Trimming the teeth with nail trimmers can cause fractures in the teeth which can lead to gum abcesses which are very nasty and hard to clean up. There is a tool called Rongeurs that can be used to trim the teeth. These are used to cut bone and are less likely to cause fractures in the tooth although they still can. With an experienced veterinarian, the rabbit should not have to be under anesthesia for tooth trimmings. This is all assuming, however, that we are talking about incisors.
Molar overgrowth is a completely different story.
Dr. Brown has an article on rabbit teeth at the Chicago HRS articles page . Also visit the House Rabbit Society web page for more information on rabbit teeth.