Figure 1. Chemical interactions and therapeutic activity of the combined treatment of Fer and SnF₂.

(A to C) Fer chemically interacts with SnF₂ (A) to enhance stability in aqueous solution without any additives (B) while boosting catalytic activity (C). (D) Further biochemical and spectrometry analyses reveal that Sn²⁺ is bound by carboxylate groups in the carboxymethyl-dextran coating of Fer. (E) Using laboratory and in vivo models, we find synergistic activities to enhance bioactivity against biofilms and caries-protective effects (without increasing fluoride exposure), while co-delivering fluoride, iron, and tin on the outer enamel surface without deleterious effects on oral tissues and the microbiota.