Comparison of facial soft tissue thickness in subjects with different malocclusions according to the lateral cephalograms of an Iranian adult population

BACKGROUND: Facial characteristics are determined by the thickness of facial soft tissue and parameters of the dentoskeletal system. OBJECTIVES: The aim of the study was to compare the soft tissue thickness in individuals with different malocclusions, based on their lateral cephalograms. MATERIAL AND METHODS: In this retrospective study, 285 lateral cephalograms of 141 males and 144 females aged between 18 and 40 years were evaluated in the following 4 groups of malocclusions: class I (n = 72); class II division 1 (n = 71); class II division 2 (n = 72); and class III (n = 70). Linear measurements of the soft tissue thickness were obtained at 9 facial midline landmarks. Angular measurements were made by calculating the ANB angle and the inclination angle of upper central incisors. The data was statistically analyzed using the χ2 test, the Shapiro-Wilk test, the t-test, analysis of variance (ANOVA), Tukey's test, and Pearson's correlation. RESULTS: A comparison of the soft tissue thickness revealed that male subjects demonstrated greater thickness than female subjects. This difference was statistically significant at all points in the skeletal class III individuals (p < 0.05). Different skeletal classes demonstrated significant differences in the soft tissue thickness at the subnasale, stomion, labrale inferius, labiomentale, and menton (p < 0.05). CONCLUSIONS: Males exhibited a greater facial soft tissue thickness than females. A statistically significant difference in the soft tissue thickness was observed among the different skeletal classes, particularly at regions located farther from the underlying bone. The class III individuals revealed an increased upper lip thickness and a decreased lower lip thickness. A decrease in the upper lip thickness and an increase in the lower lip thickness were observed in the class II individuals. This pattern suggests that the underlying skeletal discrepancy is being concealed.