Elliptic Fourier analysis of facial profiles during growth and development.

The quantitative analysis of facial soft tissues is of overwhelming importance for orthodontic patients. To assess the normal age-related variations in shape, soft tissue facial profiles were studied in 96 healthy male children 3 to 11 years of age and 16 young men (age 18). Standardized left-side photographs were taken of each subject, and facial profiles were traced between trichion and cervical point. The line joining the 2 landmarks was set as the baseline, and each outline was automatically digitized and mathematically reconstructed by a 30-harmonic elliptic Fourier series expansion. The same soft tissue profile was traced and digitized from the Bolton standards of comparable age. All profiles were standardized to the same area, and shape modifications were quantified by calculating the morphologic distance between the Fourier reconstructions of each facial profile and of (1) the 18-year-old Bolton standard (MD-18) and (2) the age-related Bolton standard. Descriptive statistics were computed for each age class. On average, MD-18 was 7.23 at 3 years of age, increased between 6 and 9 years of age, and decreased hereafter, reaching 6.86 at 18 years of age. Within-group variability peaked at 8 years of age, and was minimal at 6 and 18 years of age. The current soft tissue child profiles seemed different from the profile obtained from the Bolton standards.