What happens: Bone and connective tissues continue to be destroyed.

Symptoms: The symptoms are similar to those of moderate periodontitis, but worse. Teeth can become very loose. It may hurt to bite or chew. Because the teeth are so loosely connected to the bone, they may shift position. Pressing on the gums may produce pus. This is a sure sign of a severe infection. Pockets measure more than 7 millimeters. (One millimeter is about the same thickness as a dime.)

What can be done: This stage of the disease will require surgical treatment. Types of surgery include periodontal pocket reduction or bone regeneration. During pocket reduction surgery, the gum tissue is folded back. The disease-causing bacteria are removed. Then the tooth roots are smoothed, and the gums are stitched back in place. This helps the gum tissue to reattach to healthy bone. Bone regeneration also begins with folding back the gum tissue. Then, bone grafts or tissue-stimulating proteins are placed where the bone has been destroyed. This helps to encourage the body's natural ability to regrow the lost bone and tissue.

Loose teeth may be splinted to stabilize them. Extremely loose and/or painful teeth may need to be extracted.