Intra-individual variability in adult age-at-death estimates using incremental lines in dental cementum

The reliability of adult age-at-death estimates based on counting the incremental lines in dental cementum is uncertain because their accuracy and precision vary from one study to another. Moreover, no previous study has addressed intra-individual variability in counts of incremental lines in cementum. We quantified this variability from a sample of 51 clinically extracted teeth of 15 individuals. Incremental lines were counted on five cross sections from the median third of each tooth root. Two age estimates were calculated per tooth, taking into account (1) the maximum number of lines counted and (2) the average value of counts. Our results show that a) age estimates based on the incisor are more accurate than those based on the canine or premolar; b) age estimates based on maximum counts are more accurate than those based on average counts; c) age estimates based on mandibular incisors are more accurate than those based on maxillary incisors. Substantial variability was observed in the number of increment lines on the same tooth. For an individual, the estimated age at death between two teeth can differ by 26 years, which produces a bias in age estimations from this parameter.