A new sagittal dysplasia indicator: the YEN angle.

Aim: To develop a new cephalometric measurement to evaluate the sagittal relationship between the maxilla and mandible.

Material and methods: Seventy-five pretreatment lateral cephalograms (25 each of Class I, II, and III) were subdivided based on ANB, Wits appraisal, and Beta angle into skeletal Class I, II, and III. The same cephalograms were again classified into skeletal Class I, II, and III based purely on Beta angle. The new measurement is based on the landmarks S, M (midpoint of the anterior maxilla), and G (center at the bottom of the symphysis), which form the YEN angle measured at M.

Results: The mean and standard deviation for the YEN angle were calculated in all three skeletal groups. After using one-way analysis of variance (ANOVA) and Newman Keuls test, receiver-operating characteristic curves were obtained for the YEN angle in both types of classifications. The results showed that a patient with a YEN angle from 117 to 123 degrees could be considered to have a Class I skeletal relationship.

Conclusions: The YEN angle was developed to assess more reliably the sagittal relationship between both jaws. Subjects with a YEN angle between 117 and 123 degrees have a skeletal Class I pattern. With an angle less than 117 degrees, patients are considered to have a skeletal Class II relationship, and with an angle greater than 123 degrees, patients have a skeletal Class III.