Mice are known for their ability to chew through a variety of materials, from wood to wiring. This tendency is not born from hunger but is a biological necessity linked to the unique structure of their teeth. This constant gnawing is a feature that ensures their survival, and understanding this dental anatomy reveals why a mouse’s life depends on its instinct to chew.
Dental Structure of a Mouse
An adult mouse has sixteen specialized teeth. At the front of the jaw are four large incisors, and behind a significant gap known as a diastema, are twelve molars for grinding food. This gap allows mice to gnaw with their incisors without interference from their back teeth.
The defining characteristic of the incisors is that they are open-rooted, meaning they grow continuously throughout the mouse’s life. This growth is sustained by a rich blood supply at the base of the tooth. The front surface is coated in hard enamel, while the back consists of softer dentin.
This structural difference creates a self-sharpening mechanism. As a mouse gnaws, the softer dentin wears away more quickly than the enamel. This process hones the incisors into a sharp, chisel-like edge for cutting through materials.
The Purpose of Constant Gnawing
The continuous growth of a mouse’s incisors necessitates constant gnawing as a maintenance activity. If left unchecked, the incisors can grow as much as 0.3 millimeters per day. Gnawing is the only way a mouse can wear down its teeth and keep them at a functional length.
This instinct drives mice to chew on hard objects. In the wild, this includes seeds, plant stems, wood, or bones. In homes, this behavior extends to food pellets, wooden toys, cage bars, and household items like furniture and electrical wires.
The need to gnaw is a biological imperative, not a habit that can be broken. This drive ensures their teeth remain sharp and at the proper length for survival.
Consequences of Overgrown Teeth
If a mouse cannot wear down its incisors, it can develop malocclusion, where the teeth do not align properly. This can result from a jaw injury, a genetic defect, or a lack of hard materials for gnawing. This is a particular concern for pet mice whose environment lacks appropriate chewing items.
The effects of malocclusion are often fatal. As the incisors lengthen, they can prevent the mouse from closing its mouth. This makes it impossible to chew food, leading to malnutrition and starvation.
In extreme cases, unchecked growth leads to injuries. The lower incisors can grow upwards, piercing the roof of the mouth or nasal cavity. The upper incisors can curve downwards into the lower jaw, causing pain, infections, and abscesses that require veterinary intervention.