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Synchrotron radiation-based micro computed tomography in the assessment of dentin de- and re-mineralization

Synchrotron radiation-based micro computed tomography (SRμCT) is well established to determine the degree of mineralization in bony tissue. The present study demonstrates that the method can be likewise used for three-dimensional analyses of dentin de- and remineralization. Four dentin discs about 4 mm in diameter and 0.8 mm thick were prepared from freshly extracted human third molars. In order to study the de- and re-mineralization, three of them were treated with 10% citric acid for the period of 10 min. Nano-particulate bioactive glass made of SiO2, P2O5, CaO, Na2O served for the re-mineralization in physiological saline. This process was carried out at the incubation temperature of 37 °C for 1 and 7 d, respectively. The native and the treated discs were comparatively examined by SRμCT in absorption contrast mode. Already the visual inspection of the tomograms obtained reveals remarkable differences related to the mean X-ray absorption and internal microstructure. The de-mineralization led to a surface morphology characteristic for the treated dentin collagen matrix. The re-mineralized discs show a dependence on the period of the treatment with the bio-active glass suspension. Initial signs of the remineralization were clearly present already after 24 h of incubation. The disc incubated for 7 d exhibits a degree of mineralization comparable to the native control disc. Thus, SRμCT is a powerful non-destructive technique for the analysis of dentin de- and re-mineralization.