Remineralization of Artificial Enamel Lesions in vitro

To investigate the mechanism of remineralization, artificial (HEC) lesions in bovine enamel and etched bovine enamel were remineralized in a pH-stat controlled system at 25, 37 and 50 °C. In all experiments 3 cm2 of demineralized enamel was immersed in 15 ml of a solution containing 1.5 mM Ca, 0.9 mM PO4 at pH = 7.0. The mineral deposition was followed by monitoring the alkali uptake and the changes of the calcium and phosphate concentration in solution. From the analytical data it was concluded firstly that in all cases hydroxyapatite precipitated. Secondly it was shown that the remineralization of both lesions and etched enamel was a second order chemical reaction. The rate of lesion remineralization is primarily determined by the diffusion in the surface layer pores, as indicated by the value of the activation energy (0.38 eV). For etched enamel the activation energy is 0.70 eV suggesting a surface reaction controlled process. Since the mechanism of remineralization of lesions and etched enamel is completely different it is dangerous to extrapolate results obtained with etched enamel to the situation of the clinically interesting remineralization of white spots.