Abstract
The purpose of this study was to elucidate the influence of profile patterns on the predictability of soft tissue profile changes following surgical orthodontic treatment in mandibular prognathism. The subjects of this study were 101 Japanese adult females who underwent surgical orthodontic treatment for skeletal mandibular prognathism. Lateral cephalograms taken at the start of pre-surgical orthodontics (mean age: 22.0 ± 5.5 years) and just after post-surgical orthodontics (mean age: 25.6 ± 5.8 years) were used for the analysis. Forty hard tissue landmarks and 25 soft tissue landmarks were digitized on the cephalometric tracings. Pre-treatment facial patterns composed of soft and hard tissue profiles were obtained by a self-organizing map (SOM) with 2 × 2 processing units. The X and Y coordinates of the total of 65 landmarks were repeatedly put into the SOM as 130 dimensional data. After one million learning events, the final map was obtained with 4 virtual profile patterns on each of the 4 units. The 101 subjects were classified into the 4 patterns by calculating the Euclidean distance based on the 65 landmarks between the obtained patterns and each subject. The hard tissue changes due to surgical orthodontic treatment were analyzed using pre- and post-treatment cephalograms. The prediction of soft tissue changes was performed according to the Wolford's Surgical Treatment Objective with the actual hard tissue changes, and the predicted and the actual post-treatment soft tissue profiles were compared. As a result, the post-treatment soft tissue B point was located further backward than the predicted point in the facial patterns with a high mandibular plane angle and long lower anterior facial height. In the facial patterns with a low mandibular plane angle, the post-treatment line of the lower lip was positioned more inferiorly and further backward than the predicted lower lip line. The influence on the predictability of post-treatment soft tissue profiles might differ depending on lower lip tonicity associated with profile patterns in mandibular prognathism.
