Some considerations regarding the use of amino acid racemization in human dentine as an indicator of age at death.

An HPLC method is described for simultaneously obtaining the enantiomeric ratio of three amino acids (aspartic acid, serine, and glutamic acid) from dental collagen, with a view to using this information for estimating age at death. Results are reported from a sample of twenty three known age modern teeth, six known age 19th C. AD teeth, and two unknown age Romano-British teeth. It was found (as expected) that all three D/L ratios changed significantly with chronological age. Standard calibration techniques were used to estimate ages for the six 19th C. AD specimens from regression equations estimated from the modern specimens, and also to predict (for the first time) the error associated with such estimates. Errors using aspartic acid were found to be similar to those obtained by other methods of age estimation from dental evidence, serine, and glutamic acid providing much poorer age estimates. Additionally, a systematic difference in the age-enantiomeric ratio relationship was observed between modern and older dental samples. It is concluded that there is some fundamental difference in the observed enantiomeric ratios between modern teeth and older samples, possibly as a result of the chemical alteration of the dental proteins.