Bacteria that naturally exist in plaque break down the starches and sugars in the food you eat. A chemical reaction occurs, and as a result, an acid is produced. Like all acids, the acid produced in your mouth is corrosive, which means it dissolves other materials. Your teeth are the victims of this corrosive action. The acid dissolves their protective outer enamel layer, eventually creating holes in your teeth, also known as cavities or decay.