If there is no specific reason and it is not known how long it has existed and a hole is found in the tooth, it is most likely to be a dental caries. Dental caries is a kind of chronic progressive destruction of the hard tissues of teeth, and the cause of dental caries is mainly bacteria and includes other factors, such as host, food, time, etc. Bacteria is the first element that causes dental caries, bacteria will metabolize and produce acid on the tooth surface, gradually cause demineralization of the hard tissue of the tooth, and slowly form a cavity, if the cavity is too big, there will be pigmentation. At this time, the patient will find a hole on the tooth, if not treated in time, with the further development of the cavity, it is very likely to damage the tooth nerve and cause tooth pain. Therefore, if you find a discolored tooth with a cavity, you need to go to the hospital in time and get the right treatment.