Plotino G, Grande NM, Melo MC, Bahia MG, Testarelli L, Gambarini G. Cyclic fatigue of NiTi rotary... more Plotino G, Grande NM, Melo MC, Bahia MG, Testarelli L, Gambarini G. Cyclic fatigue of NiTi rotary instruments in a simulated apical abrupt curvature. International Endodontic Journal, 43, 226–230, 2010.Plotino G, Grande NM, Melo MC, Bahia MG, Testarelli L, Gambarini G. Cyclic fatigue of NiTi rotary instruments in a simulated apical abrupt curvature. International Endodontic Journal, 43, 226–230, 2010.AbstractAim To evaluate the cyclic fatigue resistance of five NiTi rotary systems in an abrupt apical curvature.Methodology Cyclic fatigue testing was performed in stainless-steel artificial canals with a 2-mm radius of curvature and an angle of curvature of 90° constructed to the dimensions of the instruments tested. The middle of the simulated curvature was 2.5 mm from the tip of the instrument that was placed at full working length. All instruments were new and 25 mm in length. Ten ProTaper Universal F2 (Dentsply Maillefer, Ballaigues, Switzerland); FlexMaster (VDW, Munich, Germany) tip size 25, taper 0.06; Mtwo (Sweden & Martina, Padova, Italy) tip size 25, taper 0.06; ProFile tip size 25, taper 0.06 from Dentsply Maillefer (Ballaigues, Switzerland); and ProFile tip size 25, taper 0.06 from Dentsply Tulsa (Tulsa, OK, USA) were rotated passively at 300 rpm until fracture occurred, and the number of cycles to failure (NCF) recorded. Length of the fractured tip was measured. Data were analysed by one-way anova and Tukey HSD test to determine any statistical difference amongst groups.Results Mtwo had the highest fatigue resistance compared to the other instruments (NCF 124 ± 25) (P < 0.001); there was no statistical difference between ProFile from the two different brands, although ProFile from Maillefer had the higher fatigue life (NCF 75 ± 10) compared to ProFile from Tulsa (NCF 66 ± 10). No difference was registered between FlexMaster (NCF 53 ± 5) and ProFile from Tulsa; ProTaper F2 had a significantly (P < 0.001) lower fatigue life compared to the other instruments tested (NCF 29 ± 5).Conclusions Lifespan registered for the instruments tested in an apical abrupt curvature was Mtwo > ProFile from Maillefer > ProFile from Tulsa > FlexMaster > ProTaper.Aim To evaluate the cyclic fatigue resistance of five NiTi rotary systems in an abrupt apical curvature.Methodology Cyclic fatigue testing was performed in stainless-steel artificial canals with a 2-mm radius of curvature and an angle of curvature of 90° constructed to the dimensions of the instruments tested. The middle of the simulated curvature was 2.5 mm from the tip of the instrument that was placed at full working length. All instruments were new and 25 mm in length. Ten ProTaper Universal F2 (Dentsply Maillefer, Ballaigues, Switzerland); FlexMaster (VDW, Munich, Germany) tip size 25, taper 0.06; Mtwo (Sweden & Martina, Padova, Italy) tip size 25, taper 0.06; ProFile tip size 25, taper 0.06 from Dentsply Maillefer (Ballaigues, Switzerland); and ProFile tip size 25, taper 0.06 from Dentsply Tulsa (Tulsa, OK, USA) were rotated passively at 300 rpm until fracture occurred, and the number of cycles to failure (NCF) recorded. Length of the fractured tip was measured. Data were analysed by one-way anova and Tukey HSD test to determine any statistical difference amongst groups.Results Mtwo had the highest fatigue resistance compared to the other instruments (NCF 124 ± 25) (P < 0.001); there was no statistical difference between ProFile from the two different brands, although ProFile from Maillefer had the higher fatigue life (NCF 75 ± 10) compared to ProFile from Tulsa (NCF 66 ± 10). No difference was registered between FlexMaster (NCF 53 ± 5) and ProFile from Tulsa; ProTaper F2 had a significantly (P < 0.001) lower fatigue life compared to the other instruments tested (NCF 29 ± 5).Conclusions Lifespan registered for the instruments tested in an apical abrupt curvature was Mtwo > ProFile from Maillefer > ProFile from Tulsa > FlexMaster > ProTaper.
Aim To evaluate the influence of cyclic torsional loading on the flexural fatigue resistance and... more Aim To evaluate the influence of cyclic torsional loading on the flexural fatigue resistance and torsional properties of rotary NiTi instruments.Methodology Twelve sets of new K3 instruments, sizes 20, 25 and 30 with an 0.04 taper, and sizes 20 and 25 with an 0.06 taper, were torsion tested until rupture, to establish their mean values of maximum torque and angular deflection. Twelve new K3 instruments of each of the following dimensions, size 30, 0.04 taper and sizes 20 and 25 with 0.06 taper, were tested to failure by rotation bending in a fatigue test device. Cyclic torsional loading was performed in 20 cycles from zero angular deflection to 180° and then return to zero applied torque. After cyclic loading, the same number of instruments were tested until rupture in torsion and flexural fatigue. Data obtained were subjected to a one way analysis of variance (anova) at 95% confidence level.Results Cyclic torsional loading caused no significant differences in maximum torque or in maximum angular deflection of the instruments analysed, but comparative statistical analysis between measured NCF values of new and previously cycled K3 instruments showed significant differences for all tested instrument. Longitudinal cracks, that is, cracks apparently parallel to the long axis of the instruments cycled in torsion was observed.Conclusions Cyclic torsional loading experiments in new K3 rotary endodontic instruments showed that torsional fatigue decreased the resistance of these instruments to flexural fatigue, although it did not affect their torsional resistance.
Objective. The aim of this study was to assess the influence of cyclic deformation up to one half... more Objective. The aim of this study was to assess the influence of cyclic deformation up to one half and three quarters of the fatigue life of NiTi rotary endodontic instruments on their behavior in torsion.
A comparative study of the fatigue resistance of engine-driven nickel-titanium endodontic instrum... more A comparative study of the fatigue resistance of engine-driven nickel-titanium endodontic instruments was performed, aiming to access the influence of the cutting flute design and of the size of the files that reach the working length in curved canal shaping. Geometrical conditions similar to those found in practice were used. Series 29 #5 ProFile, together with #6 and #8 Quantec instruments, were tested in artificial canals with a 45-degree angle of curvature and 5-mm radius of curvature. It was observed that the size of the instrument, which determines the maximum strain amplitude during cyclic deformation, is the most important factor controlling fatigue resistance. The effect of heat sterilization on the fatigue resistance of the instruments was also examined. The results obtained indicate that the application of five sterilization procedures in dry heat increases the average number of cycles to failure of unused instruments by approximately 70%.
Aim To correlate the mechanical behaviour in torsion, bending and fatigue tests of K3 instrument... more Aim To correlate the mechanical behaviour in torsion, bending and fatigue tests of K3 instruments with their dimensional characteristics.Methodology Instrument length, tip angle, distance between blades (pitch length) and the diameter at each millimetre from the tip of sizes 20, 25 and 30, 0.04 taper and sizes 20 and 25, 0.06 taper K3 rotary instruments were measured in an optical microscope equipped with digital micrometers. The cross-sectional area at 3 mm from the tip of the same instruments was determined using digital image analysis of scanning electron microscopy images. Maximum torque and angular deflection, as well as bending moment at 45° were measured according to specification of ISO 3630-1. Fatigue resistance of instruments size 30, 0.04 taper, and sizes 20 and 25, 0.06 taper was determined in a fatigue test bench device.Results The analysed instruments presented no uniformity in the distance between adjacent blades, but the measured diameters at each millimetre from the tip were regular, showing compliance with manufacturing standards. Torque and bending moment of the tested instruments increased significantly with diameter and cross-sectional area at 3 mm from the instrument tip. The fatigue resistance of the instruments showed a tendency to decrease as the diameter of the instruments increased.Conclusions The bending moment at 45° and the torsional resistance of K3 instruments can be predicted using instrument diameter and cross-sectional area at 3 mm from the tip. Fatigue resistance decreased as the instrument diameter increased.
Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontology, 2006
Objective. The aim of this study was to assess the influence of cyclic deformation up to one half... more Objective. The aim of this study was to assess the influence of cyclic deformation up to one half and three quarters of the fatigue life of NiTi rotary endodontic instruments on their behavior in torsion.
Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontology, 2010
The purpose of this study was to assess the influence of both the metallurgic and the geometric c... more The purpose of this study was to assess the influence of both the metallurgic and the geometric characteristics of nickel-titanium endodontic instruments on their flexibility.ProTaper Universal (PTU), K3, and EndoSequence (ES) instruments were evaluated. Their chemical composition and phase constitution were characterized by conventional analytical techniques. Instrument diameter and cross-sectional area were evaluated by image analysis. Flexibility was evaluated in bending tests according to the ISO 3630-1.K3 presented the highest average bending moment (MB), followed by PTU and ES. A linear relationship was found between MB and the instrument's diameter and cross-sectional area at 3 mm from the tip. Alloy chemical compositions were similar among the files, but transformation temperatures were lower for K3 instruments, which presented only austenite as a constituent phase.Nickel-titanium instruments from different manufacturers have unequal behavior related to their flexibility properties. Manufacturing processes changed the phase constitution and transformation temperatures of the instruments investigated and may also have influenced their flexibility.
Plotino G, Grande NM, Melo MC, Bahia MG, Testarelli L, Gambarini G. Cyclic fatigue of NiTi rotary... more Plotino G, Grande NM, Melo MC, Bahia MG, Testarelli L, Gambarini G. Cyclic fatigue of NiTi rotary instruments in a simulated apical abrupt curvature. International Endodontic Journal, 43, 226–230, 2010.Plotino G, Grande NM, Melo MC, Bahia MG, Testarelli L, Gambarini G. Cyclic fatigue of NiTi rotary instruments in a simulated apical abrupt curvature. International Endodontic Journal, 43, 226–230, 2010.AbstractAim To evaluate the cyclic fatigue resistance of five NiTi rotary systems in an abrupt apical curvature.Methodology Cyclic fatigue testing was performed in stainless-steel artificial canals with a 2-mm radius of curvature and an angle of curvature of 90° constructed to the dimensions of the instruments tested. The middle of the simulated curvature was 2.5 mm from the tip of the instrument that was placed at full working length. All instruments were new and 25 mm in length. Ten ProTaper Universal F2 (Dentsply Maillefer, Ballaigues, Switzerland); FlexMaster (VDW, Munich, Germany) tip size 25, taper 0.06; Mtwo (Sweden & Martina, Padova, Italy) tip size 25, taper 0.06; ProFile tip size 25, taper 0.06 from Dentsply Maillefer (Ballaigues, Switzerland); and ProFile tip size 25, taper 0.06 from Dentsply Tulsa (Tulsa, OK, USA) were rotated passively at 300 rpm until fracture occurred, and the number of cycles to failure (NCF) recorded. Length of the fractured tip was measured. Data were analysed by one-way anova and Tukey HSD test to determine any statistical difference amongst groups.Results Mtwo had the highest fatigue resistance compared to the other instruments (NCF 124 ± 25) (P < 0.001); there was no statistical difference between ProFile from the two different brands, although ProFile from Maillefer had the higher fatigue life (NCF 75 ± 10) compared to ProFile from Tulsa (NCF 66 ± 10). No difference was registered between FlexMaster (NCF 53 ± 5) and ProFile from Tulsa; ProTaper F2 had a significantly (P < 0.001) lower fatigue life compared to the other instruments tested (NCF 29 ± 5).Conclusions Lifespan registered for the instruments tested in an apical abrupt curvature was Mtwo > ProFile from Maillefer > ProFile from Tulsa > FlexMaster > ProTaper.Aim To evaluate the cyclic fatigue resistance of five NiTi rotary systems in an abrupt apical curvature.Methodology Cyclic fatigue testing was performed in stainless-steel artificial canals with a 2-mm radius of curvature and an angle of curvature of 90° constructed to the dimensions of the instruments tested. The middle of the simulated curvature was 2.5 mm from the tip of the instrument that was placed at full working length. All instruments were new and 25 mm in length. Ten ProTaper Universal F2 (Dentsply Maillefer, Ballaigues, Switzerland); FlexMaster (VDW, Munich, Germany) tip size 25, taper 0.06; Mtwo (Sweden & Martina, Padova, Italy) tip size 25, taper 0.06; ProFile tip size 25, taper 0.06 from Dentsply Maillefer (Ballaigues, Switzerland); and ProFile tip size 25, taper 0.06 from Dentsply Tulsa (Tulsa, OK, USA) were rotated passively at 300 rpm until fracture occurred, and the number of cycles to failure (NCF) recorded. Length of the fractured tip was measured. Data were analysed by one-way anova and Tukey HSD test to determine any statistical difference amongst groups.Results Mtwo had the highest fatigue resistance compared to the other instruments (NCF 124 ± 25) (P < 0.001); there was no statistical difference between ProFile from the two different brands, although ProFile from Maillefer had the higher fatigue life (NCF 75 ± 10) compared to ProFile from Tulsa (NCF 66 ± 10). No difference was registered between FlexMaster (NCF 53 ± 5) and ProFile from Tulsa; ProTaper F2 had a significantly (P < 0.001) lower fatigue life compared to the other instruments tested (NCF 29 ± 5).Conclusions Lifespan registered for the instruments tested in an apical abrupt curvature was Mtwo > ProFile from Maillefer > ProFile from Tulsa > FlexMaster > ProTaper.
Aim To evaluate the influence of cyclic torsional loading on the flexural fatigue resistance and... more Aim To evaluate the influence of cyclic torsional loading on the flexural fatigue resistance and torsional properties of rotary NiTi instruments.Methodology Twelve sets of new K3 instruments, sizes 20, 25 and 30 with an 0.04 taper, and sizes 20 and 25 with an 0.06 taper, were torsion tested until rupture, to establish their mean values of maximum torque and angular deflection. Twelve new K3 instruments of each of the following dimensions, size 30, 0.04 taper and sizes 20 and 25 with 0.06 taper, were tested to failure by rotation bending in a fatigue test device. Cyclic torsional loading was performed in 20 cycles from zero angular deflection to 180° and then return to zero applied torque. After cyclic loading, the same number of instruments were tested until rupture in torsion and flexural fatigue. Data obtained were subjected to a one way analysis of variance (anova) at 95% confidence level.Results Cyclic torsional loading caused no significant differences in maximum torque or in maximum angular deflection of the instruments analysed, but comparative statistical analysis between measured NCF values of new and previously cycled K3 instruments showed significant differences for all tested instrument. Longitudinal cracks, that is, cracks apparently parallel to the long axis of the instruments cycled in torsion was observed.Conclusions Cyclic torsional loading experiments in new K3 rotary endodontic instruments showed that torsional fatigue decreased the resistance of these instruments to flexural fatigue, although it did not affect their torsional resistance.
Objective. The aim of this study was to assess the influence of cyclic deformation up to one half... more Objective. The aim of this study was to assess the influence of cyclic deformation up to one half and three quarters of the fatigue life of NiTi rotary endodontic instruments on their behavior in torsion.
A comparative study of the fatigue resistance of engine-driven nickel-titanium endodontic instrum... more A comparative study of the fatigue resistance of engine-driven nickel-titanium endodontic instruments was performed, aiming to access the influence of the cutting flute design and of the size of the files that reach the working length in curved canal shaping. Geometrical conditions similar to those found in practice were used. Series 29 #5 ProFile, together with #6 and #8 Quantec instruments, were tested in artificial canals with a 45-degree angle of curvature and 5-mm radius of curvature. It was observed that the size of the instrument, which determines the maximum strain amplitude during cyclic deformation, is the most important factor controlling fatigue resistance. The effect of heat sterilization on the fatigue resistance of the instruments was also examined. The results obtained indicate that the application of five sterilization procedures in dry heat increases the average number of cycles to failure of unused instruments by approximately 70%.
Aim To correlate the mechanical behaviour in torsion, bending and fatigue tests of K3 instrument... more Aim To correlate the mechanical behaviour in torsion, bending and fatigue tests of K3 instruments with their dimensional characteristics.Methodology Instrument length, tip angle, distance between blades (pitch length) and the diameter at each millimetre from the tip of sizes 20, 25 and 30, 0.04 taper and sizes 20 and 25, 0.06 taper K3 rotary instruments were measured in an optical microscope equipped with digital micrometers. The cross-sectional area at 3 mm from the tip of the same instruments was determined using digital image analysis of scanning electron microscopy images. Maximum torque and angular deflection, as well as bending moment at 45° were measured according to specification of ISO 3630-1. Fatigue resistance of instruments size 30, 0.04 taper, and sizes 20 and 25, 0.06 taper was determined in a fatigue test bench device.Results The analysed instruments presented no uniformity in the distance between adjacent blades, but the measured diameters at each millimetre from the tip were regular, showing compliance with manufacturing standards. Torque and bending moment of the tested instruments increased significantly with diameter and cross-sectional area at 3 mm from the instrument tip. The fatigue resistance of the instruments showed a tendency to decrease as the diameter of the instruments increased.Conclusions The bending moment at 45° and the torsional resistance of K3 instruments can be predicted using instrument diameter and cross-sectional area at 3 mm from the tip. Fatigue resistance decreased as the instrument diameter increased.
Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontology, 2006
Objective. The aim of this study was to assess the influence of cyclic deformation up to one half... more Objective. The aim of this study was to assess the influence of cyclic deformation up to one half and three quarters of the fatigue life of NiTi rotary endodontic instruments on their behavior in torsion.
Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontology, 2010
The purpose of this study was to assess the influence of both the metallurgic and the geometric c... more The purpose of this study was to assess the influence of both the metallurgic and the geometric characteristics of nickel-titanium endodontic instruments on their flexibility.ProTaper Universal (PTU), K3, and EndoSequence (ES) instruments were evaluated. Their chemical composition and phase constitution were characterized by conventional analytical techniques. Instrument diameter and cross-sectional area were evaluated by image analysis. Flexibility was evaluated in bending tests according to the ISO 3630-1.K3 presented the highest average bending moment (MB), followed by PTU and ES. A linear relationship was found between MB and the instrument's diameter and cross-sectional area at 3 mm from the tip. Alloy chemical compositions were similar among the files, but transformation temperatures were lower for K3 instruments, which presented only austenite as a constituent phase.Nickel-titanium instruments from different manufacturers have unequal behavior related to their flexibility properties. Manufacturing processes changed the phase constitution and transformation temperatures of the instruments investigated and may also have influenced their flexibility.
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