Dental cementum increment analysis and estimating season at death in humans
Ralston, Claira E
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Dental cementum is a mineralized tissue that coats the root of a tooth and anchors it into the alveolar socket via the periodontal ligament. Cementum is continuously deposited and mineralized throughout the life of a tooth, preserving the complex developmental processes of root formation in optically distinct histologic layers (Hillson, 1996; 2005). Analysis of these features has several anthropological applications, specifically the analysis of cementum increments and their utility in estimating age and season at death in humans for establishing a more specific post-mortem interval (PMI). Wedel (2007) conducted a pilot study to determine whether dental cementum increment analysis can be used to establish season of death in humans. Wedel (2007) hypothesized that by identifying the timing of the transition between the bands of arrested development and the bands of increased deposition, dental cementum increment analysis can be used to identify the season at death in humans. It was demonstrated that cementum increment analysis is 99% accurate in estimating whether an individual died in either a fall/winter or spring/summer season. The purpose of the present study was to estimate whether cementum bands could accurately be assigned to fall/winter, spring/summer seasons based on their optical properties as being light or dark. A total of 143 teeth of known age and known extraction date drawn from the Boston University Collection and the Antioquia Modern Skeletal Reference Collection in Medellín, Colombia were analyzed using recent protocols for preparation, sectioning, and observing increment lines in cementum. Dental cementum increment analysis was found to be between 61.54% and 71.15% successful in accurately correlating the nature of the last cementum increment to season at death using a combination of image evaluation and through focus evaluation methods on two distinct geographic samples. A through focus evaluation was found to be more successful at identifying the last band formed and is recommended for microscopic analyses estimating season at death using dental cementum increments. Geographic origin did not have a significant influence over the accuracy of the method to estimate season at death, however the results of this study suggest that teeth extracted from cadavers versus living individuals may have some influence on the accuracy of cementum increments to estimate season at death. No significant influence of sex, age, or tooth type on the identification and correlation of the last band formed were detected in this study. An interobserver analysis using digital images of a randomly selected sample of 45 sections found that interobserver agreement on the nature of the last band formed occurred in only 28.8% of the sample. Inconsistencies in the nature of the last band formed between multiple sections prepared from the same tooth were observed, which calls into question the validity of using cementum increments to estimate season at death. The potential limitations for the reliability of using dental cementum increment analysis to determine season at death in humans include the lack of a standardized method for preparing adequate sections for viewing cementum increments, and the subjectivity of identifying the last band in a given section. It is concluded that if the validity and reliability of dental cementum increment analysis as a method for age estimation can be established and configured to meet the criteria of the Daubert Standard, specifically in the adoption of a standardized protocol of analysis, then the validity of using this method for estimating season at death can be further considered.