Cavities that do not hurt may or may not require root canal treatment, depending on the extent of the decay. If the cavity has not reached the dental nerves, there will not be noticeable pain. In such cases, since the decay is relatively superficial, direct filling, or dental restoration can be performed without the need for root canal treatment. If the cavity is severe and has reached the dental nerves, causing the nerves to become necrotic and purulent, there will be no pain due to the loss of sensory function from nerve death. In these situations, root canal treatment is needed. This involves removing the infected dental nerves, followed by medicinal treatment of the root canal, and after the inflammation is controlled, filling of the root canal is performed. In other words, a painless cavity might actually be caused by necrosis and pus formation in the dental nerves, requiring root canal treatment.