Black lines appear on the teeth, mostly occurring at the sulcus of the occlusal (coincidental) surface of the molar teeth, and the causes are mostly pigmentation and superficial caries. According to the situation, it can be treated without special treatment or caries treatment as follows: First, simple pigmentation: it is not accompanied by the defect of hard tissue of the tooth. In this case, no special treatment is usually needed, but brush the teeth carefully and keep good oral hygiene. Secondly, superficial caries: black pigment deposition appears at the sulcus point gap of the biting (dentition) surface, accompanied with enamel or dentin defect, which means superficial caries has been formed, and it needs to go to hospital for caries treatment in time. In the process of treatment, the infected and discolored hard tissues should be completely removed by high-speed turbine dental drill, and then the composite resin filling material should be used to restore the defects of the tissues.