Sexual Dimorphism in Soft Tissue Facial Form as captured by Digital Three-Dimensional Photogrammetry. Seung B. Lim
Thesis: Sexual Dimorphism in Soft Tissue Facial Form as captured by Digital Three-Dimensional Photogrammetry.
Author: Seung B. Lim
Source: University of Pittsburgh, School of Dental Medicine
Date: June 2012
Sexual dimorphism in the head and neck area is a particular interest to orthodontists who manipulate the underlying hard tissue in order to alter the overlaying soft tissue. Hard tissue differences between the sexes have been well documented in the literature with the advent of the cephalostat. With the enlightenment of the ‘soft tissue paradigm’, research has been shifted towards revealing differences in the soft tissue. Although overall size difference, with males being larger, has been a commonly recurring theme, elucidating shape differences has been more subtle. A large sample (n=586) of adults with recent European ancestry have been recruited for the study. Five direct anthropometric measurements were taken using calipers while 29 indirect anthropometric measurements were captured using a 3dMD digital stereophotogrammetry system (Atlanta, GA). Seven indices were derived and compared between the sexes. Statistical analysis was performed using a t-test as well as an analysis of covariance (ANCOVA) using height as the covariate measure. Our results confirmed that males were larger than females on all 34 measurements, and 32 of the 34 measurement differences were found to be significant according to the t-test (p<0.001). Although the upper and lower vermilion heights were absolutely larger for males, vermilion height in females was proportionally larger relative to the size of the mouth. Once height was factored in, the number of significant findings decreased to 27 of the 34 measurements according to the ANCOVA (p<0.001). Measurements such as ‘minimum frontal width’, ‘palpebral fissure length (right)’, ‘palpebral fissure length (left)’, ‘nasal protrusion’, and ‘nasal height’ were found to be non-significant when the effects of body size (height) was controlled. Three of the four index comparisons were significant according to the t-test (p<0.001). ‘Upper-middle facial depth index’ was larger in females indicating that they have a more anterior projection of nasion and/or a more posterior projection of subnasale. Females also had a larger ‘middle-lower facial index’ indicating that females have more convexity to their profile shape. Males had a larger ‘nasal index’ suggesting that they have a relatively shorter and wider nose.