Soft tissue profile typology: results of the cluster analysis.

The aim of the study was to establish a mathematical classification of normal soft tissue profile by cluster analysis based on linear and angular photogrammetric measurements.The sample consisted of 110 subjects, 52 males (mean age, 28.7 y) and 58 females (mean age, 25.7 y), with good and balanced soft tissue profile and dental class 1 occlusal relationship and were white. The measurements were made with standardized photographic records taken in natural head position.The 39 soft tissue variables (27 linear and 12 angular) were classified according to similarity by cluster analysis. Males and females were separated in an effort to identify representative values for each group. The squared Euclidean distance was used for distance measurement, and the Ward method was used for cluster analysis. Measurement variables for cluster analysis were standardized using z score. Four recognizable types of soft tissue profiles were obtained in both sexes, which differ mostly with regard to the position of the lips and prominence of the chin. This study found a highly significant sex dimorphism in the soft tissue profile, presenting that the form difference is both a size and a shape difference between male and female soft tissue profiles. The lower third of the face expressed most of the sex differences.