Tooth decay

Plaque
Main article: Dental plaque
Plaque is a biofilm consisting of large quantities of various bacteria that form on teeth.[39] If not removed regularly, plaque buildup can lead to dental cavities (caries) or periodontal problems such as gingivitis. Given time, plaque can mineralize along the gingiva, forming tartar. The microorganisms that form the biofilm are almost entirely bacteria (mainly streptococcus and anaerobes), with the composition varying by location in the mouth.[40] Streptococcus mutans is the most important bacteria associated with dental caries.
Certain bacteria in the mouth live off the remains of foods, especially sugars and starches. In the absence of oxygen they produce lactic acid, which dissolves the calcium and phosphorus in the enamel.[12][41] This process, known as "demineralisation", leads to tooth destruction. Saliva gradually neutralises the acids which cause the pH of the tooth surface to rise above the critical pH. This causes 'remineralisation', the return of the dissolved minerals to the enamel. If there is sufficient time between the intake of foods then the impact is limited and the teeth can repair themselves. Saliva is unable to penetrate through plaque, however, to neutralize the acid produced by the bacteria.
[edit] Caries (cavities)

Advanced tooth decay on a premolar.
Main article: Dental caries
Dental caries, also described as "tooth decay" or "dental cavities", is an infectious disease which damages the structures of teeth.[42] The disease can lead to pain, tooth loss, infection, and, in severe cases, death[citation needed]. Dental caries has a long history, with evidence showing the disease was present in the Bronze, Iron, and Middle ages but also prior to the neolithic period.[43] The largest increases in the prevalence of caries have been associated with diet changes.[43][44] Today, caries remains one of the most common diseases throughout the world. In the United States, dental caries is the most common chronic childhood disease, being at least five times more common than asthma.[45] Countries that have experienced an overall decrease in cases of tooth decay continue to have a disparity in the distribution of the disease.[46] Among children in the United States and Europe, 60-80% of cases of dental caries occur in 20% of the population.[47]
Tooth decay is caused by certain types of acid-producing bacteria which cause the most damage in the presence of fermentable carbohydrates such as sucrose, fructose, and glucose.[48][49] The resulting acidic levels in the mouth affect teeth because a tooth's special mineral content causes it to be sensitive to low pH. 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 preventative and prophylactic measures, such as regular oral hygiene and dietary modifications, to avoid dental caries.[50]
Low intensity pulsed ultrasound has recently proven the ability to regenerate or even regrow damaged or lost teeth in humans. A miniaturized device named LIPUS is pending clinical trials and was expected to be commercially available before the end of 2009. LIPUS system uses a small wireless ultrasound device, inserted in the mouth, to repair teeth. It then stimulates specific cell signalling that can produce tissue matrix proteins, repairing broken tooth roots.

Tooth care

Toothbrushes are commonly used to help clean teeth.
Main article: Oral hygiene
Oral hygiene is the practice of keeping the mouth clean and is a means of preventing dental caries, gingivitis, periodontal disease, bad breath, and other dental disorders. It consists of both professional and personal care. Regular cleanings, usually done by dentists and dental hygienists, remove tartar (mineralized plaque) that may develop even with careful brushing and flossing. Professional cleaning includes tooth scaling, using various instruments or devices to loosen and remove deposits from teeth.
The purpose of cleaning teeth is to remove plaque, which consists mostly of bacteria.[51] Healthcare professionals recommend regular brushing twice a day (in the morning and in the evening, or after meals) in order to prevent formation of plaque and tartar.[50] A toothbrush is able to remove most plaque, excepting areas between teeth. As a result, flossing is also considered a necessity to maintain oral hygiene. When used correctly, dental floss removes plaque from between teeth and at the gum line, where periodontal disease often begins and could develop caries. Electric toothbrushes are not considered more effective than manual brushes for most people.[52] The most important advantage of electric toothbrushes is their ability to aid people with dexterity difficulties, such as those associated with rheumatoid arthritis.
Fluoride therapy is often recommended to protect against dental caries. Water fluoridation and fluoride supplements decrease the incidence of dental caries. Fluoride helps prevent dental decay by binding to the hydroxyapatite crystals in enamel.[53] The incorporated fluoride makes enamel more resistant to demineralization and thus more resistant to decay.[54] Topical fluoride, such as a fluoride toothpaste or mouthwash, is also recommended to protect teeth surfaces. Many dentists include application of topical fluoride solutions as part of routine cleanings