An application of D- and L-aspartic acid mixtures as standard specimens for the chronological age estimation

Instead of using the control teeth, we tried to prepare standard specimens to derive the equations for calculation of the age (analytical curves) with respect to each kind of tooth of various ages. To prepare standard specimens, we determined the racemization ratio of the teeth of known age that had actually been used for the appraisal of chronological age (total control teeth). Then we mixed commercially available L-Asp and D-Asp in the same D/L ratio as the measured one in the total control teeth. As a result, we were able to obtain the racemization rate equations from the age-specific standard specimens of central and lateral incisors. These equations were closely similar to those derived from actual teeth of known age. Since the racemization rate equations obtained from the standard specimens were satisfactorily reproducible, we assumed that these equations could be used in place of those obtained from the control teeth. Actually, in the age estimation of unidentified corpses from teeth, the use of standard specimens enabled us to estimate the age almost as precisely as estimated using the control teeth. Thus, the present study has demonstrated that in the estimation of chronological age the control teeth can be substituted by the standard specimens. This shows the possibility of using the standard specimens also in other laboratories where the racemization ratio can be measured with sufficient reproducibility.