Twenty-eight 4 mm × 4 mm human dentin specimens were prepared at Indiana University from human tooth roots to mimic exposed dentin after gingival recession. Ethical approval for use of the extracted teeth was given by the Indiana University Institutional Review Board (NSO 911-07). The specimens were polished using 1200-grit paper until most of the dentin surface was flattened. The specimens were then serially polished using 4000-grit paper (Struers Inc.) followed by a 1-µm diamond polishing suspension (DP Suspension P, Struers). Highly polished surfaces are preferred to perform the analyses and to relate the findings to those of comparable studies on dentin. While patency of dentinal tubules varies, studies on artificially created, almost- completely-patent tubules are needed to study the mode of action of new interventions and to compare the efficacy between different interventions. Ten untreated specimens were then set aside for the penetration study.
To open the dentinal tubules of the remaining 18 tooth specimens for study of tubule occlusion, all were immersed in 17% EDTA solution (pH 7.4; Fisher Scientific) for 5 min. They were then randomized and allocated 1:1:1 to the test groups before being treated with either one drop (about 50 μL), applied with a microbrush, of an experimental, viscous (~30 cP at room temperature) 38% SDF solution (labeled C, based on Advantage Arrest®, patent pending), the positive control (labeled A, Advantage Arrest®, Elevate Oral Care LLC), or an aqueous placebo solution that contained neither fluoride nor silver (labeled B), following the manufacturer’s instructions for test group A, the standard product. The SDF solutions were allowed to remain on the exposed surfaces for one minute and then rinsed with running deionized water for 5 s. The test products and placebo were freshly prepared and certified by an FDA-regulated laboratory independent of the investigators, and the investigators were blind to the contents. The specimens were then immersed in artificial saliva (2.2 g/L gastric mucin, 0.381 g/L NaCl, 0.213 g/L CaCl2.H2O, 0.738 g/L KH2PO4, 1.114 g/L KCl, pH 7.0; Fisher Scientific) for 2 h [7 (link)], rinsed again with running deionized water for 5 s and the vials with excess moisture were sealed and shipped to Germany for testing at the Fraunhofer Institute.
To open the dentinal tubules of the remaining 18 tooth specimens for study of tubule occlusion, all were immersed in 17% EDTA solution (pH 7.4; Fisher Scientific) for 5 min. They were then randomized and allocated 1:1:1 to the test groups before being treated with either one drop (about 50 μL), applied with a microbrush, of an experimental, viscous (~30 cP at room temperature) 38% SDF solution (labeled C, based on Advantage Arrest®, patent pending), the positive control (labeled A, Advantage Arrest®, Elevate Oral Care LLC), or an aqueous placebo solution that contained neither fluoride nor silver (labeled B), following the manufacturer’s instructions for test group A, the standard product. The SDF solutions were allowed to remain on the exposed surfaces for one minute and then rinsed with running deionized water for 5 s. The test products and placebo were freshly prepared and certified by an FDA-regulated laboratory independent of the investigators, and the investigators were blind to the contents. The specimens were then immersed in artificial saliva (2.2 g/L gastric mucin, 0.381 g/L NaCl, 0.213 g/L CaCl2.H2O, 0.738 g/L KH2PO4, 1.114 g/L KCl, pH 7.0; Fisher Scientific) for 2 h [7 (link)], rinsed again with running deionized water for 5 s and the vials with excess moisture were sealed and shipped to Germany for testing at the Fraunhofer Institute.
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