I had root canal treatment a number of years ago. Blood sugar wasn't really affected too much while I was at my own dentist, but then I had to go to a specialist as my root was very narrow. Had to travel an hour to get there, and didn't know the dentist, so was very stressed and my blood sugar shot up on the first visit. Treatment was successful and by the last couple of visits my bloods remained stable throughout, and afterwards. The specialist kept checking with me that I wasn't going hypo, as I had my eyes shut.
Hope it all goes well for you.