Rats only have one set of teeth for their whole lifetime
Rats have incisors and molars. 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.