Effect of Calcium Phosphate Containing Fluoride Varnish on Dentin Permeability

The hydrodynamic theory of dentin sensitivity suggests that a reduction of dentin permeability will reduce dentin sensitivity. Hypotheses: The addition of calcium (Ca) and phosphate (P) salts to an F-varnish will deposit Ca/P/F on/in dentin tubules. These deposits will occlude the tubules and hence decrease dentin permeability. Objectives: Determine the effect of Ca/P containing F-varnish on occlusion and permeability of dentin. Methods: Dentin discs were etched with 12% citric acid for 60s and mounted on the measuring cell. A resin/alcohol-based 5% NaF-varnish with or without 10% calcium chloride and 5.8% sodium phosphate was then applied on dentin discs and 0.1 mL of 0.1 N NaCl solution was added on the top of the applied varnish. The varnish was removed mechanically and chemically after 12 h treatment and the permeability of the disc was evaluated by hydraulic conductance (Lp) (Pashley et al., JDR 62:956-959, 1983). The precipitates on the disc were examined by scanning electron microscopy (SEM) and the precipitates from the Ca/P/F-varnish in the 0.1 N NaCl solutions were studied by SEM, x-ray powder diffraction (XRD) and chemical analysis. Results: Mean hydraulic conductances expressed as percentage of pretreatment values (N=6) were 97.8 %±25.0 % and 29.1%±22.0 % for F-varnish and Ca/P/F-varnish treatment respectively. The Ca/P/F-varnish treatment significantly reduced the Lp compared to the F-varnish treatment alone (p<0.001, Student t-test). SEM showed that the precipitates from Ca/P/F-varnish treatment appeared to partially occlude the dentin tubules and no precipitate after F-varnish tratment. The SEM, XRD and chemical analysis indicated that precipitates were amorphous calcium phosphates and calcium fluoride. Conclusion: The treatment with calcium-phosphate-fluoride varnish significantly reduced the dentin permeability while the fluoride varnish alone did not. Theses results suggest that a Ca/P/F-varnish may reduce dentine sensitivity better than an F-varnish alone. Supported by ADAF, NIST, NNMC, & Medical Products Laboratories, Inc.