Microstructural, microchemical, and mechanical changes associated with the clinical reuse of two nickel–titanium endodontic instruments

Quantitative Evaluation of Debris Removal from NiTi Rotary Endodontic Instruments After Different Cleaning Procedures

Objectives: Endodontic instruments require thorough decontamination and sterilization before use and reuse to ensure the safety and success of treatments. However, standardized protocols are lacking. This study aimed to quantitatively assess the effectiveness of different cleaning protocols in removing debris from NiTi rotary file surfaces. Methods: Forty-eight new Mtwo NiTi rotary instruments (sizes 10/.04, 15/.05, 20/.06, and 25/.06) were randomly assigned to four groups (n = 12). A set of new sterile instruments (Group I) served as the negative control. After usage for primary endodontic treatment, instruments underwent different cleaning protocols: steam sterilization without cleaning (Group II); ultrasonic cleaning + steam sterilization (Group III); and manual cleaning with a scouring sponge + ultrasonic cleaning + steam sterilization (Group IV). Back-scattered scanning electron microscopy (SEM) micrographs of the apical, middle, and coronal sections were processed using Fiji software (version 2.14.0) to quantify debris as a percentage of the total selected area. Results: No significant differences were found among the three sections within each group, although higher debris amounts were observed from coronal to apical in Groups I and II. Group I had the least debris, while Group II showed the most, with statistically significant differences compared to other groups (p < 0.05). There was no significant difference between Groups III and IV, though Group IV showed notably less debris. Conclusions: The combination of mechanical, chemical, and ultrasonic cleaning proved most effective at removing debris from endodontic instruments. Current cleaning methods, however, remain insufficient for complete debris removal, highlighting the need for further research to standardize and improve cleaning and sterilization protocols or preferably use single-use/single-patient instruments.

Innovative Damage Assessment of Endodontic Instruments Based on Digital Image Stacking

BACKGROUND/OBJECTIVES

The damage assessment of dental instruments, such as endodontic files, is crucial to ensure patient safety and treatment quality. Conventional scanning electron microscopy (SEM) has been the gold standard for this purpose; however, its limited accessibility and complex sample preparation protocols hinder its routine use in clinical settings. This study proposes a novel system that leverages digital photography and advanced image processing techniques as a viable alternative to SEM.

METHODS

Our system accurately detects early instrument damage by capitalizing on the high resolution of digital images. Its exceptionally user-friendly interface, portability, and key features make it highly suitable for daily clinical practice.

RESULTS

Our findings suggest that the proposed system provides image quality comparable to SEM.

CONCLUSIONS

Image stacking provides a practical, efficient, and objective method for assessing endodontic instruments' morphology. By detecting early damage, this system significantly improves the safety and quality of endodontic procedures, especially for reusable NiTi files, instilling confidence and security in its use. It offers a cost-effective and user-friendly alternative to traditional methods such as visual inspection and SEM, making it a comfortable and confident choice for both research and clinical settings.

Wear Analysis of Four Different Single-File Reciprocating Instruments before and after Four Uses in Simulated Root Canals

The aim of this study is to assess the surface alterations of four reciprocating instruments before and after the shaping of four resin-simulated root canals. The following four different reciprocating instruments are selected: 10 Reciproc Blue (RB25), 10 WaveOne Gold (WOG), 10 EdgeOne Fire (EOF) and 10 recently introduced instruments OneRECI (OR), for a total of 40 new instruments. Before root canal shaping, each instrument is mounted on a stub in a standardized position and observed using a scanning electron microscope (SEM) to detect any surface alteration, such as microfractures, metal defects, deformations, blunt and disruption of cutting edges, debris, pitting and tip flattening. Micrographs are acquired at the level of the tip, 4 mm, 8 mm and 12 mm from it. After that, each instrument is used in four simulated resin root canals. SEM observation was repeated after the simulated clinical use to assess the wear resistance of the instruments. Surface alterations are registered before and after instrumentation and statistical analysis is performed using a Chi-Square test to verify homogeneity of defects distribution and GLM to evaluate the differences of RMS at baseline and after use for both groups (α level 0.05). Before simulated clinical uses, no alterations are found except for three cases of EOF with metal strips in correspondence to the tip, disruption of the cutting edge of WOG and oily spotting on two different OR. After simulated clinical use, EOF shows a statistically significant difference in terms of spiral distortion and flattening of the cutting edges. The OR shows the highest presence of debris despite the ultrasonic cleaning procedures. No instrument fractures are observed. EOF should be discarded after four clinical uses and carefully inspected after each insertion into root canals. Moreover, tough attention should be paid during disinfection and cleaning procedures after instrumentation considering the copious debris detected in each instrument, particularly in OR.