Age-Related Variations in Lower Facial Soft-Tissue Thickness: A Retrospective Cephalometric Study

Facial esthetics and orthodontic planning depend on both the craniofacial skeleton and overlying soft tissue. Lower facial soft-tissue thickness (FSTT) varies with sex, age, and ethnicity; however, age-stratified normative data remain limited for the Central Indian population. This study compared lower facial soft-tissue parameters across age groups and established age- and sex-specific reference values.

A total of 120 left lateral cephalograms (60 male and 60 female) of subjects aged 8-39 years with normal vertical skeletal pattern (SN-MP = 32° ± 2°), complete dentition, and no orthodontic/surgical history were divided into four equal age groups (I: 8-15, II: 16-23, III: 24-31, and IV: 32-39 years; 15M/15F each). Six soft-tissue parameters-upper and lower lip thickness, upper lip length, Pogonion-Pogonion' (Po-Po'), Menton-Menton' (Me-Me'), and lower facial third height-were traced manually. One-way analysis of variance (ANOVA) with Tukey's post hoc test was used to compare age groups, and independent t-tests were used to compare genders within groups (p < 0.05).

Upper lip thickness increased significantly with age (F = 4.42, p = 0.006), peaking in the 32-39-year group; male subjects exhibited significantly greater upper lip thickness from eight to 31 years (independent-samples t-test, p < 0.05). Lower lip thickness (p = 0.19) and length of upper lip (p = 0.07) did not vary significantly with age. Po-Po' rose to a peak in the 24-31-year group before declining (F = 3.91, p = 0.010). Me-Me' increased progressively with age (F = 6.77, p = 0.01). The height of the lower facial third increased significantly with age (F = 4.63, p = 0.004), with a gender difference only in the youngest group (p = 0.05).

The lower facial soft tissue continues to change well beyond skeletal maturity. Upper lip, chin, and lower facial height measurements increased significantly with age, whereas lower lip thickness and upper lip length remained comparatively stable. Sexual dimorphism is most pronounced in adolescence/early adulthood and diminishes thereafter, supporting the need for age- and sex-specific soft-tissue norms in orthodontic and esthetic practice.