New quantitative and qualitative evaluations on tooth mineral changes after de-and remineralization

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In order to evaluate tooth mineral changes after de-and remineralization quantitatively, we developed two types of the methods. In addition by means of high-resolution electron microscopy we evaluated the changed mineral qualitatively after demineralization or laser irradiation.1)Quantitative evaluations(1)Digital subtraction methodSubtraction image between two digitized microradiograms of the same enamel specimen before and after demineralization made it possible to visualized the changed mineral area by demineralization clearly. We also evaluated the changed mineral quantitatively using regression formula between gray level and alminum thickness.(2)CCD camera methodWe developed quantitative mineral profile evaluation method using CCD camera. The microradiograms of tooth root specimen after de-and remineralization were input as a digital image through CCD camera to a computer. The gray level of each pixel was transposed to the equivalent of alminium thickness according to the regression formula between alminium thickness and its gray level. By means of this method we can show the profile of the mineral vol% in an interested area on the screen simultaneously.2)Qualitative evaluationCrystllographic analysis with high-resolution electron microscopy suggested that enamel treated by demineralization andlaser could change from hydroxyapatite to alpha-or beta-TCP(tricalciumphosphate).