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Molar (tooth)

Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the name, which means "millstone". Molars differ considerably from one species to another, so there are many terms describing them:

  • Tribosphenic: This kind is found in insectivores and young platypuses (adults have no teeth). Upper molars look like three-pointed mountain ranges; lowers look like two peaks and a third off to the side.
  • Quadrate: This kind is found in humans and various other species. Four cusps are arranged in a rectangle; there may be a fifth.
  • Bunodont: The cusps, instead of being sharp peaks, are rounded hills.
  • Hypsodont: There is a lot of enamel and dentine above the gumline and the top of the pulp. This kind of molar is found in mammals that wear their teeth a lot, such as the horse.
  • Zalambdodont: The tooth has two ridges that meet at an angle, forming the letter lambda.
  • Dilambdodont: Like zalambdodont, but there are two lambdas on one tooth.
  • Lophodont: The tooth has a few ridges perpendicular to the jaw.
  • Selenodont: The tooth has a crescent-shaped ridge or ridges.
  • Loxodont: The tooth has several parallel oblique ridges on its surface. The elephant Loxodonta is named for this feature.
  • Adult humans have twelve molars, in four groups of three at the back of the mouth. The third (rearmost) molar in each group is called a wisdom tooth. It is the last tooth to appear, breaking through the surface of the gum at about the age of twenty.