Treatment of dentin hypersensitivity by calcium phosphate precipitation method.

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We have proposed calcium phosphate precipitation (CPP) method which occluded dentin tubules with apatitic mineral for the treatment of dentin hypersensitivity. In this study, we aimed (1) to assess the feasibility of other basic solutions as the post-treatment solution for clinical use of CPP method. (2) to evaluate occluding ability of CPP method in vivo using beagle dogs. The current CPP method uses 1 mol/L NaOH (pH=12.4) as the post-treatment solution. However, its strong basicity is not desirable for clinical use. We evaluated several buffer solutions to neutralize CPP solution, then we chose 1 mol/L NaHCO_3 (pH=8.1) as the post-treatment solution. It gave almost the same occluding ability of dentinal tubules with that of NaOH.Next, we evaluated the occluding ability of dentinal tubules with CPP method using vital tooth of beagle dogs. Class V cavity was prepared in cervical of molar in beagle dogs, then the tooth was etched with 50% citric acid for 2 min to open dentinal tubules. After the application of CPP method, dentin biopsy was performed to obtain dentin specimens using cylindrical diamond point. We found that dentinal tubules were occluded homogeneously and completely with the precipitate. The depth of the precipitate was approximately 5 mum, the value was approximately half of that obtained in vitro results. The Ca/P molar ratio of the precipitate was 1.5. The value indicated that the precipitate was carbonate-apatite. We concluded that CPP method is useful for the treatment of dentin hypersensitivity since it occludes dentinal tubules homogeneously with apatitic mineral even though the depth of precipitate was shallower than that of in vitro results.