Caracterização dimensional e comportamento mecânico de instrumentos rotatórios de NiTi PROFILE GT e PROFILE GT Series X

Abstract

The purpose of this study was to compare the flexural fatigue and torsional resistance of ProFile GT (Dentsply-Maillefer, Baillagues, Switzerland) and ProFile GT Series X (GTX) (Dentsply Tulsa Dental, Oklahoma, USA) instruments, taking into account theirstructural and dimensional characteristics. The 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 performedto 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. GT and GTX instruments showed approximately the same chemical composition, namely 51at%Ni-49at%Ti (56wt%Ni-44wt%Ti) and contained mainly the â-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 asteeper 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). Different structural and dimensional characteristics were found in GTX instruments in comparison with GT instruments; this is probably thecause for their higher flexural fatigue resistance and lower torsional strength.