Most of the problems that cause bleeding gums and gum disease is plaque, a sticky film-like bacteria that covers the teeth and gums. It is formed by acids secreted by the mouth after eating.
Plaque is found in spaces between your teeth. Gingivitis causes gum bleeding and if left untreated, it can lead to the more serious form of gum disease. It is long term infection which involves the progressive loss of the bone around teeth and may lead to loosening and eventual loss of teeth.