[The individualized ANB angle of Chinese adults]

The ANB angle is commonly utilized to determine sagittal jaw relationships in cephalometric analysis. The ANB angle may be affected by other factors; therefore, its correlation to another measurement should be further recognized. This will eliminate the possibility of a biased interpretation. The individual variation of the ANB angle was investigated in 80 lateral radiographic cephalograms. The sample consisted of 40 Chinese male and 40 Chinese female adults. All of the sample had neutral molar relationships (Class I), and balanced profiles; none had previously undergone orthodontic treatment. ANB, SNA, SN-MP angles and SN were calculated for each gender. Multiple regression analyses and regression equation were performed and established. The results indicate that the variation of the ANB angle can be explained by the variations of the SNA and SN-MP angles. The males had less mandibular divergency than females (p less than 0.05); resulting in a different effective pattern. The derived equations are: ANBind = 0.42 x (SNA) + 0.31 x (SN-MP) - 41.1 for males; ANBind = 0.31 x (SNA) + 0.20 x (SN-MP) - 28.9 for females. The explanation power also showed gender difference: males 56.2%, females 24.2%. The ANB angle for different facial types are presented through equation-produced lists of individualized norms. These norms aid the interpretation of the individual variations.