I reckon they'd be really useful for checking that there was no irritation of the tongue or fleshy part of the mouth.
I'd love one, but don't have the cash unfortunately
I bought 2, a vet one will long attachments (for ears and teeth) and another with short attachments for my childrens ears (recurrent ear infections, grommets etc). Cost around £30 for both and no problems at all.... Iif your not using it all the time I wouldnt buy a really expensive one, and shop around and watch a few on ebay first.