Even if you brush twice a day for two minutes, tooth decay can still occur. Plaque and tartar can build up between your teeth if you don't floss daily, leading to cavities. Cavities can also be caused by a high-carbohydrate diet, dry mouth, or pits and grooves on the chewing surfaces of your teeth where plaque can collect. Your dentist may recommend dental sealants or extra fluoride treatments throughout the year to provide additional protection if your teeth seem to be prone to cavities.