The digestive system begins with the mouth, which contains both baby teeth and permanent teeth. Baby teeth, or deciduous teeth, are the first set of teeth and include 20 teeth. They develop by age 2 and start falling out around age 6 to be replaced by 32 permanent teeth, which are usually fully developed by age 12. Teeth have several parts including the crown, root, and neck. They also have interior parts like the pulp, dentin, cementum, and enamel. Proper oral hygiene including brushing and flossing daily is important for preventing cavities, gum disease, and tooth loss.