Sexual dimorphism of the mandibular conformational changes in aging human adults: A multislice computed tomographic study by geometric morphometrics

Abstract

The aging process has an impact on mandibular bone morphology and can therefore affect shape sexual dimorphism. Understanding the effect of senescence on mandibular shape changes is particularly important to correctly estimate the sex of an individual and predict age-related conformational modifications. The purpose of this study was to assess age-related changes in mandibular shape and sexual dimorphism. The study sample comprised 160 Multi Slice Computed Tomography examinations of individuals aged 40 to 79 years. Geometric morphometric analysis of fourteen osteometric landmarks was used to examine sexual dimorphism and patterns of mandibular shape variation with age. Results showed that mandibular sexual dimorphism of shape remained significant with aging. Conformational changes occurred between 50 and 70 years and were different for male and female individuals. Females presented earlier and more marked age-related shape changes than males. These observations suggest that mandibular senescence is a sexually dimorphic process since its onset, rate, and the areas subjected to conformational changes differ from male to female individuals. Senescence-related changes present substantial variability, and further investigation is required to determine precisely the age that marks their onset.

Shape variation and sexual dimorphism of the adult human mandible evaluated by geometric morphometrics

“…Franklin et al [58] report an exceptionally high accuracy of 95%, but this needs to be interpreted with caution, as 10 variables were applied on a sample of 40 mandibles, suggesting a danger of overfitting. We did not detect an age-related shape change, in contrast to some previous reports, e.g., Costa-Mendes et al [40]. As noted above, our sample size was relatively small in the higher and lower age bins; however, we had a similar degree of edentulism in both sex groups, whereas this was not recorded in [40] and could have biased the results.…”

“…In addition to a higher ramus, more pronounced gonial and mental areas, males showed a wider inter-gonial distance. Such differences between sexes have been noted by other investigators as well [16, 40].…”

“…Studies with a few landmarks report a large fraction of variance in the first few PCs because shape is more coarsely measured (e.g. 14 landmarks: 67% shape variance in the first 2 PCs [40], 13 landmarks: 61% variance in the first 2 PCs [18, 19]).…”

Analysis of Sexual Dimorphic Features of the Jawline and Chin in White Celebrity Faces

“…The female mandible experiences more shape changes over time and becomes more like the shape of the male mandible, which experiences a decrease in curvature with age. Furthermore, the female mandible undergoes an accelerated rate of change after age 50, while male mandibles have a more constant aging rate 41 …”

“…Furthermore, the female mandible undergoes an accelerated rate of change after age 50, while male mandibles have a more constant aging rate. 41 There are both surgical and nonsurgical options for reshaping the jawline. Noninvasive techniques that address rejuvenation of the mid and lower face have been developed from the MD codes, namely, the 7-point and 9-point Shape, which address the cheek, chin, jawline, lips, and nasolabial folds.…”