DIRECT DIGITAL IMAGING WITH AND WITHOUT NIOBIUM FILTRATION FOR DETECTION OF DENSITY DIFFERENCES BENEATH STEEL ORTHODONTIC BANDS

An in vitro investigation was carried out to determine the efficacy of the RVG 32000 (Trophy Radiologie, Vincennes, France) in detecting sub tle density variations in a standard aluminum test object through stee l orthodontic bands. The density variations were of the same magnitude as those found when dental caries develops beneath bands during ortho dontic therapy. The procedure was carried out with both standard alumi num filtration and added niobium filtration. This study revealed the i maging system to have a wide recording latitude with no significant di fferences in the diagnostic decisions being made between with entrance doses ranging from 189-517 muGy without niobium, and 169-267 muGy wit h added niobium. No significant difference was found between the diagn ostic yield of images made with and without added niobium filtration. The accuracy was 89% with added niobium and 90% without added niobium. Specificity was 99% for both filtration conditions. It was generally possible to detect defects as small as 0.2-0.3 mm in 7 mm of aluminum through 0.26 mm steel orthodontic band material. It is concluded that the RVG 32000 has a wide recording latitude which permits detection of small density changes beneath orthodontic band material. The addition of niobium filtration did not interfere with this diagnostic task.