Amino Acid Racemization in Human Detine as an Estimator of Chronological Age – A Study in Karachi Pakistan

Abstract

Background: Amino acid racemisation is a reliable method to estimate age in developed countries. This pilot study was designed to determine the coefficient of amino acid racemisation (AAR) with reference to age in our population. Also as no such study has been conducted in our setting, the study also aims to discuss reproducibility of this study on a larger scale. Objective: To determine the coefficient of amino acid racemisation (AAR) with reference to age; To measure the mean error in calculating age using this method; To identify any differences from earlier observation and discuss the reproducibility in our setting. Methods: Teeth were obtained from subjects between the age of 15 and 60 years who had come for routine extraction procedure or for orthodontic procedures. Incisors, canines, premolars and, first and second molars were included. Carious tooth and third molar were excluded. Samples were stored, dried, de-mineralised, hydrolysed, and derivatised. High-Pressure Liquid Chromatography (HPLC) was performed to quantify the L- and D- forms of aspartic acid in dentin. Correlation and regression was then tabulated based on the quantification, and was compared with data from other studies. Results: Based on the analysis of selected samples, a strong positive correlation of 0.93 was observed between co-efficient of racemisation and chronological age. The regression line derived was Age = 200 (KR) + 17.306 (where KR= coefficient of racemisation).The computed regression line was tested by using coefficient of racemisation for 8 samples selected during the study and the mean error (difference between actual and calibrated age) determined came out to be 3.99±5.77. Conclusion: The correlation coefficient was strongly positive. The results strongly suggests that aspartic acid racemisation of human dentine is a precise method for estimation of chronological age in living and in dead. The methodology should be standardized to make the results more accurate and prevent fallacies. However it remains an expensive procedure, especially the laboratory equipment that would not be available in most cities of Pakistan. Key Words: Age Estimation, Amino Acid Racemisation, Forensics Sciences, HPLC, Dentin, Pakistan Epidemiology.