The effect of mineral trioxide aggregate on the apexification and periapical healing of teeth with incomplete root formation.

AIM: To evaluate the influence of mineral trioxide aggregate (MTA) on apexification and periapical healing of teeth in dogs with incomplete root formation and previously contaminated canals and to verify the necessity of employing calcium hydroxide paste before using MTA. METHODOLOGY: Twenty premolars from two 6-month old dogs were used. After access to the root canals and complete removal of the pulp, the canal systems remained exposed to the oral environment for 2 weeks. Canal preparation was then carried out using Hedström files, under irrigation with 1% sodium hypochlorite, 1 mm short of the radiographic apex. After drying, the canals of two premolars in each dog were left empty (control group). The other eight teeth in each animal were divided into two experimental groups. The apical thirds of the canals of group 1 were filled with MTA. In the teeth of group 2, the canals were dressed with a calcium hydroxide-propylene glycol paste. After 1 week, the paste was removed and the apical third was filled with MTA. All teeth were restored with reinforced zinc oxide cement (IRM) and amalgam. The animals were killed 5 months later, and blocks of the teeth and surrounding tissues were submitted to histological processing. The sections were studied to evaluate seven parameters: formation of an apical calcified tissue barrier, level of barrier formation, inflammatory reaction, bone and root resorption, MTA extrusion, and microorganisms. Results of experimental groups were analysed by Wilcoxon's nonparametric tests and by the test of proportions. The critical value of statistical significance was 5%. RESULTS: Significant differences (P < 0.05) were found in relation to the position of barrier formation and MTA extrusion. The barrier was formed in the interior of the canal in 69.2% of roots from MTA group only. In group 2, it was formed beyond the limits of the canal walls in 75% of the roots. MTA extrusion occurred mainly in roots from group 2. There was similarity between the groups for the other parameters. CONCLUSIONS: Mineral trioxide aggregate used after root canal preparation favoured the occurrence of the apexification and periapical healing. The initial use of calcium hydroxide paste was not necessary for apexification to occur, and has shown to be strongly related to the extrusion of MTA and formation of barriers beyond the limits of the root canal walls.

Ex vivo evaluation of the capacity of the Tri Auto ZX to locate the apical foramen during root canal retreatment.

AIM: To evaluate ex vivo the capacity of the Tri Auto ZX to locate the apical foramen during root canal retreatment. METHODOLOGY: The root canals of 62 maxillary and mandibular canines were prepared to a length 1 mm short of the apical foramen, to an apical size 35 using 1% sodium hypochlorite as an irrigant. Once prepared, the length of each tooth was measured directly using a size 15 K-Flexofile introduced in the canal until the tip was visible at the apical foramen. After the file was removed, its length was recorded to a precision of 0.01 mm using a calliper. These direct lengths (DL) became the 'gold standard' for comparison with the electronic lengths (EL) derived from the Tri Auto ZX. After direct measurement, the tooth was measured electronically (EL1) and the canals were filled using lateral condensation of gutta-percha cones and sealer. Seven days later the root filling was removed using solvent, Gates-Glidden burs, and K-files, and new electronic lengths determined (EL2). The electronic lengths (EL1 and EL2) were compared with the DL, and the differences were analysed statistically using the proportions test and Student's t-test. RESULTS: At a tolerance limit of +/-0.5 mm, EL1 coincided with the DL in 76% of cases. Lengths obtained in the presence of remnant of filling material (EL2) coincided in 81% of cases. The proportions test used to compare these percentages showed no statistically significant difference between EL1 and EL2 (P > 0.05). The Student's t-test revealed a statistically significant difference (P < 0.05) between the means of the differences between DL/EL1 (-0.36 mm) and DL/EL2 (-0.04 mm). CONCLUSION: The Tri Auto ZX was accurate to +/-0.5 mm in more than 80% of teeth following removal of root fillings.

Pulp therapy in a maxillary fused primary central incisor--report of a case.

This paper describes a case in which pulp therapy was provided in a fused maxillary primary central incisor in a 4-year-old patient with a history of fistula on the gingival mucosa. The tooth involved was larger than expected, suggesting fusion. The diagnosis of fusion was confirmed on radiographical examination. The clinical management of the case is described and the diagnosis and treatment discussed.