Hello, I Had Fungas/thrust In My Gum From My Teeth.

Hello, I had fungas/thrust in my gum from my teeth. The Dentist prescribed Nystatin mouth liquid that could be used in mouth. Cleared up but thought I should use Nystatin Ointment in my denture to make sure. First he wanted me to use powder, the pharmacist called and told him it was not used in the mouth, only external but he insisted, I didn't want to use it. He said now I had to use Nystatin Ointment around the inside of my denture, same thing only in ointment form, the pharmacist called him again and said we don't recommend using this in the mouth, so I said no. The dentist said he was the doctor and if I didn't use he wouldn't line my teeth for me. So I used it for 2 weeks, he said it could make me sick to stomach, I have a very sensitive stomach, stomach feeling sick off and on. My Dr. didn't know much about these 2, ointment and powder. Do you have any feeling on this and do you know anything about this med.