An inference modeling of human visual judgment of sagittal jaw-base relationships based on cephalometry: part II.

In a clinical situation, visual judgment of sagittal jaw-base relationships is described and handled as fuzzy terms, such as "slight" skeletal 3 tendency or "relatively severe" skeletal 2. The purpose of this study was to develop an inference system in order to be able to describe the degree of certainty for sagittal skeletal discrepancy automatically and in a mathematical way. Orthodontic records of 137 adult female patients were judged by 3 orthodontists. Based on these data and the multiple regression model described in Part I of this study, we developed an inference system that consisted of 2 membership functions and 6 incorporating rules. The performance reliability of the system was tested for 175 female adult cases by 7 orthodontic experts. In 97% (170 of 175) of the cases, the orthodontic experts agreed with advice proposed by the inference system. We conclude that the current model is an effective means of deriving the opinion of an experienced clinician from a cephalometric tracing and provides an interesting insight into how orthodontists are influenced by the face when attempting to judge the sagittal relationship clinically. In addition, the current system would be an initial stage in the development of the decision-making system for the orthodontic diagnosis and treatment planning.