Aspartic acid racemization with correlation to age: a forensic perspective

Objective: To estimate age through aspartic acid racemization of human dentin for forensic analysis, and to calculate the margin of error between chronological age and estimated age by racemization method. Study Design: Cross-sectional comparative study. Place and Duration of Study: Dental Outpatients' Department, Ziauddin Hospital, Karachi, from 2011 to 2014. Methodology: Patients from dental orthodontics department were selected. Verbal expressed consent was taken from the participants. Preliminary data was entered in a specially designed performa having name, chronological age, gender, socio-economic status. L and D ratio of aspartic acid were quantified in dentin for each tooth by High-Pressure Liquid Chromatography technique. Results of 100 samples with known age were used during study to estimate co-efficient of racemization. Regression equation was derived by plotting 85 samples of known age and KR as independent and dependent variables and least square equation was derived - Age = -4.391 +347.396 (co-efficient of racemization). Results: The estimated co-efficient of determination was 0.74, meaning thereby that the regression equation was 74% correct for estimating age. The calculated correlation between chronological age and co-efficient of racemization was 0.834, which is interpreted as a very strong and positive correlation. The co-efficient of racemization increased with the age. The mean chronological age (38.44 [+ or -] 13.22) years were statistically similar to the mean calibrated age (37.52 [+ or -] 12.36) years. The median of actual and calibrated age was found to be 3.4 with inter-quantile value of 13. No statistically significant difference was observed among gender (p=0.837), or socioeconomic status (p=0.35). Conclusion: Racemization of human dentin could be used as one of the reliable method for estimating age. HPLC is a reliable technique to estimate the co-efficient of racemization because it is highly reproducible, cost-effective and convenient. However, the procedure should be optimized and standardized within all laboratories for quality assurance. Key Words: Aspartic acid. Dentin. HPLC. Co-efficient of racemization (KR). Age estimation.