An in-vitro evaluation of a dental subtraction radiography system using bone chips on dried human mandibles

The aim of this in vitro study was to evaluate the ability of digital subfr action radiography to detect small differences in bone density between 2 de ntal images captured with the Digora(R) radiographic imaging system. 5 drie d human mandibles were held in a fixed position and cortical bone chips wer e superimposed on the alveolar bone between the 1st molar and 2nd premolar teeth. For each mandible, a reference image was obtained without bone chip placement. Subsequently, another image without a bone chip and a series of 10 images with bone chips ranging from 1.2 to 35.3 mg, were recorded. Each of the initial images of the 5 mandibles was then compared to the 11 subseq uent images using digital subtraction radiography. The difference in densit y between the 2 images, at the site between the Ist molar and 2nd premolar, was calculated and represented as a volume equivalent of aluminium. Regres sion analysis demonstrated a close relationship between the weight of the b one chips and the aluminium equivalent density difference between the 2 rad iographs (r(2)=0.96). Good results were obtained with the smaller bone chip s that more closely resembled the dimensions of bone changes likely to be o f clinical interest (1-8 mg). It is concluded that this subtraction radiogr aphy system is suitable for clinical investigations of localised small chan ges in alveolar bone and for the diagnosis and monitoring of destructive fo rms of periodontal diseases.