Periodontal disease, also known as gum disease, causes red, swollen gums and can mean the connective tissue and bone that hold teeth in place may be destroyed. Periodontal disease is the major cause of tooth loss. Each tooth is embedded in the gum and attached by connective tissue to bone. Healthy gums are pale, pink, smooth and firm, and form a peak or cone between adjacent teeth. They surround your teeth like a turtleneck fits your neck, with just a narrow crevice in between. In this crevice is where problems begin because it is teeming with bacteria, which produce the sticky, soft, colorless substance known as plaque. The gums support the attachment of the teeth in the mouth, and ligaments attach the teeth to the underlying bone.