Esthetic Perception of Recurring Esthetic Dental Proportion in Different Lip Line Positions Among Lay People

Background and Aim: The proportion of smile is a useful tool for creating geometric smiles which are a critical aspect in esthetic dentistry. The aim of this study was to determine the effect of lip line position on acceptable Recurring Esthetic Dental (RED) proportion among lay people. Materials and Methods: A photograph of pose smile of a young female was taken. The position of the lip was changed by Adobe Photoshop CS6 software within three positions (low, medium, and high). Then, we created three RED proportions (54%, 62%, and 70%) for each lip line position. The photographs were ranked from most to least attractive (one to nine) by 40 lay people (20 females and 20 males) with a mean age of 19.4 years. Data were collected and analyzed using Friedman test. Pairwise comparisons were made using Bonferroni correction. The impact of gender on the ratings was evaluated using repeated measures analysis of variance (ANOVA). Results: In the medium lip line group, all three proportions had approximately the same preference rates. The 54% proportion was the least attractive one in the high lip line group (mean=6.819), and the 70% proportion was the least attractive one in the low lip line group (mean=6.881). Conclusion: The acceptable RED proportion cannot be evaluated without consideration of other factors such as lip line position. Esthetics is the result of a harmonious balance between different elements.