Esthetic evaluation of lip position in silhouette with respect to profile divergence.

Introduction: The aim of this study was to determine the preferred lip position in silhouette profiles with different amounts of divergence.

Methods: A normal profile was constructed based on normal values and was altered using software (Photoshop CS, version 8.0; Adobe Systems, San Jose, Calif) to produce a series of 15 profiles in 3 sets (straight, anterior, and posterior divergent). Each set consisted of 5 photographs with different lip positions from -4 mm to +4 mm in 2-mm increments. We asked 240 people in 5 panels (79 senior dental students, 26 orthodontists, 27 maxillofacial surgeons, 27 prosthodontists, and 81 laypeople) to rate the profiles. Mann-Whitney and Kruskal-Wallis tests, and intraclass correlation coefficients were used to analyze the data.

Results: In the anterior and posterior divergent profiles, most groups tended to prefer the original lip positions for both the male and female profiles. In the straight divergent profile, the results were scattered and inconsistent in the different groups. In the posterior divergent profile, the orthodontists and the surgeons selected the 4-mm lip retrusion as the least attractive, and other groups selected the 4-mm lip protrusion as the least attractive. In the anterior and straight divergent profiles, all groups were unanimous in the selection of the 4-mm lip protrusion as the least attractive images. Significant differences were found between the raters in the rankings of some images. No significant difference was found between the male and female raters in the rankings of the profile images.

Conclusions: It is important to establish a normal lip position, especially for a patient with an anterior or a posterior divergent profile. Posterior divergent patients should be treated cautiously so that excessive lip retrusion does not result.