RESUMO
PURPOSE: Proportionality of the lower and middle thirds of the face is a key determinant of successful orthognathic treatment. A flatter profile and marked variance of the soft tissue envelope in the Japanese population complicates the accurate assessment of these proportions. This study aimed to identify gender differences and establish norms for Japanese young adults using the method of soft tissue cephalometric analysis (STCA) by Arnett et al (Am J Orthod Dentofacial Orthop 116:239, 1999). MATERIALS AND METHODS: Lateral cephalograms of 49 young normal Japanese subjects (19 men, 30 women) were selected from the archival records and analyzed with STCA. The Student t test was used to compare mean values of the male and female groups. RESULTS: Significant differences were found between women and men. Men had a flatter occlusal plane and a more acute nasolabial angle than women. Men showed larger values for upper and lower lip thickness, menton soft tissue thickness, and vertical face length, especially in the lower third of the face. Women had a more projected midface than men. Compared with established STCA norms, the Japanese have more midfacial projection. CONCLUSIONS: Significant gender differences were found in the thickness, lower third length, and midface projection in Japanese young adults, which should be taken into account when interpreting measurements for orthognathic surgical planning. These differences can serve as norms for STCA in young Japanese adults. Differences were noted between the reference values of Arnett et al and Japanese subjects.
