OCCLUSION OF DENTINAL TUBULES WITH CALCIUM-PHOSPHATE USING ACIDIC CALCIUM-PHOSPHATE SOLUTION FOLLOWED BY NEUTRALIZATION

The occlusion of dentinal tubules with calcium phosphate, by a calcium phosphate precipitation method (CPP method), was investigated in vitr o for evaluation of the potential value of this method for the treatme nt of dentin hypersensitivity. The method consists of treating the den tinal surface with a CPP solution, i.e., an acidic solution that conta ins both calcium and phosphate, followed by neutralization with basic post-treatment solution. The CPP solutions used in this study ([Ca] = 0.2 -1.0 mol/L, [PO4] = 0.2 - 4.0 mol/L) were prepared by dissolving C a(OH)(2) or CaHPO4.2H(2)O in H3PO4 or HCl, and 1 mol/L NaOH solution w as used for the post-treatment solution. Sections of human dentin disk s treated by the CPP method were observed by scanning electron microsc opy, and the precipitate in the dentinal tubules was subjected to x-ra y micro-analysis. After treatment by the CPP method, dentinal tubules were occluded to a distance of approximately 15 mu m from the surface, and the precipitate showed a Ca/P molar ratio of 1.03 +/- 0.01. To ob tain a larger amount of precipitated mineral for further analysis, we used the same procedure with glass tubes (inside diameter, 1 mm). Powd er x-ray diffraction analysis and FT-IR measurement revealed that the precipitate was dicalcium phosphate dihydrate (CaHPO4.2H(2)O). The ins tant precipitation of calcium phosphate mineral in the dentinal tubule s demonstrated the potential value of the CPP method for the occlusion of dentinal tubules; this occlusion may be useful for the treatment o f dentin hypersensitivity.