That’s what plaque looks like under a microscope Plaque is a buildup of bacteria in the form of a film that forms on the teeth. The plaque bacteria secrete acid, but in the first few hours it is neutralized by saliva. And after a few hours plaque becomes thick and dense, saliva stops penetrating it, and the acid begins to dissolve the enamel of the tooth, which eventually leads to bare dentin and tooth decay. My point is, never forget to brush your teeth at night. For some reason many people think it's not as important as it is in the morning. And it's at night that leftover food and breeding bacteria ruin your teeth.