INDIVIDUAL IDENTIFICATION BY MEANS OF CONVENTIONAL BITEWING FILM AND SUBTRACTION RADIOGRAPHY

An analysis of simulated post- and antemortem (p.m. and a.m.) victim r adiographs was performed, Existing pairs of bitewing radiographs rando mly sampled from a large population of adolescents were used. Two cate gories of individuals were included based on dental therapy conditions (none or few simple fillings). Subtraction images were performed of p airs of bitewings originating from the same individual (identical imag es) and different individuals (nonidentical images) within each group. Four observers were asked to match the bitewings and to assess the su btraction images with respect to identity based on the score system: 1 = 'eliminated', 2 = 'possible', 3 = 'likely', or 4 = 'certain'. Three observers each mismatched the film radiographs among two out of 12 in dividuals without fillings. True positive identification (identified b y scores 2 + 3 + 4) of subtraction images were made in 10-12 individua ls out of a possible 12. The range of false positive (FP) and false ne gative (FN) scorings was 3-15 and 0-2, respectively. All observers wer e capable of correctly matching bitewings originating in the 12 indivi duals with amalgam fillings. By use of subtraction radiography, 12-14 identical images out of a possible 15 were assessed correctly. The ran ge of FP and FN scorings of subtraction images in this group was 1-4 a nd 1, respectively. Defining only score 4 as positive identification t he sensitivity of the subtraction technique decreased from similar to 0.90 to 0.70 in both categories of individuals, while specificity incr eased to almost 1.00 from 0.82 vs. 0.96 in the categories with and wit hout dental restorations. Bitewing radiographs from single individuals within a group of individuals were sufficiently identical to allow fo r valid identification by a strict criterion. The subtraction techniqu e may add to the subjective matching of radiographs as a screening tes t in victim identification.