Another interesting aspect of the present

Another interesting aspect of the present case was that the tooth showed apical closure of the root. Although some researchers believe that the root sheath remains intact and resumes its function once the source of inflammation/infection has been eliminated, the exact mechanism of apical closure in such cases remains unclear (Mohammadi, 2011). The production of CH as a byproduct of the hydration reaction of MTA has been demonstrated (Fridland and Rosado, 2003), whereby MTA releases calcium and hydroxyl ions and promotes an alkaline comt inhibitors (Fridland and Rosado, 2005; Amini Ghazvini et al., 2009). Recently, the biological basis for the favorable properties of MTA has been attributed to the production of hydroxyapatite as the principal mineral in teeth and bones. Calcium ions that are released from MTA react with phosphates in the tissue fluid (Sarkar et al., 2005; Asgary et al., 2009b). This assumption is supported by the presence of granulations found when MTA is used as a biocompatible endodontic material, which is similar to the calcite crystals observed after the use of CH (Holland et al., 1999b). Furthermore, the deposition of cellular cementum adjacent to MTA as a root-end filling has been demonstrated (Torabinejad et al., 1995; Asgary et al., 2010).

Conclusion
This case report conducted a successful one-step apexification procedure in a necrotic central incisor with MTA. The accidentally extruded MTA caused no ill effects on healing at the 2-year follow-up visit. At 7years, the extruded MTA was no longer present in the apical tissues and the preoperative lesion had resolved with re-establishment of a normal PDL space and lamina dura.