The effect of mineral trioxide aggregate on the apexification and periapical healing of teeth with incomplete root formation W. T. Felippe, M. C. S. Felippe & M. J. C. Rocha School of Dentistry, Federal University of Santa Catarina, Floriano´polis, SC, Brazil Abstract 5 months later, and blocks of the teeth and surrounding tissues were submitted to histological processing. The Felippe WT, Felippe MCS, Rocha MJC. The effect of sections were studied to evaluate seven parameters: mineral trioxide aggregate on the apexification and periapical formation of an apical calcified tissue barrier, level of healing of teeth with incomplete root formation. International barrier formation, inflammatory reaction, bone and root Endodontic Journal, 39, 2–9, 2006. resorption, MTA extrusion, and microorganisms. Results Aim To evaluate the influence of mineral trioxide of experimental groups were analysed by Wilcoxon’s aggregate (MTA) on apexification and periapical heal- nonparametric tests and by the test of proportions. The ing of teeth in dogs with incomplete root formation and critical value of statistical significance was 5%. previously contaminated canals and to verify the Results Significant differences (P < 0.05) were found necessity of employing calcium hydroxide paste before in relation to the position of barrier formation and MTA using MTA. extrusion. The barrier was formed in the interior of the Methodology Twenty premolars from two 6-month canal in 69.2% of roots from MTA group only. In group old dogs were used. After access to the root canals and 2, it was formed beyond the limits of the canal walls in complete removal of the pulp, the canal systems remai- 75% of the roots. MTA extrusion occurred mainly in ned exposed to the oral environment for 2 weeks. Canal roots from group 2. There was similarity between the preparation was then carried out using Hedstro¨m files, groups for the other parameters. under irrigation with 1% sodium hypochlorite, 1 mm Conclusions Mineral trioxide aggregate used after short of the radiographic apex. After drying, the canals of root canal preparation favoured the occurrence of the two premolars in each dog were left empty (control apexification and periapical healing. The initial use of group). The other eight teeth in each animal were divided calcium hydroxide paste was not necessary for apex- into two experimental groups. The apical thirds of the ification to occur, and has shown to be strongly related canals of group 1 were filled with MTA. In the teeth of to the extrusion of MTA and formation of barriers group 2, the canals were dressed with a calcium beyond the limits of the root canal walls. hydroxide–propylene glycol paste. After 1 week, the Keywords: apexification, mineral trioxide aggregate, paste was removed and the apical third was filled with open apices, periapical healing. MTA. All teeth were restored with reinforced zinc oxide cement (IRM) and amalgam. The animals were killed Received 16 March 2005; accepted 15 August 2005 root development ceases. Consequently, the canal Introduction remains large, with thin and fragile walls, and the When teeth with incomplete root formation suffer apex remains open. These features make instrumen- pulp necrosis, the formation of dentine stops, and tation of the canal difficult and hinder the formation of an adequate apical stop. In such cases, in order to Correspondence: Wilson Tadeu Felippe, Presidente Coutinho, allow the condensation of the root filling material 179/702 Centro Floriano´polis, CEP: 88.015-230, SC, Brazil and to promote an apical seal, it is imperative to (Tel./fax: +55 0 48 224 1647; e-mail: [email protected]). create an artificial apical barrier or induce the closure 2 International Endodontic Journal, 39, 2–9, 2006 ª 2006 International Endodontic Journal Felippe et al. MTA apexification of the apical foramen with calcified tissue (apexifica- with a mixture of xilasine (Rompum, Abbott, Sa˜o Paulo, tion). SP, Brazil) and cetamine cloridrate (Ketamin, Aster, Calcium hydroxide pastes have become the material Sa˜o Paulo, SP, Brazil), the dogs were anaesthetized of choice to induce apexification (Leonardo et al. 1993, intravenously with 5% sodium thiopental solution Felippe et al. 2005). Despite its efficacy, this dressing (Thionembutal, Abbott) at the dose of 5-mg Kg)1 body has several disadvantages, such as variability of treat- weight. During the operative procedures, the animals ment time, number of appointments and radiographs, received an infusion of saline solution and intravenous difficulty in patient follow-up, delayed treatment anaesthetics, as required. (Shabahang et al. 1999) and possibility of increased Pre-operative radiographs were exposed to confirm tooth fracture after calcium hydroxide use for extended the presence of open apices. After endodontic access periods (Andreasen et al. 2002). and determination of canal length, pulp tissue was Studies have indicated mineral trioxide aggregate removed with K-files (Dentsply Maillefer, Ballaigues, (MTA) as an alternative to calcium hydroxide (Tittle Switzerland). Size 60 Hedstro¨m files (Dentsply Maillefer, et al. 1996, Shabahang et al. 1999). MTA is a powder Ballaigues, Switzerland) were introduced up to the aggregate, containing mineral oxides (Lee et al. 1993). radiographic apex and were used in a filing action to Besides its noncytotoxicity (Osorio et al. 1998), it has remove the remnants of apical pulp tissue totally. The good biological action (Torabinejad et al. 1995c,d, canals were irrigated with distilled water and after Torabinejad et al. 1998) and stimulates repair (Regan haemostasis, a cotton pellet was placed in the entrance et al. 2002, Economides et al. 2003), because it allows of each canal and the teeth were left without a coronal cellular adhesion, growth and proliferation on its restoration for 2 weeks. surface (Zhu et al. 2000). When used in dogs’ teeth After this period, radiographs were exposed that with incomplete root formation and contaminated demonstrated the presence of apical pathosis of variable canals, MTA often induced the formation of apical size associated with all roots. The canals were cleaned barrier with hard tissue (Tittle et al. 1996, Shabahang under aseptic conditions to the radiographic apex using et al. 1999). size 50–60 K-files. Hedstro¨m files sizes 70 and 80 were From experimental studies described in the literature subsequently used 1 mm short of the radiographic (Tittle et al. 1996, Shabahang et al. 1999), clinical apex, using gentle filing movements. During prepar- protocols (Shabahang & Torabinejad 2000), as well as ation, the canals were irrigated with 1% sodium clinical cases (Torabinejad & Chivian 1999, With- hypochlorite solution. After drying with sterile paper erspoon & Ham 2001, Giuliani et al. 2002, Levenstein points, the canals of two premolars of each dog were 2002, Maroto et al. 2003), MTA was placed into canals left unfilled (control group); the coronal restoration only after the use of calcium hydroxide paste for consisted of reinforced zinc oxide cement (IRM) and 1 week. Therefore, the reaction of the apical tissues amalgam. For the other eight premolars in each when this material is applied immediately after canal animal, the canals were dried with sterile paper points. preparation, in teeth with incomplete root formation, is The teeth were randomly assigned to two experimental not known. groups. The aim of this study was to evaluate the effect of In group 1, 16 canals were filled with a mixture of MTA on apexification and periapical healing in dogs’ MTA (Pro Root MTA, Dentsply Tulsa Dental, Tulsa, OK, teeth with incomplete root formation and contamin- USA) with distilled water, in a proportion of 3 : 1. The ated canals, and to verify whether calcium hydroxide MTA was placed into the canals with a lentulo-spiral, paste was required prior to the use of MTA. introduced 3 mm short of the radiographic apex and condensed in the apical third by gentle packing with paper points. The teeth were radiographed to check the Material and methods MTA apical plug and a sterile cotton pellet was then The research project was approved by the Animal placed in the access cavity. The coronal restoration Ethics Screening Committee of the Federal University of consisted of IRM and amalgam. Santa Catarina (Floriano´polis, SC, Brazil). In group 2, 16 canals received a calcium hydroxide The procedures were performed as described by paste (pure calcium hydroxide, 0.612 mg, Reagen, Rio Felippe et al. (2005). A total of 40 root canals from 20 de Janeiro, RJ, Brazil) mixed with propylene glycol maxillary and mandibular premolars of two 6-month (0.4 mL, Quimidrol, Joinville, SC, Brazil). The paste was old Beagle dogs were used. After intramuscular sedation placed into the canals with a lentulo-spiral, introduced ª 2006 International Endodontic Journal International Endodontic Journal, 39, 2–9, 2006 3 MTA apexification Felippe et al. 3 mm short of the radiographic apex. The teeth were some disruption of structure, or (iii) severe – extensive radiographed for complete filling of the canals, and inflammatory cell infiltrate with replacement of tissues, sealed with IRM. After 1 week the canals were abscess irrigated with saline solution, and a size 80 K-file • Bone resorption: characterized by the presence of was introduced 1 mm short of the radiographic apex clastic cells on the bone surface and enlargement of the and gently manipulated to remove the paste. Irriga- periodontal space tion was repeated until the solution was clear of any • Root resorption: characterized by the presence of calcium hydroxide residue. After drying, the apical clastic cells on the root surface or by perceptible 3–4 mm of the canals was filled with MTA. All other exposed dentine surface procedures and the coronal restoration were similar to • Extrusion of MTA: presence of material beyond the group 1. limits of the root walls Five months after mechanical canal preparation, • Microorganisms: presence of microorganisms in the the animals were killed and the jaws dissected and root canal, inside dentinal tubules or in the periodontal fixed in 10% formol solution.