Radiation reduction using a modified collimated lateral skull radiograph during orthodontic treatment.

The aim of the study was to investigate whether routine 'during-treatment' clinical cephalometric measurements could be obtained from a lateral skull radiograph collimated to show the maxilla and mandible. The sample consisted of 30 lateral skull radiographs, taken during treatment, of patients with upper and lower fixed appliances. These conventional cephalograms (CC) were copied to give a radiograph with modified collimation (MC) showing the maxilla and mandible and the dentition only. Both types of radiographs were digitised and the readings compared to determine whether the same during-treatment cephalometric values were obtained from both types of radiographs. The limits of agreement obtained, when comparing cephalometric values obtained from the CC and MC lateral skull radiographs, were only marginally larger than those for CC alone. Therefore, the use of an MC lateral skull radiograph to show the maxilla and mandible is a viable alternative for cephalometric measurements for patients wearing two arch fixed appliances.