Our dogs have rawhide chews. I have never had their teeth cleaned or tried to do it. Our last Goldie got to 14 and a half before he left us, with never any trouble. On the other hand our Bichon Frise (a rescue, came through a family member, not my choice of dog bless him!) had to have all his teeth out a couple of years ago - his first owners, who had special needs, fed him purely on human food, including Gaviscon and Paracetamol, poor little thing! My guess is that it depends what they're fed on. Too much processed human food may be a cause of problems in dogs - as it is in ourselves!