Five methods for the treatment of teeth with an incompletely formed apex (open apex) and a necrotic pulp are discussed. The methods discussed include the use of (1) a customized cone (blunt-end, rolled cone): (2) a short-fill technique: (3) periapical surgery (with or without a retrograde seal). (4) apexification (apical closure induction) , and (5) one-visit apexification. The apexification techniques, which use various formulations of calcium hydroxide to induce closure, are stressed. Based on the review of the literature and clinical experience of the authors, it was concluded hat successfull treatment of an immature puipless tooth can partly result from the antibacterial and calcificationinducing action of calcium hydroxide.