What I can't stand is the way dentists sadistically stuff your mouth with cotton wool after an extraction or whatever and then expect you to answer questions for their book-keeping..
Name?- "wobop...bobop...mmm"
Address?- "mmm..glop...wobop..blobop....mmmm.."
Date of birth?- "mmm..glopob...bopob....mmm...."
(Needless to say they always ensure the humiliation is carried out in front of a full adience in the waiting room)