Causes

In most cases, the development of periodontitis starts with plaque — a sticky film composed mainly of bacteria. If left untreated, here's how plaque can eventually advance to periodontitis:

• Plaque forms on your teeth when starches and sugars in food interact with bacteria normally found in your mouth. Brushing your teeth twice a day and flossing once a day removes plaque, but plaque re-forms quickly.
• Plaque can harden under your gumline into tartar (calculus) if it stays on your teeth. Tartar is more difficult to remove and it's filled with bacteria. The longer plaque and tartar remain on your teeth, the more damage they can do. You can't get rid of tartar by brushing and flossing — you need a professional dental cleaning to remove it.
• Plaque can cause gingivitis, the mildest form of gum disease. Gingivitis is irritation and inflammation of the part of your gum tissue around the base of your teeth (gingiva). Gingivitis can be reversed with professional treatment and good home oral care.
• Ongoing gum inflammation can cause periodontitis, eventually causing pockets to develop between your gums and teeth that fill with plaque, tartar and bacteria. In time, these pockets become deeper, filling with more bacteria. If not treated, these deep infections cause a loss of tissue and bone, and ultimately you may lose one or more teeth. Also, ongoing chronic inflammation can put a strain on your immune system.