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Gianluca Gambarini - One of the best experts on this subject based on the ideXlab platform.
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influence of temperature on Cyclic Fatigue resistance of protaper gold and protaper universal rotary files
Journal of Endodontics, 2017Co-Authors: Gianluca Plotino, Nicola M Grande, Luca Testarelli, Montse Mercade Bellido, Gianluca GambariniAbstract:Abstract Introduction The aim of this study was to evaluate the Cyclic Fatigue resistance of ProTaper Universal (PTU; Dentsply Maillefer, Baillagues, Switzerland) and ProTaper Gold (PTG, Dentsply Maillefer) nickel-titanium rotary files at room and intracanal temperatures. Methods A total of 120 files were used to test the Cyclic Fatigue resistance of PTU (S1 and F2) and PTG (S1 and F2) in an artificial canal at room temperature (20°C) and at intracanal temperature (35°C). The number of cycles to failure and the fracture length of the fragment were recorded, and data were subjected to statistical analysis. Results PTG registered no differences in Fatigue life between the 2 temperatures tested ( P > .05), whereas PTU showed a statistically significant reduction in Fatigue life at intracanal temperature compared with room temperature ( P P P > .05). Conclusions Intracanal temperature influenced the Cyclic Fatigue resistance of instruments produced with traditional nickel-titanium, whereas it did not influence the Fatigue life of instruments produced with gold heat treatment. Gold heating treatment enhances the resistance to Cyclic Fatigue of ProTaper instruments.
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Cyclic Fatigue of instruments for endodontic glide path
Odontology, 2015Co-Authors: Gianluca Gambarini, Gianluca Plotino, Gianpaolo Sannino, Dina Al Sudani, Nicola Maria Grande, Alessio Giansiracusa, Lucila Piasecki, Ulisses Xavier Silva Neto, Luca TestarelliAbstract:Endodontic glide path is the creation of a smooth patency from canal orifice to apex, which can be performed manually or with small tapered NiTi rotary instruments. The use of stainless steel (SS) hand K-files inserted in a reciprocating handpiece can be a possible alternative to create a mechanical glide path. The aim of this study was to compare the Cyclic Fatigue resistance between SS K-files used in a reciprocating motion and NiTi rotary instruments in artificial curved canals. Ten SS size 15 K-files used with the M4 handpiece (SybronEndo, Glendora, CA, USA) and ten PathFiles (Maillefer-Dentsply, Ballaigues, CH, Switzerland) NiTi rotary instruments size 16, 0.02 taper were tested for resistance to Cyclic Fatigue. The time to fracture inside an artificial curved canal was recorded for each instrument. Data were analyzed by one-way ANOVA and Tukey HSD test. Mean time (and SD) to failure was 464 s (±40.4) for the Group PF (NiTi rotary PathFile), and 1049 s (±24.8) for the Group M4 (SS K-files reciprocating) with a statistically significant difference between the two groups ( p = 0.033). The SS 15 K-files used with the M4 handpiece showed a significant greater resistance to Cyclic Fatigue when compared to the NiTi rotary PathFiles. Therefore, the use of small size SS files in a reciprocating motion might be a rational choice for the creation of a mechanical endodontic glide path in curved root canals.
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blue treatment enhances Cyclic Fatigue resistance of vortex nickel titanium rotary files
Journal of Endodontics, 2014Co-Authors: Gianluca Plotino, Nicola M Grande, Luca Testarelli, Elisabetta Cotti, Gianluca GambariniAbstract:Abstract Introduction The aim of the present study was to evaluate the difference in Cyclic Fatigue resistance between Vortex Blue (Dentsply Tulsa Dental, Tulsa, OK) and Profile Vortex nickel-titanium (Dentsply Tulsa Dental) rotary instruments. Methods Two groups of nickel-titanium endodontic instruments, ProFile Vortex and Vortex Blue, consisting of identical instruments in tip size and taper (15/.04, 20/.06, 25/.04, 25/.06, 30/.06, 35/.06, and 40/.04) were tested. Ten instruments from each system and size were tested for Cyclic Fatigue resistance, resulting in a total of 140 new instruments. All instruments were rotated in a simulated root canal with a 60° angle of curvature and a 5-mm radius of curvature of a specific Cyclic Fatigue testing device until fracture occurred. The number of cycles to failure and the length of the fractured tip were recorded for each instrument in each group. The mean values and standard deviation were calculated, and data were subjected to 1-way analysis of variance and a Bonferroni t test. Significance was set at the 95% confidence level. Results When comparing the same size of the 2 different instruments, a statistically significant difference ( P P = 1.000). No statistically significant difference ( P > .05) was noted among all groups tested in terms of fragment length. Conclusions Vortex Blue showed a significant increase in Cyclic Fatigue resistance when compared with the same sizes of ProFile Vortex.
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Cyclic Fatigue of NiTi instruments used in complex curvatures with continuous or reciprocating rotation
Giornale Italiano di Endodonzia, 2014Co-Authors: Luca Testarelli, Gianluca Gambarini, Ermanno Putortì, Simone Staffoli, Federico Valenti Obino, Dario Di Nardo, Gabriele Miccoli, Valerio Milana, Alessio Giansiracusa RubiniAbstract:Abstract Aim The aim of present study was to compare Cyclic Fatigue resistance of Twisted files (TF, Sybron Endo, Glendora, CA) instrument used with continuous rotation and the new Motion (TFAdaptive rotating reciprocation), to evaluate if the new reciprocating motion could affect the lifespan of tested instruments. Methodology 30 new TF instruments were submitted to Cyclic Fatigue tests. Group 1 instruments were tested using a TFA motion (TFA) while group 2 instruments were used in continuous rotation at 500 rpm (CR). The Cyclic Fatigue testing device used in the present study has been used for studies on Cyclic Fatigue resistance previously. The artificial canal was manufactured to provide the instrument with a very challenging trajectory 60° curvature, with a 2 mm radius. All instruments were rotated or reciprocated until fracture occurred. The time to fracture was recorded. All data were subjected to statistical evaluation with analysis of variance test. Results TFA reciprocating motion showed a significant increase ( p Conclusions In accordance with those findings, the results of the present study showed a significant increase of Cyclic Fatigue resistance of instruments used with the TFA motion. This can be explained by the alternance of engaging/disengaging movements, since the motion can be defined as a non-continuous rotation, while the traditional continuous rotation movement continuously engages and stresses the instruments.
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Influence of file motion on Cyclic Fatigue of new nickel titanium instruments.
Annali di stomatologia, 2013Co-Authors: Alessio Giansiracusa Rubini, Luca Testarelli, Giancarlo Pongione, Gianpaolo Sannino, Dina Al Sudani, Jeeraphat Jantarat, Massimo De Luca, Gianluca GambariniAbstract:Aim.The aim of the present study was to compare the resistance to Cyclic Fatigue of Hyflex® (Coltene-Whaledent, Allstatten, Switzerland) size 40 taper.04 nickel titanium instruments used in continuous rotation versus the use with a reciprocating motion. The null hypothesis was that different file motions had no influence on the lifetime of instruments subjected to a Cyclic Fatigue test. Methodology.24 Hyflex® size 40 taper.04 nickel titanium instruments were randomly divided in two groups (n=12each), and submitted to a Cyclic Fatigue test. The firstgroup (CR group) were used with a continuous rotation,while the second one (RCP group) with a reciprocating motion. The Cyclic Fatigue tests were performed by using a stainless steel block containing an artificial canal shaped with a 135° angle. All instruments were rotated or reciprocated until fracture occurred. The time to fracture was recorded visually with a 1/100 second chronometer. Data were recorded and statistically analysed. Results. Results indicated that instruments used with are ciprocating motion showed a significant increase in the meantime to failure when compared to those used in continuous rotation. Conclusions. The null hypothesis was rejected. Results ofthe present study showed that reciprocating motion extended resistance to Cyclic Fatigue of the tested nickel titanium instruments, when compared to continuous rotation.
Gianluca Plotino - One of the best experts on this subject based on the ideXlab platform.
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influence of temperature on Cyclic Fatigue resistance of protaper gold and protaper universal rotary files
Journal of Endodontics, 2017Co-Authors: Gianluca Plotino, Nicola M Grande, Luca Testarelli, Montse Mercade Bellido, Gianluca GambariniAbstract:Abstract Introduction The aim of this study was to evaluate the Cyclic Fatigue resistance of ProTaper Universal (PTU; Dentsply Maillefer, Baillagues, Switzerland) and ProTaper Gold (PTG, Dentsply Maillefer) nickel-titanium rotary files at room and intracanal temperatures. Methods A total of 120 files were used to test the Cyclic Fatigue resistance of PTU (S1 and F2) and PTG (S1 and F2) in an artificial canal at room temperature (20°C) and at intracanal temperature (35°C). The number of cycles to failure and the fracture length of the fragment were recorded, and data were subjected to statistical analysis. Results PTG registered no differences in Fatigue life between the 2 temperatures tested ( P > .05), whereas PTU showed a statistically significant reduction in Fatigue life at intracanal temperature compared with room temperature ( P P P > .05). Conclusions Intracanal temperature influenced the Cyclic Fatigue resistance of instruments produced with traditional nickel-titanium, whereas it did not influence the Fatigue life of instruments produced with gold heat treatment. Gold heating treatment enhances the resistance to Cyclic Fatigue of ProTaper instruments.
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Cyclic Fatigue resistance of two nickel–titanium rotary instruments in interrupted rotation
International endodontic journal, 2016Co-Authors: Eugenio Pedulla, Nicola M Grande, Gianluca Plotino, Ernesto Rapisarda, A. Lizio, M. Scibilia, Simona Boninelli, G. Lo GiudiceAbstract:Aim To investigate the influence of interrupted rotation on Cyclic Fatigue of two nickel–titanium rotary instruments. Methodology Cyclic Fatigue of 300 new ProTaper Next size X1; X2 and Mtwo size 10, .04 taper; size 15, .05 taper; size 20, .06 taper and size 25, .06 taper instruments was tested in continuous or interrupted rotation. Fifty files of the same brand and size were randomly assigned to five groups (n = 10). Group 1 instruments were tested in continuous rotation; groups 2 and 3 in paused rotation for 1 s every 10 or 20 s, respectively; groups 4 and 5 in interrupted rotation for 5 s every 10 or 20 s, respectively. Cyclic Fatigue was expressed in time to fracture (TtF) in an artificial canal with 60° angle and 5 mm radius of curvature. The fracture surface was examined with a scanning electron microscope (SEM). Data were evaluated by two-way analysis of variance. Results Cyclic Fatigue of groups 2 and 4 of ProTaper Next X2 and Mtwo size 25, .06 taper was significantly lower than that of group 1 of the same instruments (P 0.05). Fatigue of other instruments was not affected by interrupted rotation (P > 0.05). Conclusions Interrupted rotation reduced Cyclic Fatigue resistance of ProTaper Next X2 and Mtwo size 25, .06 taper, especially when a higher number of interruptions was performed.
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Cyclic Fatigue of instruments for endodontic glide path
Odontology, 2015Co-Authors: Gianluca Gambarini, Gianluca Plotino, Gianpaolo Sannino, Dina Al Sudani, Nicola Maria Grande, Alessio Giansiracusa, Lucila Piasecki, Ulisses Xavier Silva Neto, Luca TestarelliAbstract:Endodontic glide path is the creation of a smooth patency from canal orifice to apex, which can be performed manually or with small tapered NiTi rotary instruments. The use of stainless steel (SS) hand K-files inserted in a reciprocating handpiece can be a possible alternative to create a mechanical glide path. The aim of this study was to compare the Cyclic Fatigue resistance between SS K-files used in a reciprocating motion and NiTi rotary instruments in artificial curved canals. Ten SS size 15 K-files used with the M4 handpiece (SybronEndo, Glendora, CA, USA) and ten PathFiles (Maillefer-Dentsply, Ballaigues, CH, Switzerland) NiTi rotary instruments size 16, 0.02 taper were tested for resistance to Cyclic Fatigue. The time to fracture inside an artificial curved canal was recorded for each instrument. Data were analyzed by one-way ANOVA and Tukey HSD test. Mean time (and SD) to failure was 464 s (±40.4) for the Group PF (NiTi rotary PathFile), and 1049 s (±24.8) for the Group M4 (SS K-files reciprocating) with a statistically significant difference between the two groups ( p = 0.033). The SS 15 K-files used with the M4 handpiece showed a significant greater resistance to Cyclic Fatigue when compared to the NiTi rotary PathFiles. Therefore, the use of small size SS files in a reciprocating motion might be a rational choice for the creation of a mechanical endodontic glide path in curved root canals.
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blue treatment enhances Cyclic Fatigue resistance of vortex nickel titanium rotary files
Journal of Endodontics, 2014Co-Authors: Gianluca Plotino, Nicola M Grande, Luca Testarelli, Elisabetta Cotti, Gianluca GambariniAbstract:Abstract Introduction The aim of the present study was to evaluate the difference in Cyclic Fatigue resistance between Vortex Blue (Dentsply Tulsa Dental, Tulsa, OK) and Profile Vortex nickel-titanium (Dentsply Tulsa Dental) rotary instruments. Methods Two groups of nickel-titanium endodontic instruments, ProFile Vortex and Vortex Blue, consisting of identical instruments in tip size and taper (15/.04, 20/.06, 25/.04, 25/.06, 30/.06, 35/.06, and 40/.04) were tested. Ten instruments from each system and size were tested for Cyclic Fatigue resistance, resulting in a total of 140 new instruments. All instruments were rotated in a simulated root canal with a 60° angle of curvature and a 5-mm radius of curvature of a specific Cyclic Fatigue testing device until fracture occurred. The number of cycles to failure and the length of the fractured tip were recorded for each instrument in each group. The mean values and standard deviation were calculated, and data were subjected to 1-way analysis of variance and a Bonferroni t test. Significance was set at the 95% confidence level. Results When comparing the same size of the 2 different instruments, a statistically significant difference ( P P = 1.000). No statistically significant difference ( P > .05) was noted among all groups tested in terms of fragment length. Conclusions Vortex Blue showed a significant increase in Cyclic Fatigue resistance when compared with the same sizes of ProFile Vortex.
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Cyclic Fatigue resistance of two reciprocating nickel titanium instruments after immersion in sodium hypochlorite
International Endodontic Journal, 2013Co-Authors: Eugenio Pedulla, Nicola M Grande, Gianluca Gambarini, Gianluca Plotino, F Palermo, Ernesto RapisardaAbstract:Aim To assess resistance to Cyclic Fatigue of reciprocating nickel–titanium ( NiTi ) files (Reciproc and WaveOne) after immersion in NaOCl solution over several time periods. Methodology A total of 90 new Reciproc R25 and WaveOne Primary were tested. The 45 files of the same brand were randomly assigned to three groups (n = 15) and submitted to the following immersion protocol in 5% NaOCl at 37 °C for 16 mm: no immersion (control), 1 or 5 min dynamically. The dynamic immersion and the following Cyclic Fatigue tests were performed using the appropriate preset reciprocation modes (‘RECIPROC ALL’ or ‘WAVEONE ALL’) in a specially designed endodontic motor. Resistance to Cyclic Fatigue was determined by recording time to fracture (TtF) in a stainless steel artificial canal with a 60° angle of curvature and 5 mm radius of curvature. The artificial canal was manufactured reproducing the instrument's size and taper. Data were analysed by 2-way analyses of variance. Results Resistance to Cyclic Fatigue of the same NiTi file was not significantly affected by immersion in NaOCl . Reciproc R25 was associated with a higher Cyclic Fatigue resistance in all groups compared to WaveOne Primary (P < 0.0001). Conclusions Reciprocating dynamic immersion in NaOCl for 1 or 5 min did not reduce the Cyclic Fatigue resistance of NiTi files significantly. However, the type of reciprocating instrument influenced Cyclic Fatigue resistance with Reciproc R25 being more resistant than WaveOne Primary.
Nicola M Grande - One of the best experts on this subject based on the ideXlab platform.
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influence of temperature on Cyclic Fatigue resistance of protaper gold and protaper universal rotary files
Journal of Endodontics, 2017Co-Authors: Gianluca Plotino, Nicola M Grande, Luca Testarelli, Montse Mercade Bellido, Gianluca GambariniAbstract:Abstract Introduction The aim of this study was to evaluate the Cyclic Fatigue resistance of ProTaper Universal (PTU; Dentsply Maillefer, Baillagues, Switzerland) and ProTaper Gold (PTG, Dentsply Maillefer) nickel-titanium rotary files at room and intracanal temperatures. Methods A total of 120 files were used to test the Cyclic Fatigue resistance of PTU (S1 and F2) and PTG (S1 and F2) in an artificial canal at room temperature (20°C) and at intracanal temperature (35°C). The number of cycles to failure and the fracture length of the fragment were recorded, and data were subjected to statistical analysis. Results PTG registered no differences in Fatigue life between the 2 temperatures tested ( P > .05), whereas PTU showed a statistically significant reduction in Fatigue life at intracanal temperature compared with room temperature ( P P P > .05). Conclusions Intracanal temperature influenced the Cyclic Fatigue resistance of instruments produced with traditional nickel-titanium, whereas it did not influence the Fatigue life of instruments produced with gold heat treatment. Gold heating treatment enhances the resistance to Cyclic Fatigue of ProTaper instruments.
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Cyclic Fatigue resistance of two nickel–titanium rotary instruments in interrupted rotation
International endodontic journal, 2016Co-Authors: Eugenio Pedulla, Nicola M Grande, Gianluca Plotino, Ernesto Rapisarda, A. Lizio, M. Scibilia, Simona Boninelli, G. Lo GiudiceAbstract:Aim To investigate the influence of interrupted rotation on Cyclic Fatigue of two nickel–titanium rotary instruments. Methodology Cyclic Fatigue of 300 new ProTaper Next size X1; X2 and Mtwo size 10, .04 taper; size 15, .05 taper; size 20, .06 taper and size 25, .06 taper instruments was tested in continuous or interrupted rotation. Fifty files of the same brand and size were randomly assigned to five groups (n = 10). Group 1 instruments were tested in continuous rotation; groups 2 and 3 in paused rotation for 1 s every 10 or 20 s, respectively; groups 4 and 5 in interrupted rotation for 5 s every 10 or 20 s, respectively. Cyclic Fatigue was expressed in time to fracture (TtF) in an artificial canal with 60° angle and 5 mm radius of curvature. The fracture surface was examined with a scanning electron microscope (SEM). Data were evaluated by two-way analysis of variance. Results Cyclic Fatigue of groups 2 and 4 of ProTaper Next X2 and Mtwo size 25, .06 taper was significantly lower than that of group 1 of the same instruments (P 0.05). Fatigue of other instruments was not affected by interrupted rotation (P > 0.05). Conclusions Interrupted rotation reduced Cyclic Fatigue resistance of ProTaper Next X2 and Mtwo size 25, .06 taper, especially when a higher number of interruptions was performed.
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blue treatment enhances Cyclic Fatigue resistance of vortex nickel titanium rotary files
Journal of Endodontics, 2014Co-Authors: Gianluca Plotino, Nicola M Grande, Luca Testarelli, Elisabetta Cotti, Gianluca GambariniAbstract:Abstract Introduction The aim of the present study was to evaluate the difference in Cyclic Fatigue resistance between Vortex Blue (Dentsply Tulsa Dental, Tulsa, OK) and Profile Vortex nickel-titanium (Dentsply Tulsa Dental) rotary instruments. Methods Two groups of nickel-titanium endodontic instruments, ProFile Vortex and Vortex Blue, consisting of identical instruments in tip size and taper (15/.04, 20/.06, 25/.04, 25/.06, 30/.06, 35/.06, and 40/.04) were tested. Ten instruments from each system and size were tested for Cyclic Fatigue resistance, resulting in a total of 140 new instruments. All instruments were rotated in a simulated root canal with a 60° angle of curvature and a 5-mm radius of curvature of a specific Cyclic Fatigue testing device until fracture occurred. The number of cycles to failure and the length of the fractured tip were recorded for each instrument in each group. The mean values and standard deviation were calculated, and data were subjected to 1-way analysis of variance and a Bonferroni t test. Significance was set at the 95% confidence level. Results When comparing the same size of the 2 different instruments, a statistically significant difference ( P P = 1.000). No statistically significant difference ( P > .05) was noted among all groups tested in terms of fragment length. Conclusions Vortex Blue showed a significant increase in Cyclic Fatigue resistance when compared with the same sizes of ProFile Vortex.
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Cyclic Fatigue resistance of two reciprocating nickel titanium instruments after immersion in sodium hypochlorite
International Endodontic Journal, 2013Co-Authors: Eugenio Pedulla, Nicola M Grande, Gianluca Gambarini, Gianluca Plotino, F Palermo, Ernesto RapisardaAbstract:Aim To assess resistance to Cyclic Fatigue of reciprocating nickel–titanium ( NiTi ) files (Reciproc and WaveOne) after immersion in NaOCl solution over several time periods. Methodology A total of 90 new Reciproc R25 and WaveOne Primary were tested. The 45 files of the same brand were randomly assigned to three groups (n = 15) and submitted to the following immersion protocol in 5% NaOCl at 37 °C for 16 mm: no immersion (control), 1 or 5 min dynamically. The dynamic immersion and the following Cyclic Fatigue tests were performed using the appropriate preset reciprocation modes (‘RECIPROC ALL’ or ‘WAVEONE ALL’) in a specially designed endodontic motor. Resistance to Cyclic Fatigue was determined by recording time to fracture (TtF) in a stainless steel artificial canal with a 60° angle of curvature and 5 mm radius of curvature. The artificial canal was manufactured reproducing the instrument's size and taper. Data were analysed by 2-way analyses of variance. Results Resistance to Cyclic Fatigue of the same NiTi file was not significantly affected by immersion in NaOCl . Reciproc R25 was associated with a higher Cyclic Fatigue resistance in all groups compared to WaveOne Primary (P < 0.0001). Conclusions Reciprocating dynamic immersion in NaOCl for 1 or 5 min did not reduce the Cyclic Fatigue resistance of NiTi files significantly. However, the type of reciprocating instrument influenced Cyclic Fatigue resistance with Reciproc R25 being more resistant than WaveOne Primary.
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Cyclic Fatigue of reciproc and waveone reciprocating instruments
International Endodontic Journal, 2012Co-Authors: Gianluca Plotino, Nicola M Grande, Luca Testarelli, Gianluca GambariniAbstract:Plotino G, Grande NM, Testarelli L, Gambarini G. Cyclic Fatigue of Reciproc and WaveOne reciprocating instruments. International Endodontic Journal, 45, 614–618, 2012. Abstract Aim To evaluate the Cyclic Fatigue resistance of Reciproc® and WaveOne® instruments in simulated root canals. Methodology Two groups of 15 NiTi endodontic instruments of identical tip size of 0.25 mm were tested, group A; Reciproc® R25 and group B: WaveOne® primary. Cyclic Fatigue testing was performed in a stainless steel artificial canal manufactured by reproducing the instrument’s size and taper. A simulated root canal with a 60° angle of curvature and 5-mm radius of curvature was constructed for both the instruments tested. The centre of the curvature was 5 mm from the tip of the instrument and the curved segment of the canal was approximately 5 mm in length. The Reciproc® instruments were activated using the preset programme specific for the Reciproc® instruments, whilst the WaveOne® instruments were activated using the preset programme specific for the WaveOne® instruments. All instruments were rotated until fracture occurred and the time to fracture (TtF) and the length of the fractured tip were recorded and registered. Means and standard deviations of TtF and fragment length were calculated for each system and data were subjected to Student’s t-test (P < 0.05). Results A statistically significant difference (P 0.05) in the mean length of the fractured fragments between the instruments. Conclusions Reciproc® instruments were associated with a significantly higher Cyclic Fatigue resistance than WaveOne® instruments.
Ove A Peters - One of the best experts on this subject based on the ideXlab platform.
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effect of Cyclic Fatigue on static fracture loads in protaper nickel titanium rotary instruments
Journal of Endodontics, 2005Co-Authors: Cheryl J Ullmann, Ove A PetersAbstract:The aim of the present study was to evaluate static fracture loads of ProTaper Nickel-Titanium instruments that had been subjected to various degrees of Cyclic Fatigue. Torque and angle at failure of new instruments and instruments that had been stressed to 30, 60, or 90% of their Cyclic Fatigue rotations in a simulated canal (90 degrees and 5 mm radius) were tested according to ISO 3630-1. With unused ProTaper instruments, resistance to Cyclic Fatigue decreased with diameter increase and ranged from 158 to 450 rotations. Torque at failure ranged from 0.5 to 2.1 Ncm and showed a strong linear relationship to instrument diameter (r = 0.9) while angle at failure was weakly related to diameter (r = 0.46). Cyclic prestressing significantly reduced torsional resistance in finishing files, while shaping files were largely unaffected. In conclusion, build-up of tension within NiTi rotary instruments depends on instrument diameter. Clinically, larger instruments that have been subjected to some Cyclic Fatigue should be used with great care or discarded.
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effect of Cyclic Fatigue on static fracture loads in protaper nickel titanium rotary instruments
Journal of Endodontics, 2005Co-Authors: Cheryl J Ullmann, Ove A PetersAbstract:Abstract The aim of the present study was to evaluate static fracture loads of ProTaper Nickel-Titanium instruments that had been subjected to various degrees of Cyclic Fatigue. Torque and angle at failure of new instruments and instruments that had been stressed to 30, 60, or 90% of their Cyclic Fatigue rotations in a simulated canal (90° and 5 mm radius) were tested according to ISO 3630-1. With unused ProTaper instruments, resistance to Cyclic Fatigue decreased with diameter increase and ranged from 158 to 450 rotations. Torque at failure ranged from 0.5 to 2.1 Ncm and showed a strong linear relationship to instrument diameter ( r 2 = 0.9) while angle at failure was weakly related to diameter ( r 2 = 0.46). Cyclic prestressing significantly reduced torsional resistance in finishing files, while shaping files were largely unaffected. In conclusion, build-up of tension within NiTi rotary instruments depends on instrument diameter. Clinically, larger instruments that have been subjected to some Cyclic Fatigue should be used with great care or discarded.
Yiu-wing Mai - One of the best experts on this subject based on the ideXlab platform.
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Cyclic Fatigue mechanisms in partially stabilized zirconia
1995Co-Authors: Mark Hoffman, Shuichi Wakayama, Masanori Kawahara, Yiu-wing Mai, Teruo KishiAbstract:Cyclic Fatigue crack growth rate and crack resistance curve testing were undertaken on 6 different grades of Mg-PSZ. The width of the transformation zone at the flanks of the cracks was determined using Raman spectroscopy and, combined with R-curve toughening values, used to ascertain the level of crack-tip shielding during Cyclic Fatigue crack growth and hence the crack-tip stress intensity factor amplitude. By normalizing the crack-tip stress intensity factor amplitude with the intrinsic toughness of the material, it was found that the Cyclic Fatigue threshold stress intensity factor was independent of the extent of crack-tip shielding and a function of the stress intensity factor at the crack tip. In situ SEM observations of Cyclic Fatigue revealed crack bridging by uncracked ligaments and the precipitate phase. Under Cyclic loading the precipitate bridges were postulated to undergo frictional degradation at the precipitate/matrix interface with the degree of degradation determined by the Cyclic amplitude. Acoustic emission testing revealed acoustic emissions at three distinct levels during the loading cycle: firstly, near the maximum applied stress intensity factor caused by crack propagation; secondly, at the mid-range of the applied stress intensity factor attributed to crack closure near the crack tip, presumably as a result ofmore » transformation induced dilation; and thirdly, intermittently near the base of the loading cycle as a result of fracture surface contact due to surface roughness at a significant distance behind the crack tip. Crack closure near the crack tip due to dilation is proposed to significantly reduce the crack tip stress intensity factor amplitude and hence the degree of Cyclic Fatigue.« less
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Cyclic Fatigue of a sintered Al2O3/ZrO2 ceramic
Journal of Materials Science, 1995Co-Authors: Kai Duan, Yiu-wing Mai, B. CotterellAbstract:A systematic experimental and theoretical study on the crack growth behaviour of a sintered Al2O3/ZrO2 ceramic under Cyclic loading is presented. It is found that in the Cyclic Fatigue experiments conducted on the single-edge-notched beam (SENB) geometry, for similar testing conditions, the crack growth rates are significantly faster than those under static Fatigue. Al2O3/ZrO2 therefore suffers genuine mechanical Fatigue. Further experiments with the compact tension (CT) geometry show that the mechanical Fatigue effect arises mainly from the degradation of the bridging mechanism. A theoretical analysis based on the compliance technique and a power law relationship between the crack-wake bridging stress and the crack-face separation is developed to evaluate quantitatively the degradation of the bridging stress due to Cyclic Fatigue.
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The effects of material microstructure on Cyclic Fatigue crack growth in transformation-toughened ceramics
Advanced Materials '93, 1994Co-Authors: Mark Hoffman, Yiu-wing MaiAbstract:The Cyclic Fatigue properties of Mg-PSZ samples of varying grain size and heat treatment condition were tested. It was found that the main factors affecting performance under Cyclic load were the level of crack-tip shielding and the intrinsic toughness of the material. Cyclic Fatigue threshold was found to vary with delta phase and tetragonal phase content but no correlation was found between Cyclic Fatigue threshold and tetragonal precipitate size. It was found that the size of the transformation zone around a Vicker's indentation as seen using Nomarski interference microscopy was closely related to the Cyclic Fatigue threshold.
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Cyclic Fatigue lifetime predictions of partially stabilized zirconia with crack resistance curve characteristics
Journal of the European Ceramic Society, 1993Co-Authors: Mark Hoffman, Werner Lentz, Michael V. Swain, Yiu-wing MaiAbstract:Abstract Predictions of static and Cyclic Fatigue crack growth of indentation-initiated strength-limiting flaws in a Mg-PSZ material are compared with observations. The extent of environmental effects on Cyclic loading lifetime prediction is determined by integrating the Cyclic stress cycle following determination of crack growth parameters from static Fatigue data. The effect of crack tip shielding as a result of the crack resistance curve is also included. The true Cyclic Fatigue effect is then determined. Crack growth dependence on the maximum stress intensity, K max , and ΔK and possible mechanistic explanations of Cyclic Fatigue effect are also considered.
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Cyclic Fatigue behaviour of eutectoid aged Mg-PSZ ceramics with processing flaws
Journal of the European Ceramic Society, 1993Co-Authors: Tianshun Liu, Yiu-wing Mai, Michael V. SwainAbstract:Abstract The Cyclic Fatigue behaviour of Mg-PSZ in the asfired state and after eutectoid aging (1400°C for 2 and 16 h) were investigated in four-point bending tests. A large number of specimens with processing flaws were used to measure the initial strength distribution and the Cyclic Fatigue lifetime at a stress ratio R = 0·3. From these experimental data a modified ‘stresstime-probability’ (S-T-P) diagram can be constructed using a statistical approach. The residual strength of the survivor specimens, which is lower than their corresponding initial strength, has also been measured, confirming that pronounced Cyclic Fatigue damage does occur in these Mg-PSZ ceramics. The experimental results are discussed in terms of transformation toughening, microcracking and precipitate hardening mechanisms.
