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Types of teeth Types of tissue in teeth In Humans In Aardvarks Teeth (singular, tooth) are structures found in the jaws of many vertebrates. The primary function of teeth is to tear and chew food, and in some animals, particularly carnivores, for fighting and, or defense. The roots of the teeth are covered by gums. The protective enamel covers the teeth and helps prevent cavities. Adult teeth naturally darken with age as the pulp within the tooth shrinks and dentin is deposited in its place. Teeth are among the most distinctive features of mammal species and fossils as well. Paleontologists use them to identify fossil species and their relationships. The shape of the teeth is related to the animal's diet. For example, plant matter is hard to digest, so herbivores have many molars for chewing. Carnivores need canines to kill and tear and they can swallow without molars to chew since meat is easy to digest. While humans only have two sets of teeth, some animals have many more. Sharks grow a new set of teeth every two weeks, and other animals grow just one set. Rodent teeth grow and wear away continually through the animal's gnawing, maintaining approximately constant length. Human teeth
Plaque Plaque is a soft white layer which forms on teeth, containing large amounts of bacteria of various types, particularly Streptococcus mutans. Left unchecked for a few days plaque will harden, especially near the gums, forming tartar. Certain bacteria in the mouth live off the remains of foods, especially sugars. In the absence of oxygen they produce lactic acid, which dissolves the calcium and phosphorus in the enamel in a process known as demineralisation. Enamel demineralisation takes place below the critical pH of about 5.5. 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 (two to three hours) then the impact is limited and the teeth can repair themselves. Caries (Cavities) This section should be into Dental caries. Caries is a term used to describe the process in which some bacteria produce cavitation of the teeth. This group of bacteria, which are a part of the normal oral flora, have a complex relationship with the host in which they use sugar that the host consumes to metabolize as energy and produce acid which subsequently dissolves the teeth. Caries refers to many, not one, species of bacteria including lactobacillus and viridians streptococci, that use ingested carbohydrates for metabolism and produce acid which subsequently dissolves the teeth. Pits and fissures and interproximal smooth surfaces are the most commonly colonized areas of the teeth. Attempts to prevent dental caries involves reducing the factors that cause demineralisation, and increasing the factors leading to remineralisation. Unchecked demineralisation leads to cavities, which may penetrate the underlying dentine to the tooth's nerve-rich pulp and lead to toothache. In moderation, fluoride is known to protect the teeth against cavities. It toughens the teeth by replacing the hydroxyapatite and carbonated hydroxyapatite minerals of which the enamel is made with fluorapatite, which is harder to dissolve by acid. It also reduces the production of acids by bacteria in the mouth by reducing their ability to metabolize sugars. The addition of fluoride (sodium monofluorophosphate) to toothpaste is now very common, and may explain the decline in dental caries in the Western world in the past 76 years. Some believe that a diet rich in fluorine salts, particularly in childhood, can lead to a stronger enamel which is less susceptible to decay. Fluoridation of drinking water remains a controversial issue. However, in many parts of the world, the natural water supply may be sufficiently rich in fluorides to supply the needs of children without additional sources being required. Caries is an infectious disease and is treated only by prevention. Once the decay process begins, caries can be eliminated only through the removal of the bacteria. Fluoride can be used to remineralize decalcified enamel, but new tooth structure cannot be regrown. When a patient gets a filling, the dentist mechanically removes the bacterial flora and dead tooth structure and replaces it with a restorative material (metal or glass). This was, traditionally, achieved using gold or a compound of metals called amalgam. Amalgam fillings have been the cause of some public concern because they contain mercury. Modern tooth-colored composite or ceramic are used in addition to traditional amalgam fillings. As a last resort, teeth affected by caries may be extracted, preferably under local or general anaesthetic. The extracted teeth may be either replaced with a denture or if extracted much before permanent teeth erupts, the space may be maintained by specialized ortho appliances called as Space Maintainers. Tooth care Regular brushing is recommended by healthcare professionals twice a day. *. Studies show that the minimum required time interval is once every two days. A mirror may be used to see if the plaque is completely removed during brushing. The actual term 'brushing' is rather inaccurate. Though a toothbrush is used, it is not designed to deliver mechanical abrasive action. Rather, the surface of the brush is meant to be held at a forty five degree angle to remove plaque from the periodontal margin (the space in between the gum and tooth). Thus, the term 'cleaning teeth' is far more accurate. In research, levels of plaque were recorded before and after brushing and found that plaque removal steadily improved as brushing times and pressure were increased. However, their results showed that when people brush for longer than two minutes, at a pressure higher than 150 grams (the weight of an orange), they are not removing any additional plaque, and may be causing permanent damage to the teeth and gums. Brushing teeth immediately after eating acidic foods is not recommended, because acid softens the enamel, which can then be damaged by brushing. It is better to wait at least half an hour after eating acidic foods before brushing. Rinsing the mouth and eating non-acidic foods can also speed up this process. Electric toothbrushes are no more effective than the manual variety, according to research. However, "rotation-oscillation" electric toothbrushes out-performed manual brushing, removing around 7% more plaque and leading to 17% less gum disease than manual brushes. * Any kind of electric toothbrush does tend to help people who are not as good at cleaning their teeth and as a result have had oral hygiene problems. As noted above, eating certain cheeses such as cheddar Parmasean soon after eating potentially harmful foods have been noted to be helpful in preventing tooth decay as well. In the future, tooth decay may be banished by treatment with a genetically modified bacterium, according to research at the University of Florida. * Dentures and "false" teeth In societies that have high sugar diets, tooth decay can damage teeth badly enough that they need to be removed. This leads to the creation of replacement teeth such as dentures and other tooth replacements. Some of the earliest artificial teeth were made by the Etruscans and their use was adopted in Ancient Rome for the wealthy citizens who often dined on food containing damaging sugars. Abnormalities of the dentition Development of teeth There are three stages in the embryonic development of teeth, the Bud Stage, the Cap Stage and the Bell Stage. The Bud stage begins at the 7th week of intrauterine life. Facts about teeth in non-human animals
People and characters famous for their teeth See also | |||||||||||
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