Three months. If you can do that, you can quit entirely. And don't worry about the ten pounds you will gain over the first 8 months; you will lose it. Start drinking 60-70 ounces of water, juice, seltzer (put ice, lime, lemon in it and drink 6-8 oz before each meal; start walk routine with 5 minutes, 3 days per week and gradually work up to a brisk walk 40 min 5day/wk. Reduce meal size. Get a coach to help.
Tooth extraction. The danger in smoking after a tooth extraction is getting what is called a "dry socket, " the blood clot that is over the extraction site will come loose and this can be very painful. The general recommendation is to wait several days but your dentist should explain specifically what he thinks is the right course of action is.