Preparation of dentin standard samples for age estimation based on increased aspartic acid racemization rate by heating.

ABSTRACT

Age estimation in adults based on aspartic acid racemization (AAR) provides fewer errors and higher precision than that based on bone morphology for the identification of cadavers. The technique has been established in some labs as a routine method. However, as the essential requisites for the technique, a wide age range of teeth of the same type as the target tooth must be collected for calibration for each examination. We investigated whether dentin standard samples could be prepared by increasing the AAR rate via heat. Powdered dentin was prepared from a maxillary first premolar (13 years) and heated for 0-72 h at 110 °C. The extent of AAR increased significantly with heating time and the correlation was strong (r = 0.913; p < 0.01). Similar results were found for a mandibular canine (24 years, r = 0.948; p < 0.01) and a maxillary third molar (20 years, r = 0.944; p < 0.01). We attempted to estimate the age of four maxillary first premolars of persons aged 25-58 years by using the heated samples (18 years, 12 h to 7 days). The differences between the actual and estimated ages were within ±5 years. The stability of the AAR rates in the powdered dentin during storage at 22-25 °C, 4 °C, and -30 °C was examined after 1 year and no significant changes had occurred. We were able to prepare dentin standard samples and created a calibration curve. This is a pilot study that needs to be validated before it can be used in forensic practice.