Effects of hexafluorosilicate on the precipitate composition and dentine tubule occlusion by calcium phosphate

Objectives: To improve the calcium phosphate precipitation (CPP) method for the occlusion of dentine tubules with calcium phosphate, the addition of calcium hexafluorosilicate (CaSiF₆) to CPP solution was evaluated in vitro with respect to its occluding capacity and the composition of the precipitate. Methods: The occlusion of dentine tubules was evaluated by SEM observations and by measurements of dentine permeability. The composition of the precipitate was determined by measuring the calcium to phosphorus (Ca/P) ratio of the precipitate in dentine tubules by energy dispersive X-ray spectroscopy (EDS). Results: The addition of CaSiF₆ to the CPP solution resulted in an increase of the Ca/P ratio in the precipitate not only on the dentine surface but also inside the dentine tubules; indicating that the precipitate became more apatitic in nature. The addition of CaSiF₆ had no effect on occluding capacity in terms of measurements of dentine permeability or SEM observations. Dentine permeability decreased to approximately 4% of pretreatment values and the dentine tubules were occluded for approximately 10-15 μm from the dentine surface. Conclusion: It is concluded that the addition of CaSiF₆ to CPP solution was desirable, since it provided a more apatitic precipitate in the dentine tubules, not only on the dentine surface but also inside the tubules, and there were no drawbacks with respect to its occluding capacity.