A novel quantitative method for evaluating surface roughness using dual-angle images from a field emission scanning electron microscope

Abstract

Abstract This study aims to assess the impact of pre-clinical (ex vivo) use including autoclave sterilization on the surface roughness of reciprocating NiTi instruments using a new treatment of two images with different angles captured by field-emission scanning electron microscopy (FE-SEM) and Mountains software. A pre-clinical study was conducted to evaluate surface roughness changes in NiTi instruments after three instrumentations. Using a repeated-measures design in which each instrument served as its own control, Instruments were examined using FE-SEM and analyzed with Mountains software to quantify roughness parameters (Sa, Sq, Sz) at two locations: the cutting edge and the adjacent flute. Three-dimensional surfaces were reconstructed from dual-angle stereo-pair micrographs per ISO 25178-2. Pre- and post-instrumentation roughness measurements were statistically compared using repeated-measures ANOVA and Friedman tests. There was no significant difference in surface roughness between experimental groups in the pre-clinical environment at the edge of the One RECI instrument. However, there is a linear trend of the increase of the Sa and Sq parameters at the cutting edge of the instrument after several human-extracted root canal instrumentations. There is a significant difference in surface roughness in Sa parameter between experimental groups in the pre-clinical environment at the flute of the One RECI instrument. Pre-clinical use leads to measurable increases in surface roughness in reciprocating NiTi instruments, particularly at the cutting-edge. These findings highlight the importance of monitoring instrument wear to ensure optimal performance and safety.