Analysis:
(1) Primary dentin is chipped from the dentino-enamel junction using a diamond disk cooled with water. The pieces are powdered using a vibratory mill.
(2) The dentin is then demineralized with 0.5 M sodium EDTA adjusted to pH 7.4.
(3) The dentin is hydrolyzed with 6 M hydrochloric acid at 100°C for 6 hours.
(4) Amino acids are derivatized into isopropyl esthers using isopropanol and acetyl chloride. This is then derivatized with trifluoroacetic acid anhydride.
(5) The sample is then injected into a GC or HPLC. The signal is reported in mV and the elapsed time in minutes.
ratio of D-asparatic acid to L-aspartic acid =
= (area of peak for D-aspartic acid) / (area of peak for L-aspartic acid)
coefficient of racemization = KR =
= LN ((1 + (ratio of the enantiomers)) / (1 - (ratio of the enantiomers)))
Regression equation 1 (page 1230) for 71 persons between the ages of 15 and 95 (R = 0.93):
age of the patient in years =
= ((coefficient of racemization) – 0.0352) / 0.0006 =
= 1666.67 * ((coefficient of racemization) – 0.0352)
Regression equation 2 (page 1230) for 46 persons between the ages of 15 and 60 (R = 0.96):
age of the patient in years =
= ((coefficient of racemization) – 0.02269) / 0.0009 =
= 1111.11 * ((coefficient of racemization) – 0.02269)
Performance:
• The estimate is considered reliable provided the preparation and analysis are conducted precisely. Inaccuracies at any step in the process can affect the result.
