Objective: To evaluate the effect of sodium fluoride rinse on sucrose-induced decrease in plaque pH with interdental plaque pH telemetry. Methods: Six participants wearing partial lower prostheses incorporating a miniature glass pH electrode were included. The measurement of plaque pH was performed after 6 days of plaque accumulation. Three experiments were performed to test the effects of fluoride administered before (experiment I) or 10 min after (experiment II) and 25 min after (experiment III) a sucrose rinse. In experiment I, the subjects rinsed with 0.05% NaF solution before rinsing with 10% sucrose to examine the effect of fluoride on the sucrose-induced pH drop. In experiment II, the subjects first rinsed with 10% sucrose and then followed no subsequent rinsing or rinsing with tap water 10 min after sucrose expectoration, or 0.05%, 0.02% or 0.01% NaF solution for 2 min. In experiment III, the subjects first rinsed with 10% sucrose and then 25 min after sucrose expectoration, they rinsed with 0.05% NaF for 2 min. The plaque pH was continuously recorded for about 120 min. Results: Without any subsequent rinses, the plaque pH decreased at 10 min to 4.36 and stayed below the critical pH 5.7 for about 85 min after the sucrose rinse. Subsequent water rinses showed little effect on the sucrose-induced decrease in plaque pH. Pretreatment of 0.05% NaF solution showed no effect on the subsequent sucrose-induced pH drop. Subsequent rinses with NaF solutions at 10 min after the sucrose rinse inhibited the sucrose-induced pH drop in a dose-dependent manner. Subsequent rinses with NaF solutions after the sucrose rinse also significantly reduced the time below pH 5.7 and the area of plaque pH curve under 5.7 (AUC5.7). Furthermore, the AUC5.7 value (3.99) of 0.05% NaF rinse at 10 min after the sucrose rinse was much smaller than that (57.01) of 0.05% NaF rinse at 25 min after the sucrose rinse. Conclusion: Rinsing with 0.05% fluoride after carbohydrate consumption effectively reduced the acidogenicity of the plaque and could enhance the anticaries functions of fluoride. Keywords: fluoride, plaque pH, caries prevention, sucrose, Stephan curve