I t has been shown that approximately 6-19% of adolescent have suffered dental trauma. If this occurs at a young age, when the root development is incomplete, the clinician faces difficult case of an immature permanent tooth with thin dentine walls and a wide open apex in need of endodontic treatment. For many years the treatment of choice in this cases has been the apexification technique using calcium hydroxide which is known to induce the formation of a hard tissue barrier in the apex, allowing for the obturation of the root canal to be completed. Recently, a new material has been developed for endodontic treatment that appears to be a significant improvement over other materials used against bone. This material is mineral trioxide aggregate (MTA). Traditionally, calcium hydroxide has been the material of choice for the apexification of immature permanent teeth but MTA holds significant promise as an alternative to multiple treatment with calcium hydroxide.