Influence of cyclic flexural deformation on the torsional resistance of CM files in comparison to conventional NITI instruments

• Ano de defesa: 2016
• Autor(a) principal: Eufemia Carolina Pelaez Acosta
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Instrumentos CM; Instrumentos rotatórios de NiTi; Resistência; Torcional; Resistência à fadiga; Instrumentos odontológicos; Resistencia de materiais
• Link de acesso: http://hdl.handle.net/1843/ODON-ACWP5R

Introduction: To evaluate the influence of cyclic deformation on the torsional resistance of NiTi controlled memory (CM) files, when compared to superelastic (SE) instruments with similar geometric and dimensional characteristics. Methods: New 30/.06 HyFlex (HF; Coltene/Whaledent,Inc, Cuyahoga Falls, OH), Typhoon (TYP; Clinicians Choice Dental Products, New Milford, CT), RaCe (RC; FKG, La-Chaux De Fonds, Switzerland), and ProTaper Universal F2 instruments (F2; Dentsply Maillefer, Ballaigues, Switzerland) were assessed. Diameter, pitch length and helical angle were measure along the activepart of the instruments. Flexural fatigue and torsion to failure tests for each file (n = 10) were carried out. Ten new instruments of each type of file were fatigued to 3/4 of their fatigue life and then submitted to torsion until rupture. The longitudinal surface, as well as the fracture surface after fatigue was examined with a scanning electron microscope.Data were analyzed using one-way analysis of variance ( = .05). Results: CM files had a significantly higher mean number of cycles to fracture (Nf) when compared to SE instruments, HF exhibiting the highest Nf (P = .001). The mean torque value for F2 was the highest (P = .001). CM files pre-cycled to 3/4 Nf had a significantly lower torque than the new files (HF P = .003, TYP P = .001), whereas the SE instruments displayed no significant differences (F2 P = .059, RC P = .079). The surface fracture of CM files displayed larger smooth areas and smaller dimple region than SE instruments. Conclusion: Fatigue life of CM instruments was significantly higher than SE instruments, with HF displaying the highest mean Nf values. Torque value for F2 was significantly higher among all of the instruments. Cyclic flexural loading significantly reduced the torsional resistance of CM instruments.