Objective: The aim of this study was to evaluate the cyclic fatigue, torsional behavior and bending resistance of EdgeTaper Platinum [ETP (tip 25, taper 0.06)], Flex Gold [FG (tip 25, taper 0.08)], Pro-T [PT (tip 25, taper 0.08)] and ProTaper Gold [PTG (tip 25, taper 0.08)] systems. Methods: Rotary instruments of ETP, PT, FG, and PTG were used (n=30). Cyclic fatigue tests were performed using an artificial stainless-steel canal with a 60o angle and a 5-mm radius of curvature at body temperature (35°±1°C). The time and number of cycles to fracture (NCF) was recorded. The torsional test evaluated the torque and angle of rotation to failure at 3 mm from the tip according to ISO 3630-1. The fractured surface of each fragment was observed by using scanning electron microscopy (SEM). The bending test evaluated the torque required to bend the instruments at an angular deflection of 60°. Data were analyzed using one-way ANOVA and Tukey tests, and the level of significance was set at 5%. Results: The ETP had highest time until fracture and NCF than all the groups (P<0.05). The PTG had the highest torsional strength, followed by FG (P<0.05). The ETP had the highest angular rotation, followed by PT and PTG (P<0.05). The FG showed the highest bending resistance, followed by the PTG (P<0.05). Conclusion: In conclusion, the ETP and PT exhibited higher cyclic fatigue resistance, higher angular deflection values and lower bending force than FG and PTG. The PTG instruments showed the highest torsional strength and the lowest cyclic fatigue resistance.

Enterococcus faecalis and Candida albicans have been associated with cases of secondary and persistent root canal infections, been resistant to calcium hydroxide. So, the evaluation of the susceptibility of these microorganisms biofilms to new drugs is an important practice for establishing the best drug and consequently success of treatment. For this, in vitro biofilm formation of E. faecalis and C. albicans was induced separately on blocks obtained from bovine teeth. After the period of specimen incubation for biofilm maturation, the samples were immersed in the pastes: 1 – calcium hydroxide (CH), 2 – chlorhexidine (C), 3 – ciprofloxacin (CP), 4 – metronidazole (MT), 5 – ketoconazole (KE), 6 – double antibiotic (DB), 7 – triple antibiotic (TA), 8 – ciprofloxacin + ketoconazole (CPKE); 9 – ciprofloxacin + metronidazole + ketoconazole (CPMTKE), 10 – metronidazole + ketoconazole (MTKE), and 11 – control (CO) for 7 days. Next, the specimens were live/dead stained for analysis by confocal microscopy. By means of the Bioimage program, the biovolume and percentage of live cells were measured. The data were statistically compared (p = .05). For the C. albicans biofilm, the best antimicrobial action was found for MTKE, CPKE, and MT groups. Whereas for E. faecalis biofilm, the lowest percentage of live bacteria was found in TA, DB, and CP groups; however, KE, CPKE, CPMTKE, and MTKE groups shown to be effective. The authors concluded calcium hydroxide paste and chlorhexidine was not effective for both biofilms. The MTKE and CPKE pastes presented effectiveness for both biofilms. TA and DB pastes were effective just in the E. faecalis biofilms.

This study investigated the cyclic fatigue, bending, torsional resistance and angular deflection of Pro‐R 25.08, Logic RT 25.08, MK Retreatment 25.08 (MK RT) and ProTaper Retreatment D2 instruments. Cyclic fatigue test was performed until fracture in a custom stainless‐steel device with water bath equipment to simulate body temperature. Fracture time was recorded. A number of cycles were calculated. Resistance to bending at 45°, torsional resistance and angular deflection were evaluated. The fracture surfaces were examined by scanning electron microscopy. Statistical analysis was performed with one‐way ANOVA and Tukey and Kruskal–Wallis and Dunn tests. Pro‐R and Logic RT presented the highest cyclic fatigue (P < 0.05). D2 had higher strength to bend than Pro‐R and Logic RT (P < 0.05). Logic RT showed the highest torque and angular deflection (P < 0.05), without differences when compared to D2 (P > 0.05). Instrument performances were dependent on their geometrical features and heat treatments.

Victor de Moraes CRUZ (a) Bruno Carvalho de VASCONCELOS (b) Marcus Vinícius Reis SÓ (c)

Objetivo: O objetivo deste estudo foi avaliar a resistência à fadiga cíclica e torcional dos sistemas reciprocantes WFile 25.07 (WF, TDKaFile, Cidade do México, México) e X1 Blue File 25.06 (X1 BF, MK Life, Porto Alegre, Bra- sil) à temperatura corporal. Material e Métodos: Foram utilizados 40 instrumentos reciprocantes WFile 25.07 (WF 25.07) e X1 BF 25.06 (n=20, cada grupo). O teste de fadiga cíclica foi realizada à temperatura corporal (36±1°C). Os instrumentos foram ativados com movimen- to reciprocante em um canal artificial de aço inoxidável com ângulo de 60o e 5mm de raio de curvatura (n=10). O teste torcional avaliou o torque e o ângulo de rotação necessários para a fratura dos instrumentos (n=10) nos 3mm iniciais da parte ativa do instrumento, de acordo com a norma ISO 3630-1. Os fragmentos fraturados foram avaliados em microscopia eletrônica de varredura (MEV). Os dados obtidos foram submetidos aos testes estatísticos de Kolmogorov-Smirnov e t de Student, sendo utilizado o nível de significância de 5%. Resultado: O X1BF25.06 apresentou maior tempo e número de ciclos para a fratura do que o WF 25.07 (p<0,05). O teste de torção demonstrou que o WF 25.07 apresentou maior torque do que o X1 BF 25.06 (p<0,05). Em relação ao ângulo de rotação, o X1 BF 25.06 apresentou maiores valores do que o WF 25.07 (p<0,05). Conclusão: O X1 BF apresentou maior resistência à fadiga cíclica e maior ângulo para a fratura do que o WF 25.07. Entretanto, o WF 25.07 apresentou maior torque para a fratura do que o X1 BF 25.06.