Cephalometric assessment of sagittal relationship between maxilla and mandible.

This investigation was undertaken to evaluate if palatal plane could be used as a skeletal plane of reference in lateral cephalometric radiographs to evaluate sagittal maxillomandibular relationship. Various cephalometric landmarks in the maxilla and the mandible were projected to the palatal plane, and the linear distances between them were measured. In this three-part study, the first part evaluated changes in the inclination of palatal plane and in the linear distances from the age of 6 to 24 years in longitudinal records of 86 patients (46 male, 40 female). The second part established acceptable adult norms by evaluating 111 white dental students (89 men, 22 women) with Class I molar relationships, no history of orthodontic treatment, and good facial balance. The third part evaluated the proposed measures in pretreatment radiographs of 445 patients (171 men, 274 women) with a variety of malocclusions to compare the results of various diagnostic criteria for assessment of sagittal jaw relationships. The first part indicated the inclination of the palatal plane was stable throughout the growth period studied. The distance between projections from points A and B on the palatal plane (App-Bpp) was found to be the best indicator of sagittal jaw relationship. This was the least variable of the four measures considered in part two of the study. When compared with the angle ANB, the Wits appraisal and measurement of landmarks to a perpendicular from nasion in 50 patients, it was a more reliable diagnostic criterion than the other measures. Among the patients whose malocclusions were incorrectly diagnosed. Wits appraisal was consistently biased in the Class III direction. The methods using the ANB angle and the nasion perpendicular plane did not indicate any definitive trend.