Anything really can raise blood sugar levels. But I would say infection, stress being 2 definite ones. So I'm sure a tumor could and then add on the stress of upcoming surgery. If you've raised your levels, just be careful after surgery, you can't always tell when your body will decide when to be normal again. And mouth surgery you probably won't be eating or consuming as much and I bet your insulin needs will drop from that alone by quite a bit. I know when I injured my back and just wasn't eating much it really made me super insulin sensitive.