How are a rat's teeth arranged? - briefly
Rats have one pair of continuously growing incisors in each upper and lower jaw, located at the front of the mouth. A diastema separates these incisors from three rows of cheek teeth—premolars and molars—on each side.
How are a rat's teeth arranged? - in detail
Rats possess a distinctive dental formula that reflects their gnawing lifestyle. The upper and lower jaws each contain two large incisors at the front, followed by a toothless gap (the diastema) and a series of six molars on each side. The complete count amounts to sixteen teeth: four incisors and twelve molars, with no canines or premolars present.
Incisors are open‑rooted and grow continuously throughout life. Enamel coats only the labial (front) surface, while dentine forms the lingual (rear) side. This differential composition produces a self‑sharpening edge as the softer dentine wears faster than the enamel. The incisors are positioned at a right angle to each other, allowing the upper incisors to cut against the lower incisors during gnawing.
Molars are closed‑rooted, cease growing after eruption, and feature a complex occlusal surface composed of multiple cusps. The upper molars display three longitudinal rows of cusps (tricuspid pattern), whereas the lower molars present a complementary arrangement that ensures efficient grinding of food. Enamel completely covers molar crowns, providing durability for mastication.
The spatial layout can be summarized:
- Incisors: 2 upper, 2 lower; open‑rooted, enamel on labial surface only.
- Diastema: toothless zone separating incisors from molars, facilitating manipulation of food.
- Molars: 6 upper, 6 lower; closed‑rooted, fully enamelled, multiple cusps for grinding.
The alignment of the incisors and molars, combined with the diastema, creates a functional chain that enables rats to gnaw, cut, and pulverize a wide variety of materials while maintaining dental health through constant wear and regrowth.