Because diabetes reduces the body's resistance to infection, the gums are at risk for gingivitis, an inflammation usually caused by the presence of bacteria in plaque. Plaque is the sticky film that accumulates on teeth both above and below the gum line. Without regular dental check-ups, gum disease may result if gingivitis is left untreated. It also can cause inflammation and destruction of tissues surrounding and supporting teeth, gums, bone and fibers that hold the gums to the teeth.