M Asaizumi, T Kato, T Kuga, N Oode, T Oda, T Sakurada, K Thomson, T Tabara, RL Karlinsey. Submicron X-ray computed tomography of human dentin treated with topical fluoride modalities. EC Dental Science 5, 992 (2016).
Objective: Characterization studies on demineralized dentin are important in understanding, preventing and addressing dentinal hypersensitivity. Multiple microscopy techniques, including an advanced synchrotron radiation (SR) X-ray computed tomography (CT) experiment, were used to assess the submicron morphology, composition and structure of sound and demineralization human dentin, as well as demineralized dentin treated with three different fluoride formulations. Methods: Dentin samples were obtained and prepared from extracted human bicuspids and arranged into five groups (N = 5): sound dentin; demineralized dentin; and, demineralized dentin treated with either a 0.2% NaF prophy paste, 1.1% NaF dentifrice or 5% NaF varnish. Specimens were then submitted to an advanced SR X-ray CT technique involving microscope optics providing submicron spatial resolution. Multiple comparison statistical analyses (Tukey HSD, p < 0.05) were performed on X-ray linear attenuation coefficients (LACs) for each group. Specimens were further assessed for morphology and composition using digital light microscopy (DLM), field-emission scanning electron microscopy (FE-SEM) and focused ion beam (FIB) techniques. CT, FE-SEM and FIB data files were then imported into software packages to create volume renderings for visualization purposes. Results: LAC values were obtained via SR X-ray CT and used to estimate mineral concentrations within dentin tubules as well as in the inter-tubular regions. Our investigation yielded region-specific trends in mineral concentrations for sound and demineralized dentin, and demineralized dentin treated with each of the fluoride formulations. Statistical differences were observed among treatment groups as a function of depth into dentin. Complimenting SR X-ray CT, DLM, FE-SEM and FIB provided morphological and compositional detail. Conclusion: SR X-ray CT provided submicron resolution of tubular and inter-tubular demineralized dentin treated with different fluoride modalities, including a prophy paste, dentifrice and varnish. The use of SR X-ray CT to probe region-specific processes provides important insight into dentinal structure and may find further applications in addressing and understanding dentinal hypersensitivity.
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