Estimation of age from dentin by using the racemization reaction of aspartic acid.

To confirm the usefulness of the whole dentin in longitudinal sections for estimating age using the racemization ratio (D/L ratio) of aspartic acid, we compared longitudinal and transverse sections prepared from bilateral teeth in the same jaw of the same subjects. The D/L ratio was measured by gas chromatography. A better correlation between the D/L ratio and true age was observed when using longitudinal sections (r = 0.995) than when using transverse sections (r = 0.984-0.987). In the low age group, the D/L ratio was high in the crown and decreased toward the root apex. In the middle-advanced age groups, however, the D/L ratio was high in the crown as well as the area close to the root apex. The racemization reaction rate was higher in longitudinal than in transverse sections. These results suggest that the whole dentin in longitudinal sections of the central area of the tooth should be examined for accurate estimation of age.