Development of cephalometric norms using a unified facial and dental approach.

OBJECTIVE

To develop a cephalometric determination of anteroposterior skeletal occlusion on the basis of a clinically rational "gold standard" and objectively determined cut points.

MATERIALS AND METHODS

Pretreatment cephalograms from 10- to 18-year-old Caucasian patients with a normal vertical face dimension were digitized. Facial profile line drawings were judged by orthodontist raters as Class I, II, or III. Subjects who met all inclusion criteria were divided into Class I, Class II, and Class III on the basis of the matched skeletal (facial) and dental occlusion and comprised our gold standard for anteroposterior skeletal occlusions. Cephalometric variables included ANB angle, McNamara analysis, Harvold unit differential, anteroposterior dysplasia index (APDI), and Wits analysis. Half the sample was used to derive skeletal classification norms using receiver operator characteristic (ROC) curves, and half the sample was used to test for diagnostic ability and to compare the diagnoses based on traditional cephalometric norms with the new norms.

RESULTS

Results of the study showed that ANB and McNamara analysis performed well with traditional and ROC-derived norms, whereas Wits, Harvold unit differential, and APDI showed fewer errors in diagnosis with ROC norms compared with traditional norms.

CONCLUSIONS

The use of a single set of diagnostic norms for each analysis to distinguish between the skeletal classifications for the 10- to 18-year-age group proved to be highly successful for each of the analyses and performed as well or better than when using traditional norms based on age and sex.