INTRODUCTION: The purpose of this study was to compare the flexural fatigue and torsional resistance of ProFile GT and GT Series X instruments, taking into account their structural and dimensional characteristics. METHODS: Instrument diameter at each millimeter from the tip and pitch length were the dimensional parameters measured. Chemical composition was determined by energy-dispersive x-ray spectroscopy and phase constitution by x-ray diffraction. Vickers microhardness measurements were performed to assess instrument strength. One group of 20/.06 GT and GTX instruments (n = 10 each) was tested until failure in a flexural fatigue test device, whereas another group of 20/.04 files (n = 10 each) was tested in torsion based on ISO 3630-1. RESULTS: GT and GTX instruments showed approximately the same chemical composition, namely 51at%Ni-49at%Ti (56wt%Ni-44wt%Ti) and contained mainly the beta-phase. GTX instruments showed higher intensity x-ray diffraction peaks and a statistically higher Vickers microhardness. There was a significant decrease in the diameter of GTX in relation to GT instruments from D6 to D9 for 20/.04 instruments and from D4 to D7 for 20/.06 instruments. Pitch length increased along the active part of both instruments, with a steeper increase in GTX. In general, GT Series X instruments were significantly more resistant to flexural fatigue than were similar GT instruments (p < 0.001) but exhibited lower torsional strength (p < 0.001). CONCLUSIONS: Different structural and dimensional characteristics were found in GTX instruments in comparison with GT instruments; this is probably the cause for their higher flexural fatigue resistance and lower torsional strength. Copyright (c) 2010 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.
INTRODUCTION: The purpose of this study was to compare the flexural fatigue and torsional resistance of ProFile GT and GT Series X instruments, taking into account their structural and dimensional characteristics. METHODS: Instrument diameter at each millimeter from the tip and pitch length were the dimensional parameters measured. Chemical composition was determined by energy-dispersive x-ray spectroscopy and phase constitution by x-ray diffraction. Vickers microhardness measurements were performed to assess instrument strength. One group of 20/.06 GT and GTX instruments (n = 10 each) was tested until failure in a flexural fatigue test device, whereas another group of 20/.04 files (n = 10 each) was tested in torsion based on ISO 3630-1. RESULTS: GT and GTX instruments showed approximately the same chemical composition, namely 51at%Ni-49at%Ti (56wt%Ni-44wt%Ti) and contained mainly the beta-phase. GTX instruments showed higher intensity x-ray diffraction peaks and a statistically higher Vickers microhardness. There was a significant decrease in the diameter of GTX in relation to GT instruments from D6 to D9 for 20/.04 instruments and from D4 to D7 for 20/.06 instruments. Pitch length increased along the active part of both instruments, with a steeper increase in GTX. In general, GT Series X instruments were significantly more resistant to flexural fatigue than were similar GT instruments (p < 0.001) but exhibited lower torsional strength (p < 0.001). CONCLUSIONS: Different structural and dimensional characteristics were found in GTX instruments in comparison with GT instruments; this is probably the cause for their higher flexural fatigue resistance and lower torsional strength. Copyright (c) 2010 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.