Influence of Dissolution Method and Calcium on Varnish Total Fluoride

Objectives:   Recently introduced dental varnish formulations utilize calcium as TCP(tri-calcium-phosphate), CPP-ACP(casein phosphopeptide-amorphous-calcium-phosphate) and ACP(amorphous-calcium-phosphate).  It is challenging to measure total fluoride in these varnishes since varnish rosin often encapsulates fluoride and calcium often binds with fluoride.  The objective of this study is to evaluate the efficacy of two different methods for determining total fluoride in commercially available varnishes.  Products tested include: A=Colgate™Duraphat™Varnish-(no-calcium), B=3M™ESPE™Vanish™WhiteVarnish-(TCP), C=Premier™EnamelPro™Varnish-(ACP), D=GC™MIVarnish™-(CPP-ACP), E=MPL™VarnishAmerica™(no-calcium), F=Control-5%NaF-solution and G=DI-Water.

Methods:   Varnishes were evaluated for fluoride content using both method X and Y.  Method X adds mixed varnish (0.08g±0.02g, n=5) first to chloroform (4mL), followed by TISAB (10mL), vigorous shaking, stirring (90min), and centrifugation.  Method Y adds mixed varnish (0.08g±0.02g, n=5) first to TISAB(10mL)-chloroform(4mL) mixture, shaking, and settling 30-min on the bench.  Once settled, the aqueous top layer (1.0mL, either method) is mixed with DI water (1.0mL) and 18.0mL of a 50/50 TISAB/water solution.  The sample is measured using a calibrated fluoride-ion selective electrode and NaF standards at 1,2,10,50,100 ppm-F in an equal volume of TISAB solution.

Results:   Mean F-ppm values and standard deviations are shown in the table below.  *Indicates statistically equivalent to control A(no-calcium) and amount indicated on label 5%NaF(22,624ppmF).  Recovered fluoride was consistently higher using method X since chloroform fully dissolves rosin and phase separation is aided by centrifugation.  Method Y is ineffective for varnish B, as the rosin encapsulates fluoride and doesn't readily dissolve once exposed to water.  Method Y is inadequate for varnishes C&D as the ACP-complex increases the time needed for phase-separation.  Products containing calcium are aided by the centrifugation to enforce phase separation.

Conclusions:   The most efficient method to isolate fluoride from varnish rosin and calcium-complexes is method X, where varnish is dissolved in chloroform before adding TISAB, centrifuged to enforce phase separation, and analyzed in TISAB/Water using F-ion-selective electrode.

Sponsored by 3M-ESPE