Periodontal disease is an infection of the tissues that support your teeth. Periodontal disease, also known as gum disease, is one of the most common infections today. More than 75% of North Americans over 35 years of age have some form of periodontal disease. Although many are infected, few know they actually have the disease. In a recent study, 8 out of 10 people surveyed believed they did not have periodontal disease, 7 out of 10 exhibited one or more symptoms.