Q. Hi my crown of 20 years has for the past few years been coming off and won’t stick. My dentist did some work on it 10 years ago- as the previous dentist had left cotton wool in it and it used to hurt. so i don’t know if this caused the tooth to become weak. He said nothing can be done as there is no tooth there – but i was thinking of a filling over it – i think he did mention this and then could the crown not be stuk to that-as opposed to bare gum,