Decay is a process of tooth breakdown. It is caused when bacteria in the mouth react with sugars from food that you eat or drink to produce an acid. The acid attacks the surface enamel of the tooth to weaken it. Every time you eat, the bacteria produce acid. The more times you eat, the more times your tooth enamel is weakened.
The tooth can be repaired in early stages with the help of fluoride and minerals in the saliva. If, however, the decay progresses and breaks through the enamel to the dentin of the tooth the damage is permanent. The decay must be cleaned out and the cavity filled. If left untreated, the decay will worsen and lead to pain and tooth nerve damage.
Tooth decay can happen at any age. For more information on tooth decay in very young children see Early Childhood Tooth Decay. Another location for decay, which is more common in older adults, is the root of a tooth. This group may have exposed tooth roots. They are more likely to have dry mouth, which increases the risk of decay. Dry mouth is often caused by medications and should be discussed with the doctor or pharmacist.
Cavities can be prevented by reducing the amount of plaque and bacteria in the mouth. Floss daily and brush at least twice a day with fluoride toothpaste. Fluoride in toothpaste reverses the acid damage to enamel. Limit sweet snacks and drink less juice and soft drinks. Chewing sugarless gum, especially with xylitol, can help reduce decay and increase the flow of saliva. Your oral health care provider can evaluate your risk of dental decay and suggest appropriate fluoride treatments. In children, permanent molars can be protected by applying a pit and fissure sealant as soon as the teeth erupt.
Once a tooth is affected by a cavity, it will forever be at risk for more problems. Preventing decay in the first place is key!