A comparative study of two methods of quantifying the soft tissue profile

One of the most important components of orthodontic diagnosis is the evaluation of the patient's soft tissue profile. There have been many attempts to quantify the soft tissue profile based on the lateral cephalogram. Yet, the methodology used to evaluate the profile varies widely among studies, and there has been no consistency in the way straight lines are constructed in the analysis of the soft tissue contours. The purpose of the current study was to compare the values obtained by 2 drawing methods (tangent line and anatomic points) of constructing angles, and to assess the intraobserver and interobserver reproducibility for both methods. There were statistically significant differences between the 2 methods for 9 of the 10 measurements evaluated. In the comparison of reproducibility assessed by Pearson correlation analysis, both methods showed statistically significant correlations between repeated measurements. The anatomic point method, however, showed greater reproducibility by means of a paired t-test. In the analysis of intraobserver reproducibility, 2 measurements showed significant differences with the anatomic point method and 4 measurements demonstrated significant differences when the tangent line method was used. In the analysis of interobserver reproducibility, 5 measurements showed significant differences in the anatomic point method, while 6 measurements represented significant differences in the tangent line method. Our results indicate that a precise description of the methodology used in the analysis of the soft tissue must be provided because of the differences between methods. In the analysis of soft tissue contours, the construction of lines with the anatomic point method is more reproducible than the tangent line method.