Estimating age through the amino acid racemization of acid-soluble dentinal peptides.

We studied the possibility of estimating age through the amino acid racemization of acid-soluble dentinal peptide (SP). The correlation of the D/L ratio of aspartic acid and the actual age was the highest in the SP extracted with 1 M HCl (r = 0.996, sigma = +/- 0.8), followed by the total amino acids (TAA:r = 0.995, sigma = +/- 1.0), and the SP extracted with 2 M HCl (r = 0.980, sigma = +/- 1.9) and then SP extracted with 5 M HCl (r = 0.951, sigma = +/- 2.7). The rate of the racemization reaction decreased in the order of SP extracted with 1 M HCl, 2 M HCl, 5 M HCl and the total amino acids (TAA). Consequently, an extraction with 1 M HCl seemed best for estimating the age from SP to serve actual cases.