<prompt> Apexification is the treatment of choice for a permanent tooth with wide open apex when:The pulp is necroticThe pulp is vitalThe pulp and root canals are calcifiedThere is traumatic pulp exposure during cavity preparation  <response>: Apexification is the process of inducing the development of the root and the apical closure in an immature pulpless tooth with an open apex.The main aim of apexification is to preserve the Hertwigs root sheath and apical pulp tissue.Ref :Textbook of endodontics, Nisha Garg and Amit Garg, 3rd edition, pg no:548 