Black and yellow teeth may be caused by long-term smoking, improper diet and other physiological factors, or may be caused by dental fluorosis, dental calculus and other diseases, which need to be removed by general treatment, physical therapy and other ways to address the cause of the disease. 1. Physiological factors: long-term smoking, improper diet may lead to pigment accumulation on the surface of the teeth, appearing black teeth yellow. Daily need to quit smoking, diligent brushing, reasonable diet, keep the oral cavity clean and clean. If necessary, you need to take ultrasonic cleaning, so as to improve the role of black teeth and yellow teeth. 2. Dental fluorosis: black teeth and yellow teeth may also be caused by dental fluorosis. Patients can follow the doctor’s instructions to take composite resin repair, abrasion or acid erosion coating method. Some patients can also choose laser whitening treatment to improve the symptoms of black teeth and yellow teeth. 3. Dental calculus: black teeth and yellow teeth are also considered to be caused by dental calculus. Patients can take supragingival scaling, subgingival scraping and other methods, so as to remove the plaque and pigment left by the calculus, and improve the symptoms of black teeth and yellow teeth. There are many reasons that lead to black teeth and yellow teeth, it is recommended that patients go to the regular hospital, relevant examination, identify the cause of the disease, and then actively take treatment measures.