A comparative study of thespecificities and sensitivities of KB angle and ANB angle in evaluating anteroposterior relationship between maxilla and mandible

Abstract

Objective To establish a normal reference value of the KB angle of Chinese adults with normal occlusion in Shandong province. To compare its specificity and sensitivity with ANB angle in evaluation of the anteroposterior relationship between maxilla and mandible. Methods 123 adults from Shandong province with normal occlusion were included, 60 males and 63 females, age 19 to 26 years old. Lateral cephalometric radiograph of each subject was taken. KB angle and ANB angle of each subject were measured, and the means and standard deviations were calculated. SPSS Statistics 11.0 were used for analyses. Specificties of KB angle and ANB angle was compared by using mean±1.96 standard deviation and mean±standard deviation as boundary values to screen normal occlusion. Sensitivities of KB angle and ANB angle was compared by using mean±1.96 standard deviation and mean±standard deviation as boundary values to screen 227 adults of Angle Class I, Ⅱ, Ⅲ malocclusion. Results The normal reference value of KB angle of Chinese adults with normal occlusion in Shandong province was established. There was no significant difference between the specificities of KB angle andANB angle. In subjects with Angle Class Ⅱ malocclusion, sensitivity of KB angle was about 22% higher than that of ANB angle by using either of the two boundary values; In subjects with Angle Class Ⅲ malocclusion, sensitivity of KB angle was about 18% higher than ANB angle by using mean±standard deviation as boundary value. Conclusions The study proposes the KB angle as a completely new cephalometric measurement in evaluating anteroposterior relationship between maxilla and mandible, and the normal reference value of the KB angle of Chinese adults with normal occlusion in Shandong province is established. Compared with the ANB angle, in either Angle Class Ⅱ or Class Ⅲ malocclusion subjects, the sensitivity of KB angle is relatively higher when using mean±standard deviation as boundary value. Key words: Normal occlusion; Cephalometrics; Adult; KB angle; ANB angle; Specificity; Sensitivity