Semester

Spring

Date of Graduation

2026

Document Type

Thesis

Degree Type

MS

College

School of Dentistry

Department

Orthodontics

Committee Chair

Peter Ngan

Committee Co-Chair

Khaled Alsharif

Committee Member

Guoqiang Guan

Committee Member

R. Constance Wiener

Abstract

Background and Objectives: The objective of this study is to evaluate whether there is a difference in aesthetic preferences of lip position between dental professionals and the general public, which we will refer to throughout the paper as lay people. In addition, age and gender differences will be determined to evaluate whether there is a need to re-evaluate the accepted normative values for lips to Esthetic plane (E-plane).

Experimental Design and Methods: A cross sectional, observational study design was used. The study aim was to evaluate the perception and opinions regarding lip position and fullness of both lay people (n=61) and dental professionals (n=64). A photograph of a Caucasian female, age 28, was modified to show 5 levels of varying upper and lower lip position.  These photos were included in a survey that asked for individual evaluation of the appearance of the lips relative to the facial profile. A side-by-side evaluation of the varying degrees of lip position was shown, and they were asked to choose the profile that is the most appealing, with the most balanced facial harmony. Statistical analyses of the data were carried out using SAS (version 9.4, 2013, SAS Institute Inc., Cary, NC). Descriptive analysis was performed, and median and interquartile of ratings were calculated for each image and each rater group. The comparisons of rating facial attractiveness between the two rater groups (dental professional and lay-people) per image were conducted by Wilcoxon Rank Sum test. Fisher’s Exact test was utilized to assess associations between image preference and age group, sex, as well as rater group. All statistical tests were two-sided; and a p-value of less than 0.05 was considered statistically significant.

Results: Descriptive analysis of rater scores revealed that the image with the upper lip 2mm retrusive to the E-plane and lower lip touching the E-plane (image 3) was consistently identified as the most esthetic lip position. Dental professionals assigned that image a median rating of 4.0 (IQR = 1.0), while lay-people assigned it a median of 3.0 (IQR = 1.0). At the extreme ends of the distance scale, both groups showed lower preference, particularly for the image with the upper lip 6mm retrusive to the E-plane and the lower lip 4mm retrusive to the E-plane (image 1), which received a median rating of 2.0 from both groups. The association between rater demographics and image preference were determined by the Fisher’s Exact Test. A statistically significant association was found between rater group and preference (p = 0.02). While 45.3% of dental professionals chose Image 3 as their preferred, lay-people were more distributed in their choices, with 11.5% and 8.2% preferring the extremes; images 1 and 5, respectively. Notably, no dental professionals selected the image with the upper lip 2mm protrusive to the E-plane and the lower lip 4mm protrusive to the E-plane (image 5) as their preferred image. In contrast, no significant associations were found between image preference and age group (p = 0.33) or sex (p = 0.38).

Conclusions:   Raters showed greatest preference, and highest agreement for the image which was 2mm protrusive to the normative values of E-plane. While clinical training aligns professionals toward a specific aesthetic ideal, patients (lay people) exhibit a broader tolerance for deviation. Success in clinical treatment should balance technical “ideal” measurements with the patient’s individual subjective preference, as age and sex do not significantly alter these aesthetic goals.

Download

Share

COinS