Effect of Fluoride, Calcium and Phosphate on Releases from Varnishes

Fluoride (F) varnishes are effective in preventing caries and reducing dentin sensitivity. The addition of calcium (Ca) and phosphate (PO₄) salts may influence the F release rate and also induce formation of calcium/phosphate/fluoride as persistent F reservoirs. The hypothesis is that F release rate can be optimized with the F content and the addition of Ca and PO₄ salts.  Objectives: To study the effect of the F content and the Ca and PO₄ salts on the ion release and precipitation of F varnishes. Methods: The varnish containing 1670 ppm or 22600 ppm fluoride with or without Ca salt (10%) and PO₄ salt (5.8%) was painted on a 2x2 cm plastic substrate and immersed in a 0.03 mol/L NaCl solution (n=3). The released ions were measured with pH, Ca, and F electrodes under slow stirring at 22 ^oC for 3 days. The concentrations of Ca and PO₄ were analyzed by spectrophotometric methods. The precipitated calcium phosphate fluoride was characterized with X-ray Powder Diffraction and Scanning Electron Microscope.  Results: Table shows the % ± S.D. of released F; the releases increased with the increase in F content and addition of Ca and PO₄ salts.

 

Varnish	1670ppm	1670ppm+Ca/P	22600ppm	22600+Ca/P
1 Day	5.1 ± 3.3%	17.3 ± 1.6%	9.6 ± 4%	41 ± 15%
3 Day	9.7 ± 7.3%	51.1 ± 5.6%	28 ± 14%	79 ± 14%

With  F-varnishes containing Ca/PO₄, the Ca and PO₄ concentrations increased together with the pH increase and then decreased due to the precipitation of spherical calcium fluoride and amorphous calcium phosphate nanoaggregates.  Conclusions: The release rate of F can be optimized with the F content and the addition of Ca and PO₄ salts in the varnish.  These salts may prolong the retention of the released F by the precipitation of mixed phases of calcium phosphate fluorides.