The Relationship between the Lip Length and Smile Line in a Malaysian Population: A Cross-Sectional Study

Abstract

Objective: Smile line is an inevitable element in esthetic dentistry; does the lip length have any correspondence to the smile line? Our study provides scientific data as part of an evidence-based assessment regarding the relationship between the upper lip length and smile line in a Malaysian population. Materials and Methods: A randomized sample, consisting of 238 Malaysian aged between 18 - 35 years was used to carry out this study. Upon screening, the participant was asked to relax the lip and the lip length is recorded with a calibrated caliper. Measurement of the lip length was taken from subnasale to stomion superius. Smile line was then assessed by posed smile. All the data was taken in presence of at least 2 examiners to enable cross-checking of measurements. The Chi-Square test was then used to test the significance between both the variables. Results: The lip lengths obtained from the sample ranged from 18 - 29 mm with mean 22.7 mm and standard deviation of 2.53. Both males and females have majority of average smile line. The Indians and Malays have mostly average smile lines, however, the Chinese showed more of high smile lines. In this study, the chi-square statistic exceeded the conventionally accepted significance level of 0.05, where p-value = 0.265. In other words, there is no statistically significant increase in smile line with increased lip length. Conclusion: From our study, the lip length does not affect the smile line of an individual.