To put it simply, human teeth are hollow and the teeth can be divided into enamel, dentin and pulp cavity from the outside in. The pulp cavity is hollow and rich in blood vessels, nerves, lymph and connective tissues. The pulp tissue has nutritional repair and keen sensory functions, and when a tooth is extensively chipped due to trauma or deep decay, the pulp chamber inside the tooth can often be seen. Once the pulp nerve in the pulp cavity becomes inflamed, a sharp and unbearable pain will be felt. It is necessary to go to the dentist to have the pulp completely removed and then undergo root canal treatment. The strength of the tooth is significantly reduced due to the lack of nourishment from the pulp, and when the tooth is subjected to a large external force, it is easy to fracture the tooth, and it is best to protect the tooth with a crown sleeve at this time.