If someone has severe periodontal disease, the infection causes the gums to pull away from the roots of the teeth. It becomes impossible to brush or floss placque out of the resulting gap because the gap, which is called a pocket, is just too deep for that. These pockets fill up with pus and bacteria, and they become progressively deeper. The infection destroys both bone and tissue over time. Eventually, once too much bone has been destroyed, the dentist may have no choice but to pull the tooth out.
Before that day comes, it may be possible for the dentist to solve the problem by performing flap surgery. To do that, the dentist lifts the gums back from the roots of the teeth and removes the tartar that is the source of the infection. It may also be necessary to smooth the damaged bone so that bacteria can’t find a place to hide. Then the dentist sutures the gums back in place. Once the source of the infection is gone, the now-healthy gum tissue can reattach itself to the bone and the roots.