Hard black teeth in the grooves of the teeth may be food pigmentation, caries manifestations, etc., and can be removed by methods such as scaling and filling. 1. Scaling method: food pigmentation is easily deposited in the crevices of the tooth grooves, which can lead to hard black teeth, which can be removed by ultrasonic cleaning, or using sandblasting and other methods. 2. Filling method: In the early stage of caries, because the tissues of the teeth are affected by the acids secreted by the bacteria, especially in the gaps of the grooves of the teeth, a large number of bacteria will be accumulated, which will lead to the shedding of tooth tissues and become black and hard substances, and then it is necessary to carry out the filling treatment for caries. Therefore, if you find that there is a black hard substance in the groove gap of your teeth, it is recommended that you go to a regular dental hospital for a comprehensive examination to determine the diagnosis and then carry out targeted treatment.