Dental trouble

Again Ansh's teeth are giving trouble. It all started last night when he refused to brush his teeth saying that they pain. I did brush his teeth very gently but there was a lot of resistance. Today morning again, he cried a lot when i tried to brush his teeth. We had to do "zabardasti". I just don't know how to tackle the sitution.Ansh would have nothing to do with the dentist!! I am bummed!!