The bad effects of dental calculus are: lead to bad breath, gingivitis, periodontitis and so on. 1. Bad breath: the formation of dental calculus is related to poor oral hygiene, lifestyle habits and other factors, if you don’t brush your teeth on time, there will be a lot of food debris and bacteria in the mouth, and after staying on the surface of the teeth for a long time, bad breath will occur. 2. Gingivitis: after the formation of dental calculus will stimulate the gums, and it is not easy to remove the calculus through brushing, its surface is also covered with a lot of plaque, and will damage the gums, causing gingivitis, red, swollen gums, pain and other symptoms. 3. Periodontitis: gingivitis, if not treated in time, it is easy to lead to the occurrence of periodontitis, so that the gums, periodontal membrane, alveolar bone and dental bone was destroyed, with the progress of the disease will also appear teeth displacement and loosening, gum recession and other symptoms. Therefore, when usually pay attention to oral hygiene, to avoid the formation of dental calculus, regular oral examination, if the formation of dental scaling should be carried out in a timely manner to prevent oral diseases.