The Influence of the Hourglass Form of the Neck on Perceptions of Frontal Esthetics.

The purpose of this investigation was to evaluate the effect of the neck concavity angle (NCA) on different occupational groups' perceptions of frontal esthetics. An online survey was developed using Google Forms and sent to the observers through WhatsApp. Male and female frontal silhouettes were created, and NCAs that comprise the hourglass form of the neck were altered in 5 degrees increments from 120 degrees to 170 degrees. Observers were asked to score the images using 0 to 10 numerical rating scale. In all, 279 observers (97 orthodontists, 92 oral-maxillofacial surgeons, and 90 laypeople) participated in this study. For the male and female silhouettes, an NCA of 145 degrees was perceived as the most esthetic, while an NCA of 170 degrees was perceived as the least esthetic by all groups. Generally, an NCA greater than 145 degrees was perceived as less esthetic than an NCA smaller than 145 degrees. There was no significant difference between the scores of the observer groups for the silhouettes except for the female silhouettes with an NCA of 125 degrees or 150 degrees and the male silhouettes with an NCA of 145 degrees or 150 degrees. For both the female and male silhouettes, the further the NCA increased or decreased from 145 degrees, the less esthetic it was perceived to be. A significant increase in NCA was perceived as less esthetic than a significant decrease. The range of NCAs perceived as esthetic varied between 120 degrees and 145 degrees for women and between 130 degrees and 150 degrees for men. These ranges of variability of NCA may provide clinicians with useful information for orthognathic surgical planning.