Dental caries, also described as tooth decay, is one of the most common of all disorders, second only to the common cold. It usually occurs in children and young adults but can affect any person. It is the most important cause of tooth loss in younger people. It is an infectious disease which damages the structures of teeth. The disease can lead to pain, tooth loss, infection, and, in severe cases, death.
There is a long history of dental caries, with evidence showing the disease was present in the Bronze, Iron, and Medieval ages but also prior to the neolithic period. The largest increases in the prevalence of caries have been associated with diet changes.

Epidemiology

An estimated 90% of schoolchildren worldwide and most adults have experienced caries, with the disease being most prevalent in Asian and Latin American countries and least prevalent in African countries. In the United States, dental caries is the most common chronic childhood disease, being at least five times more common than asthma. It is the primary pathological cause of tooth loss in children. Between 29% and 59% of adults over the age of fifty experience caries.

The number of cases has decreased in some developed countries, and this decline is usually attributed to increasingly better oral hygiene practices and preventive measures such as fluoride treatment. Nonetheless, countries that have experienced an overall decrease in cases of tooth decay continue to have a disparity in the distribution of the disease. Among children in the United States and Europe, 60-80% of cases of dental caries occur in 20% of the population. A similarly skewed distribution of the disease is found throughout the world with some children having none or very few caries and others having a high number. Some countries, such as Australia, Nepal, and Sweden, have a low incidence of cases of dental caries among children, whereas cases are more numerous in Costa Rica and Slovakia.

The anatomy of tooth

To understand how a cavity works, we need to have a basic understanding of the anatomy of the tooth. A tooth is composed of several layers. The outermost layer (above the gum-line) is called the enamel. Enamel is the hardest and most mineralized substance in the body. Beneath the gum-line, a substance called cementum covers the tooth roots. Under the enamel and cementum is the dentin. The dentin is about as hard as bone, and, unlike the enamel, dentin contains nerve endings. Beneath the dentin is the dental pulp. The pulp is a vascular tissue, composed of capillaries, larger blood vessels, connective tissue, nerve fibers, and cells including odontoblasts, fibroblasts, macrophages, and lymphocytes. The pulp is needed to nourish the tooth during its growth and development. After a tooth is fully mature, the only function of the pulp is to let us know if it is damaged or infected by transmitting pain.

Causes and risk factors

Bacteria are normally present in the mouth. The bacteria convert all foods — especially sugar and starch — into acids. Bacteria, acid, food debris, and saliva combine in the mouth to form a sticky substance called plaque that adheres to the teeth. It is most prominent on the back molars, just above the gum line on all teeth, and at the edges of fillings. Plaque that is not removed from the teeth mineralizes into tartar. Plaque and tartar irritate the gums, resulting in gingivitis and ultimately periodontitis.

Plaque begins to accumulate on teeth within 20 minutes after eating (the time when most bacterial activity occurs). If this plaque is not removed thoroughly and routinely, tooth decay will not only begin, but flourish.

The acids in plaque dissolve the enamel surface of the tooth and create holes in the tooth (cavities). Cavities are usually painless until they grow very large inside the tooth and destroy the nerve and blood vessels in the tooth. If left untreated, a tooth abscess can develop. Untreated tooth decay also destroys the internal structures of the tooth (pulp) and ultimately causes the loss of the tooth.

Carbohydrates (sugars and starches) increase the risk of tooth decay. Sticky foods are more harmful than nonsticky foods because they remain on the surface of the teeth. Frequent snacking increases the time that acids are in contact with the surface of the tooth.

Risk Factors

Although everyone who has teeth is at risk of getting them, some factors increase the risk that you’ll get a cavity or develop tooth decay. These risk factors include:

  • Certain foods and drinks. Some foods and drinks are more likely than others to cause decay. Fermentable carbohydrates are the biggest problem. These foods cling to your teeth for a long time. Fermentable carbohydrates include all sugars and most cooked starches. Examples include milk, honey, table sugar, soda, raisins, cake, hard candy, breath mints, dried fruit, cookies, dry cereal, bread and potato chips. Some food that may seem like obvious culprits may not be after all. For instance, although candy bars, jelly beans and caramels are sticky and sugary, they’re easily washed away by saliva, making them less of a threat than are potato chips, which stubbornly stick to your teeth.
  • Frequent snacking or sipping. When it comes to your teeth, the amount of sugary snacks you eat is less important than when you eat them. If you frequently snack or sip sodas, acid has more time to attack your teeth and wear them down. This is also why parents are encouraged not to give babies bottles filled with milk, formula, juice or other sugar-containing liquids at bedtime. The beverage will remain on their teeth for hours and cause erosion — often called baby bottle tooth decay. If you’re nursing or feeding an infant formula, talk to your health care providers about how to prevent early tooth decay. They may suggest having your baby drink some water after eating to help rinse away the sugary milk or formula.
  • Not brushing. If you don’t clean your teeth after eating and drinking, plaque builds up, eroding your teeth.
  • Bottled water. Adding fluoride to public water supplies has helped decrease tooth decay by offering protective minerals for tooth enamel. But today, many people drink bottled or filtered water that doesn’t contain fluoride, and they may miss out on the protective benefits of fluoride. On the other hand, some bottled water may contain added fluoride, and if your drinking water also contains fluoride, babies and children could then get too much fluoride. Talk to your child’s dentist about the amount of fluoride he or she may be getting and check ingredient labels on your bottled water.
  • Older age. An increasing number of older adults still have their natural teeth. However, over time, these teeth can wear down and become more vulnerable to tooth decay and cavities. Older adults also have more decay on root surfaces.
  • Receding gums. When your gums pull away from your teeth, plaque can form on the roots of your teeth. Tooth roots are naturally covered with a coating called cementum, but the cementum is quickly lost when the root surface is exposed. The underlying dentin is softer than enamel and can become decayed more easily, leading to root decay.
  • Weak or rough dental fillings. Over the years, dental fillings can become weak and begin to breakdown, or the edges can become rough. Either of these situations can allow plaque to build up more easily and make it harder to completely remove plaque.
  • Eating disorders. Anorexia and bulimia can lead to significant tooth erosion and cavities. Stomach acid from vomiting, for instance, washes over the teeth and erodes the enamel. Eating disorders can also interfere with saliva production. In addition, some people with eating disorders sip soda or other acidic drinks throughout the day, which creates a continual acid bath over the teeth.
  • Heartburn. Gastroesophageal reflux disorder (GERD), acid reflux and heartburn can cause stomach acid to flow into your mouth, wearing away the enamel of your teeth.
  • Close contact. Some harmful, decay-causing bacteria in the mouth can be passed from one person to another by kissing or sharing eating utensils. Parents or even child care providers may pass along harmful bacteria to infants and children, for example.
  • Certain cancer treatments. Having radiation to your head or neck areas can increase the risk of getting cavities by changing the saliva produced in the mouth, which allows more cavity-producing bacteria to thrive.

Other risk factors

  • Reduced saliva is also associated with increased caries rate since the buffering capability of saliva is not present to counterbalance the acidic environment created by certain foods. As a result, medical conditions that reduce the amount of saliva produced by salivary glands, particularly the parotid gland, are likely to cause widespread tooth decay. Some examples include Sjögren’s syndrome, diabetes mellitus, diabetes insipidus, and sarcoidosis. Medications, such as antihistamines and antidepressants, can also impair salivary flow. Moreover, 63% of the most commonly prescribed medications in the United States list dry mouth as a known side effect. Radiation therapy to the head and neck may also damage the cells in salivary glands, increasing the likelihood for caries formation.
  • The use of tobacco may also increase the risk for caries formation. Smokeless tobacco frequently contains high sugar content in some brands, possibly increasing the susceptibility to caries. Tobacco use is a significant risk factor for periodontal disease, which can allow the gingiva to recede. As the gingiva loses attachment to the teeth, the root surface becomes more visible in the mouth. If this occurs, root caries is a concern since the cementum covering the roots of teeth is more easily demineralized by acids in comparison to enamel. Currently, there is not enough evidence to support a causal relationship between smoking and coronal caries, but there is suggestive evidence of a causal relationship between smoking and root-surface caries.

Signs and symptoms of tooth decay

The signs and symptoms of cavities and tooth decay vary depending on the severity and location of the cavity. When a cavity or decay is just beginning, you may not have any symptoms at all.

But as decay gets worse, it may cause such symptoms as:

  1. Toothache or tooth pain
  2. Tooth sensitivity
  3. Mild to sharp pain when eating or drinking something sweet, hot or cold
  4. Pain that lasts even after you stop eating or drinking
  5. Visible holes or pits in your teeth
  6. Pain when you bite down
  7. Pus around a tooth

The earliest sign of a new carious lesion, referred as incipient decay, is the appearance of a chalky white spot on the surface of the tooth, indicating an area of demineralization of enamel. As the lesion continues to demineralize, it can turn brown but will eventually turn into a cavitation, a “cavity”. The process before this point is reversible, but once a cavitation forms, the lost tooth structure cannot be regenerated. A lesion which appears brown and shiny suggests dental caries was once present but the demineralization process has stopped, leaving a stain. A brown spot which is dull in appearance is probably a sign of active caries.

How do Dentists Detect Cavities?

Cavities are detected a number of ways. The most common are clinical (hands-on) and radiographic (x-ray) examinations. During a clinical exam, the dentist uses a hand held instrument called an explorer to probe the tooth surface for cavities. If the explorer “catches,” that means the instrument has found a weak, acid damaged part of the tooth, a dental cavity. Dentists can also use a visual examination to detect cavities. Teeth that are discolored, usually brown or black, can sometimes indicate a dental cavity. Dental x-rays, especially check-up or bitewing x-rays, are very useful in finding cavities that are wedged between teeth, or under the gum-line. These “hidden” cavities are difficult or impossible to detect visually or with the explorer. In some cases, none of these methods are adequate, and a dentist must use a special disclosing solution to diagnose a suspicious area on a tooth.

Atlas of dental caries

  1. A tooth surface without caries.
  2. The first signs of demineralization, a small “white spot” has been formed (initial caries, incipient caries). It is not yet a cavity, the surface is still hard. It is not calculated as “D” (Decayed) according to WHO criteria. With proper measures, the caries process can be halted here and even reversed.
  3. The enamel surface has broken down. We have got a “lesion” with a soft floor. It is now calculated as a “D” tooth or surface.
  4. A filling has been made, but as can be seen, the demineralization has not been stopped and the lesion is surrounding the filling. It is sometimes called “Secondary caries” but in fact, it is usually the “same” disease that is in progress. The tooth is both “F” (Filled) and “D” (Decayed). In caries indices it is normally calculated as a D tooth only.
  5. The demineralization proceeds and undermines the tooth.
  6. The tooth has fractured - an effect of a process which could have been stopped at an early stage!

Treatment of dental caries

Destroyed tooth structure does not fully regenerate, although remineralization of very small carious lesions may occur if dental hygiene is kept at optimal level. For the small lesions, topical fluoride is sometimes used to encourage remineralization. For larger lesions, the progression of dental caries can be stopped by treatment. The goal of treatment is to preserve tooth structures and prevent further destruction of the tooth.

Generally, early treatment is less painful and less expensive than treatment of extensive decay. Anesthetics — local, nitrous oxide (”laughing gas”), or other prescription medications — may be required in some cases to relieve pain during or following treatment or to relieve anxiety during treatment. A dental handpiece (”drill”) is used to remove large portions of decayed material from a tooth. A spoon is a dental instrument used to remove decay carefully and is sometimes employed when the decay in dentin reaches near the pulp. Once the decay is removed, the missing tooth structure requires a dental restoration of some sort to return the tooth to functionality and aesthetic condition.

Restorative materials include dental amalgam, composite resin, porcelain, and gold. Composite resin and porcelain can be made to match the color of a patient’s natural teeth and are thus used more frequently when esthetics are a concern. Composite restorations are not as strong as dental amalgam and gold; some dentists consider the latter as the only advisable restoration for posterior areas where chewing forces are great. When the decay is too extensive, there may not be enough tooth structure remaining to allow a restorative material to be placed within the tooth. Thus, a crown may be needed. This restoration appears similar to a cap and is fitted over the remainder of the natural crown of the tooth. Crowns are often made of gold, porcelain, or porcelain fused to metal.

In certain cases, root canal therapy may be necessary for the restoration of a tooth. Root canal therapy, also called “endodontic therapy”, is recommended if the pulp in a tooth dies from infection by decay-causing bacteria or from trauma. During a root canal, the pulp of the tooth, including the nerve and vascular tissues, is removed along with decayed portions of the tooth. The canals are instrumented with endodontic files to clean and shape them, and they are then usually filled with a rubber-like material called gutta percha. The tooth is filled and a crown can be placed. Upon completion of a root canal, the tooth is now non-vital, as it is devoid of any living tissue.

An extraction can also serve as treatment for dental caries. The removal of the decayed tooth is performed if the tooth is too far destroyed from the decay process to effectively restore the tooth. Extractions are sometimes considered if the tooth lacks an opposing tooth or will probably cause further problems in the future, as may be the case for wisdom teeth. Extractions may also be preferred by patients unable or unwilling to undergo the expense or difficulties in restoring the tooth.

Prevention

Good oral and dental hygiene can help prevent cavities and tooth decay. Follow these tips to help prevent cavities:

  • Brush after eating or drinking. Brush your teeth at least twice a day and ideally after every meal, using fluoride-containing toothpaste. To clean between your teeth, floss or use an interdental cleaner. If you can’t brush after eating, at least try to rinse your mouth with water.
  • Rinse your mouth. If your dentist feels you are at higher risk of developing a cavity, using a fluoridated mouth rinse can help reduce your risk.
  • Visit your dentist regularly. Get professional tooth cleanings and regular oral exams, which can help prevent problems or spot them early. Your dentist can recommend a schedule for your situation.
  • Consider dental sealants. A sealant is a protective plastic coating that’s applied to the chewing surface of back teeth — sealing the grooves in the teeth most likely to get cavities. The sealant protects tooth enamel from plaque and acid. Sealants can help both children and adults. The Centers for Disease Control and Prevention strongly recommends sealants for all school-age children. Sealants last for several years before they need to be replaced.
  • Drink some tap water. Adding fluoride to public water supplies has helped decrease tooth decay significantly. But today, many people drink bottled water that doesn’t contain fluoride.
  • Avoid frequent snacking and sipping. Whenever you eat or drink something, you help your mouth create acids that destroy your tooth enamel. If you snack or drink throughout the day, your teeth are under constant attack.
  • Eat tooth-healthy foods. Some foods and beverages are better for your teeth than others. Avoid foods that get stuck in grooves and pits of your teeth for long periods, such as chips, candy or cookies. Instead, eat food that protects your teeth, such as cheese, which some research shows may help prevent cavities, as well as fresh fruits and vegetables, which increase saliva flow, and unsweetened coffee, teas and sugar-free gum, which wash away food particles.
  • Consider fluoride treatments. Your dentist may recommend a fluoride treatment, especially if you aren’t getting enough fluoride naturally, such as through fluoridated drinking water. In a fluoride treatment, your dentist applies concentrated fluoride to your teeth for several minutes. You can also use fluoridated toothpaste or mouthwash.
  • Ask about antibacterial treatments. Some people are especially vulnerable to tooth decay, perhaps because of medical conditions, for instance. In these cases, your dentist may recommend special mouth rinses or other antibacterial treatments to cut down on harmful bacteria in your mouth.

Check with your dentist to see which methods are best for you.

Sources: Mayoclinic, Wikipedia, Howstuffworks

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