[Examination of the degree of agreement among dental findings used for personal identification (Part 4)--Lapse of time between features of dentition at time of death and those in the last dental record].

In cases of personal identification of corpses, there is usually a lapse of several years between the features of dentition at the time of death and the features documented in the last dental records. We therefore investigated the degree of agreement of the dental findings in the same subject under these circumstances. For the study, 6,000 records of dental examinations carried out between grades 1-6 for 1,000 dental students in their 20's (740 males and 260 females) were examined. These documents were then divided according to the number of years that had elapsed from 1 to 5 years, and were collated. In this investigation, the former dental features on certain grade student were regarded as antemortem data, and the latter dental features elapsing several years were regarded as the postmortem data. The total number of records collated was 15,000. The records were classified according to four criteria: (1) intact teeth (non-carious and non-treated), (2) carious teeth (C1-C4), (3) treated teeth (crown, inlay etc.), and (4) missing teeth (including pontic and denture). The results obtained were as follows: 1. Correlation between number of corresponding teeth and lapse of time: When the number of corresponding teeth was 28-26, the frequency of tooth agreement in the same subject declined with time. When 24 teeth or less were present, the frequency increased. 2. Correlation between changes in dental findings and tooth regions in the same subject: The anterior teeth tended to remain intact, the first premolars changed from intact to missing, and second premolars changed from intact to treated. The dental findings for the first molars tended to change from treated to treated and missing. The second molars showed diverse changes. 3. Correlation between lapse of time and patterns of change in the dental findings: There was a tendency for cases showing the same states of dentition to become fewer, and for cases showing changes from intact and carious to treated and missing teeth to become more frequent, excluding the mandibular anterior teeth. 4. Correlation between tooth regions and frequency of inconsistent changes in dental findings: A change from treated to intact was frequently observed in maxillary incisors (3.1-3.2%) and second molars (2.5%), and a change from treated to carious was also observed in the mandibular molars (2.2-2.3%). Inconsistent changes in the mandibular anterior teeth were seldom observed.