Microprobe analysis of calcifying matrices and formative cells in developing mouse molars.

The distribution of Calcium and Phosphorus and of Na, K, S and Cl was studied in the mineralizing matrices and strata of ameloblasts and odontoblasts in developing mouse molars (5-14 days). Sections cut in a cryostat were prepared by freeze-drying and examined in an SEM by the method of energy dispersive x-ray analysis. In enamel a gradient of mineralization was observed with respect to age and topography. Progesssive loss of sulfur was also demonstrated. Less striking mineralization gradients were found in dentin. Predentin accumulated Ca at a concentration about 2% that of dentin and the Ca/P ratio was lower than that for apatite. Significant concentrations of calcium were localized in ameloblast and odontoblast strata. The concentration increased five-fold in ameloblasts as the cells matured and enamel mineralization entered the final phases, levels in odontoblasts remained stable. With age in both cellular strata, potassium counts decreased. In maturing ameloblasts the concentrations of sodium and chloride rose.