Finite element study of the fatigue behaviour of nickel-titanium endodontic files utilised with pecking motion technique

The purpose of the study is to evaluate the influence of the pecking motion (reciprocal axial motion) surgical technique on the durability behaviour of the Nickel-Titanium endodontic files using Finite Element Analysis (FEA). A commonly used endodontic file, ProTaper Universal F2, is selected for the study. Root canal treatment procedure is simulated on a test-bench (simulated root canal) proposed by G. Gambarini for cyclic fatigue loading of endodontic files with and without the pecking motion via FEA. The hysteresis energy density is used as evaluation criteria for low cycle fatigue life estimation of Shape Memory Alloy files. In an additional study, the root canal treatment procedure is also simulated for an FEA model of a molar tooth with significant root canal curvature to understand the influence of the realistic curvature of a root canal on the fatigue behaviour of endodontic files. For the simulated root canal, analysis accurately predicts the endodontic file's failure location, and fatigue life estimation based on the hysteresis energy density is shown to increase significantly with the introduction of the pecking motion, an observation confirmed by reported experimental results. Molar tooth simulations reveal greater file fatigue resistance than in simulated root canals, confirming the pecking motion's efficacy in enhancing file durability, even in real root canal conditions. Simulations indicate that the pecking motion technique increases the fatigue life of endodontic files for simulated as well as real root canals and the hysteresis energy is confirmed as an acceptable parameter to quantify fatigue life of Nickel-Titanium endodontic files.

The Use and Reprocessing of Endodontic Files in Saudi Arabia: A Cross-Sectional Study

Objectives This study aimed to assess the awareness, implementation, and compliance with the infection control policy recommended by the Saudi Ministry of Health (MOH) for the use and reprocessing of endodontic files and to examine the association between compliance and gender, experience, clinical ranks, and workplace sector. Methods This was a cross-sectional study conducted using a validated self-administered electronic questionnaire created and distributed to dentists who perform endodontic treatment in Saudi Arabia. Data were collected between June and July 2023. Descriptive statistics were reported as counts and percentages. Comparisons among the demographic groups were done using the Kruskal-Wallis and Mann-Whitney tests. Results A total of 402 dentists completed the survey. The results showed that 76.1% (n=306) of respondents claimed that they were aware of the infection control policy recommended by the Saudi MOH for the use and reprocessing of endodontic files in dental clinics. Only 13.2% (n=53) of dentists used single-use endodontic files, and 36.6% (n=147) did not use an endodontic box in their dental clinics. The most commonly reported method of tracing the number of uses of endodontic files was to write the ID of the patient or the number of uses on the sterilization pouch as reported by 37.6% of participants (n=151). The average compliance score percentage was 63.5 ± 16.7. Most of the respondents showed moderate to high levels of compliance (51.7% (n=208) and 42.0% (n=169) of dentists, respectively). Dentists with less than 5 years of experience showed significantly less compliance than dentists with more than 10 years of experience (p = 0.005). Gender, clinical rank, and workplace sector were not significantly associated with the extent of adhering to the evaluated infection control policy. Conclusions Our findings indicate a relatively high level of compliance with the Saudi MOH policy of using and reprocessing endodontic files. However, critical measures such as the single-use of endodontic files, sterilizing new endodontic files, and using the sterilized endodontic box for each patient need improvement. Hence, this study recommends enhancing awareness through continuous education and training.

Effect of Different Irrigant Activation Techniques on the Penetration of Calcium Hydroxide, an Intracanal Medicament: An In Vitro Study

Background and objective The main goal of root canal treatment is to eliminate microorganisms from the canal and to prevent re-infection. To achieve these goals, instrumentation must be combined with adequate irrigation and the placement of intracanal medicament. This study aims to compare the effect of different irrigation activation techniques, i.e., passive ultrasonic irrigation (PUI), EndoActivator (EA), and conventional needle irrigation on the penetration of calcium hydroxide (CH), an intracanal medicament into dentinal tubules. Methodology A total of 60 single-rooted extracted human teeth were selected, which were de-coronated to standardize the root length of 12 mm. An access cavity was prepared, and biomechanical preparation was done. The samples were randomly assigned to three experimental groups: Group I received conventional needle irrigation, Group II underwent EA irrigation, and Group III was subjected to PUI. All the samples were filled with CH paste mixed with Rhodamine B dye, and the orifice openings were sealed with Cavit. The samples were stored in an incubator for 24 hours and were subsequently sectioned horizontally at the coronal, middle, and apical thirds using a hard tissue microtome. These were observed under a confocal laser scanning microscope to evaluate the depth of medicament penetration. Statistical analysis was performed using IBM SPSS Statistics for Windows, Version 25.0 (IBM Corp., Armonk, NY). The Shapiro-Wilk test was employed to assess normality, while ANOVA and Tukey's post hoc analysis were utilized to determine significance. Results It was observed that the depth of penetration of CH into dentinal tubules was highest in Group III (PUI), followed by Group II (EA irrigation), with the least penetration observed in Group I (conventional needle irrigation). All the groups showed maximum penetration at the coronal third followed by the middle and apical third. Conclusions Passive ultrasonic irrigant activation resulted in more penetration of CH into the dentinal tubules followed by EA irrigant activation.

Prognostic Health Management Using IR Thermography: The Case of a Digital Twin of a NiTi Endodontic File

Prognostic and health management technologies are increasingly important in many fields where reducing maintenance costs is critical. Non-destructive testing techniques and the Internet of Things (IoT) can help create accurate, two-sided digital models of specific monitored objects, enabling predictive analysis and avoiding risky situations. This study focuses on a particular application: monitoring an endodontic file during operation to develop a strategy to prevent breakage. To this end, the authors propose an innovative, non-invasive technique for early fault detection based on digital twins and infrared thermography measurements. They developed a digital twin of a NiTi alloy endodontic file that receives measurement data from the real world and generates the expected thermal map of the object under working conditions. By comparing this virtual image with the real one acquired by an IR camera, the authors were able to identify an anomalous trend and avoid breakage. The technique was calibrated and validated using both a professional IR camera and an innovative low-cost IR scanner previously developed by the authors. By using both devices, they could identify a critical condition at least 11 s before the file broke.

Force and vibration analysis in biomechanical preparation of root canals using reciprocating endodontic file system: In vitro study

The shaping and cleaning of the root canal are very important in root canal treatment. The excessive force and vibration during biomechanical preparation of the root canal may result in failure of the endodontic file. In this study, force and vibration analysis was carried out during root canal preparation. The samples of human extracted (premolar) teeth were provided by the College of Dental Science and Hospital. Endodontic instruments for reciprocating motion, such as the WaveOne Gold file system, had been used for root canal preparation. Force and vibration signals were recorded by dynamometer and accelerometer, respectively. The acquired signals were denoised using the db4 (SWT denoising 1-D) wavelet. Four levels of decomposition were carried out for each signal. The signal denoising technique was used to remove unwanted noise from the acquired signal. FESEM analysis was used to visualize the levels of severity of endodontic files during the cleaning and shaping of the root canal. In most of the cases, the failure occurred due to the improper use of the root canal instrumentation. The optimum amount of force was used to avoid the file failure and provided the proper instrumentation. The curve fitting regression model was used to find the interdependency between force and vibration.

Comparison of Accuracy of Calibration Ring Placement on 4 Different Endodontic Files

INTRODUCTION

The purpose of the current study was to evaluate the accuracy and consistency of the placement of calibration rings on 4 file types: K3 (SybronEndo, Orange, CA), Vortex Blue (Tulsa Dentsply, Tulsa, OK), Kontrol Flex (Brasseler USA, Savannah, GA), and Lexicon (Tulsa Dentsply, Tulsa, OK).

METHODS

Forty endodontic files, 10 of each type, were measured using a measuring microscope (Model W122; Gaertner Scientific Corp, Skokie, IL). Measurements were made from the file tip to the leading edge of 2 calibration rings and to the handle of each file. Each file measurement was performed 3 times by the same operator to ensure internal validity, and the 3 measurements were used to generate a mean for each file measurement.

RESULTS

Based on a 1-factor analysis of variance and Tukey post hoc test (α = 0.05), K3 files displayed significantly greater accuracy and consistency in calibration ring and handle position. In contrast, Vortex Blue files were the least accurate, whereas both Kontrol Flex and Lexicon files were marked with similar precision.

CONCLUSIONS

Calibration rings have been used by some operators to measure files during canal instrumentation. This study showed there was variation in placement of calibration rings and handles. Reliance on calibration rings and file handles as the sole means of measuring endodontic files may lead to inaccuracy in canal instrumentation.

The permanent deformation of the self-adjusting files when used in canals of extracted teeth

AIM

To examine the permanent deformation of self-adjusting files (SAF) when used by endodontists with no previous experience with this system.

METHODOLOGY

The canals of extracted human molars were initially prepared with glide path up to size 20 K-file. The operators were first instructed on the use of the SAF in simulated canals in plastic blocks then applied the SAF in natural root canals of extracted teeth. Every 4 min, each file was withdrawn from the canal and inspected for integrity. If intact, it was used in another canal for an additional 4 min and checked again. This was repeated until all 19 SAF files were deformed. The files were collected for inspection at ×50 magnification. All teeth were then examined radiographically for the presence of any metal fragments in the root canals. Permanent deformation was categorized according to the type and location occured. Three types were defined as follows: (i) detachment of one component of the file at one end while the component is retained (ii) detachment of a component at both ends and the component missing and (iii) permanent twisting of the component. Recordings were made and statistically analysed using McNemar's test.

RESULTS

Mechanical failures on the 5-arch-side of SAF (odd side) were significantly more frequent in comparison with the even side (P = 0.039). Similarly, mechanical failures in arches on the odd side were also significantly more frequent compared with the even ones (P = 0.012) Longitudinal beams fractured significantly less often compared with arcs or struts (P < 0.001). In no case did complete file fracture occur, nor were metal fragments retained in the root canal.

CONCLUSIONS

Deformation of SAF files occurred mainly as detachment of one of the arches or struts at connection points on the odd side of the file. In no case did its mechanical failure result in metal fragment retention in the root canal.