The reasons why teeth will grow black spots include drinking strong tea, coffee, enamel hypoplasia, tetracycline teeth, composite resin filled cavities, etc., as follows: a. Drinking strong tea and coffee: when patients have the habit of smoking, drinking tea and coffee, smoke spots, tea stains and coffee stains can be deposited on the surface of teeth to form black patches. Second, enamel hypoplasia: when suffering from enamel hypoplasia or poor mineralization, the enamel layer will form substantial defects and easily adsorb exogenous pigments to produce black spots. Tetracycline teeth: When tetracycline teeth or fluorosis occurs, the drug will combine with dentin and produce yellow-brown or black-brown plaque on the enamel surface. 4.Composite resin filling cavity: When applying composite resin filling cavity, if the surface is rough and not polished, a large amount of food residue and soft scale will adhere to the surface of filling body and form black plaque.