A new craniofacial diagnostic technique: The Sydney diagnostic system

Introduction: A new nonradiographic craniofacial imaging technique is described and evaluated. The Sydney diagnostic system (SDS) image is formed from a standardized lateral head digital photograph and a standardized digital photograph of the study models. The SDS image was designed for orthodontic diagnosis and treatment planning without a lateral cephalogram. Methods: Measurements from the composite facial and study model images of 35 randomly selected patients were compared with the same measurements from cephalograms to assess their validity and reliability. The measurements involved soft-tissue profile landmarks, landmarks on the ear, and hard-tissue landmarks identified on the study models including Point A, Point B, and dental landmarks. Results and Conclusions: The new imaging technique is reliable and valid for orthodontic treatment planning when compared with a lateral cephalogram if the inherent distortion between images is considered. Most soft-tissue measurements were more reliable than hard-tissue measurements, but some soft-tissue landmarks were less reliable. The ear was a reliable soft-tissue landmark. Maxillary incisor edge was the most reliable hard-tissue landmark, and neither Point A nor Point B could reliably be found on the study model images.