The reproducibility of cephalometric measurements: a comparison of analogue and digital methods.

The aim of this study was to compare the reproducibility of longitudinal cephalometric measurements between analogue and digital methods using two different resolutions. Cephalometric radiographs of 20 patients were selected at the start (T1) and end (T2) of treatment: 24 cephalometric variables were calculated at T1 and T2, and their increments (T2 - T1) were also evaluated. All measurements were performed twice by two observers. Quality of methods [analogue, digital: 300 and 600 dots per inch (DPI) resolution] was evaluated by comparing the reliability coefficients and the total error between the digital and analogue methods. The inter-observer agreement was good. The 300 DPI was comparable to the analogue method. The reproducibility for the variables was comparable, but mandibular incisor increments tended to show better results with the 300 DPI method, whereas skeletal jaw relationship increments were not reliable with either method. Maxillary incisor increments, however, were reliable with both methods. The 300 and 600 DPI resolutions were found to be comparable. Scanning of cephalometric radiographs at a resolution of 300 DPI is sufficient for clinical purposes and comparable to analogue cephalometrics. However, all methods were found to be poor in assessing skeletal jaw relationships longitudinally.