In the second episode of our series "Stages of Tooth Decay," Wendy explains why, and how, tooth decay begins. In short, plaque in our teeth contains bacteria that eat sugars and secrete acids. The acids weaken our teeth, a process called demineralization. Behaviors such as smoking, conditions such as acid reflux disease, and our food choices can speed up tooth decay. Fortunately, there are easy ways to prevent decay, or to slow down the process.