When a tooth filling turns black, you should first find out the cause of the blackening and then deal with it accordingly. In general, there are 3 types of black fillings. The first one is the darkening of teeth caused by exogenous staining. For example, some patients often smoke, drink tea, coffee or eat chocolate, and at the same time, the oral cleaning like brushing is not particularly timely, so the corresponding tooth surface is prone to pigmentation over time. In this case, the exogenous pigmentation can be removed by sandblasting combined with polishing. In the second case, there is a secondary caries on the filled tooth, in this case, it is necessary to repair the filled tooth again, it may be necessary to remove the original repair, remove the new blackened caries, and then repair the caries again. The last case is the darkening of the entire tooth, which is often caused by the necrosis of the dental pulp. For pulpal necrosis, the filling material should be removed directly, root canal treatment should be performed, and finally crown restoration should be applied to protect the tooth. This is the only way to treat this type of pulpal necrosis, which causes a change in the color of the tooth.