This is true. I know lots of surgeons, including oral surgeons and plastic surgeons who won’t work on you if you have smoked within a week of the surgery. It is possible to reduce the risks if you use a nicotine patch prior to surgery and don’t smoke. Look at that woman in France who had the face transplant! She couldn’t refrain from smoking, and her surgery failed.
I believe smoking restrict capillaries and all blood vessel so it would have and adverse affect on healing