Effect of mono- and divalent ions on diffusion and binding in bovine tooth enamel

A radiochemical method was used to determine quantitatively the effect of RbCl, CaCl 2 and MgCl 2 on the transport of [ 3 H]-sorbitol, [ 14 C]-glycerol, 45 Ca 2+ , 36 Cl − and 86 Rb + through dental enamel. The findings indicate that the transport of 45 Ca 2+ is influenced strongly by surface exchange reactions. The influence of Ca 2+ and Mg 2+ on the transport of 86 Rb + and 36 Cl − indicates that, at a concentration of ~10mmol/l, these ions alter the fixed charge of enamel from negative to less negative, or positive values. Previously adsorbed 45 Ca 2+ ions are desorbed at higher Ca 2+ and Mg 2+ concentrations. Rb + ions at 10 mmol/l have no such effect. The results indicate that Ca 2+ and Mg 2+ can be adsorbed reversibly on the crystal surfaces or in their Stern layers in the pores of dental enamel.