I had my wisdom teeth out while on Imuran, and I was not required to take antibiotics beforehand. There were some problems during the surgery, but not due to meds (primarily, they couldn't get one side numb, so I screamed through the entire thing, then his equipment got stuck between my teeth, and he sprained my jaw trying to wriggle it out). The only thing the Imuran didn't help with was that it didn't heal properly. I had two separate infections in a gum pocket that didn't heal, and the dentist told me that it would continue to happen unless the oral surgeon went in and cleaned it up. I had to have another surgery last year, and haven't had any problems since.
You should talk to your oral surgeon and let him know what kind of medications you are on. Chances are, there will be some kind of precedent for that kind of thing.
Diagnosed with Crohn's in 2008 at the age of 22. Also dealing with gastroparesis & GERD.
Currently on: Remicade, Imuran, Pentasa, Tramadol, Welchol, Phenergan, Ambien, Reglan, Prilosec, Hyoscyamine