Gum (periodontal) disease is a bacterial infection caused by plaque – the sticky, colorless, bacteria-filled film that adheres to your teeth. As plaque builds up on teeth, it hardens and becomes tartar, which can be difficult to remove. The bacteria in plaque produce toxins that irritate the gums and cause inflammation and gingivitis. If bacteria are not removed and the inflammation continues, the gum tissues can be destroyed and more advanced stages of gum disease may follow. Learn more about gum disease.