The mechanism of action of topically applied sodium fluoride includes all of the following EXCEPT-

Mechanism of action of sodium fluoride – When sodium fluoride solution is applied on the tooth surface as a topical agent, it reacts with the hydroxy apatite crystals in enamel to form calcium fluoride which is the main end  product of the reaction. As a thick layer of calcium fluoride gets formed, it interferes with the further diffusion of fluoride from the topical fluoride  solution  to  react with hydroxyapatite and blocks further entry of fluoride ions. This sudden stop of the entry of fluoride is termed as "Choking off effect". Fluoride then slowly leaches from the calcium fluoride. Thus calcium fluoride acts as a reservoir for fluoride release (It is for this reason that after each application of sodium fluoride on to the tooth surface, it is left to dry for 4 minutes). The calcium fluoride formed reacts with the hydroxyapatite crystals to form fluoridated hydroxyapatite. The  hydroxyapatite  thus formed  increases  the  concentration  of fluoride on enamel surface, which in turn makes the tooth surface resistant against caries attack through the action of fluoride.