Remineralization of Artificial Enamel Lesions in vitro

To investigate the mechanism of mineral deposition during remineralization, artificial (HEC) lesions were remineralized in a 45Ca-labelled solution containing 1.5 mM Ca, 0.9 mM PO4 at pH 7.0 and 37 °C. In a second part of the study, specimens were also subjected to leaching in a non-mineralizing solution or to prolonged remineralization in a non-labelled but otherwise identical remineralizing solution. Mineral deposition was determined as a function of depth by grinding off layers from the specimen and measuring the radioactivity. The results show that during remineralization mineral is initially deposited near the surface layer. During leaching or prolonged remineralization this deposit is easily dissolved. The percentage and absolute amount of mineral deposited in the interior of the lesion increases with time with an accumulation at the point of minimum mineral density (lesion body). Compared to the surface layer this material is present in a less soluble state. Possibly the precipitation conditions are favourable in the region between the point of minimum mineral density and the sound enamel (‘dark zone’).