The diagnosis of cracked tooth is difficult in the early stage because the symptoms are not consistent, and often a crack line is not visible. Early detection and proper treatment of cracked tooth are important because all cracks have the potential to become a split tooth.1. Be reminded that cracked tooth occurs usually on mandibular and maxillary first molars in patients in their 40s and 50s. If the tooth has a large restoration such as gold inlay or amalgam filling, then cracks occur easily.1232. If pulp status is reversible pulpitis, remove the old restoration and crack line carefully because cracks are always colonized by bacterial biofilms. Fill the cavity with bonded direct or indirect restoration.2456 If biting pain persists, then make a provisional crown and reevaluate the necessity of root canal treatment.3. If pulp status is irreversible pulpitis or necrotic, perform root canal treatment initially and make a provisional crown.247 If symptom disappears, then make a final crown.4. If a crack extends subgingivally and deep periodontal pocket is associated with the crack, explain the poor prognosis to the patient and decide whether to treat or extract the cracked tooth.8