Perioral soft tissue evaluation of skeletal Class II Division 1: A lateral cephalometric study

• We evaluated soft tissue thickness and length in skeletal Class II Division 1 subjects.
• Upper lip strain was influenced by maxillary incisor anteroposterior position.
• Upper lip strain was not influenced by skeletal variables.
• Lower lip thickness and length were greater with a high mandibular plane angle than with low.
• Lip strain and lip thickness were affected by skeletal and dental patterns.

IntroductionTo obtain the balance and harmony of the soft tissue facial profile in orthodontic treatment, it is necessary to identify the characteristics of overlying soft tissues according to the horizontal and vertical skeletal patterns. The aim of this study was to evaluate the perioral soft tissue characteristics of skeletal Class II Division 1 subjects (group II) with various vertical patterns compared with skeletal Class I subjects (group I).MethodsLateral cephalograms of 99 Korean adults (44 women, 45 men; mean age, 23.4 years) were divided into 4 groups based on horizontal and vertical skeletal pattern (SN-MP angle): group I, 22 subjects; group II-low angle (<27°), 14 subjects; group II-normal angle (27°-36°), 33 subjects; and group II-high angle (>37°), 30 subjects. The correlations and multiple linear regression tests were used to determine the skeletal and dental variables influencing soft tissue characteristics.ResultsGroup II-high angle showed significantly greater values than did group II-low angle for basic lower lip thickness and lower lip length. The perioral soft tissue measurements of group II were correlated with the inclination and anteroposterior position of the maxillary and mandibular incisors along with facial depth (N-Go) and facial length (S-Gn). Upper lip strain of group II was not influenced by any skeletal variables but only by the inclination and anteroposterior position of the maxillary incisors.ConclusionsClinicians need to evaluate lip strain and lip thickness based on the skeletal pattern as well as dental inclination to obtain balance in the perioral muscle activity.