Age- and sex-related changes in three-dimensional lip morphology

Abstract

The objective of this study was to supply information about: (1) normal sex-related dimensions of mouth and lips (linear distances, ratios, angles, area, volume); and (2) growth changes between childhood and old age. The three-dimensional coordinates of several soft-tissue landmarks on the lips and face were obtained by a non-invasive, computerized electromagnetic digitizer in 532 male and 386 female healthy subjects aged 4-73 years. From the landmarks, linear distances (mouth width, width of the philtrum, vermilion heights of the upper, lower and total lips, total lip height), the vermilion height-to-mouth width ratio, areas (vermilion of the upper, lower and total lip) and volumes (upper, lower, and total lip volume) were calculated and averaged for age and sex. Comparisons were performed by factorial analysis of variance. Mouth width, width of the philtrum, total lip height, and lip volumes were significantly larger in men than in women (p<0.01), increased with age (p<0.001), and had age x sex interactions (p<0.001). Vermilion areas and heights of the lower and total lips progressively increased with age until late adolescence, and then decreased with aging (p<0.001). The vermilion height-to-mouth width ratio was larger in women than in men (p<0.001), and decreased with age (p<0.001). Data collected in the present investigation could serve as a database for the quantitative description of human lip morphology during normal growth, development and aging. Forensic applications (evaluations of traumas, craniofacial alterations, teratogenic-induced conditions, facial reconstruction, aging of living and dead persons, personal identification) may also benefit from age- and sex-based data banks.