This procedure encourages the root to continue development as the pulp is healed. The injured pulp is covered with medication to encourage growth. The tip of the root (apex) will continue to close as a child gets older. In turn, the walls of the root canal will thicken. The more mature the root becomes, the better the chances of saving the tooth.
In this case, the unhealthy pulp is removed. The endodontist places medication into the root to help a hard tissue form near the root tip. This hardened tissue provides a barrier for the root canal filling. At this point, the root canal walls will not continue to develop, making the tooth susceptible to fractures. So it is important to have the tooth properly restored by your dentist.