The temperature dependency of 45Ca diffusion in bovine enamel

The diffusion of 45Ca ions in sound bovine enamel at pH 7.0 was studied as a function of temperature in the range 20 degrees-40 degrees C. The experimental data show that the diffusion is governed by two processes with activation energies of about 0.7 and 1.3 eV respectively. These values are considerably larger than the activation energy of calcium ion diffusion in water (0.2 eV). The diffusion process with the activation energy of 1.3 eV is dependent upon the calcium concentration in solution. A model based on the complex pore structure of enamel and on interactions of diffusing ions with the enamel constituents is discussed.