Structure of Rat Teeth

Rats have an unusual tooth structure that is specifically adapted for survival. Like all toothed animals, healthy teeth are important for defense, eating and biting. Understanding the tooth structure of rats will help you understand your rat's needs better, as well as to know what is or is not normal for a rat.

  1. Incisors

    • Rats have four incisors, two on the top and two on the bottom. The incisors are the teeth that a rat uses for gnawing, and they begin to appear once a rat is between 8 and 10 days old. The incisors are typically yellow to orange in color. This is normal and is the color of healthy rat teeth; it is caused by an iron-containing pigment. The side of the incisors that faces the lips is coated with enamel, while the interior side is coated with dentin. This results in teeth that have a different hardness on different sides of the tooth, as dentin is much softer than enamel. This means that the back of the tooth wears down faster than the front, resulting in a very sharp, chisel-like shape that is efficient for chewing.

    Molars

    • A rat has twelve molars, six on the top and six on the bottom. Rats lack canines, which are conical in shape and are typically used for fighting or hunting, as well as premolars, which are teeth designed for grinding found between the canines and molar. Instead, there is a gap between a rat's incisors and molars. Like human molars, a rat uses its molars to grind food into smaller, more digestible particles. A rat's molars begin to appear after the incisors, about 18 days after birth, and a rat has its full set of teeth by the time it is six weeks old.

    Growth

    • Humans have two sets of teeth during a lifetime, while rats only have one. However, a rat's teeth grow throughout its lifetime. A rat's molars grow at a very slow rate, while the incisors of a healthy adult can grow at a rate of about four to five inches per year. As a result, rats chew constantly to wear down their teeth, keeping them sharp and preventing health problems from rampant growth. A rat may chew on objects or grind its teeth, called bruxing. During bruxing, a rat moves its jaw forwards or backwards to grind the upper and lower teeth separately. When a rat bruxes, it may display a phenomenon called eye-boggling. The eyes will move in and out of the socket slightly because a muscle controlling the jaws runs behind the eyes. While this may appear somewhat alarming, it is normal and is a sign that that rat is healthy and unstressed.

    Health

    • A rat's incisors may become misaligned due to injury, tumors or other problems. If this happens, the rat is unable to chew and grind down its teeth properly. This can result in the teeth growing out of control. If a rat's teeth become so long that they reach the roof of the mouth, they may damage the soft palate, causing infection and abscesses. This typically results in the death of the rat due to starvation. You should check your rat's teeth for splaying, pus, bad odors, tumors or any other sign of infection regularly. A vet can trim a rat's teeth, helping to counteract growth and encourage better alignment, or you can do it yourself using a guillotine-style dog nail clippers.