Indication and limitations of using palatal rugae for personal identification in edentulous cases

To explore the availability and the limitations of using the palatal rugae pattern in forensic practice for personal identification in edentulous cases, we set up an experiment, which involved 48 patients who had both old and new complete dentures and we observed their rugae. First, we made 48 pairs of maxillary casts from their old and new dentures and a further 50 maxillary casts from complete dentures at random, to use as variables. All the initial impressions taken from the mucosal surfaces of complete dentures were made from alginate impression materials, and the maxillary casts were made from hard dental plaster. Secondly, all 146 casts were trimmed so that all the areas except for the rugae area were removed. Subsequently, 50 examiners were given the 48 casts from the old dentures and were then asked to compare them with the other 98 casts for possible matches. The case numbers, which matched correctly, were recorded. The median percentage of correct matches among the 50 examiners was 94%, despite variations in their experience with forensic identification, and this accuracy does not differ significantly from that in dentate cases, as described in previous publications. The median percentage of correct matches among the 48 cases was 90%. Analyzing the incidence of obtaining a correct match in each case revealed that there were three major misleading shapes that could give rise to a low rate of correct matches; (1) severely low and poorly demarcated eminences of rugae, (2) change of palatal height, and (3) non-complex rugae pattern. These features are mainly due to the shape of the edentulous palate itself and rarely due to the dentures, and could lead to difficulties in finding unique points for use in matching rugae patterns. The results suggest that an appropriate selection of cases, taking into consideration the above misleading shapes, may establish an increased rate of accuracy for identification with this method, thereby bringing the percentage of correct matches closer to 100% in edentulous cases, which is also the percentage of correct matches previously reported in dentate cases.