The racemization of which of the following in is used for age estimation from teeth

Aspaic acid racemization: Of all amino acids, aspaic acid has one of the fastest racemization rates and most commonly used for age estimation. During the course of aging, L-forms of amino acids are transformed by racemization to D-forms. Thus, the extent of racemization of amino acids may be used to estimate the age . The analysis has been done on both tooth enamel and crown dentin with analysis of dentin giving more accurate age estimation than enamel.