Wisdom tooth

This article deals with the anatomy of wisdom teeth. For wisdom teeth removal surgery see: Impacted wisdom teeth
Wisdom tooth

Wisdom teeth

Identifiers
TA A05.1.03.008

Anatomical terminology

A wisdom tooth or third molar is one of the three molars per quadrant of the human dentition. It is the most posterior of the three. Wisdom teeth generally erupt between the ages of 17 and 25.[1] Most adults have four wisdom teeth, one in each of the four quadrants, but it is possible to have fewer or more, in which case the extras are called supernumerary teeth. Wisdom teeth commonly affect other teeth as they develop, becoming impacted. They are often extracted when this occurs.

Anatomy

Main article: Human tooth

Variation

Agenesis of wisdom teeth differs by population, ranging from practically zero in Tasmanian Aborigines to nearly 100% in indigenous Mexicans.[2] The difference is related to the PAX9 gene (and perhaps other genes).[3]

Function

Wisdom teeth are vestigial third molars that helped human ancestors to grind plant tissue. It is thought that the skulls of human ancestors had larger jaws with more teeth, which possibly helped to chew foliage to compensate for a lack of ability to efficiently digest the cellulose that makes up a plant cell wall.[4] As human diets changed, smaller jaws gradually evolved, yet the third molars, or "wisdom teeth", still commonly develop in human mouths.

Clinical significance

A wisdom tooth protrudes outwards from the gumline with inflamed tissue at the back (pericoronitis; green arrow)

Wisdom teeth (often notated clinically as M3 for third molar) have long been identified as a source of problems and continue to be the most commonly impacted teeth in the human mouth. The oldest known impacted wisdom tooth belonged to a European woman of the Magdalenian period (18,000–10,000 BCE).[5] A lack of room to allow the teeth to erupt results in a risk of periodontal disease and dental cavities that increases with age.[6] Less than 2% of adults age 65 years or older maintain the teeth without cavities or periodontal disease and 13% maintain unimpacted wisdom teeth without cavities or periodontal disease.[7]

Some problems which may or may not occur with third molars: A Mesio-impacted, partially erupted mandibular third molar, B Dental caries and periodontal defects associated with both the third and second molars, caused by food packing and poor access to oral hygiene methods, C Inflamed operculum covering partially erupted lower third molar, with accumulation of food debris and bacteria underneath, D The upper third molar has over-erupted due to lack of opposing tooth contact, and may start to traumatically occlude into the operculum over the lower third molar. Unopposed teeth are usually sharp because they have not been blunted by another tooth.

Impacted wisdom teeth are classified by the direction and depth of impaction, the amount of available space for tooth eruption and the amount soft tissue or bone that covers them. The classification structure allows clinicians to estimate the probabilities of impaction, infections and complications associated with wisdom teeth removal.[6] Wisdom teeth are also classified by the presence of symptoms and disease.[8]

Treatment of an erupted wisdom tooth is the same as any other tooth in the mouth. If impacted, treatment can be localized to the infected tissue overlying the impaction,[9]:440–441 extraction[10] or coronectomy.[11]

The upper left (picture right) and upper right (picture left) wisdom teeth are distoangularly impacted. The lower left wisdom tooth is horizontally impacted. The lower right wisdom tooth is vertically impacted (unidentifiable in orthopantomogram).

History

Although formally known as third molars, the common name is wisdom teeth because they appear so late – much later than the other teeth, at an age where people are presumably "wiser" than as a child, when the other teeth erupt.[12] The term probably came as a translation of the Latin dens sapientiae. Their eruption has been known to cause dental issues for centuries, it was noted at least as far back as Aristotle:

The last teeth to come in man are molars called 'wisdom-teeth', which come at the age of twenty years, in the case of both sexes. Cases have been known in women upwards. of eighty years old where at the very close of life the wisdom-teeth have come up, causing great pain in their coming; and cases have been known of the like phenomenon in men too. This happens, when it does happen, in the case of people where the wisdom-teeth have not come up in early years.
— Aristotle, The History of Animals[13]

See also

This article uses anatomical terminology; for an overview, see Anatomical terminology.

References

  1. ↑ "Wisdom Teeth". American Association of Oral and Maxillofacial Surgeons. Archived from the original on July 28, 2010. Retrieved 2010-09-28. This generally occurs between the ages of 17 and 25
  2. ↑ Rozkovcová, E.; Marková, M.; Dolejší, J. (1999). "Studies on agenesis of third molars amongst populations of different origin". Sborník lékařský. 100 (2): 71–84. PMID 11220165.
  3. ↑ Pereira, Tiago V.; Salzano, Francisco M.; Mostowska, Adrianna; Trzeciak, Wieslaw H.; Ruiz-Linares, Andrés; Chies, José A. B.; Saavedra, Carmen; Nagamachi, Cleusa; et al. (2006). "Natural selection and molecular evolution in primate PAX9 gene, a major determinant of tooth development". Proceedings of the National Academy of Sciences. 103 (15): 5676–81. Bibcode:2006PNAS..103.5676P. doi:10.1073/pnas.0509562103. JSTOR 30050159. PMC 1458632Freely accessible. PMID 16585527.
  4. ↑ Cooper, Rachele (February 5, 2007). "Why Do We Have Wisdom Teeth?". Scienceline.org. Archived from the original on 2016-05-03.
  5. ↑ "Magdalenian Girl is a woman and therefore has oldest recorded case of impacted wisdom teeth" (Press release). Field Museum of Natural History. March 7, 2006. Retrieved February 15, 2013.
  6. 1 2 Juodzbalys, Gintaras; Daugela, Povilas (Apr–Jun 2013). "Mandibular Third Molar Impaction: Review of Literature and a Proposal of a Classification (review)". J Oral Maxillofac Res. 4 (2): e1. doi:10.5037/jomr.2013.4201. PMC 3886113Freely accessible. PMID 24422029.
  7. ↑ Marciani RD (2012). "Is there pathology associated with asymptomatic third molars (review)". J Oral Maxillofac Surg. 70 (Suppl 1): 15–19. doi:10.1016/j.joms.2012.04.025.
  8. ↑ Dodson TB (Sep 2012). "The management of the asymptomatic, disease-free wisdom tooth: removal versus retention. (review)". Atlas Oral Maxillofac Surg Clin North Am. 20 (2): 169–76. doi:10.1016/j.cxom.2012.06.005. PMID 23021394.
  9. ↑ Newman MG, Takei HH, Klokkevold PR, Carranza FA (2012). Carranza's Clinical Periodontology. Elsevier Saunders. ISBN 978-1-4377-0416-7.
  10. ↑ Pogrel MA (2012). "What are the Risks of Operative Intervention (review)". J Oral Maxillofac Surg. 70 (Suppl 1): 33–36.
  11. ↑ Ghaeminia H (2013). "Coronectomy may be a way of managing impacted third molars (systematic review)". Evid Based Dent. 14 (2): 57–8. doi:10.1038/sj.ebd.6400939. PMID 23792405.
  12. ↑ "Wisdom tooth". Oxford English Dictionary. Oxford: Oxford University Press. 1989. ISBN 0-19-861186-2.
  13. ↑ Aristotle (2015). The History of Animals. Translated by D'Arcy Wentworth Thompson. Aeterna Press. p. 49.
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