Perioral soft tissue evaluation of skeletal Class II division 1 : a cephalometric study

Abstract

The purpose of this study was to evaluate the perioral soft tissue characteristics of skeletal Class II division 1 (Group II) with low (<27°), normal (27°-36°) and high (>36°) SN-MP angle (Group IIL, IIN and IIH, respectively) compared with skeletal Class I (Group I). Lateral cephalograms of 99 individuals were divided into 4 groups according to skeletal pattern (Group I: 22 subjects, Group IIL: 14 subjects, Group IIN: 33 subjects, Group IIH: 30 subjects). For each group, the skeletal, dental and soft tissue variables were assessed by cephalometric analysis and one-way ANOVA was performed for statistical evaluation. The correlations between the skeletal, dental variables and soft tissue variables were studied and multiple linear regression tests were used to determine the variables influencing soft tissue characteristics. The results of the present study are as follows.1.Lower lip thickness showed statistically greater value in Group II than in Group I (Group I, 15.16±1.30 mm; Group IIL, 17.24±2.56 mm, p < 0.05). Upper lip thickness showed no statistical difference between groups.2.Group IIH exhibited significantly greater values than Group IIL and IIN for basic lower lip thickness and lower lip length (p < 0.05).3.The measurements of perioral soft tissue thickness of Group II were correlated with inclination and anteroposterior position of upper and lower incisors along with facial depth and/or facial length.4.Basic upper lip thickness and upper lip thickness of Group II were greatly correlated with the inclination of lower incisors (p < 0.01).5.In Group II, upper lip strain was influenced by the inclination and anteroposterior position of maxillary incisors and was not influenced by any skeletal variables.These results revealed the characteristics of perioral soft tissue thickness of skeletal Class II division 1, providing practical information and guidelines for orthodontic diagnosis and treatment.