Periodontal disease is an infection of the teeth and gums, as well as the bone that surrounds the teeth. If left untreated, it causes supporting bone to be lost from around the teeth. Periodontal disease is the number-one cause of tooth loss in the United States today. There are three stages to periodontal disease—gingivitis, periodontitis, and advanced periodontitis.

Plaque, a sticky film of food and bacteria, forms constantly on teeth. If it isn't removed daily, it begins to harden and forms tartar (calculus). In this early stage, before bone loss has occurred, the gums become red and swollen; this is gingivitis.

As the plaque and tartar work their way down below the gum line, the gums begin to separate away from the teeth, forming pockets. Once a pocket has formed, the process accelerates, as new, even more destructive types of bacteria begin to populate the pocket. If the tartar isn't removed by dental professionals, your body's defensive reaction to the infection produces enzymes that cause the loss of supporting bone; this is periodontitis.

Over time, if periodontitis continues unchecked, this bone loss continues. Eventually, so much bone is lost that some of the teeth begin to become loose. This is advanced periodontitis.