Abstract
BACKGROUND: This study aimed to investigate the influence of multiple variations, such as different metallurgies available on the market in comparison with stainless steel, and simultaneously real-time reading and monitoring of apical sensing during instrumentation with various kinematic movements. METHODS: Three stages of experiment on two allocated groups of artificial root canals were conducted for the study as follows: metallurgy experiment with passive measurement of working lenght, with a gold standard apex locator device, correlation analysis of the apex locator device and an apex locator integrated engine-driven motor with passive measurement, and kinematics experiment with dynamic monitoring. For the metallurgy and kinematics experiments, the same preshaped artificial root canals (n = 26) and for correlation analysis of the devices unshaped root canals were used (n = 15). Stainless steel, conventional NiTi, M wire, CM gold, CM blue, TM wire, C wire, CM EDM, special NiTi heat-treated wire, and R phase file systems were selected for the metallurgy experiment. For the apex locator integrated engine-driven instrumentation, test groups were arranged according to movements and metallurgy (M wire-reciprocating/rotational, CM gold-reciprocating/rotational) and conducted on the same 26-block set. Shapiro‒Wilk, Wilcoxon, Mann‒Whitney U, and Kruskal‒Wallis tests were performed for the statistical analysis (p < 0.050). RESULTS: All tested metallurgies presented correlated measurements (p = 0.139); however, tapered instrumentation affected the working length (p < 0,001). The dynamic measurements (rotational/reciprocating) presented a statistically significant difference compared to the passively established actual working length (p < 0.001). A statistically difference was also obtained between reciprocating and rotational CM gold (p = 0.003); however, there was no difference between reciprocating and rotational M wire (p = 0.084). CONCLUSIONS: Tapered instrumentation changes the initial working length. Different metallurgies have no variational impact on the determination of electronic working length. During apex locator integrated instrumentation, M wire files and rotational movement exhibit a more stable attitude; however, apical overextensions may be observed in all kinematics regardless of the metallurgies. Caution is recommended when using CM gold files with apex locator integrated engine-driven instrumentation, especially in reciprocating motion. CLINICAL RELEVANCE STATEMENT: Maintaining the real-time working length between preparation stages is essential to preserve the apical structure. Dynamic monitoring of apical limit, regardless of motion type, as a supporter may promote treatment outcomes; however, using apex locator integrated instrumentation as a primary way for working length determination, as well as preparation, may cause an extension beyond safe limits.