Darkening of teeth may be caused by pigmentation, or it may be caused by caries, pulpitis and other diseases. 1. Hyperpigmentation: If the patient has the habit of smoking for a long time or does not have the habit of brushing teeth, it will lead to the phenomenon of hyperpigmentation on the surface of the teeth, so the patient will have the phenomenon of blackened teeth. 2. Caries: caries is mainly due to bacterial infection, diet and other factors, the patient’s main symptoms are yellowish-brown teeth, soreness, cavities, etc., which will lead to the symptoms of blackened teeth. 3. Pulpitis: The causes of pulpitis are numerous, including bacterial infection, physical as well as chemical stimulation. The main symptoms of pulpitis are temperature stimulated pain, spontaneous pain, pus, necrosis, etc., which can also lead to the phenomenon of blackening of the teeth. When patients experience symptoms of blackened teeth, it may be caused by dental stains and does not require special treatment. If it is caused by disease, patients should go to the hospital in time to identify the specific disease and take regular treatment measures under the guidance of the doctor to avoid aggravating the condition.