Title: 0219 - Fluoride Release and Concentration at the Varnish/Tooth Interface


Clifton Carey (Presenter)
University of Colorado


Objectives: Fluoride release has been reported for many F-varnish products. Unfortunately, fluoride release measures the amount of fluoride that does not stay near the dentition and is useless for predicting F-varnish efficacy to prevent caries. We evaluate a model experimental system designed to simultaneously assess the fluoride release and fluoride concentration at the varnish/tooth interface.

Methods: The experimental system uses two fluoride ion-selective electrodes (F-ISE) and a combination pH/reference electrode. The pH electrode is calibrated at pH 5, 6, and 7 and both F-ISE (F1 and F2) are calibrated in fluoride standards made in pH 6.0 buffer from (5x10-6 to 1x10-3) mol/L. F2 is then placed on a balance and tared and ~20-30mg of varnish was painted onto the sensing crystal and the amount recorded. The pH and F1 are placed in 30.0 mL of pH 6.0 buffer with a stir bar and monitored until steady potentials are obtained. Then F2 is put into the buffer and the potentials for all electrodes monitored for at least 24h. Five commercially available 5 % NaF-varnish products were tested, one contained amorphous calcium-phosphate (ACP) forming salts, one contained protein stabilized ACP, n≥4. The maximum concentration of released fluoride at 10 h (Max-F1) and time for half of the Max-F1 (t½) was determined. Time of hydration was defined as the point where the F2-ISE begins to sense fluoride. The maximum fluoride concentration at the surface of F2 was identified during the 48h experiments.

Results: The pH did not change from 6 by more than 0.02 units throughout these experiments. The fluoride release results are shown in the table (n≧4).
Ranked comparisons at p≤0.05:
10h F Max: MI>EPro>ProF~VA>D
t½ of F Max: D>MI~EPro~VA~ProF
Max F2 of Surface: D~VA>MI>EPro
Time for F2 Hydration: MI~EPro<VA<D

Conclusions: The experimental system yielded reproducible results that are informative about the mode of action for F-releasing varnishes. Calcium-phosphate containing products released significantly greater amounts of fluoride to the external solution; thick hydrate-able products without calcium-phosphate generated highly concentrated waves of fluoride at the varnish/electrode interface. This later observation may point to the caries preventive mechanism of F-releasing varnish.


  10h Max F1
External [F]
External [F]
t½ (hr)
of F2 (hr)
Max F2
Surface [F]
Duraphat (D) 0.70 ± 0.14 1.13 ± 0.24 0.37 ± 0.19 69878 ± 45677
EnamelPro (EPro) 12.49 ± 3.12 2.28 ± 0.59 0.03 ± 0.01 7757 ± 1619
MI Varnish (MI) 21.47 ± 1.58 2.26 ± 0.33 0.03 ± 0.01 12971 ± 3489
VarnishAmerica (VA) 1.11 ± 0.46 2.94 ± 0.75 0.07 ± 0.03 61852 ± 4635
Profluorid (ProF) 1.72 ± 0.48 3.06 ± 0.63 > 48 Noise

Disclosure Statement:
The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: None