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Introduction: This study evaluated the cross section, resistance to bending and buckling of Reciproc and WaveOne instruments. Methods: Reciproc R25 (VDW, Munich, Germany) and WaveOne Primary (Dentsply Maillefer, Ballaigues, Switzerland) instruments, all of them 25-mm long, with D0 diameter of 0.25 mm and taper of 0.08 mm/mm along the first 3 mm from the tip, had their cross section analysed and were subjected to bending and buckling resistance tests. The data from both tests were analysed using the Student t test. Results: A statistically significant difference was observed between the maximum load to bend Reciproc 25 and WaveOne Primary instruments (P < 0.05). Higher values were necessary to bend WaveOne Primary instruments when compared with Reciproc R25. In contrast, there was no statistically significant difference between the maximum load to buckle Reciproc 25 and WaveOne Primary instruments (P > 0.05). Conclusions: Both instruments exhibited similar behaviour in terms of buckling resistance. However, Reciproc R25 was more flexible, which is an important instrument property for the shaping of narrow and curved root canals. [ABSTRACT FROM AUTHOR]

Objective: this study tested the null hypothesis that the surface grooves orientation does not influence the NiTi wire cyclic fatigue. Material and methods: Segments of NiTi wire (Moreli, Sorocaba, Brazil) measuring 30mm and with a 0.40mm of diameter were used. Grooves were created in the longitudinal direction, at 45 degrees and 90 degrees. The wire was analyzed with SEM and the roughness was quantified by interferometry. The number of cycles until fracture (NCF) was determined by the cyclic fatigue test. Results: the roughness between 45 and 90 degrees groups presented differences (p<0.05). The group without grooves presented the highest NCF (p<0.05). The group with 45 degrees grooves presented better NCF in comparison to the group with 90 degrees (p<0.05). Conclusions: the direction of the grooves influences the fatigue life. The NCF increases with the reduction of the angle of the grooves in relation to the long axis, regardless of the depth of the grooves. [ABSTRACT FROM AUTHOR]

Introduction: This study compared the flexibility and torsional resistance of two types of instruments manufactured with special NiTi alloys, and one with conventional NiTi. Methods: Twisted File (TF) instruments manufactured with the R-phase of NiTi (SybronEndo, Orange, CA), and ProFile Vortex instruments (Dentsply Tulsa Dental, Tulsa, OK, USA) made of M-Wire NiTi were compared with RaCe (FKG Dentaire, La Chaux-de-Fonds, Switzerland) instruments made of conventional NiTi. Flexibility and torsion assays were carried out using twenty 25/0.06 instruments from each manufacturer. Statistical analysis was performed by ANOVA. Results: The mechanical resistance of the instruments tested was significantly different. TF were the most flexible instruments, followed by RaCe and ProFile Vortex (P < 0.01). In the torsion assay, ProFile Vortex instruments endured the greatest maximum load and maximum torque values prior to fracture, followed by RaCe and TF (P < 0.01). The torsional resistance values of RaCe and TF were not significantly different (P = 0.061). Conclusion: We observed a relationship between flexibility and torsional resistance (maximum torque and maximum angular deflection in torsion). The most flexible instrument (TF) was the least resistant to torsion, while the least flexible (ProFile Vortex) was the most resistant to torsion. RaCe presented intermediate results for both flexibility and torsional resistance. [ABSTRACT FROM AUTHOR]