[Age estimation by amino acid racemization in dentin--application of fractionation and extraction].

This study was made to improve the validity of age estimation from teeth using amino acid racemization. The correlation between actual age and the D/L ratio of aspartic acid was investigated by analyzing not only total amino acid but its fractionated substances, insoluble collagen and soluble peptide. The coefficient values of correlation between the D/L ratio and actual age in lower central incisors were 0.996 (sigma = 1.0 years) for total amino acid, 0.998 (sigma = +/- 1.8 years) for insoluble collagen, and 0.997 (sigma = +/- 0.9 years) for soluble peptide. The corresponding figures in upper and lower first premolars were 0.991 (sigma = +/- 1.6 years), 0.989 (sigma = +/- 1.9 years), and 0.994 (sigma = +/- 1.4 years), respectively. The reactive velocity of aspartic acid racemization was highest for soluble peptide both in lower central incisors and upper and lower first premolars, approximately three times as rapid as that for total amino acid. The velocity for insoluble collagen was slightly lower than that for total amino acid. Age estimation was attempted from the teeth of an unknown body. As a result, age estimated from the analysis of soluble peptide was most accurate. These results suggest that the analysis not only of total amino acid in dentin but its fractionated and extracted substances can lead to higher reliability in age estimation. Soluble peptide, in particular, has been found to be most effective.