molar tooth
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size : cast (left), stereolithography (middle) and transparent model magnified 5 times
The molars (Austrian also cane teeth ) of mammals are used to grind the food that has been pre- ground by the incisors . In humans, they are also known as posterior teeth . The molars are divided into two groups:
- front (small) molars ( premolars , dentes premolares )
- rear (large) molars ( molars , dentes molares )
The first large molar (molar, teeth 16, 26, 36 and 46 ) is called the six-year molar because it usually erupts around the age of six.
The mammalian ancestors ( Therapsida ) originally had four premolars and three molars in each half of the jaw , as can still be found in pigs today. In the course of evolution, however , this maximum number is reduced in many species , premolars can also be completely absent. Unlike the premolars molars have no milk tooth precursor, but only appear in the permanent dentition .
The molars of mammals, in which the tooth crowns are provided with cusps, are called bunodont . If there are four cusps, the teeth are oligobunodont , if there are more cusps they are polybunodont . The tooth type occurs mainly in omnivores , e.g. B. in pigs , bears and humans.
Lophodont , zygodont or zygomatic are the molars of herbivorous mammals. With them, the tooth cusps are connected by comb-like melt strips (cross yokes).
Cloven ungulates mainly have selenodontic teeth. The enamel of the tooth cusps forms crescent to V-shaped structures as a result of the wear and tear from the hard plant food.
Web links
Individual evidence
- ^ Keyword "bunodont." In: Herder-Lexikon der Biologie. Volume 2, Verlag Herder, 1984. ISBN 3-451-19642-5
- ↑ Keyword “lophodont.” In: Herder-Lexikon der Biologie. Volume 5, Verlag Herder, 1984. ISBN 3-451-19645-X
- ↑ Keyword “selenodont.” In: Herder-Lexikon der Biologie. Volume 7, Verlag Herder, 1984. ISBN 3-451-19647-6