Occult tooth fracture, also known as incomplete tooth fracture, or dental microfracture, refers to small, non-physiological cracks on the surface of the tooth crown that are often not easily detected. Cracks in cryptocracks, which often penetrate deep into the dentin structure, are one of the causes of toothache, weakness of the tooth structure, large cusp slope, traumatic force, etc. Treatment: I. Superficial cryptocracks with no obvious symptoms and normal pulp vitality can be treated to reduce the lateral splitting force and prevent the crack from deepening, or the cavity can be prepared to do prophylactic filling after grinding away the crack as much as possible. Second, for deeper cracks, or for those with pulp lesions, a large number of cusp bevels should be adjusted at the same time as the pulp treatment to completely remove the fracture-causing force on the affected tooth, and to restore it with a full crown in a timely manner after treatment. During the endodontic treatment, the cavity was opened on the tooth surface, resulting in a significant reduction of the crack tolerance to the force. Although the occlusion is lowered during treatment, the tooth is very prone to splitting from the crack during treatment due to chewing and other reasons. Therefore, at the beginning of endodontic treatment, a band ring can be made to adhere on to protect the crown. After the endodontic treatment, full crown restoration should be done.