If your hands bled when you washed them, you would be concerned. Yet, many people think it's normal if their gums bleed when they brush or floss.Swollen and bleeding gums are early signs that your gums are infected with bacteria. If nothing is done, the infection can spread and destroy the structures that support your teeth in your jawbone. Eventually, your teeth can become so loose that they have to be extracted.What Is Periodontal Disease?"Perio"means around, and "dontal" refers to teeth. Periodontal diseases are infections of the structures around the teeth, which include the gums, periodontal ligament and alveolar bone. In the earliest stage of periodontal disease — gingivitis — the infection affects the gums. In more severe forms of the disease, all of the tissues are involved.For many years scientists have been trying to figure out what causes periodontal disease. It is now well accepted that various types of bacteria in dental plaque are the major villains. Researchers also are learning more about how an infection in your gums can affect your overall health.Researchers are studying possible connections between gum disease and:What Causes Periodontal Disease?Periodontal disease is caused by bacteria in dental plaque, the sticky substance that forms on your teeth a couple of hours after you have brushed. Interestingly, it is your body's response to the bacterial infection that causes most of the problems. In an effort to eliminate the bacteria, the cells of your immune system release substances that cause inflammation and destruction of the gums,periodontal ligament or alveolar bone. This leads to swollen, bleeding gums,signs of gingivitis (the earliest stage of periodontal disease), and loosening of the teeth, a sign of severe periodontitis (the advanced stage of disease.)Practicing good oral hygiene and visiting your dentist regularly (about once every six months, or more often if you have gum disease) can prevent periodontal disease. Daily brushing and flossing, when done correctly, help remove most of the plaque from your teeth. Professional cleanings by your dentist or dental hygienist will keep plaque under control in places that are harder for a toothbrush or floss to reach.If oral hygiene slips or dental visits become irregular, plaque builds up on the teeth and eventually spreads below the gum line. There, the bacteria are protected because your toothbrush can't reach them.Good flossing may help dislodge the plaque; but if it is not removed, the bacteria will continue to multiply,causing a more serious infection. The buildup of plaque below the gum line leads to inflammation of the gums. As the gum tissues become more swollen, they detach from the tooth forming a space, or "pocket," between the tooth and gums. In a snowball effect, the pockets encourage further plaque accumulation since it becomes more difficult to remove plaque. If left untreated, the inflammatory response to the plaque bacteria may spread to the periodontal ligament and alveolar bone, causing these structures to be destroyed.Another problem is that if plaque is allowed to build up on teeth, over time it becomes calcified, or hardened, and turns into calculus (commonly called tartar). Since calculus is rougher than tooth enamel or cementum (a layer that covers the tooth root), even more plaque attaches to it, continuing this downward spiral.Using tartar-control toothpaste may help slow accumulation of calculus around your teeth, but it can't affect the tartar that has already formed below the gum line.Although bacterial plaque buildup is the main cause of periodontal disease, several other factors, including other diseases, medications and oral habits, also can contribute. These are factors that can increase your risk of gum disease or make it worse once the infection has set in.