Evaluation of the substantivity of chlorhexidine in association with sodium fluoride in vitro

the efficacy of the fluoride-chlorhexidine association in the prevention of gingivitis and caries has been advocated for a number of years5,7,14. the objective of the association of these therapeutic agents is a synergistic action. the aim of the present study was to determine the substantivity of chlorhexidine associated or not to sodium fluoride at different intervals of time, in vitro. bovine enamel surfaces were treated with 0.12% chlorhexidine gluconate (periogard？ - colgate？) or 0.05% sodium fluoride with 0.12% chlorhexidine (duplak？ - dentsply？) solutions for one minute. fragments were placed in distilled water and samples were collected at intervals of 5, 30 and 360 minutes and analyzed by spectrophotometry in the visible ultraviolet region. substantivity was evaluated by the measurement of chlorhexidine desorption from the treated slabs. the mean values obtained were statistically analyzed by student's t-test. the results showed that the concentration of chlorhexidine decreased when it was used in association with sodium fluoride. the difference between the groups was statistically significant (p < 0.05). these in vitro results suggest that the association between sodium fluoride and chlorhexidine in the studied concentrations appears to have no beneficial effect because of the decrease in the substantivity of chlorhexidine.