A size-standardized analysis of soft tissue facial profile during growth.

A method for the quantitative and qualitative analysis of the facial soft tissue profile has been developed and applied to analyze the age differences in lateral cephalograms for the annual Bolton standards from ages 1 to 18 years. To standardize for different facial sizes, profiles were traced in polar coordinates without modifications of facial shape. Most of the soft tissue landmarks showed progressive modifications from birth to 18 years of age. Soft tissue nasion and lower lip had a steep change between 2 and 3 years of life, pronasale between 3 and 5 years of life, A', upper lip, and stomion between 4 and 5 years of life. Hereafter, all these landmarks but N' had several minor modifications progressing toward the adult value. Soft tissue nasion did not modify significantly after 2 years of age. Conversely, changes in the relative positions of B' and Pg' were more scattered in the analyzed period. Age-related size differences were more linear than shape modifications, with gradual increments from 1 to 18 years of age. The method allowed a simple and rapid quantitative evaluation of soft tissue profiles during facial growth. An approximate evaluation of the soft tissue thickness at nose, lips, and chin was also possible. No particular mathematical knowledge was required at any step of the analysis. Results were in good agreement with the well-known patterns of normal growth and development, thus confirming the practical possibilities of the method.