Antibacterial properties of silver nanoparticles as a root canal irrigant against Enterococcus faecalis biofilm and infected dentinal tubules.

AIM: To evaluate the antimicrobial action of an irrigant containing silver nanoparticles in an aqueous vehicle (AgNp), sodium hypochlorite and chlorhexidine against Enterococcus faecalis biofilm and infected dentinal tubules. METHODOLOGY: Bovine dentine blocks were used for E. faecalis biofilm development for 21 days and irrigated with 94 ppm AgNp solution, 2.5% NaOCl and 2% chlorhexidine for 5, 15 and 30 min. For infection of dentinal tubules with E. faecalis, dentine specimens from bovine incisors were submitted to a contamination protocol over 5 days, with eight centrifugation cycles on every alternate day, and irrigated with the same solutions and time intervals used for the biofilm. The specimens were stained with the Live/Dead technique and evaluated using a confocal laser scanning microscope (CLSM). The bioImage_L software was used for measurement of the total biovolume of biofilm in µm3 and percentage of viable bacteria (green cells) in biofilm and in dentinal tubules found after the irrigation. Statistical analyses were performed using Kruskal-Wallis and Dunn's tests for quantification of viable cells in biofilm, the Friedman test for comparisons of viable bacteria in dentinal tubules in different areas of the root canal and the Mann-Whitney U-test to compare the action of the irrigants between the two methods (P < 0.05). RESULTS: The AgNp solution eliminated fewer bacteria, but was able to dissolve more biofilm compared with chlorhexidine (P < 0.05). NaOCl had the greatest antimicrobial activity and biofilm dissolution capacity. AgNp solution had less antimicrobial action in infected dentinal tubules compared with NaOCl (P < 0.05). The AgNp solution after 5 min was more effective in eliminating planktonic bacteria in dentinal tubules than in biofilm, but at 30 min fewer viable bacteria were observed in the biofilm compared with intratubular dentine (P < 0.05). CONCLUSIONS: AgNp irrigant was not as effective against E. faecalis compared to solutions commonly used in root canal treatment. NaOCl is appropriate as an irrigant because it was effective in disrupting biofilm and in eliminating bacteria in biofilms and in dentinal tubules.

Influence of powder-to-water ratio on radiopacity, setting time, pH, calcium ion release and a micro-CT volumetric solubility of white mineral trioxide aggregate.

AIM: To evaluate the radiopacity, setting time, pH level, calcium ion release and solubility of white mineral trioxide aggregate (MTA; Angelus, Londrina, Pr, Brazil) with different powder-to-water ratios. METHODOLOGY: Three MTA groups were prepared using 4 : 1, 3 : 1 and 2 : 1 powder-to-water ratios. For the radiopacity analysis, the 10 × 1 mm specimens were arranged on occlusal films with a cylinder of dentine and an aluminium stepwedge. The digitized radiographs were evaluated with Digora 1.51 software to determine the radiographic density. The setting time test was performed according to the American Society for Testing and Materials 266/08 standard specifications, but the specimens were made according to International Organization for Standardization 6876:2001. Thirty acrylic teeth with root-end filling material were immersed in ultrapure water for measurement of pH level and calcium ion release (atomic absorption spectrophotometer) at 3, 24, 72 and 168 h. In the solubility test, the root-end fillings of 30 acrylic teeth were scanned twice by a Micro-CT, before and after immersion in ultrapure water for 168 h. Digital data were reconstructed, and the volume (mm(3) ) of the samples was obtained using CTan software (CTan v1.11.10.0, SkyScan). The data were statistically analysed by the anova, Tukey, Kruskal-Wallis and Dunn's tests. RESULTS: The radiopacity was higher (P < 0.05) when the 4 : 1 proportion was utilized. The setting time was longer, and the pH level and calcium ion release were higher (P < 0.05) with a greater volume of water. The group with more water (2 : 1) had significantly (P < 0.05) more material volume loss (6.46%) compared with the other groups. CONCLUSIONS: The ratio of powder/water significantly interfered with the physical and chemical properties of white MTA Angelus.

Analysis of four gutta-percha techniques used to fill mesial root canals of mandibular molars.

AIM: To compare the percentage of gutta-percha, sealer and voids and the influence of isthmuses in mesial root canals of mandibular molars filled with different techniques. METHODOLOGY: Canals in 60 mesial roots of mandibular first molars were prepared with ProTaper instruments to size F2 (size 25, 0.08 taper) and filled using a single-cone, lateral compaction, System B or Thermafil techniques. An epoxy resin sealer was labelled with Rhodamine-B dye to allow analysis under a confocal microscope. The percentage of gutta-percha, sealer and area of voids was calculated at 2, 4 and 6 mm from the apex, using Image Tool 3.0 software. Statistical analysis was performed using nonparametric Kruskal-Wallis and Dunn tests (P < 0.05). The influence of isthmuses on the presence or absence of voids was evaluated using the Fisher test. RESULTS: At the 2 mm level, the percentage of gutta-percha, sealer and voids was similar amongst the System B, lateral compaction and single-cone techniques. The single-cone technique revealed significantly less gutta-percha, more sealer and voids in comparison with the Thermafil technique at the 2 and 4 mm level (P < 0.05). The analysis of all sections (2, 4 and 6 mm) revealed that more gutta-percha and less sealer and voids were found in root canals filled with Thermafil and System B techniques (P < 0.05). The Fisher test revealed that the presence of isthmuses increased the occurrence of voids in the lateral compaction group only (P < 0.05). CONCLUSION: Gutta-percha, sealer filled area and voids were dependent on the canal-filling technique. The presence of isthmuses may influence the quality of root filling.

Analysis of the gutta-percha filled area in C-shaped mandibular molars obturated with a modified MicroSeal technique.

AIM: To analyse the gutta-percha filled area of C-shaped molar teeth root filled with the modified MicroSeal technique with reference to the radiographic features and the C-shaped canal configuration. METHODOLOGY: Twenty-three mandibular second molar teeth with C-shaped roots were classified according to their radiographic features as: type I--merging, type II--symmetrical and type III--asymmetrical. The canals were root filled using a modified technique of the MicroSeal system. Horizontal sections at intervals of 600 mum were made 1 mm from the apex to the subpulpal floor level. The percentage of gutta-percha area from the apical, middle and coronal levels of the radiographic types was analysed using the Kruskal-Wallis test. Complementary analysis of the C-shaped canal configurations (C1, C2 and C3) determined from cross-sections from the apical third was performed in a similar way. RESULTS: No significant differences were found between the radiographic types in terms of the percentage of gutta-percha area at any level (P > 0.05): apical third, type I: 77.04%, II: 70.48% and III: 77.13%, middle third, type I: 95.72%, II: 93.17%, III: 91.13% and coronal level, type I: 98.30%, II: 98.25%, III: 97.14%. Overall, the percentage of the filling material was lower in the apical third (P < 0.05). No significant differences were found between the C-shaped canal configurations apically; C1: 72.64%, C2: 79.62%, C3: 73.51% (P > 0.05). CONCLUSIONS: The percentage of area filled with gutta-percha was similar in the three radiographic types and canal configuration categories of C-shaped molars. These results show the difficulty of achieving predictable filling of the root canal system when this anatomical variation exists. In general, the apical third was less completely filled.

Three-rooted maxillary second premolar.

The possibility of three canals in maxillary second premolars is quite small; however, it must be taken into account in clinical and radiographic evaluations during endodontic treatment. Many times their presence is noticed only after canal treatment, due to continuing postoperative discomfort. This article describes a clinical case of three-canal maxillary second premolars that are endodontically treated.