Your mouth is an important site from which to explore the effects of smoking.
What you smoke first passes over your teeth and through your gums so your mouth is central to the impact of the nicotine. Yellow teeth and bad breath are just a few effects of what smoking does to your oral health.
In a healthy mouth, the gums stay snug up around the base of the teeth, providing protection to the roots. Smoking irritates gum tissue and reduces blood flow to the gums, causing damage that can result in the gums pulling away from the teeth (gum recession). This recession exposes the roots leaving them in danger of tooth decay and this can be worsened by food getting trapped in the loose gums. In turn the bacteria inside the mouth feed on the decaying food and can create infections.
As the gums continue to deteriorate, bacterial growth can lead to bad breath, cavities, mouth sores, infections and increased plaque growth. If plaque remains in the mouth long enough, it contributes to the development of biofilm, a destructive bacterial coating on teeth that resists brushing. Eventually, plaque hardens into tartar, a hard, cement-like layer around the gums and between teeth. Tartar makes the gum situation worse, causing additional irritation, bleeding and pain.
If the gums that support your teeth and hold them in place are damaged this can eventually lead to them falling out.
Smoking can also cause bone loss in the jaw, inflammation of the salivary glands and delayed healing from oral and other surgeries. Smokers are also more prone to oral cancers than nonsmokers.
There is also research being carried out into the link between oral health and whole body health which shows that there is likely a connection between poor oral health and infections, inflammation and other problems throughout the body. Heart disease, rheumatoid arthritis, respiratory infections and some cancers may be linked to bacteria introduced through the mouth.
(source – health.howstuffworks.com)