Periodontal disease is caused by bacteria in the mouth that form plaque below the gum line. There are more than 500 bacterial species that can be found in plaque, and brushing alone does not remove the bacteria below the gum line. The disease typically does not cause pain until it’s in an advanced stage. At that point, much of the damage has been done. The disease causes receding gums, bone damage in the mouth and loss of teeth. It also can increase the risk of heart disease, diabetes, rheumatoid arthritis and even cancer.