Racemization of aspartic acid in human cementum with age.

This study explored the application of the racemization reaction to forensic dental medicine in relation to estimation of age from tooth cementum. Cementum from the cervical two-thirds and the apical one-third of 16 upper incisor teeth gave ratios of D-/L-aspartic acid that correlated highly with actual age, the correlation coefficients being r = 0.993-0.996. For whole cementum from lower central and lateral incisors, first and second premolars (n = 8) the correlation coefficients were r = 0.984-0.997. Incisors gave more reliable results than premolars. The study was extended to compare cementum, enamel and dentine from first premolar teeth of the same individuals. The correlation of the ratio of D-/L-aspartic acids with actual age was highest for dentine (r = 0.992), followed by cementum (r = 0.988) and enamel (r = 0.961). These results indicate that the racemization reaction in cementum proceeds in a constant manner, and confirm that cementum remains stable throughout the individual's life. Accurate estimation of age is thus possible when cementum is subjected to the amino-acid racemization method.