You may have periodontal disease without knowing it. This disease is the primary cause of tooth loss in people over the age of 35. If caught in the early stages, however, periodontal disease can be reversed. Periodontal, or gum disease, is caused by plaque that mixes with the starches and sugars in the diet, forming acids and other by-products in the mouth. These irritate the gums and cause them to become red, tender and swollen with the propensity to bleed easily. If not removed daily, plaque hardens to form calculus (tartar) around the necks of teeth. This eventually leads to the gums being pulled away from the tooth structure, allowing pockets in the gums to form, which then also fill up with more plaque. In time, the bone structure supporting the teeth can be destroyed.