Apical extrusion of bacteria when using reciprocating single-file and rotary multifile instrumentation systems.

AIM: To evaluate ex vivo, apical bacterial extrusion associated with two reciprocating single-file systems (WaveOne and Reciproc) compared with a conventional multifile rotary system (BioRace). METHODOLOGY: Forty-five human single-rooted mandibular incisors were used. Endodontic access cavities were prepared, and root canals were contaminated with an Enterococcus faecalis suspension. Following incubation at 37 °C for thirty days, the contaminated teeth were divided into three groups of 15 specimens each (G1 - Reciproc, G2 - WaveOne and G3 - BioRace). Positive and negative controls consisted of 5 infected teeth and 3 uninfected incisors that were instrumented with one of the tested NiTi systems, respectively. Bacteria extruded from the apical foramen during instrumentation were collected into vials containing 0.9% NaCl. The microbiological samples were taken from the vials and incubated in brain heart agar medium for 24 h. The resulting bacterial titre, in colony-forming units (CFU) per mL, was determined, and these data were analysed by Wilcoxon matched-pairs signed rank test and Kruskal-Wallis H-test. The level of significance was set at α = 0.05. RESULTS: No significant difference was found in the number of CFU between the two reciprocating systems (P = 0.41). The conventional multifile rotary system group was associated with significantly higher CFU than both of the two reciprocating groups (P = 0.01). CONCLUSIONS: All instrumentation systems extruded bacteria beyond the foramen. However, both reciprocating single-file systems extruded fewer bacteria apically than the conventional multifile rotary system.

The ability of the Reciproc R25 instrument to reach the full root canal working length without a glide path.

AIM: To assess the frequency in which the Reciproc instrument reaches the full working length (FWL) of mandibular molar canals without a glide path. METHODOLOGY: From a pool of mandibular molars, 253 root canals were classified as straight (G1) and, 249 root canals as moderately curved (G2) following Schneider's method. A R25 Reciproc instrument (VDW, Munich, Germany) was advanced in the canals without any previous glide path. All cases where Reciproc instruments reached the FWL were classified as 'Reaching the FWL' (RFWL). When the FWL was not reached by the R25, the root canals were classified as 'Not Reaching the FWL' (NRFWL). Pearson's χ(2) test compared (i) the frequency distributions of root canals classified as RFWL and NRFWL for each group and (ii) the frequency distributions of NRFWL canals between the groups. RESULTS: In G1, 9 cases (3.56%) and in G2, 23 canals (9.34%) were classified as NRFWL. The difference between NRFWL and RFWL was significant in both groups (P = 0.00, χ(2) = 217.2 for G1; P = 0.00, χ(2) = 167.8 for G2). The frequency of NRFWL was significantly higher for G2 (P = 0.02, χ(2) = 5.452). CONCLUSION: The R25 Reciproc instrument is able to reach the FWL of straight- and moderate-curved mandibular molar canals without a glide path in a large proportion of cases.

The sealing ability of GuttaFlow in oval-shaped canals: an ex vivo study using a polymicrobial leakage model.

AIM: To compare systematically the sealing ability provided by four endodontic cements: AH Plus, Pulp Canal Sealer EWT, RoekoSeal and GuttaFlow. METHODOLOGY: A sample of 100 human mandibular incisors with oval-shaped canals was selected from an initial sampling of two hundred teeth. The root canals in 80 teeth were prepared and filled by the same operator using the cold lateral compaction technique with one of the following four cements (n = 20): G1: AH Plus; G2: Pulp Canal Sealer EWT; G3: RoekoSeal and G4: GuttaFlow. Ten teeth with intact crowns served as negative controls and 10 teeth that were not root filled served as positive controls. All teeth were mounted in a two chamber apparatus and then exposed to human saliva. The number of days over a 9-weeks-period was recorded for the appearance of turbidity in the BHI broth. A Log-rank test was used to analyse the leakage data. RESULTS: Overall, 30% of the samples of the AH Plus group (G1) and 35% of the Pulp Canal Sealer EWT group (G2) were fully contaminated after 9 weeks, whereas 15% of RoekoSeal (G3) and GuttaFlow (G4) groups were fully contaminated. There was a significant difference between (G1/G2) and (G3/G4) (P < 0.05). There was no significant difference between G1 and G2 or between G3 and G4 (P > 0.05). CONCLUSION: The silicone-based sealers revealed the best results throughout the experimental period. Leakage patterns of AH plus and Pulp Canal Sealer were statistically similar.

Co-site digital optical microscopy and image analysis: an approach to evaluate the process of dentine demineralization.

AIM: To introduce and explore the potential of digital optical co-site microscopy and image analysis for the observation of changes in dentine surfaces during demineralization. The effect of ethylenediamine tetraacetic acid (EDTA) was evaluated quantitatively and longitudinally. METHODOLOGY: Three maxillary human molars were sectioned transversely at the cemento-enamel junction, and the crowns discarded. Subsequently, discs approximately 3 mm thick were cut in the cervical third of the root and a standardized smear layer produced. Co-site image sequences of the dentine surface subjected to 17% EDTA were obtained over the experimental period (15, 30, 60, 180 and 300 s). Sixteen images were obtained in each dentine sample for each experimental time, thus, a total of 48 image fields were obtained. For each field, an image analysis routine automatically discriminated open dentine tubules and measured their number, area fraction and minimum diameter, thus allowing the quantification of the demineralization process. The Student t-test was used to analyse the data. RESULTS: The number of open tubules remained essentially constant during the demineralization process. The area fraction increased from 9% to 32%. Tubule minimum diameter increased from 1.5 to 3.0 microm. The changes over time for the area fraction and minimum diameter were significant for comparison between all experimental times (P<0.05). CONCLUSIONS: The methodology developed for longitudinal observation of dentinal surfaces was fast, robust and reproducible. It could be easily extended to other chelating substances, thus contributing to the understanding of the demineralization process and in establishing an optimal time-effect relationship in the clinical application.