# Tooth formula

The **tooth formula** (also called **dentition formula** ) is an overview of the teeth found in mammals . As a rule, it is only shown for one half of the upper and lower jaw, since the teeth are always vertically mirror-symmetrical. In humans, the teeth are divided into four quadrants and numbered from the first incisor to the back. In animals, the tooth shapes (as letters) and the respective number are placed next to one another. The four tooth shapes are I ( *incisor* , incisor ), C ( *canine* , canine ), P ( *premolar* , Vormahlzahn) and M ( *Molar* , Molar). For example, M1 designates the first molar.

Most mammals change their teeth after birth . In the primary dentition fewer teeth are always present as in the permanent dentition.

Knowledge of the tooth formulas enables the identification of non-formed teeth. In animal breeding, such individuals are often excluded from breeding.

In zoology , a shorter type of tooth formula is used to compare the dentition of different species or higher taxa : Here, too, only one half of the jaw is shown, but the number of teeth of each type of tooth in the order: incisors · canines · premolars · molars “(See example with dog ↓ ).

## Tooth formula of different living things

### Tooth naming

The naming of teeth in dogs, horses and cats is based on the Triadan tooth scheme . The dentist Hugo Triadan developed it in 1972 at the University of Bern . It was based on the FDI human tooth scheme . In the FDI scheme, the quadrant digits are placed in front of the tooth's code number. The quadrants are numbered counterclockwise. The teeth, in turn, are numbered from the center backwards. In the Triadan tooth scheme, the quadrant digits are separated from the tooth digits by a "0" to distinguish them. Accordingly, the upper right incisor is named “101” (in humans “11”), the lower left canine is named “304”, whereby not the number, but the digits are pronounced separately (“three - zero - four”).

### human

The dental formula for human teeth common in Europe was established as an international standard by the Fédération Dentaire Internationale in 1970 and is known as the FDI scheme. This dental chart is used by specialist journals, in scientific papers and by dentists in many countries. In addition, some other tooth schemes were and are in use.

### dog

3 | · | 1 | · | 4th | · | 2 | = 42 |

3 | · | 1 | · | 4th | · | 3 |

3 | · | 1 | · | 3 | · | 0 | = 28 |

3 | · | 1 | · | 3 | · | 0 |

The dog's permanent set of teeth has 42 teeth. In each half of the jaw it has three incisors ( *incisors* , I), one canine tooth ( *canine* , C), four front molars ( *premolars* , P) and two in the upper jaw and three rear molars ( *molars* , M) in the lower jaw . One of the molars, always the third from the last, is particularly strong and is known as the *fang* ( *Dens sectorius* ). In the upper jaw it is the P4, in the lower jaw the M1. Both interlock like scissors and are used to cut pieces of meat and to separate meat from the bones, the two back molars are used to grind the food.

The milk teeth of dogs have 28 teeth. The P1 and the posterior molars have no primary teeth. The types of teeth in the deciduous dentition are usually marked with small letters .

### cat

3 | · | 1 | · | 3 | · | 1 | = 30 |

3 | · | 1 | · | 2 | · | 1 |

3 | · | 1 | · | 3 | · | 0 | = 26 |

3 | · | 1 | · | 2 | · | 0 |

The cats' permanent set of teeth only have 30 teeth. It has 3 incisors ( *Incisivi* , I) and a canine or hook tooth ( *Caninus* , C) in each half of the jaw . There are 3 anterior molars ( *premolars* , corresponding to P ^{2} - P ^{4} or P _{3} and P _{4} ) in the upper jaw and only 2 in the lower jaw . In each half of the jaw there is only one posterior molar ( *molar* , corresponds to M1). As with dogs, P ^{4} and M _{1 form} a pair of fangs, which in cats are the penultimate or last tooth in the row of teeth.

The milk teeth of cats have 26 teeth. The posterior molars have no deciduous predecessors .

### Rabbit-like

The permanent dentition of the rabbit-like has 28 teeth. In each half of the jaw it has a large incisor tooth (incisive tooth) ( *dens incisivus major* , I maj), behind which there is a small pin tooth ( *dens incisivus minor* , I min) in the upper jaw . The large and the small incisor behind it in the upper jaw are typical of all rabbits and clearly distinguish them from rodents . The front large incisors even as *incisors* called, but rabbits are not rodents. Canines ( *Canini* ) are not developed. In rabbits there are 3 anterior molars in the upper jaw and only 2 in the lower jaw ( *premolars* , P). There are 3 rear molars ( *molars* , M) in each half of the jaw .

All rabbit- like teeth are rootless teeth . They have a tooth cavity (pulp cavity) that is open towards the tooth socket and grow throughout their life.

The tooth formula of the rabbit-like can be expressed graphically as follows:

I maj I min |
- | P1 P2 P3 | M1 M2 M3 |

I maj | - | P1 P2 - | M1 M2 M3 |

The milk teeth of the rabbit-like have 16 teeth. The large incisors have no milk tooth predecessors, but have already erupted as permanent teeth at birth. The small incisors of the upper jaw are changed. As usual, the molars have no primary teeth. The milk teeth are marked with small letters (but note the capital I for I maj, no milk tooth), the tooth formula can be represented as follows:

I maj i min |
- | p1 p2 p3 | |

I maj | - | p1 p2 - |

### Rodents

The most important feature on the bit of rodents ( *Rodentia* ) the enlarged central incisors ( incisors ) in the upper and the lower jaw.

Mice have some of the hardest teeth with a value of 9.6 on the Mohs hardness scale. (A diamond is worth 10).

The permanent set of teeth has 16 or 20 teeth. It has an incisor in each half of the jaw ( *dens incisivus* , I, incisor tooth). The incisor teeth of the lower jaw are usually longer than those of the upper jaw. Behind them follows a gap called the diastema . Canines are not developed. Anterior molars ( *premolars* , *P* ) are also not developed in most species, but there is one in the guinea pig relatives (Caviomorpha, for example guinea pigs , chinchillas ). There are 3 back molars ( *molars* , *M* ) in each half of the jaw .

A change of teeth usually does not take place ( *monophyodontics* ), only guinea pig *relatives* have milk teeth, which are replaced by permanent ones before birth.

The incisor teeth are generally rootless teeth . They have a tooth cavity (pulp cavity) that is open towards the tooth socket and grow throughout their life. The molars, on the other hand, have limited growth in most species. An exception is again made by guinea pigs, in which all teeth are rootless. That is why the molars of pets must also be checked regularly.

The tooth formula of most rodents can be expressed graphically as follows:

I1 | - | - | M1 M2 M3 |

I1 | - | - | M1 M2 M3 |

For guinea pig relatives, the following formula applies:

I1 | - | P1 | M1 M2 M3 |

I1 | - | P1 | M1 M2 M3 |

### horse

The horse's permanent set of teeth has 36–44 teeth. The variation comes about because C and P1 can be missing. The dentition has 3 incisors ( *incisors* , I) in each half of the jaw . The canine or hook tooth ( *Caninus* , C) usually only breaks through in stallions. It is also applied to mares, but rarely breaks through the gums. The first of the 4 front molars ( *premolars* , P) is rudimentary and not developed in all animals. When it is put on, it appears only as a small, stubby tooth and is known as a " wolf tooth ". The 3 rear molars ( *molars* , M) are always well developed. The horse's tooth formula can be expressed graphically as follows:

I1 I2 I3 | C1 | (P1) P2 P3 P4 | M1 M2 M3 |

I1 I2 I3 | C1 | (P1) P2 P3 P4 | M1 M2 M3 |

The deciduous teeth of the foals have 24–28 teeth, depending on whether the deciduous canines erupt (which is only rarely the case). The wolf tooth and the rear molars have no milk tooth precursors, so the tooth formula can be represented as follows:

i1 i2 i3 | (c1) | p2 p3 p4 | |

i1 i2 i3 | (c1) | p2 p3 p4 |

i1 and p2–4 usually break through around birth, i2 appears at the end of the first month of life, i3 at around six months to nine months.

The approximate age of a horse can be determined on the basis of the tooth eruption, the change of teeth and the typical signs of wear and tear of the teeth (see tooth age estimation ).

### pig

The permanent set of teeth in pigs has 44 teeth. It has 3 incisors ( *Incisivi* , I) and a canine or hook tooth ( *Caninus* , C) in each half of the jaw . The molars are subdivided into 4 anterior molars ( *premolars* , P) and 3 posterior molars ( *molars* , M). The P1 in the lower jaw is missing on one or both sides in about a third of the individuals. This is not an abnormality, but a sign of ongoing evolution. If the P1 is present, the 44-tooth dentition represents the original mammalian dentition. Apart from the pig in Europe, only the mole has all 44 teeth .

The canines of the male animals ( boars , boars ) are rootless teeth . They have a tooth cavity (pulp cavity) that is open towards the tooth socket, grow throughout their life and reach a considerable length, so that they protrude laterally from the gap in the mouth. In male pigs, the lower canine is also known as a tusk or “rifle”, and the shorter of the upper jaw is also called a “haderer”. Upper and lower canines grind each other, making them a sharp, dangerous weapon. In domestic pigs, they are usually pinched off to protect the caregivers.

This tooth formula can be expressed graphically as follows:

I1 I2 I3 | C1 | P1 P2 P3 P4 | M1 M2 M3 |

I1 I2 I3 | C1 | P1 P2 P3 P4 | M1 M2 M3 |

The milk teeth of the piglets / piglets have 28 teeth. The P1 and the molars have no milk tooth precursors, so the tooth formula can be represented as follows:

i1 i2 i3 | c1 | p2 p3 p4 | |

i1 i2 i3 | c1 | p2 p3 p4 |

### ruminant

The permanent set of teeth in ruminants ( cattle , sheep , goats ...) has 32 teeth. It has 3 incisors ( *Incisivi* , I) in each lower *half of* the jaw, there are no incisors in the upper jaw. The canine tooth ( *Caninus* , C) is also only present in the lower jaw of many ruminants, it occurs only in some deer. In each half of the jaw there are 3 front molars ( *premolars* , P), whereby phylogenetically the first is missing and therefore counting starts with P2, as well as 3 rear molars ( *molars* , M). The ruminant tooth formula can be expressed graphically as follows:

- - - | - | P2 P3 P4 | M1 M2 M3 |

I1 I2 I3 | C1 | P2 P3 P4 | M1 M2 M3 |

The milk teeth of ruminants have 20 teeth. Incisors and canines are missing in the upper jaw. The rear molars have no primary teeth, so the tooth formula can be represented as follows:

- - - | - | p2 p3 p4 | |

i1 i2 i3 | c1 | p2 p3 p4 |

### Predatory game

In the following donkey bridge, only the molars and premolars of one half of the dentition are mentioned. There are also three incisors and one canine.

### Mnemonics

Fox and dogs have stayed at the

top six and the bottom seven.

The martens and badgers

above five and below six.

The polecat and the weasel animal

below five and above four.

And the otter in the swamp

five above and five below.

Only the cat, with a lot of yelling,

has four above and three below.

## literature

- Franz-Viktor Salomon:
*teeth.*In: Franz-Viktor Salomon, Hans Geyer, Uwe Gille (Ed.):*Anatomy for veterinary medicine .*Georg Thieme Verlag, 2008, ISBN 978-3-8304-1112-3 . - Joachim Wahl:
*Tooth formula*, in: Archeology in Germany. AiD lexicon

## Web links

**Wiktionary: Tooth formula**- explanations of meanings, word origins, synonyms, translations

## Individual evidence

- ^ Johann Martin Kreutzer: Outline of the entire veterinary medicine: with a detailed description of all diseases that are particularly important in terms of medical and veterinary police, judicial, practical and comparative science . Palm and Enke, 1853, pp. 133-.
- ↑ Markus Eickhoff: Dentistry, oral medicine and maxillofacial medicine for small and domestic animals . Georg Thieme Verlag, 2005, ISBN 978-3-8304-1038-6 , p. 10.
- ↑ Wilczek, Christa, Merl, Kristin: MemoVet. Veterinary practice guide . 7th edition. Schattauer, Stuttgart, ISBN 978-3-7945-2865-3 .
- ^ Carsten Vogt: Textbook of dentistry in horses . Schattauer Verlag, 2011, ISBN 978-3-7945-2690-1 , pp. 3–.
- ↑ Overview and explanations of wild animal tooth formulas.