2013 Volume 56 Issue 1 Pages 17-24
Purpose: We have developed a novel dentin desensitizing treatment consisting of sequential application of surface reaction type pre-reacted glass-ionomer fine powder (S-PRG powder, 0.8 μm average particle size) and 13% polyacrylic acid. The purpose of this study was to assess the treatment in terms of dentinal tubule occluding potential and acid resistance of underlying dentin by using SEM and transversal microradiography (TMR). Methods: Dentin specimens were cut from bovine roots, and test surfaces were smoothed using 2,000-grit waterproof abrasive paper and the dentinal tubules were opened. The specimens were then divided into S-PRG, MS coat and control (no treatment) groups. In the S-PRG group, a micro applicator was dipped in deionized water and dredged with the S-PRG powder. The S-PRG powder was then applied on the simulated hypersensitive dentin area with opened dentinal tubules by rubbing for 15 seconds. Then, 13 % polyacrylic acid was applied for five seconds. The MS coat was applied in accordance with the manufacturer's instructions. After immersing in deionized water for 24 hours, dentinal tubule occlusion in the surface and torn surface was observed by SEM. The acid resistance test was performed by exposing the test surface to pH 5.0 acetic acid gel for 7 days. After the acid resistance test, SEM observation was done in the same way, and the acid resistance of the underlying dentin was evaluated by TMR. The integrated mineral loss (IML) was measured using the dedicated software TMR 2000. Results: The control group with no treatment revealed opened dentinal tubules, simulating a hypersensitive dentin surface. Dentin surfaces treated with S-PRG were completely covered with thin films and plugs that may have represented the reaction products of S-PRG filler and polyacrylic acid, even after the acid resistance test. The plugs penetrated to a depth of approximately 20 μm. In the MS group, however, some dentinal tubules were opened even before the acid resistance test, and more tubules were opened after the test. TMR showed that the S-PRG group demonstrated lesion profiles with high mineral volume %, whereas the control and MS groups showed severely demineralized lesions. The IML of the S-PRG group was significantly lower than that of the other two groups (p<0.05). Conclusion: These results showed that the novel treatment with S-PRG powder and polyacrylic acid caused the occlusion of dentinal tubules and prevented the demineralization of underlying dentin, suggesting that the treatment may be effective for dentin desensitization.
