Calcium Exchange in Enamel and Dentin as Shown by Calcium

Abstract

The adsorption of Ca45 by powdered dentin and enamel from aqueous Ca solns. (1.25 x 10-2, x 10-2, x 10-3, and x 10-4 .[image]) has been measured in vitro. On glycol-ashed dentin, the rapid phase of Ca adsorption is an exchange reaction in which as much as 1/5 of the total Ca atoms of the dentin may ultimately take part. In fresh dentin, a slower but even more extensive exchange may occur. On enamel, only 2% of the Ca atoms appear to exchange. The adsorption probably takes place on the surfaces of the ultra-microscopic hydroxylapatite crystals. These crystals are much larger in enamel (10-4 cm. in length) than in dentin (10-6 cm.).