It is important to see your dentist as soon as the crown or cap came off. There are various reasons why crowns come off like decay, fracture or simply that the cement dissolved. If the tooth did not have a prior root canal treatment, it may be sensitive to hot/cold foods and liquids now that it is not protected by the crown again. Call our office and we can determine is the crown may be re-cemented or if there is any additional treatment needed.