A new in vitro method to evaluate radio-opacity of endodontic sealers.

OBJECTIVES: To evaluate a new method for assessing the radio-opacity of endodontic sealers and to compare radio-opacity values with a well-established standard method. METHODS: The sealers evaluated in this study were AH Plus(®) (Dentsply DeTrey GmbH, Konstanz, Germany), Endo CPM Sealer (EGEO SRL, Buenos Aires, Argentina) and MTA Fillapex(®) (Angelus Dental Products Industry S/A, Londrina, Parana, Brazil). Two methods were used to evaluate radio-opacity: (D) standard discs and (S) a tissue simulator. For (D), ten standard discs were prepared for each sealer and were radiographed using Digora(®) phosphor storage plates (Soredex; Orion Corporation, Helsinki, Finland), alongside an aluminium stepwedge. For (S), polyethylene tubes filled with sealer (n = 10 for each) were radiographed inside the simulator as described. The digital images were analysed using Adobe Photoshop(®) software v. 10.0 (Adobe Systems, San Jose, CA). To compare the radio-opacity among the sealers, the data were analysed by ANOVA and Tukey's test, and to compare methods, they were analysed by the Mann-Whitney U test. To compare the data obtained from dentin and sealers in method (S), Student's paired t-test was used (=0.05). RESULTS: In both methods, the sealers showed significant differences, according to the following decreasing order: AH Plus, MTA Fillapex and Endo CPM. In (D), MTA Fillapex and Endo CPM showed less radio-opacity than aluminium. For all of the materials, the radio-opacity was higher in (S) than in (D). Compared with dentin, all of the materials were more radio-opaque. CONCLUSIONS: The comparison of the two assessment methods for sealer radio-opacity testing validated the use of a tissue simulator block.

Determining cutting efficiency of nickel-titanium coronal flaring instruments used in lateral action.

AIM: To develop a method to evaluate the cutting behaviour of nickel-titanium (NiTi) coronal flaring instruments. METHODOLOGY: BioRaCe BR0 (BR), HyFlex CM 1 (HY), ProFile OS No. 2 (PF) and ProTaper Sx (PT) instruments were used in simulated coronal flaring using a lateral action against bovine dentine blocks, at 250 and 500 rpm. Cutting efficiency was assessed by three methods: first, areas of notches produced by instruments were directly measured under a stereomicroscope. Second, dentine specimens were then analysed by surface profilometry to determine the maximum cutting depth and finally by microcomputed tomography to assess the volume of removed dentine. Data were compared using parametric tests with the significance level set at 0.05. RESULTS: For all three methods, HY and PF were the most and the least cutting-efficient instruments, respectively (P < 0.05). Significant differences were detected between 250 and 500 rpm for HY and PT (area); for BR, HY and PT (depth); and for BR and HY (volume). There were strong positive correlations between the results obtained with those three different methods with r-values ranging from 0.81 to 0.92. CONCLUSION: Measuring the amount of material removed in a specific time under stereomicroscopy is a simple and rational way to assess the cutting behaviour of NiTi rotary instruments in lateral action. HyFlex, manufactured with thermomechanically treated NiTi wire, was the most efficient instrument, and increased rotational speed was associated with increased cutting efficiency.

Antibacterial activity of two MTA-based root canal sealers.

AIM: To evaluate the pH and antibacterial activity of Endo CPM Sealer and MTA Fillapex by two different methods, using white MTA and Endofill as references for comparison. METHODOLOGY: Antibacterial activity was evaluated against Enterococcus faecalis (ATCC 29212). The agar diffusion test (ADT) was performed to evaluate the effect before setting. The materials were placed in four equidistant wells made in ten agar plates. After incubation at 37 °C for 48 h, the inhibition zones were measured using a digital paquimeter. The direct contact test (DCT) was performed to assess the antibacterial effect after setting. Suspensions of crushed materials were prepared and mixed with E. faecalis. After different periods of time (1, 6, 15 and 60 min), the survival of bacteria was assessed by using 10-fold serial dilution and cultivated on agar plates in triplicate. Colony-forming units (CFU) mL(-1) were calculated after incubation. pH values were also measured in triplicate. Comparison between sealers in the ADT and DCT was performed by the Kruskal-Wallis test. RESULTS: In the ADT, inhibition zones were found with MTA Fillapex and Endofill. They were similar to each other and greater than the other sealers (P < 0.05). None of the tested sealers demonstrated antibacterial activity in the DCT, and thus, all sealers had similar bacterial counts compared with the negative control group (P > 0.05). White MTA and Endo CPM Sealer suspensions had pH values >11, whilst MTA Fillapex and Endofill had lower values. CONCLUSIONS: MTA Fillapex and Endofill had an antibacterial effect against E. faecalis before setting, but none of the sealers maintained antibacterial activity after setting, despite the high pH of the MTA-based materials.

Comparative in vivo analysis of the sealing ability of three endodontic sealers in post-prepared root canals.

AIM: To compare the sealing ability of the endodontic sealers AH Plus, Sealer 26 and Endofill in premolar teeth of dogs exposed to the oral cavity after post-preparation. METHODOLOGY: Forty teeth with two canals each underwent root canal cleaning and shaping. Before filling, the canals were randomly distributed into three groups according to the sealer to be used: Group 1 - AH Plus; Group 2 - Sealer 26; and Group 3 - Endofill (Dentsply, Indústria e Comércio Ltda.). Immediately after filling, the gutta percha and sealer were partially removed from the canals, leaving material only in the apical third of the root. The teeth were temporarily sealed with glass ionomer sealer for 72 h to ensure setting. The coronal seal was then removed and the canals were exposed to the oral cavity for 45 days. The animals were euthanased and their mandibles and maxillae were removed. After abundant irrigation with distilled water, the canals were dried and filled with India ink. The teeth were sealed again for 96 h before extraction. The roots of the extracted premolars were separated and stored in labelled test tubes. The roots were cleared and the extent of dye penetration was measured with a 20x stereoscopic magnifying lens. RESULTS: Statistical analysis revealed that there were significant differences between the sealers studied (P < 0.001). Means for the extent of dye penetration for AH Plus, Endofill and Sealer 26 were, respectively, 0.13, 2.27 and 3.08 mm. CONCLUSIONS: After 45 days exposure to the oral cavity, none of the sealers was capable of preventing leakage and coronal dye penetration. There were significant differences between the sealers studied, in terms of mean dye penetration.