Teeth with necrotic pulp or irreversible pulpitis require root canal treatment. The outcome of endodontic treatment depends on various factors such as: diagnosis, correct instrumentation, disinfection and tight seal obturation of the root canal system. These procedures are routinely performed in fully developed teeth. An optimal filling of the root canal system of non-vital immature teeth with open apices is always problematic for dental practitioners (1, 2). The immature teeth have incomplete root development. Root walls are thin and divergent and the apical foramen is wide opened, therefore it is impossible to seal the root canal with traditional obturation methods (2).

Apexification is root canal treatment in immature permanent teeth in which root formation ceased due to pulpal necrosis or irreversible pulpitis. The purpose of this procedure is to removal of necrotic pulp, debridement of the canal, control of infection and induce root end closure by forming a barrier to facilitate obturation of the canal (2, 3). There are generally two ways to reach this goal. First one is based on multiple visits when the internal dressing of the root is changed in 3-6 months periods. Calcium hydroxide is the most common preparation used for this purpose (2, 3), since its antimicrobial and odontotropic action limits bacterial infection and enables the formation of an natural calcified apical barrier. However, calcium hydroxide has some relevant disadvantages, including high solubility and low mechanical stability, which may pose risk of fracture to the thin root walls (3-6). Moreover, the average time for apical barrier formation ranges from 5 to 24 months necessitating multiple-visit treatment, during which a leakage around provisional restoration may result in bacterial re-contamination of the root canal system (2, 6-8). As all these factors may lead to the failure, other materials have also been used as a root-end filling in the apexification procedure. One of them is MTA (Mineral Trioxide Aggregate), which consists of hydrophilic particles of calcium, magnesium, silicone, ferrous oxides that in wet conditions create colloidal gel. Material sets to a hard structure in about 3 hours after application and its compressive strength are similar to that of IRM® (Immediate Restorative Material) or super-EBA® (Ethoxy Benzoic Acid) cements (7). One of the main reasons for using MTA as root canal filling material in apexification is its biocompatibility, osteogenic properties, great sealing ability and marginal adaptation. MTA is considered as a bacteriostatic and bactericidal material due to release of hydroxyl ions during setting and maintaining high pH. Formation of mineralized layer between MTA and dentin as well as the fact that MTA can penetrate dentinal tubules provide challenging conditions for bacterial survival including Enterococcus faecalis and Candida albicans that are often cause of unsuccessful endodontic treatment. What is more, setting properties of MTA are not susceptible to moisture and bleeding. MTA in contrast to calcium hydroxide does not undergo disintegration in time (8-11).

During apexification procedure MTA is placed at the apical part of the root. This enables to create an artificial hard apical barrier, also known as “apical stop” or “apical plag”, on a single visit and reduces risk factors connected with using calcium hydroxide. Before next appointment the material is hardened and the apical closure is achieved. Then, the backfill part of the obturation using gutta-percha may be carried out.

Apexification with the use of MTA was carried out in 5 patients: in 4 patients in central maxillary incisors due to traumatic injuries and in 1 patient in mandibular premolar due to caries. The clinical examination showed that treated teeth were non vital and the radiographs revealed incomplete root development. All procedures were completed under dental operating microscope after obtaining an informed consent from the parents. Patients were locally anesthetized with articaine with 1:200 000 epinephrine. Instrumentation of root canal with crown-down technique was made after placing a rubber dam and the radiographic working length determination. Preparation of the root canal was mainly chemical due to their thin walls. The canals were irrigated with 2% sodium hypochlorite and 0.9% saline solution. Calibrated paper points were used to dry the canals. A portion of absorbable collagen sponge (Biokol, Stalmed Kielce or Spongostan, Ferrosan) was placed at the root end to allow MTA to be placed within the confines of the canal large space to prevent its extrusion (12, 13). In four teeth ProRoot MTA (Dentsply Maillefer, Tulsa, OK, USA) was applicated with a special carrier and then condensed in the apex using Gutta-Condensers and paper points. The final apical plug thickness was 3-4 mm. Subsequently, the wet cotton pellet was placed in the pulp chamber and the cavity was closed with glass ionomer. In one case fast setting Bio MTA (Cerkamed, Stalowa Wola, Poland) was used in the apexification procedure (12, 13). The X-ray was taken to confirm the correct position of the apical plug. In four teeth with MTA on the next appointment the temporary filling was removed and the canal was backfilled using Obtura (Spartan) with thermoplastic gutta-percha with AH Plus Sealer (Dentsply De Trey) and the crown was finally restored with a composite material. In one tooth in which Bio MTA was used the canal was backfilled with Obtura System on the same visit. Another X-ray was taken in the end of the treatment. An amoxicilline was prescribed in all cases. The patients attended recall appointments, after 6, 12 months or longer period – 30 and 36 months, during which a control radiographic examination was performed.

A 10-year-old boy with Class II malocclusion suffered trauma to the upper central left incisor 1.5 years before initial examination. A buccal sinus tract was noted near the apex. The radiograph confirmed chronic periapical periodontitis (fig. 1a). After application of rubber dam and endodontic access preparation the procedure of apexification was conducted as described above (figs. 1b, c). At the same visit a portion of collagen sponge and ProRoot MTA material were placed in the canal at the root end. After 7 days canal was backfilled using Obtura system. The follow-up appointments after 6 and 12 months showed proper clinical function of the tooth, healing of sinus tract and absence of clinical symptoms. The radiographic examination after 6 and 12 months revealed the continuous decrease of periapical lesion and formation of apical barrier (fig. 1d).