RACEMIZATION OF ASPARTIC-ACID IN THE EXTRACELLULAR-MATRIX PROTEINS OFPRIMARY AND SECONDARY DENTIN

The accumulation with age of D-aspartic acid in primary and secondary human dentin was determined. In primary dentin, the plot of the D/L As p ratio vs. age was found to fit first-order kinetics in accordance wi th the literature. But the secondary dentin behaved in an irregular ma nner and showed, in the great majority of cases, significantly increas ed D/L Asp ratios. Possible reasons for these findings, such as differ ences in protein composition and/or in the prevailing temperature, are discussed.