Morphological alterations of rotary nickel-titanium protaper® instruments analyzed by SEM: effect of nitrogen ion implantation

Alex Niederauer Becker,Elias Pandonor Motcy De Oliveira,Ruth Hinrichs,Carlos Frederico Brilhante Wolle,Marcos Antônio Zen Vasconcellos

doi:10.15448/1980-6523.2014.2.13046

Abstract

Abstract Purpose:This study evaluated the morphological alterations that occur in rotary nickel-titanium instruments during nitrogen-ion implantation. Methods: Instruments were divided into three groups: Group A- ProTaper SX instruments were subjected to ionic implantation with bands of nitrogen ions at 100 keV, ion dose was 1.0 X 1017 ions/cm², Group B- ProTaper SX instruments were subjected to ionic implantation with bands of nitrogen ions at 200 keV, ion dose was 1.0 X 1017 ions/cm², and Group C instruments served as unmodified controls. Each instrument was utilized to prepare five canals in epoxy resin blocks with a brushing motion. The instruments were examined by scanning electron microscopy (SEM) before use and after 60 s and 300 s of work inside canals in epoxy resin blocks. Results: Material loss and distortion were statistically similar in all groups. However, while only one instrument in group A and only one instrument in group B fractured during use, three instruments in group C fractured during use. Conclusion: Nitrogen ion implantation can improve the properties of nickel-titanium rotary instruments. However, widespread adoption by the dental industry may not yet be tenable due to the cost (nitrogen ion implantation is a costly process) and relatively small benefit.

Highlights

Stainless steel instruments do not possess the necessary flexibility to ensure safe and reliable instrumentation of root canals with complex anatomy
Instruments treated by ionic implantation at either dose yielded better results than the untreated control group, the differences were not significant
Nitrogen ion implantation creates a layer of titanium nitride on the surface of components by using a low-energy accelerator (~100 to 400 keV) to bombard the NiTi surface with nitrogen ions [12]

Summary

Introduction

Stainless steel instruments do not possess the necessary flexibility to ensure safe and reliable instrumentation of root canals with complex anatomy. The introduction of nickel-titanium (NiTi) instruments seemed to overcome this difficulty [1], the preparation of curved root canals results in morphological alterations, including wear, disappearance of the cutting edge, microfractures, and surface defects, to the instrument surface [2,3,4,5,6,7]. Most studies of nitrogen ion implantation have investigated implantation at doses of ~1017 nitrogen ions/cm2 [8,9,10,11,12] In these studies, ion implantation produced better outcomes compared to nitrided or untreated instruments [8,9,10,11,12]. Nitrogen ion implantation creates a layer of titanium nitride on the surface of components by using a low-energy accelerator (~100 to 400 keV) to bombard the NiTi surface with nitrogen ions [12]. Nitrogen doses of 1017 ions/cm may produce titanium nitride layers of up to 100 nm thick [12]

Methods

Results

Conclusion