Aim: This study aimed to use the micro-computed tomography to evaluate the interfacial adaptation and the presence of gaps of NeoMTA Plus, BioRoot RCS, and MTA in the root-end cavities. Methodology: Thirty standardized bovine roots measuring 15 mm in length were selected. Chemical-mechanical preparation was performed up to instrument #80 and obturation with the cold lateral compaction technique with cement based on zinc oxide and eugenol. The roots were kept at 37º C for seven days. Afterward, apicectomy of the apical 3mm and a root-end filling cavity was performed at 3mm depth. Micro-computed tomography (micro-CT) was performed to measure the volume of the retroactivity. The roots were divided by stratified randomization into three groups according to the retro-end filling material: NeoMTA Plus, BioRoot RCS, and MTA. A new micro-CT was performed to assess the presence of voids in the root-end filling material and between it and the canal wall. One-way ANOVA and Tukey tests were performed using the BioEstat 4.0 program. Results: There was no difference in the initial volume values of the root-end cavities (P > 0.05). After the insertion of root-end filling materials, the most significant volumes of voids were observed in the NeoMTA Plus group (P < 0.05), with no difference for the BioRoot RCS and MTA Angelus groups (P > 0.05). Conclusion: Micro-computed tomography showed that MTA and BioRoot RCS have better interfacial adaptation and presented fewer number of gaps than NeoMTA Plus when used as root-end filling materials.

Introduction: This study aimed to evaluate the cyclic and torsional fatigue resistance of a new nickel-titanium (Flat File 25.04) instrument on continuous and reciprocating motion. Methods: Sixty instruments of the ProDesign Logic2 25.03 and 25.05 (Easy Equipamentos Odontológicos, Belo Horizonte, Brazil), and MK Flat File 25.04 (n=20) (MK Life, Porto Alegre, Brazil) were used. For the cyclic fatigue test, an artificial stainless steel simulated canal with an angle of 60° and a radius of curvature of 5mm located 5mm from its tip was used. Torque and angle of rotation at failure of instruments on torsional fatigue test was based on the ISO 3630-1 protocol, in which the 3mm tip of each instrument was fixed and connected to an electric motor and a load cell. The fractured surface of each fragment was examined by scanning electron microscopy. Data were analyzed using 1-way analysis of variance and Tukey’s test with a significance level of 5%. Results: Flat File 25.04 had lower cyclic fatigue in both kinematics than the Logic instruments (P < .05). Reciprocating motion improved the cyclic fatigue of the tested instruments (P < .05). Flat File 25.04 had similar torque to Logic2 25.05 (P < .05), and both were superior to Logic2 25.03 (P < .05). The angular deflection values were different for the three tested instruments (P < .05), in the decreasing order: Logic2 25.03, 25.05, and Flat File 25.04. Conclusion: Flat File presented acceptable resistance to cyclic and torsional fatigue resistance. Reciprocating motion improved the cyclic fatigue resistance of the instruments and can be considered when using programmable motors.