Never heard of them either. Rats know how to take care of their teeth by themselves. Provide things to chew on so they have an option to choose. I give my girls old popsicle sticks and also you can get a stew bone and boil it to cook it and then let them chew on it. Always check your rats teeth from time to time to make sure they're aligned and proper length.
I check my girls teeth from time to time to make sure they're healthy. I'm sure Lil Spaz has photos of properly aligned teeth to compare.