Dental caries is the gradual darkening of the tooth surface due to long-term bacterial attack, and the gradual loss of enamel, forming cavities. If caries is not treated in time, it can easily develop into pulpitis, which is the gradual invasion of bacteria into the tooth and directly reaches the pulp cavity area. Caries is very treatable, as long as the decayed part is completely removed, it can be refilled with a resin-based material and has no effect on the pulp. If it develops to the point of pulpitis before treatment, the whole tooth loses the nourishment of nerves and blood vessels, and gradually becomes brittle and prone to fracture. If pulpitis develops and remains untreated, it develops into periapical inflammation, which can cause resorption of the periapical bone.