In dentistry, calculus or tartar is a form of hardened dental plaque. It is caused by precipitation of minerals from saliva and gingival crevicular fluid (GCF) in plaque on the teeth (From Wikipedia). Serious dental calculus causes bad breath, receding gums, gingivitis, periodontitis and other oral diseases. Therefore, it is necessary to remove calculus. 

Brushing and flossing are effective to remove food residue and bacteria, which forming calculus. However, once calculus formed, it is hard to remove them with a tooth brush. 

There are three methods of dental cleaning: ultrasonic scaling, sandblasting cleaning and hand instruments scaling. All these three methods can effectively remove plaque and calculus, giving back the original color of your teeth. Among them, ultrasonic cleaning and sandblasting cleaning are frequently used. 

Ultrasonic scaling, is effective in removing calculus by crushing calculus with high vibrational energy. It vibrates at high speeds, between 18,000 and 50,000Hz. It works best in removing calculus, tobacco stains and tea plaque. Sandblasting cleaning is using a powerful stream of aluminum oxide to clean teeth, removing calculus, stains and plaque. 

Bleaching is another way to remove calculus. However, this will harm teeth in a certain extent and it is not recommended. 

Regular oral checkups are very important to remove calculus. If you found you have calculus, talk to your dentist and choose the most suitable method to remove them.