Artigo JOE ABRIL - Flexural Fatigue and Torsional Resistance of ProFile GT and ProFile GT Series X Instruments

Flexural Fatigue and Torsional Resistance of ProFile GT and ProFile GT Series X Instruments

Isabella Faria da Cunha Peixoto, DDS, MS,* E´ rika Sales Joviano Pereira, DDS, MS,* Jacqueline Gonc¸alves da Silva, DDS,* Ana Cecı´lia Diniz Viana, DDS, MS,* Vicente Tadeu Lopes Buono, BS, MS, PhD,† and Maria Guiomar de Azevedo Bahia, DDS, MS, PhD*

Abstract

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 β-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.


Key Words: Diameter, flexural fatigue, GT Series X, microhardness, NiTi rotary instruments, pitch length, torsional strength.