UNIVERSITY OF COLORADO DENVER ANSCHUTZ MEDICAL CAMPUS 27th ANNUAL STUDENT RESEARCH FORUM and STUDENT RESEARCH AWARDS CONVOCATION COLLEGE OF NURSING GRADUATE SCHOOL SCHOOL OF DENTAL MEDICINE SCHOOL OF MEDICINE SCHOOL OF PHARMACY SCHOOL OF PUBLIC HEALTH

FLUORIDE RELEASE AND UPTAKE INTO HYDROXYAPATITE FROM EXPERIMENTAL DENTAL VARNISH. I Ahmed (D.D.S., SODM), S Coleman, and CM Carey, School of Dental Medicine, University of Colorado, Denver, CO. Fluoride releasing dental varnishes (F-varnish) typically contain 5% sodium fluoride (NaF) within a resin or rosin base. The concentration NaF that yields optimal fluoride enamel uptake, release, and anticaries efficacy is unknown. Also, there is controversy on whether the release rate of fluoride into saliva is predictive of the fluoride uptake into enamel. Objectives: measure fluoride uptake (looselyand tightly-bound) into hydroxyapatite (HAp) discs and fluoride release as a function of NaF concentration in F-varnish. Methods: triplicate sets of F-varnish containing 5.0%, 2.5%, 1.25%, and 0.625% (wt/wt) NaF were prepared. 0.01-0.02 g F-varnish was applied to one side of an HAp disc. Fluoride release into a continuous flow of 30 mmol/L KCl at 1 mL/min was measured over 3 h. The HAp discs were then cleaned and loosely-bound fluoride extracted overnight in KOH (1.0 mL, 1.0 mol/L). Tightly bound fluoride was extracted via serial extractions in HClO4 (1.0 mL, 0.5 mol/L). The extraction solutions were neutralized and analyzed via fluoride ion-selective electrode. Results: the cumulative fluoride release profile increased hyperbolically over 3 h. The total fluoride released at 3 h ([F]180) increased as a function of NaF concentration. The time for 50% (t50) of the fluoride to be released was ≤ 32 min for all varnishes. Looselyand tightly-bound fluoride increased to 2.5% NaF and plateaued. [NaF]% [F] Tightly bound [F] Loosely bound [F]180 released t50 (μg/mL) (μg/mL) (μgF/mgVarnish) (minutes) 0.625 0.10(0.03)a 0.09(0.05)c 0.07(0.23)f 4.40 1.25 0.15(0.02)a 0.26(0.12)d 1.87(0.86)g 31.95 2.5 0.25(0.03)b 1.20(0.40)e 2.47(0.47)g 26.10 5.0 0.19(0.05)b 1.18(0.07)e 3.82(0.84)h 19.70 Values in the table are mean(standard error). Letters indicate groups that are not significantly different in each category (ANOVA, Newman-Keuls, p