Periodontal (gum) disease is an infection of the tissues that hold your teeth in place. It’s mainly caused by poor brushing and flossing habits that allow plaque (a sticky film of bacteria) to build up on the teeth and harden. Periodontitis is a serious gum infection that damages the soft tissue and without treatment, can destroy the bone that supports your teeth. Periodontitis can cause teeth to loosen or even lead to tooth loss. Periodontitis is common but largely preventable.