A summary five-factor cephalometric analysis based on natural head posture and the true horizontal.

A simple and clinically practical five-factor cephalometric summary analysis is described that is based on the true horizontal and natural head posture. Special reference is made to the AB/horizontal angle as an improved method for the assessment of the sagittal skeletal pattern. A Class I clinical normal range of 12 degrees to 18 degrees was established. In comparison to analyses based on conventional intracranial reference planes, the new methods are more valid in two important respects: (1) the true horizontal reference plane displays less variance when the head is observed in natural posture; (2) the new methods better describe the dentoskeletal and profile features as they appear in life. Hence, they are more clinically meaningful. Data from a large cephalometric population study were used selectively to illustrate the benefits of the new methods. Previous conventional cephalometric analyses of the Chinese male had shown the average pattern to be skeletal Class II, with retrognathic mandible, when compared to the Caucasian male. However, when observed in natural head posture and using the methods based on the true horizontal, the true life skeletal pattern has been shown to be Class III. Analysis of individual subjects produced differing interpretations of craniofacial form, depending upon whether the conventional intracranial planes were used as reference or the true horizontal. It was concluded that conventional methods may result in significant errors in analysis, diagnosis, and treatment. The new methods produce valid supplementary data.