Crown height (tooth)

from Wikipedia, the free encyclopedia

According to the crown height , mammals distinguish between low and high crowned teeth . Teeth with a high crown are further divided into those with a late closing root and rootless teeth with a non-closing root and unlimited growth. The boundaries between the different shapes are fluid.

Brachyodontia or brachydontia

Niederkronige or brachy (o) donte teeth (from ancient Greek βραχύς brachys shortly 'and ὀδόντος odontos , teeth') have well-developed roots that form early for short-term growth of the teeth. Your crown lies completely outside the tooth socket and is low compared to the roots. Most mammalian teeth are brachydont.

Hypsodontia or hypselodontia

High-crowned , hypsodontic or hypselodontal teeth (from ancient Greek ὕψος hýpsos 'height' or ὑψηλος hypselos 'high' and ὀδόντος odóntos 'teeth') have roots that close late or not at all, so that the teeth grow correspondingly long. The conceptual separation between hypsodont and hypselodont is handled differently and in opposite directions, so that Álvaro Mones (1982) recommends the use of the unmistakable terms protohypsodont and euhypsodont instead .

In order to adapt to silicic acid-containing foods such as grasses , high-crowned molars have often developed independently of one another in grain- and herbivorous mammals. They withstand the increased abrasion when chewing longer than low-crowned teeth. High-crowned teeth are completely encased in cement during the installation . Due to the varying degrees of wear of cement, dentin and tooth enamel , ridges are exposed on the crown, between which strips of cement ( caries and tartar ) remain. The cusps and ridges grow in height and a complicated pattern of ridges and loops with sharp melting edges can form.

In the back of the dentition , the sockets of high-crowned teeth require a lot of space and the skull is redesigned. In the case of cloven-hoofed and odd-toed ungulates, the eye socket is shifted to the rear and in rodents the space requirement is usually at the expense of the rear nasal cavity and the eye socket.

Protohypsodontia

Protohypsodontic teeth (from ancient Greek πρῶτος prôtos 'first', ὕψος hýpsos 'height' and ὀδόντος odóntos 'teeth') have limited growth and their roots close late.

Euhypsodontia

Rootless or euhypsodontic teeth (from ancient Greek εὖ eu 'good', ὕψος hýpsos 'height' and ὀδόντος odóntos 'teeth') have unlimited growth and their pulp cavity is not restricted in its expansion by secondary dentine.

Rootless molars are found in rabbits , many rodents, and some snakes . In addition, incisors and canines such as the incisor teeth of rodents and rabbits, the tusks of elephants and corresponding teeth in pigs , hippos and walruses can be designed as rootless teeth.

The premolars and molars of horses and some cloven-hoofed animals are hypselodontic rather than rootless. They are mature in their system and do not continue to grow, but are pushed in according to the abrasion, which leads to an expansion of the maxillary sinus . The pulp cavity is gradually filled with secondary dentine in order to avoid opening the cavum dentis.

literature

  • Erwin J. Hentschel , Günther H. Wagner: Dictionary of Zoology . 7th edition. Spectrum Academic Publishing House (Elsevier), Heidelberg 2004, ISBN 3-8274-1479-2 .
  • Àlvaro Mones: An equivocal nomenclature: What means hypsodonty? In: Paleontological Journal . tape 56 , no. 1-2 , 1982, ISSN  0031-0220 , pp. 107-111 .
  • Arno Hermann Müller: Textbook of paleozoology. Volume III: Vertebrates. Part 3: Mammalia . 2nd Edition. VEB Gustav Fischer Verlag, Jena 1989, ISBN 3-334-00223-3 .
  • Jochen Niethammer, Franz Krapp (Hrsg.): Handbook of mammals in Europe. Volume 1: Rodents 1 . Akademische Verlagsgesellschaft, Wiesbaden 1978, ISBN 3-400-00458-8 .
  • Dietrich Starck: Textbook of Special Zoology. Volume II: Vertebrates. Part 5: Mammals . Gustav Fischer Verlag, Jena / Stuttgart / New York 1995, ISBN 3-334-60453-5 .
  • Wilfried Westheide, Reinhard Rieger (Hrsg.): Special zoology. Part 2: vertebrates or skulls . Spectrum Academic Publishing House (Elsevier), Heidelberg / Berlin 2004, ISBN 3-8274-0307-3 .

Remarks

  1. ↑ a b Niethammer and Krapp, 1978 (p. 37)
  2. ↑ a b c d e f Müller, 1989 (p. 29, p. 32)
  3. ↑ Hentschel and Wagner, 2004 (keyword "brachyodont")
  4. ↑ Mones, 1982 (p. 107)
  5. ↑ Gerhard Storch: Mammalia, mammals. In: Westheide and Rieger, 2004, pp. 445–454 (p. 450)
  6. ↑ a b Starck, 1995 (p. 167)
  7. ↑ Hubert Hendrichs, Roland Frey: Artiodactyla (Paraxonia), even-toed ungulate. In: Westheide and Rieger, 2004, pp. 608–630 (p. 617)
  8. ↑ Wolfgang Maier: Rodentia, rodents . In: Westheide and Rieger, 2004, pp. 531–547 (p. 533)
  9. ↑ Harald Schliemann: Integument and appendage organs. In: Westheide and Rieger, 2004, pp. 14–30 (p. 27)
  10. ↑ Westheide and Rieger, 2004 (p. 533, p. 526, p. 663, p. 621, p. 622, p. 606)