Release of fluoride and chlorhexidine from rosin with water-soluble additive

Objective: To test the hypothesis that a water-soluble additive can change the release of F^¯ and chlorhexidine from a rosin-based oligomer. Methods: A commercial rosin, and CaF₂ and chlorhexidine diacetate powder were used to formulate two controls with 8.4 parts of CaF₂ and 10 parts of chlorhexidine in 100 parts of rosin. Additional groups were prepared from CaF₂ control by adding 10 parts of chlorhexidine (F-C), 10 parts of sodium acetate (F-N), or a combination of the two compounds (F-C-N). Approximately 70 mg of mixture was applied on soda-lime glass slides (25 mm x 9.5 mm) resulting in 1-mm thick coatings. Individual samples (N=10 per group) were placed in 5 mL of pH 4.0 acetate buffer solution at 37°C for measurement of F^¯ and chlorhexidine release. The buffer solutions were replaced periodically up to 2880 h. The F^¯ release was analyzed by a fluoride-ion electrode. The chlorhexidine release was measured with a UV-spectrophotometer. The adjusted quantities of cumulative F^¯ and chlorhexidine release (Y, µg/cm²) were fit to: Y = a·time/(time+t_½) + b·(time)^½, to estimate the values of b, the coefficient for long-term Fickian release. Results: The mean b (SD) values (in µg/cm²·h^½) for F^¯ release were 9.3 (0.2), 6.8 (0.3), 3.5 (0.2) and 1.8 (0.3) for groups F-C-N, F-N, F-C, and CaF₂ control, repectively. The mean b (SD) for chlorhexidine release were 43.1 (2.3), 45.4 (3.4) and 46.9 (7.9), for groups F-C-N, F-C and chlorhexidine control. ANOVA showed that F^¯ release increased in the presence of chlorhexidine (P<0.0001) and sodium acetate (P<0.0001). However, the presence or CaF₂  or sodium acetate have no influence on the chlorhexidine release (P=0.2574). Conclusion: Water-soluble additive can be used to manipulate the F^¯ release from rosin without altering the release of chlorhexidine. Supported by NIH/NIDCR Grant DE13412 and the DSR at the University of Florida.