Aging and the shape of the mandible.

[BACKGROUND] The clinical observation has been made that the shape of the mandible changes with age in certain individuals. Because the shape and size of the mandible are so important to the human perception of youth, this observation was subjected to a pilot study.

[METHODS] Longitudinal data available at the Bolton Brush Growth Study were evaluated. Only dentate individuals were included in the study. Serial frontal radiographs were analyzed from the same individual taken during youth and maturity for 16 individuals, eight female subjects and eight male subjects (n = 16). The mean age for youth was 16.2 years for female and male subjects. The mean age at maturity was 56.1 years for female subjects and 56.4 years for male subjects. Tracings were made of the mandibular border for each individual, at youth and at maturity. The only reliable way to analyze shape is the modern technique of geometric morphometric analysis, which was therefore used in this study. Other techniques, such as angular values and two-dimensional linear measurements, were dismissed because they have been shown to be unreliable for evaluating shape.

[RESULTS] There was a statistically significant difference in shape for both male subjects and female subjects that occurred with age (p = 0.02 for female subjects and p = 0.001 for male subjects). The mandible continued to grow: the shape changed because some areas continued to grow faster than other areas. This is in accordance with the principle of differential growth of the facial skeleton.

[CONCLUSIONS] It is important for the cosmetic surgeon to evaluate the lower face before surgery and to understand that both bone and soft tissue can play a role in the appearance of the lower face in older individuals. A small lower face is highly attractive and conveys the impression of youth, and any soft-tissue procedure that can create the illusion of a diminutive lower face will improve the cosmetic result of the face lift procedure.