Rat Teeth

Introduction to rat teeth

http://www.ratbehavior.org/Teeth.htm

Mammals have four kinds of teeth, that differ in shape, function, position in the mouth, and whether or not they are replaced. The four types are incisors, canines, premolars, and molars.

Figure 1. Drawing of a rat skull, showing the placement of the molars, incisors and diastema. © anne_rats

Rats have incisors and molars (Fig 1). Incisors are the frontmost teeth in mammals. In rats, these are the four, long, sharp front teeth, two on top and two on the bottom. Rat incisors are highly specialized for gnawing. They are open-rooted, which means they grow throughout life. Molars are the rearmost teeth in the mouth, used for grinding food prior to swallowing it. Rats have 12 molars, six on the top and six on the bottom (and three on each side of each jaw). Molars are never replaced. Rats have only one set of teeth during their life (called monophyodont).

Rats do not have canines (the conical, pointed teeth used for holding prey, defense, and combat), or premolars (grinding teeth behind the canines and in front of the molars). The rats have a long, toothless space in their mouth where the second incisors, canines and premolars would be. This space is called the diastema.

The number of different types of teeth in a species is described with a dental formula, which is written as: I n/n C n/n P n/n M n/n where I, C, P and M refer to the incisors, canines, premolars and molars respectively, and n/n refers to the number of upper and lower teeth of each type found on one side of the mouth. So, the rat's dental formula is: I 1-1, C 0-0, P 0-0, M 3-3. Rats have 8 teeth on the lower jaw and 8 on the upper, a total of sixteen teeth.