or short lip lengths. Exclusion criteria had orthognathic surgery patients or crowding of ≥6 mm. Lateral cephalograms taken pre- treatment and post-space closure, were analysed for changes in lip length, lip strain and lip fall in normal and short lip length groups. Results: The two factors were assessed with the correlation test of Pearson. Data normality was verified using the Kolmogorov–Smirnov test, which confirmed a normal distribution. Consequently, an independent sample t-test was applied to compare two independent variables. P ≤0.05 was deemed statistically significant. The impact of independent variables on dependent variables was evaluated by simple linear regression analysis. Conclusion: Lip length increased significantly more in short lip length group. Lip fall and strain had more clinical significance in the short lip length group than the normal lip length group.