Reliability and validity of the Digigraph 100 in orthodontic diagnosis

Cephalometric analyses of lateral cephalograms allow important statements to be made on diagnosis and treatment planning. Such radiographs should, however, be taken with a considerable reduction in radiation exposure. With the Digigraph 100 (Dolphin Imaging Systems Inc., USA) a cephalometric technique based on distance measurements of emitted sonic signals is now available. This study was aimed at determining the degree to which this procedure can cope with the requirements of reliability and validity in the field of orthodontics. For this purpose 50 volunteers were examined by conventional cephalometry with manual tracing of lateral cephalograms as well as by sonic cephalometry, with Jarabak analysis in both cases. In addition an option was available for reading lateral cephalograms into the Digigraph by means of a radiograph evaluation program. The 31 evaluated parameters were subjected to modified statistical analysis. Good reliability was recorded in the range between 0.96 and 0.99 for eleven sonic cephalometric measurements, whereas 26 values were between 0.69 and 0.95. The validity was significantly lower in comparison to radiocephalometry. In particular, measurements related to landmarks which were difficult to access or could be only indirectly determined, such as the sella point, the articulare point or the apices of the incisors, proved to be weak points of sonic cephalometry. The device is thus indicated rather in the field of communication with the patient or for intermediate examination without radiation exposure. Cephalometry without radiation exposure would represent decisive progress in orthodontic diagnostics. However, some developmental work on the processing software or even the development of a specific sonic cephalometry which deliberately dispenses with parameters that are difficult to record with this procedure is still needed.