Draft:Teeth

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These are the teeth of the sea perch, Tautogolabrus adspersus. Credit: Matthieu Godbout.
This is an image of the sea perch Tautogolabrus adspersus. Credit: derekkeats.

Teeth are found in the mouths of humans and many other animals. The word teeth is the plural of the word tooth. Teeth are of various shapes, sizes and lengths.

Normally adult humans have 32 teeth in their mouth which help chew food.

Teeth have a natural coating which is called enamel.

Necessary care needs be excercised while cleaning or brushing them. Teeth in good condition have aesthetic appeal that attracts and pleases viewers.

Theoretical teeth[edit]

The image is a model of a human molar-like tooth. 1. Tooth 2. Enamel 3. Dentin 4. Dental pulp ::5. cameral pulp ::6. root pulp :7. Cementum :8. Crown ::9. Cusp ::10. Sulcus :11. [Cementoenamel junction] Neck :12. Root ::13. Furcation ::14. Root apex :::15. Apical foramen 16. Gingival sulcus
17. Periodontium
:18. Gingiva: ::19. free or interdental ::20. marginal ::21. alveolar :22. Periodontal ligament :23. Alveolar bone 24. Vessels and nerves: :25. dental :26. periodontal :27. alveolar through alveolar canals. Credit: Jmarchn.

Def. a "hard, calcareous structure present in the mouth of many vertebrate animals, generally used for eating"[1] is called a tooth.

The pattern of incisors, canines, premolars and molars is found only in mammals, and to varying extents, in their evolutionary ancestors, but the numbers of these types of teeth vary greatly between species; zoologists use a standardised dental formula to describe the precise pattern in any given group.[2]

Visuals[edit]

This is a frontal view of the teeth of a human adult male. Credit: David Shankbone.
A chimpanzee displays its teeth. Credit: Richard from Canton, United States.

Teeth of humans are small, calcified, hard, whitish structures found in the mouth. They function in [mastication] mechanically breaking down items of food by cutting and crushing them in preparation for swallowing and digestion. The roots of teeth are embedded in the maxilla (upper jaw) or the mandible (lower jaw) and are covered by gingiva or gums. Teeth are made of multiple tissues of varying density and hardness.

Cetaceans[edit]

Like human teeth, whale teeth have polyp-like protrusions located on the root surface of the tooth are made of cementum in both animals, but in human teeth, the protrusions are located on the outside of the root, while in whales the nodule is located on the inside of the pulp chamber, with the roots of human teeth made of cementum on the outer surface, whales have cementum on the entire surface of the tooth with a very small layer of enamel at the tip only seen in older whales where the cementum has been worn away to show the underlying enamel.[3]

Horse[edit]

An adult horse has between 36 and 44 teeth, where the enamel and dentin layers of horse teeth are intertwined.[4]

All horses have 12 premolars, 12 molars, and 12 incisors.[5]

Generally, all male equines also have four canine teeth (called tushes) between the molars and incisors, but, few female horses (less than 28%) have canines, and those that do usually have only one or two, which many times are only partially erupted.[6]

A few horses have one to four wolf teeth, which are vestigial premolars, with most of those having only one or two, equally common in male and female horses and much more likely to be on the upper jaw; if present these can cause problems as they can interfere with the horse's bit contact; therefore, wolf teeth are commonly removed.[5]

Dogs[edit]

In dogs, the teeth are less likely than humans to form dental caries (cavities) because of the very high pH of dog saliva, which prevents enamel from demineralizing.[7]

Sometimes called cuspids, these teeth are shaped like points (cusps) and are used for tearing and grasping food.[8]

Rodents[edit]

Many rodents such as voles and guinea pigs, but not mice, as well as leporidae like rabbits, have continuously growing molars in addition to incisors.[9][10]

Sharks[edit]

In cartilaginous fish, such as sharks, the teeth are attached by tough ligaments to the hoops of cartilage] that form the jaw.[2]

Evolution[edit]

Teeth appear to have first evolved in sharks, and are not found in the more primitive jawless fish – while lampreys do have tooth-like structures on the tongue, these are in fact, composed of keratin, not of dentine or enamel, and bear no relationship to true teeth.[2] Though "modern" teeth-like structures with dentine and enamel have been found in late conodonts, they are now supposed to have evolved independently of later vertebrates' teeth.[11][12]

Genes[edit]

The genes governing tooth development in mammals are homologous to those involved in the development of fish scales.[13] Study of a tooth plate of a fossil of the extinct fish Romundina stellina showed that the teeth and scales were made of the same tissues, also found in mammal teeth, lending support to the theory that teeth evolved as a modification of scales.[14]

Prehistory[edit]

These teeth are from an animal of prehistorical importance. Credit: Nevit Dilmen.

Teeth are a common fossil that occurs in many strata in the history of Draft:rocks on Draft:Earth.

The prehistory period dates from around 7 x 106 b2k to about 7,000 b2k.

Hypotheses[edit]

  1. The teeth of Tyrannosaurus rex come from the same gene as those of the sea perch, Tautogolabrus adspersus.

See also[edit]

References[edit]

  1. tooth. San Francisco, California: Wikimedia Foundation, Inc. June 11, 2014. Retrieved 2014-07-01.
  2. 2.0 2.1 2.2 Alfred Sherwood Romer and Thomas S. Parsons (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 300–310. ISBN 978-0-03-910284-5.
  3. Common Characteristics Of Whale Teeth. Retrieved 18 July 2014.
  4. Gummed Out: Young Horses Lose Many Teeth, Vet Says. Retrieved 6 July 2014.
  5. 5.0 5.1 Patricia Pence (2002). Equine Dentistry: A Practical Guide. Baltimore: Lippincott Williams & Wilkins. ISBN 978-0-683-30403-9.
  6. Al Cirelli (2000). Equine Dentition. Nevada: University of Nevada. http://www.unce.unr.edu/publications/files/ag/2000/sp0008.pdf. Retrieved 7 June 2010. 
  7. Hale, FA (2009). "Dental caries in the dog". Can. Vet. J. 50 (12): 1301–4. PMID 20190984. PMC 2777300. //www.ncbi.nlm.nih.gov/pmc/articles/PMC2777300/. 
  8. Types of Teeth, Dental Anatomy & Tooth Anatomy | Colgate®. www.colgate.com.
  9. "Root or crown: a developmental choice orchestrated by the differential regulation of the epithelial stem cell niche in the tooth of two rodent species". Development 130 (6): 1049–57. March 2003. doi:10.1242/dev.00332. PMID 12571097. http://dev.biologists.org/content/130/6/1049.full.pdf. Retrieved 28 February 2017. 
  10. Hunt AM (1959). "A description of the molar teeth and investing tissues of normal guinea pigs". Journal of Dent. Res. 38 (2): 216–31. doi:10.1177/00220345590380020301. PMID 13641521. 
  11. McCOLLUM, MELANIE; SHARPE, PAUL T. (July 2001). "Evolution and development of teeth". Journal of Anatomy 199 (1–2): 153–159. doi:10.1046/j.1469-7580.2001.19910153.x. PMID 11523817. PMC 1594990. //www.ncbi.nlm.nih.gov/pmc/articles/PMC1594990/. 
  12. nature.com, Fossil scans reveal origins of teeth, 16 October 2013
  13. Sharpe, P. T. (2001). "Fish scale development: Hair today, teeth and scales yesterday?". Current Biology 11 (18): R751–R752. doi:10.1016/S0960-9822(01)00438-9. PMID 11566120. 
  14. Jennifer Viegas (June 24, 2015). First-known teeth belonged to fierce fish. Australian Broadcasting Corporation (ABC) Science. Retrieved June 28, 2015.

External links[edit]

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