Q. I have been in terrible pain under an old crown, an x-ray showed infection and I am on antibiotics. the dentist says this will solve the problem but I am concerned – how did the infection get there and secondly wedsites suggest drainage of infection is necessary and antibiotics are not enough. I have never known pain like this – it throbs all the time and my crown is painful to touch. Ithink i had root canal treatment when I had the crown – so why does it hurt?