Teeth

plaque(牙斑) hardens and becomes tartar/calculus, which lead to cavities and tooth decay, then further to gingivitis(牙龈炎) and even periodontitis(牙周炎).

Tips to Help Control Tartar

• Brush regularly, twice a day for 2 minutes a time. A 30-second scrub twice a day won’t remove plaque or prevent tartar. Use a brush with soft bristles that is small enough to fit into your mouth. Be sure to include the hard-to-reach surfaces behind your teeth and on your rear molars.
• Studies have found that electronic, or powered, toothbrushes may get rid of plaque better than manual models. No matter which type you use, be sure it has the American Dental Association (ADA) seal of approval. These have undergone rigorous quality control and safety tests.
• Choose tartar-control toothpaste with fluoride. It can help prevent plaque from hardening into tartar. Plus, the fluoride will help repair enamel damage. Some products have a substance called triclosan that fights the bacteria in plaque.
• Floss, floss, floss. No matter how good you are with a toothbrush, dental floss is the only way to remove plaque between your teeth and keep tartar out of these hard-to-reach areas.
• Watch your diet. The bacteria in your mouth thrive on sugary and starchy foods. When they’re exposed to those foods, they release harmful acids. Try to eat a healthy diet and limit the amount of sugary foods you eat. That goes for snacks, too. Every time you eat, you also feed the bacteria in your mouth. You don't have to give up sweets or between-meals munches. Just be mindful about how often you indulge. Brush and drink plenty of water during and after meals.
• Don't smoke. Studies show that people who smoke cigarettes or use other tobacco products are more likely to have tartar.

For details, refer to http://health.howstuffworks.com/wellness/natural-medicine/home-remedies/home-remedies-for-tartar-and-plaque1.htm