On the occlusal and buccolingual surfaces of the large teeth, there are generally more gaps that exist, which are called punctate sulci. These locations often appear to have a black performance, mainly a bit of the following two possibilities: 1, may be the presence of pigmentation inside the gap sulcus of the teeth. If you often eat darker foods, such as chocolate, coffee or other foods with color, it is likely that the pigment will be deposited inside the gap. In general, there is no need to worry, there will not be any obvious disease and clinical symptoms, just brush your teeth properly. 2, the black color inside the crevice may be caries, and it is very common for caries to occur in the sulcus. If cavity occurs, X-ray film can be taken or clinical examination can be conducted by the doctor. Once there is caries inside the crevice, we have to carry out the filling treatment of caries, otherwise, the caries of point gap and sulcus can easily progress rapidly and become the caries of small mouth and big bottom, which will slowly hurt the nerve of the tooth.