Technical notes for age estimation using the femur: influence of various analytical conditions on D-aspartic acid contents

In order to make a better estimate of the individual age using bone samples, we evaluated the effects of various criteria on the analytical measurement of D-aspartic acid contents. Using compact bone from a male femur, we varied six analytical conditions (sample volume, sample particle size, hydrolysis temperature, hydrolysis time, hydrochloric acid volume during hydrolysis, and hydrochloric acid concentration during hydrolysis). D-form/L-form ratios were affected most by hydrolysis, temperature (estimated age differences were 3.03 years/degreesC), followed in order by hydrochloric acid volume (1.44 years/ml) and hydrochloric acid concentration (0.69 years/0.1 M). Larger sample particle sizes and hydrochloric acid volumes during hydrolysis tended to result in lower racemization rates. Nonetheless, within a range of 5-50 mg, sampling volume did not affect the detected D-aspartic acid contents. Since the racemization reaction rate in femur compact bone is slower than in dentin, bone samples seem to be more greatly influenced by analytic conditions than dentin. Tests must therefore be performed with caution, especially with regard to the hydrolysis temperature, hydrochloric acid volume and concentration when estimating age using femur samples.