Everything about Dentition totally explained
Dentition is the
development of
teeth and their arrangement in the
mouth.
All
mammals except the
monotremes, the
edentates, the
pangolins, and the
cetaceans have up to four distinct types of teeth, with a maximum number for each. These are the
incisor (cutting), the
canine, the
premolar, and the
molar (grinding). Mammals that have distinct types of teeth are
heterodont; others are
homodont.
The number of teeth of each type is written as a dental formula for one side of the mouth, with the upper and lower teeth shown on separate rows. The number of teeth in a mouth is twice that listed as there are two sides. In each set,
incisors are indicated first,
canines second,
premolars third, and finally
molars. For example, the formula 2.1.2.3 for upper teeth indicates 2 incisors, 1 canine, 2 premolars, and 3 molars on one side of the upper mouth.
The
human dental formula is:
Of
cats it is:
The last upper premolar and first lower molar of the cat, since it's a
carnivore, are called
carnassials and are used to slice meat and skin. The
armadillo, being homodont, has a dental formula that's simply 7/7.
The maximum dental formula for
placental mammals is:
Non-placental mammals such as
marsupials can have more teeth than placentals. The
opossum's dental formula is:
In many mammals the children have a set of teeth that fall out and are replaced by adult teeth. These are called
deciduous teeth,
baby teeth or
milk teeth. Animals that have two sets of teeth, one followed by the other, are said to be
diphyodont. Normally the formula for milk teeth is the same as for adult teeth except that the premolars are missing.
The milk tooth formula for humans is:
The
kitten has 26 teeth.
Teeth are numbered starting at 1 in each group, except the premolars which end at 4. This means that the carnassials are always the fourth upper premolar and the first lower molar. Thus the human teeth are I1, I2, C1, P3, P4, M1, M2, and M3.
Other uses: Dentition in archaeology
Dentition, or the study of teeth, is an important area of study for archaeologists, especially those specializing in the study of older remains. Dentition affords many advantages over studying the rest of the skeleton itself (
osteometry). The structure and arrangement of teeth is constant and, although it's inherited, doesn't undergo extensive change during environmental change, dietary specializations, or alterations in use patterns. The rest of the skeleton is much more likely to exhibit change because of adaptation. Teeth also preserve better than bone, and so the sample of teeth available to archaeologists is much more extensive and therefore more representative.
Dentition is particularly useful in tracking ancient populations' movements, because, although all humans have the same basic 32 teeth, there are subtle differences in the shapes of incisors, the number of grooves on molars, and extra cusps on particular teeth. These differences can not only be associated with different populations across space, but also change over time so that the study of the characteristics of teeth could say which population one is dealing with, and at what point in that population's history they are.
Further Information
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