Three-dimensional (3D) tower structure biofilm on the dental enamel surface and the antibacterial mechanism of polyunsaturated fatty acids (PUFA) against Streptococcus mutans (S. mutans). (A) Biofilm 3D tower structure includes S. mutans and other bacteria. (B) PUFA combines with the carriers or is inserted within the lipid bilayer, preventing the transportation of electrons or protons. (C) Due to the addition of PUFAs, the fluidity and permeability of cell membranes are over-enhanced. Pores appear on the membrane's surface, and the bacteria's nutrients are lost. (D) PUFA also binds with adenosine triphosphate (ATP) synthase to directly affect the synthesis of ATP. In addition, it penetrates the cell membrane to separate the protons in the carboxyl group, thereby reducing the proton gradient to hinder the synthesis of ATP.