Cyclic flexural fatigue resistance of NiTi Controlled Memory and Blue Technology instruments after torsional preloading.

Objective The aim of this study was to evaluate the influence of torsional preloading on the cyclic flexural fatigue resistance of thermally treated NiTi instruments. Material and Methods Ten new instruments New Hyflex CM (HF 30.06; Coltene/Whaladent Inc.), Typhoon CM (TYP 30.06; Clinician's Choice Dental Products) and Vortex Blue (VB 30.06; Dentsply Tulsa Dental) were chosen, based on geometry and specific characteristics of the manufacturing process. The new instruments of each system were tested in a bench device to determine their fatigue resistance through mean value of number of cycles to failure (Nf) (Control Group - CG). Another group of 10 new HF, TYP and VB instruments were submitted to 20 cycles of torsional straining between 0° and 180° (Experimental Group - EG) and then submitted to fatigue until rupture under the same conditions of the CG. Tested instruments were examined by scanning electron microscopy (SEM). Data were analyzed using one-way analysis of variance and post hoc Tukey's test (α=.05). Results Higher fatigue resistance was accomplished by HF instruments, followed by VB and TYP (p<0.05). During the torsional preloading, the lowest mean torque value was observed for TYP instruments (p<0.05). The torsional preload caused a significant reduction in the Nf values (p<0.05) of about 20%, 39% and 45% for instruments HF, VB and TYP, respectively. Longitudinal cracks, generated during the torsional preloading, were present in VB files, but were not observed in the CM instruments (HF and TYP). Conclusions In conclusion, the flexural fatigue resistance of thermally treated instruments is diminished after cyclic torsional loading.

Cyclic flexural fatigue resistance of NiTi Controlled Memory and Blue Technology instruments after torsional preloading

Abstract Objective The aim of this study was to evaluate the influence of torsional preloading on the cyclic flexural fatigue resistance of thermally treated NiTi instruments. Material and Methods Ten new instruments New Hyflex CM (HF 30.06; Coltene/Whaladent Inc.), Typhoon CM (TYP 30.06; Clinician's Choice Dental Products) and Vortex Blue (VB 30.06; Dentsply Tulsa Dental) were chosen, based on geometry and specific characteristics of the manufacturing process. The new instruments of each system were tested in a bench device to determine their fatigue resistance through mean value of number of cycles to failure (Nf) (Control Group - CG). Another group of 10 new HF, TYP and VB instruments were submitted to 20 cycles of torsional straining between 0° and 180° (Experimental Group - EG) and then submitted to fatigue until rupture under the same conditions of the CG. Tested instruments were examined by scanning electron microscopy (SEM). Data were analyzed using one-way analysis of variance and post hoc Tukey's test (α=.05). Results Higher fatigue resistance was accomplished by HF instruments, followed by VB and TYP (p<0.05). During the torsional preloading, the lowest mean torque value was observed for TYP instruments (p<0.05). The torsional preload caused a significant reduction in the Nf values (p<0.05) of about 20%, 39% and 45% for instruments HF, VB and TYP, respectively. Longitudinal cracks, generated during the torsional preloading, were present in VB files, but were not observed in the CM instruments (HF and TYP). Conclusions In conclusion, the flexural fatigue resistance of thermally treated instruments is diminished after cyclic torsional loading.

Influence of Cyclic Flexural Deformation on the Torsional Resistance of Controlled Memory and Conventional Nickel-titanium Instruments.

INTRODUCTION: The aim of this study was to evaluate the influence of cyclic deformation on the torsional resistance of controlled memory (CM) nickel-titanium files in comparison with superelastic (SE) instruments with similar geometric and dimensional characteristics. METHODS: New 30/.06 HyFlex (HF; Coltene/Whaledent, Inc, Cuyahoga Falls, OH), Typhoon (Clinician's Choice Dental Products, New Milford, CT), RaCe (FKG, La-Chaux De Fonds, Switzerland), and ProTaper Universal F2 instruments (F2; Dentsply Maillefer, Ballaigues, Switzerland) were assessed. The diameter and pitch length were measured along the active part of the instruments. The number of cycles to failure (Nf) in flexural fatigue and the torsional resistance were evaluated for new files (n = 10). Ten new instruments of each type were fatigued to 3/4 of their fatigue life and then submitted to torsion until rupture. Data were analyzed using 1-way analysis of variance (α = .05). RESULTS: New CM files had a significantly higher Nf when compared with SE instruments; HF exhibited the highest value (P = .001). The mean torque value for F2 was the highest (P = .001). CM files precycled to 3/4 Nf had a significantly lower torque than the new files (HF: P = .003, Typhoon: P = .001), whereas the SE instruments displayed no significant differences (F2: P = .059, RaCe: P = .079). CONCLUSIONS: Cyclic flexural loading significantly reduced the torsional resistance of CM instruments.

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

As propriedades mecânicas dos instrumentos endodônticos são afetadas por fatores como microestrutura, diâmetro, geometria, composição química, e tratamentos termomecânicos aplicados durante o processo de fabricação. Os instrumentos de NiTi com Memória Controlada (CM) sofrem um tratamento térmico especial que os tornam mais flexíveis e resistentes à fadiga que instrumentos de NiTi convencional. O objetivo deste estudo é avaliar como a fadiga influencia nas propriedades torcionais dos instrumentos CM, quando comparados com instrumentos superelásticos (SE) com geometria e características dimensionais similares. Instrumentos novos Hyflex CM (HF; Coltene/ Whaladent Inc.), Typhoon CM (TYP; Clinician´s Choice Dental Products), RaCe (RC; FKG, La-Chaux De Fonds, Switzerland) e Protaper Universal F2 (F2; Dentsply Maillefer, Ballaigues, Switzerland), todos de calibre e conicidade 30/.06, foram avaliados. Características geométricas e dimensionais como o diâmetro, comprimento de pitch e ângulo helicoidal foram medidos ao longo da parte ativa dos instrumentos. A fadiga flexural (Nf) e a resistência torcional para cada instrumento (n=10) foram determinadas de acordo com a especificação ISO-3630. Dez novos instrumentos de cada sistema foram fadigados a 3/4 de Nf e depois submetidos à torção até a ruptura. Os dados foram analisados utilizando o teste ANOVA (α=.05). A superfície longitudinal, bem como a superfície de fratura após a fadiga foi examinada com um microscópio eletrônico de varredura (MEV). Os resultados mostram que os instrumentos CM tiveram valores de Nf significativamente maiores quando comparados aos instrumentos SE, com HF exibindo o maior Nf (P = .001). Os valores de torque médio para F2 foram os mais elevados (P = .001), seguido de TYP, HF e RC. Instrumentos CM pré-carregados a 3/4 de Nf e submetidos à torção até a ruptura tiveram valores de torque menores quando comparados aos instrumentos não carregados (HF P = .003; TYP P =.001), enquanto os instrumentos SE não apresentaram diferenças significativas (F2 P = .059; RC P =.079). A superfície de fratura dos instrumentos CM mostraram maiores superfícies lisas de fraturas e menores regiões de dimples, em relação aos instrumentos SE. Conclui-se que a vida em fadiga dos instrumentos CM foi significativamente maior quando comparada aos instrumentos SE, com o instrumento HF apresentando o valor de Nf maior. Os valores de torque para F2 foram maiores entre todos os instrumentos. Portanto a resistência torcional dos instrumentos CM pode ser comprometida após o pré carregamento em fadiga

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; Clinician's 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 active part 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 (α = .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