Dental caries, also known as tooth decay or cavity, is a disease where bacterial processes damage hard tooth structure （enamel, dentin and cementum）. These tissues progressively break down, producing dental cavities （holes in the teeth）. Two groups of bacteria are responsible for initiating caries, Streptococcus mutans and Lactobacilli. If left untreated, the disease can lead to pain, tooth loss, infection, and, in severe cases, death. Today, caries remains one of the most common diseases throughout the world. Cariology is the study of dental caries.
The presentation of caries is highly variable, however the risk factors and stages of development are similar. Initially, it may appear as a small chalky area which may eventually develop into a large cavitation. Sometimes caries may be directly visible, however other methods of detection such as radiographs are used for less visible areas of teeth and to judge the extent of destruction.
Tooth decay is caused by specific types of acid-producing bacteria which cause damage in the presence of fermentable carbohydrates such as sucrose, fructose, and glucose. The mineral content of teeth is sensitive to increases in acidity from the production of lactic acid. Specifically, a tooth （which is primarily mineral in content） is in a constant state of back-and-forth demineralization and remineralization between the tooth and surrounding saliva. When the pH at the surface of the tooth drops below 5.5, demineralization proceeds faster than remineralization （i.e. there is a net loss of mineral structure on the tooth's surface）.This results in the ensuing decay. Depending on the extent of tooth destruction, various treatments can be used to restore teeth to proper form, function, and aesthetics, but there is no known method to regenerate large amounts of tooth structure. Instead, dental health organizations advocate preventive and prophylactic measures, such as regular oral hygiene and dietary modifications, to avoid dental caries.
Though more than 95% of trapped food is left packed between teeth after every meal or snack, over 80% of cavities develop inside pits and fissures in grooves on chewing surfaces where the brush cannot reach and there is no access for saliva and fluoride to neutralise acid and remineralise demineralised tooth. Few cavities occur where saliva has easy access.
Chewing fibre like celery after eating helps force saliva into trapped food to dilute carbohydrate like sugar, neutralise acid and remineralise demineralised teeth.