Calculus is mainly in the opening of salivary glands, easy to deposit on the surface of the teeth, especially the neck of the teeth, such as the lingual side of the mandibular anterior teeth, the buccal side of the maxillary posterior teeth, and have the habit of chewing on the lateral side, the side of the unchewed food, can be removed by the following habits: 1, oral hygiene: such as after eating, morning and evening brushing; 2, between the gaps of the teeth, flossing can be used to clean the soft tartar that is not easy to be brushed by the toothbrush; 3, regular dental cleaning: in a normal state, about once a year can be done, periodontitis, gingivitis patients, every six months, or even once a quarter to do dental cleaning.