Plaque and soft tartar in the gaps between teeth can gradually form calculus through calcification. The formation of calculus is a long term process and can be removed by brushing at the initial stage of formation. Once calcified and firmly attached to the teeth, it can only be removed by regular scaling or scraping. The formation of calculus has a lot to do with the presence of plaque. Normal brushing can effectively remove plaque and the soft scale attached to teeth, but incomplete brushing or too little times will cause plaque to accumulate in the mouth. On the other hand, human saliva is alkaline and can precipitate calcium ions, which can gradually precipitate when contacting plaque. After a long period of calcification and hardening, the plaque will be firmly attached to the teeth. The main methods of calculus removal include supragingival scaling and subgingival scaling. Supragingival scaling is used to remove calculus from the exposed gums, using ultrasonic waves to shatter the calculus and polish the tooth surface, which not only cleans thoroughly but also prevents the reattachment of calculus. Subgingival scaling is used to remove calculus below the gums including the gingival sulcus and periodontal pockets. Subgingival calculus is more tightly and firmly attached than supragingival calculus, and because subgingival calculus cannot be seen by the naked eye, it needs to be combined with a probe to check whether it has been removed. Since calculus is formed continuously, a single cleaning cannot guarantee that no more calculus will grow for the rest of your life, and regular scaling is required to maintain a clean mouth. In addition, you should brush your teeth carefully and thoroughly, pay attention to the inside and outside of the teeth, the occlusal surface and the adjacent surfaces, and keep the brushing time above 2 minutes to maintain the correct oral cleaning method, which can effectively reduce the production of dental calculus.