The synergistic effect of nanosilver fluoride (NSF) with L-arginine on early carious lesions was evaluated. NSF was synthesized from chitosan, acetic acid, silver nitrate, sodium borohydride, and sodium fluoride. NSF + Arg was synthesized by adding L-arginine. After demineralization the enamel slabs from extracted molar, remineralization agents were applied by randomly dividing them into five groups (n = 15): sodium fluoride varnish (NaF), silver diamine fluoride (SDF), NSF, NSF + Arg, and control. The surface microhardness (SMH), remineralization effects using microcomputed tomography and color changes using a spectrophotometer were measured before and after pH cycling. SMH was analyzed by Kruskal-Wallis test with Dunn's test. Remineralization effects, and color changes were analyzed using the one-way analysis of variance with Duncan's test
p-value <
0.05 was considered significant. SMH recovered to similar levels in all groups (p >
0.05), except in the control group after pH cycling. The NSF + Arg and SDF groups showed a higher remineralization than the NaF and NSF groups (p <
0.05). SDF caused the largest discoloration (p <
0.05). The other groups showed no difference in discoloration. NSF + Arg could be an alternative to SDF given its ability to remineralize early caries lesions without discoloration.