Effects of the Ca2+ and PO43− ion flow on the lengthwise growth of octacalcium phosphate in a model system of enamel crystal formation with controlled ionic diffusion

Abstract An amount of Ca 2+ and PO 4 3− ions transported into the enamel matrix change during tooth enamel crystals formation. Effects of the Ca 2+ and PO 4 3− ion flow on the lengthwise growth of octacalcium phosphate were studied at 37°C and at pH 6.5 in a model system of tooth enamel formation, where a cation selective membrane and a dialysis membrane were used to control the ionic diffusion. An amount of Ca 2+ and PO 4 3− ions that flow into the reaction space between the membranes was changed by using 5, 10, 30 mM Ca and PO 4 solutions as ionic sources. The length increased while the width decreased with an increase in concentration of Ca and/or PO 4 solutions. As a result, the length to width ( L / W ) ratio increased and the width to thickness ( W / T ) ratio decreased with an increase in concentration, resulting in narrower and longer ribbon-like crystals. It was suggested that growth of enamel crystals is, in part, affected by the change in the amount of Ca 2+ and PO 4 3− ions, that flow into the enamel matrix.