Periodontitis is the inflammation and destruction of bone that supports
the teeth.  This is caused by plaque and tarter and is treated with
periodontal therapy.  The best way to fight the disease is to simply keep
the teeth as clean as possible.  The end result of the disease if not
treated is loss of teeth, because of the lack of supporting bone.  
Symptoms can be swollen gums, pain, and loose teeth.
Periodontal Disease