pH gradients in the developing teeth of young mice from autoradiography of [14C]DMO

The distribution of the weak acid [14C]DMO was studied in mice, 10-19 days old, by an autoradiographic technique that does not translocate or remove the compound. Calculations of pH values in areas of the developing teeth of these animals were made by comparing the photometric density of the distribution of [14C]DMO, as an indicator of pH, with that of 14C]NAAP, as an indicator of water content, which was reported in the companion paper. The cellular layers, i.e., odontoblasts, ameloblasts, etc., had pH values of 7.1 +/- 0.1; the pH values in enamel, predentine, and dentine ranged from 7.3 to 8.5. It is suggested that an alkaline matrix promotes nucleation and growth of hydroxyapatite.