IADR Abstract Archives
44Ca doped pH-cycling study on Dentin Remineralization by Isotope Microscopy
Objectives: In this preliminary study by means of isotope microscopy, Ca distribution following pH-cycling models was distinguished between re-deposition of dissolved dentin mineral (intrinsic 40Ca) or mineral-uptake from remineralization solution (extrinsic 44Ca).
Methods: Remineralization solution was prepared using stable Ca isotope (44Ca), which contained 1.5 mmol/L CaCl2（44Ca),0.9 mmol/L KH2PO4, 130 mmol/L KCl, 20 mmol/L HEPES buffer pH 7.0 ）. The pH cycling was employed for 14 days on bovine root dentin by demineralization (pH 5.0) for 2 hrs, incubation in 0% (control) and 0.2% NaF (900ppm fluoride) for 2 hrs and 44Ca doped remineralization for 20 hrs. The samples were sectioned longitudinally through the lesion center into 220 ±20 µm thickness and polished. Isotope imaging of 40Ca+and 44Ca labeled mineral distribution was observed by a high mass-resolution stigmatic SIMS instrument (Camera IMS 1270, Gennevilliers Cedex, France). The 130μm2 diameter on sample surface was irradiated by O– primary beam (23 KeV, 5 nA). Secondary ions 40Ca+and 44Ca+ was constructed as a mass-filtered ion image using stigmatic ion optics of IMS 1270 and visualized when directly projected on a pixel matrix of stacked CMOS-type active pixel sensor.
Results: Uptake of 44Ca (extrinsic) was greater in intensity for the fluoride group than the control, especially in superficial lesion. The control groups (n=4) showed 40Ca (intrinsic) distribution in subsurface lesion and superficial lesion as well, while the fluoride groups (n=4) showed 40Cadistribution limited on subsurface lesion. For the fluoride groups, the isotope ratio (44Ca/ 40Ca) was more intensified on the superficial lesion. The total Ca (44Ca+ 40Ca) image reveals more homogeneously for the controls than the fluoride groups.
Conclusions: Extrinsic Ca uptake was increased by the use of fluoride at superficial lesion; however, intrinsic Ca loss was more predominant the lesion, resulting that total Ca was less in subsurface lesion (between arrows in Figure).
Methods: Remineralization solution was prepared using stable Ca isotope (44Ca), which contained 1.5 mmol/L CaCl2（44Ca),0.9 mmol/L KH2PO4, 130 mmol/L KCl, 20 mmol/L HEPES buffer pH 7.0 ）. The pH cycling was employed for 14 days on bovine root dentin by demineralization (pH 5.0) for 2 hrs, incubation in 0% (control) and 0.2% NaF (900ppm fluoride) for 2 hrs and 44Ca doped remineralization for 20 hrs. The samples were sectioned longitudinally through the lesion center into 220 ±20 µm thickness and polished. Isotope imaging of 40Ca+and 44Ca labeled mineral distribution was observed by a high mass-resolution stigmatic SIMS instrument (Camera IMS 1270, Gennevilliers Cedex, France). The 130μm2 diameter on sample surface was irradiated by O– primary beam (23 KeV, 5 nA). Secondary ions 40Ca+and 44Ca+ was constructed as a mass-filtered ion image using stigmatic ion optics of IMS 1270 and visualized when directly projected on a pixel matrix of stacked CMOS-type active pixel sensor.
Results: Uptake of 44Ca (extrinsic) was greater in intensity for the fluoride group than the control, especially in superficial lesion. The control groups (n=4) showed 40Ca (intrinsic) distribution in subsurface lesion and superficial lesion as well, while the fluoride groups (n=4) showed 40Cadistribution limited on subsurface lesion. For the fluoride groups, the isotope ratio (44Ca/ 40Ca) was more intensified on the superficial lesion. The total Ca (44Ca+ 40Ca) image reveals more homogeneously for the controls than the fluoride groups.
Conclusions: Extrinsic Ca uptake was increased by the use of fluoride at superficial lesion; however, intrinsic Ca loss was more predominant the lesion, resulting that total Ca was less in subsurface lesion (between arrows in Figure).
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