A cigarette to your teeth and mouth is what a burning wood log to furnace!
Periodontal disease i.e. gum diseases are the main burden the smokers invite by smoking. Because smoking weakens our immune system, consequently the body’s power to fight against infections reduces. Smoking reduces flow of oxygen in the bloodstream and affect healing. Besides gum disease, nicotine and tar in the tobacco smoking can also lead to teeth staining, tooth loss (especially in youth, it is the biggest cause of tooth loss), and in some-most cases mouth cancer.
Smoking can affect your teeth’ bone structure (look at the image above) so severely that in some cases teeth/tooth may fall out. Smoking increases this risk twice in a smoker in comparison of a non-smoker. Continuous and longer smoking even hinders the treatment of gum diseases in many cases rather make it worse to worst.
Smoking leverages germs (bacteria) on your teeth which if stay longer, forms layers of plaque and tartar that leads to gingivitis (initial stage of gum disease). When it becomes more dangerous it creates spaces between your teeth by impacting mouth & bones and tissues, leading it to final and severe stage of gum disease which is called as periodontitis.
So if you smoke then stop it immediately and consult your dentist for recovering the might be damages already have happened to your teeth due to it. A good habit of brushing (cleaning below the gum line) at least twice a day and flossing can at least sustain your oral health and bring you out of gingivitis situation, though the severe stage of periodontitis may require prescribed medicines and even surgery.