Filou has had dental cleaning under anesthesia 2 times and he never bleeded from the mouth. He would never let me do it and our vet says he might loose his confidence in us if we forced him to clean his teeth. Unfortunately he seems to produce lots of acids and whatever.
My human dentist says that it is the same with humans. Some of them get more plaque than others from the consistence of their saliva. (Filou doesn't smoke anyway ).