ObjectivesResin composites containing surface pre-reacted glass-ionomer (S-PRG) fillers have been reported to inhibit Streptococcus mutans growth on their surfaces, and their inhibitory effects were attributed to BO33− and F− ions. The aim of this study was to evaluate S. mutans acid production through glucose metabolism on resin composite containing S-PRG fillers and assess inhibitory effects of BO33− and F− on S. mutans metabolic activities. MethodsThe pH change through S. mutans acid production on experimental resin composite was periodically measured after the addition of glucose. Inhibitory effects of BO33− or F− solutions on S. mutans metabolism were evaluated by XTT assays and measurement of the acid production rate. ResultsThe pH of experimental resin containing S-PRG fillers was significantly higher than that of control resin containing silica fillers (p < 0.05). OD450 values by XTT assays and S. mutans acid production rates significantly decreased in the presence of BO33− and F− compared with the absence of these ions (p < 0.05). ConclusionspH reduction by S. mutans acid production was inhibited on resin composite containing S-PRG fillers. Moreover, S. mutans glucose metabolism and acid production were inhibited in the presence of low concentrations of BO33− or F−. Clinical significanceBO33− or F− released from resin composite containing S-PRG fillers exhibits inhibitory effects on S. mutans metabolism at concentrations lower than those which inhibit bacterial growth.