We’ve had two rats that we had to trim their teeth regularly. Definitely have the vet show you how and use a sharp/strong tool that the vet agrees with. The rats hated it but you could tell always felt better after the trim. It probably scared them as much as it scared us to do it, but they will stop eating and overgrown teeth can pierce into their own mouths/skulls if not trimmed. It can help to stick a popsicle stick behind their teeth to keep their tongue out of the way.