Changes in D-aspartic acid in human deciduous teeth with age from 1-20 years

The racemization ratio (D/L ratio) of aspartic acid in the dentin (collagen) of deciduous teeth was studied, using dentin of permanent teeth as a reference. D-aspartic acid in deciduous teeth was found to increase almost linearly with aging. The reaction velocity constant of racemization (kyr(-1)) in deciduous teeth (1.1915 x 10(-3)yr(-1)) was approximately double the value for permanent teeth (6.2550 x 10(-4)yr(-1)). Th, velocity of the racemization reaction was similar between deciduous teeth and permanent teeth in a dry state. The D/L ratio determined using transverse sections of deciduous teeth tended to be high in the crown and low in the root. The reaction velocity of racemization is considered to be affected to some extent by the tooth material, ambient temperature and salivary pH, but most importantly by physiologic resorption of deciduous teeth at the root associated with age.