Objective: To determine the ability of a Nanohydroxyapatite toothpaste (ApagardŽ Renamel) to occlude the dentin tubules as surrogate measure of its antihypersensitivity effect. Methods: Dentin blocks were produced with the pulpal and cemental surfaces polished to create flat planoparallel surfaces. Then the smear layer from polishing was removed by either 90 seconds sonication in 1% citric acid (pH 4.0) to create opened-dentin-tubules (OD), or sonication in distilled water to retain natural-dentin-tubules (ND). Each group was further subgrouped into treated (ODt and NDt) and untreated (ODnt and NDnt). Treated samples (12/group) were brushed with the test toothpaste for 2 min in each occasion for a total of 10 treatments, while the non-treated (12/group) received no treatment. Then all samples were subjected to a dye penetration test with 0.1 % methylene blue at a flow speed of 0.216 ml/min for 5 minutes. Penetrated dye was collected in distilled water and the color intensity was quantified using spectrophotometer (595 nm) as a measure of the amount of dye that penetrated through the tubules. The treated and untreated subgroups of each group were compared using t-tests, while the four subgroups (ODt/ODnt/NDt/NDnt) were compared by Duncan multiple comparison test. Results: In both OD and ND, dye penetration was significantly (p<0.01, n=12, α=0.05) greater in untreated subgroups (ODnt/NDnt) when compared with the treated (ODt/NDt). Comparing the subgroups, dye penetration was significantly (P<0.01) higher in ODnt compared to ODt, NDnt or NDt. No significant difference was observed in dye penetration in ODt and NDnt. There was no dye penetration through NDt. Conclusion: The study highlighted that the developed dye penetration method can be used to test the tubule occlusion action of antihypersensitivity toothpastes, and demonstrated that the test toothpaste occluded both natural and widened dentin tubule.
Keywords: Dentifrices, Dentin, Hypersensitivity, Methodology and Oral hygiene
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