Measurement of Surface Deformation in NiTi Endodontic Reciprocating Instruments Manufactured by Machining

This study aimed to develop a methodology to quantify the surface deformation of WaveOne-Gold-Primary instruments after in vitro use. Fifteen reciprocating instruments were used to prepare artificial canals composed of diallyl-phthalate, bisphenol-A, and duralumin (n = 5 per group). Optical microscopy was employed to determine Euler-Almansi strains, scanning electron microscopy (SEM) was used to identify shear bands and characterize fracture surfaces, and energy-dispersive X-ray spectroscopy (EDS) was used to analyze elemental composition. An ANOVA (95%) was conducted to assess significant differences in the strains. The instruments used in polymer canals exhibited untwisting and pronounced elongation, indicative of plastic deformation associated with ductile fractures. Although, atomic percentages of Ni and Ti remained relatively stable, a slight reduction in Ni was observed in the coating of the sterilized instruments. A mathematical model was proposed to correlate the strains with the number of pecks. This methodology provides a robust framework for measuring the deformation of machined NiTi instruments, contributing to a better understanding of their failure and potential prediction implications.