Torsional, Static and Dynamic Cyclic Fatigue Resistance of Reciprocating and Continuous Rotating NiTi Instruments

Comparative Analysis of NiTi Instruments with Different Alloy Treatments

This study aims to compare the cyclic fatigue resistance of nickel-titanium (NiTi) endodontic instruments, focusing on the impact of various alloy treatments and manufacturing processes across different generations of these instruments; Twenty instrumentation systems from different generations, comprising both continuous and reciprocating motion designs, were tested. Four hundred instruments underwent cyclic fatigue testing using an INSTRON machine, with the time and number of cycles to fracture (NCF) recorded for each instrument. Statistical analyses were performed to compare the fatigue resistance between systems, generations, and motion types; Instruments treated with advanced thermal processing, such as Excalibur, Reciproc Blue, and TruNatomy, demonstrated superior resistance to fracture, whereas systems like Protaper Universal, K3XF, and 2Shape showed the lowest resistance. Reciprocating instruments generally exhibited higher cyclic fatigue resistance than continuously rotating instruments; Technological advancements in NiTi instrument design, especially the implementation of heat-treated alloys, have improved cyclic fatigue resistance, enhancing the safety and efficiency of endodontic treatments. Reciprocating systems, in particular, exhibit superior fracture resistance, suggesting their greater utility in challenging clinical conditions.

Evaluation of Cyclic Fatigue Resistance of Novel Replica-Like Instruments in Static Test Model

Introduction

The aim of our study is to comparatively analyze the canal cyclic fatigue resistance of widely used rotary file systems, including EndoArt Touch Gold (ETG), Perfect MTF Plus Gold (PPG), Fanta V-Taper Gold (FVG), and ProTaper Next (PTN).

Methods

Stainless steel canals with a 60° angle and a 3-mm curvature radius were specially prepared. The canals were shaped with each rotary file system and tested for resistance using a cyclic fatigue testing apparatus. The number of fracture cycles (NFC; K file tip separation) was measured. Data were analysed by one-way ANOVA and post hoc LSD tests.

Results

PTN and PPG rotary file systems exhibited the highest NFC. The NFC value for PTN was 589 ± 63, and for PPG, it was 507 ± 51.

Conclusion

The results of this study demonstrate that rotary file systems such as PTN and PPG exhibit higher cyclic fatigue resistance. ETG and FVG rotary file systems also possess generally acceptable cyclic fatigue resistance levels.

The Role of Pecking Motion Depths in Dynamic Cyclic Fatigue Resistance: In Vitro Study

OBJECTIVE

This is the first study evaluating the impact of different pecking motion depths on dynamic cyclic fatigue resistance of different endodontic instruments.

METHODS

Four nickel-titanium systems (Hyflex EDM OneFile 25/. ∼; Rotate 25/0.6; Mtwo 25/0.6; Reciproc Blue R25) were tested. Forty instruments from each group were subjected to 4 different pecking movements to evaluate their cyclic fatigue resistance. The distances for the pecking motion were 3-mm forward and backward, 1-mm (3-mm forward and 2-mm backward), 2-mm (4-mm forward and 2-mm backward), and 3-mm (5-mm forward and 2-mm backward). Speeds were 100 and 200 mm/min for the descending and ascending motion, respectively. The times to fracture (TtF) in seconds were recorded for each instrument. Data were statistically analysed by using 2-way ANOVA and Bonferroni multiple comparison post hoc test (P < .05).

RESULTS

All instruments had a significant increase in cyclic fatigue resistance during the forward dynamic motion compared with the axial continuous. Overall, the heat-treated instruments reported higher fatigue strength than the untreated files (P < .05). Reciproc Blue and Hyflex EDM showed higher TtF in the forward movements of 1-/2-mm and 2-mm (P < .05), respectively while Mtwo 25.06 and Rotate 25.06 in the forward movement of 3-mm (P < .05).

CONCLUSIONS

Within the limits of this in vitro study, the pecking motion depths had varying impacts on the cyclic fatigue resistance of instruments. Reciproc Blue and Hyflex EDM performed significantly better with pecking motions of 1-and 2-mm. Improving endodontic instrument durability through specific pecking depths has the potential for improving clinical performance and reducing instrument failures.

Effect of Movement Kinematics and Heat-Treated Alloys on the Apical Extrusion of Debris: An In Vitro Study

BACKGROUND

Apically extruded debris can be affected by some features of the file systems such as kinematics or metallurgic properties.

AIMS

This in vitro study aimed to evaluate the effect of movement kinematics (reciprocation or rotation) and heat-treated alloys (C.Wire) on the amount of debris extrusion.

METHODS

Seventy-two mesiobuccal root canals were assigned into three experimental groups related to the single-file system used (n = 24): two rotational; One Shape (Conventional Ni-Ti), One Curve (C.Wire), and one reciprocating; and One Reci (C.Wire). The file systems were used according to the advisable speed and torque according to the manufacturers' suggestion. The weight of debris was calculated by subtracting the preweights from postweights of Eppendorf tubes. Kruskall-Wallis and Mann-Whitney U tests were used to analyze the data (P = 0.05).

RESULTS

One Shape produced the greatest amount of extruded debris compared with One Curve (P < 0.001) and One Reci (P < 0.001), respectively. No statistical difference was found between One Curve and One Reci concerning amount of apical debris extrusion (P = 0.489).

CONCLUSION

Metallurgical properties of files may affect apical debris extrusion. Alloy type is an important factor in the amount of debris extrusion. File kinematics does not affect apical debris extrusion.

Impact of pecking amplitude on cyclic fatigue of new nickel-titanium files

OBJECTIVES

The aim of this study is to determine the cyclic fatigue resistance of Mtwo Minimal in static and dynamic tests, with different amplitudes of pecking movements, at intracanal temperature.

MATERIALS AND METHODS

Two hundred new 25-mm Mtwo Minimal rotary files (#10/0.035, #17.5/0.045, #25/0.05, #40/0.03, #45/0.03) were tested in static and dynamic cyclic fatigue tests at 35°C (±1°C). An artificial stainless-steel canal was used. In the dynamic mode, axial movements were set at 1 and 3 mm. The number of cycles to fracture (NCF) was recorded and statistically analyzed by one-way analysis of variance (p < 0.05).

RESULTS

The 3-mm dynamic test showed significantly increased NCF than the other tests for the #10/0.035, #17.5/0.045, and #25/0.05 files (p < 0.05). The #40/0.03 and #45/0.03 files showed no significant differences in all the tests (p > 0.05).

CONCLUSION

Mtwo Minimal showed higher cyclic fatigue resistance in the dynamic test than the static test, except for the larger instruments. The 3-mm pecking amplitude increased the cyclic fatigue resistance of the smaller instruments.

Upper First and Second Molar Pulp Chamber Endodontic Anatomy Evaluation According to a Recent Classification: A Cone Beam Computed Tomography Study

(1) The possibility of knowing information about the anatomy in advance, in particular the arrangement of the endodontic system, is crucial for successful treatment and for avoiding complications during endodontic therapy; the aim was to find a correlation between a minimally invasive and less stressful endodontic access on Ni-Ti rotary instruments, but which allows correct vision and identification of anatomical reference points, simplifying the typologies based on the shape of the pulp chamber in coronal three-dimensional exam views. (2) Based on the inclusion criteria, 104 maxillary molars (52 maxillary first molars and 52 maxillary second molars) were included in the study after 26 Cone Beam Computed Tomography (CBCT) acquisitions (from 15 males and 11 females). And linear measurements were taken with the CBCT-dedicated software for subsequent analysis. (3) The results of the present study show data similar to those already published about this topic. Pawar and Singh's simplified classification actually seems to offer a schematic way of classification that includes almost all of the cases that have been analyzed. (4) The use of a diagnostic examination with a wide Field of View (FOV) and low radiation dose represents an exam capable of obtaining a lot of clinical information for endodontic treatment. Nevertheless, the endodontic anatomy of the upper second molar represents a major challenge for the clinician due to its complexity both in canal shape and in ramification.

Comparative Evaluation of the Canal Shaping Ability, Pericervical Dentin Preservation, and Smear Layer Removal of TruNatomy, WaveOne Gold, and ProTaper Ultimate-An Ex Vivo Study in Human Teeth

INTRODUCTION

Innovative file systems have been recently introduced, claiming improved effectiveness and superior ability to preserve the tooth structure, still allowing an efficient preparation and disinfection up to the apical region. Regardless, few data are available on the comparative effectiveness of the most recently developed systems. Thus, this ex vivo study aimed to comparatively evaluate, for the first time, the functionality of WaveOne Gold (WOG), TruNatomy (TN), and ProTaper Ultimate (PU) file systems regarding canal shaping, dentin preservation, and smear layer removal ability.

METHODS

Human maxillary incisors were randomly divided for instrumentation with one of the assayed systems. Canal shaping ability and pericervical dentin preservation were characterized through microtomographic evaluation and morphometric assessment (n = 15). Smear layer removal ability was evaluated by scanning electron microscopy (SEM) (n = 6).

RESULTS

TN and PU presented the lowest canal volume variation upon instrumentation, found to be significantly lower than that attained with WOG (P < .05). Pericervical dentin was reduced in all groups upon instrumentation, with TN evidencing the highest preservation, quantitatively similar to PU, and significantly higher than that attained with WOG (P < .05). SEM imaging revealed the presence of scattered remnants of the smear layer and partially opened dentinal tubules at the apical portion, with no significant differences between systems.

CONCLUSIONS

TN and PU allowed for the highest tissue preservation, reporting the lowest volume variation and the highest preservation of the pericervical dentin. None of the assessed systems provided a complete removal of the smear layer in the apical region.

Phase transformation and mechanical properties of heat-treated nickel-titanium rotary endodontic instruments at room and body temperatures

BACKGROUND

The aim of this study was to evaluate the phase composition, phase transformation temperatures, bending property, and cyclic fatigue resistance of different heat-treated nickel-titanium (NiTi) rotary instruments with the same tip diameter and taper at room (RT; 25 ± 1 °C) and body (BT; 37 ± 1 °C) temperatures.

METHODS

Five heat-treated NiTi rotary instruments, HyFlex EDM (EDM), HyFlex CM (CM), Vortex Blue (VB), RE file CT (RE) and JIZAI, and a non-heat-treated NiTi rotary instrument (Mtwo) with a size 40, 0.04 taper were investigated. Temperature-dependent phase transformation was examined with differential scanning calorimetry (DSC). The bending loads of the instruments at RT and BT were evaluated using a cantilever-bending test. Cyclic fatigue resistance at RT and BT was measured using a dynamic test, during which the instruments were rotated in combination with a 2-mm back-and-forth motion in an artificial curved canal, and the number of cycles to failure (NCF) was determined. The results were analyzed using two-way repeated measures analysis of variance, a simple main effect test, and the Bonferroni test (α = 0.05).

RESULTS

DSC results indicated that EDM and Mtwo were primarily composed of martensite/R-phase and austenite, respectively, while the other heat-treated instruments were composed of a mix of martensite/R-phase and austenite at the tested temperatures. Regardless of the temperature setting, the bending loads of heat-treated instruments were significantly lower than those of Mtwo (p < 0.05). EDM showed the lowest bending loads and highest NCF at both temperatures (p < 0.05). CM, VB, and JIZAI showed significantly higher bending loads at BT than at RT (p < 0.05). The NCF of all the heat-treated instruments, except VB, was lower at BT than at RT (p < 0.05). At BT, the NCF of CM, VB, RE, and JIZAI were not significantly higher than that of Mtwo (p > 0.05).

CONCLUSIONS

Heat-treated NiTi instruments exhibited lower bending loads and higher NCF values than Mtwo. However, this tendency was less pronounced at BT than at RT, especially in the NCF values of instruments with a mixture of martensite/R-phase and austenite phases at the tested temperatures.

Comparison of the Effects of WaveOne Gold, TruNatomy, and Conventional Hand Files on Remaining Dentin Volume in the Coronal Part of the Root and Preparation Efficiency in Mandibular Molars

INTRODUCTION

The use of file systems that work with different principles in root canal treatment is becoming widespread. The aim of this study was to evaluate the remaining dentine volume in the coronal region of the root and preparation efficiency after the use of conventional hand files, WaveOne Gold, which works with reciprocating motion, and TruNatomy, which works with rotational motion, in the root canal treatment of mandibular molar teeth.

METHODS

All canals of permanent mandibular molars (n = 36) were used. Root canals in each group (n = 12) were prepared with conventional hand files, WaveOne Gold, and TruNatomy. The three-dimensional images were evaluated for remaining dentine volume in the coronal two-millimeter region of the root and change in volume of the entire root canal space.

RESULTS

There was no statistically significant difference between the groups in terms of mean differences pre- and post-preparation (P >.05). The mean differences after preparation were observed the most in the WaveOne Gold group and the least in the TruNatomy group in the coronal two-millimeter region of the root and entire canal volume, but the differences were not significant (P>.05,P>.05, respectively).

CONCLUSIONS

Conventional hand files, WaveOne Gold working with reciprocating motion, and TruNatomy working with rotational motion, which are the file systems used in the study, are not superior to each other in terms of remaining dentin volume in the coronal two-millimeter region of the root and preparation efficiency in the entire root canal space in mandibular molars.

A review of the latest developments in rotary NiTi technology and root canal preparation

The introduction of nickel-titanium (NiTi) mechanical instruments dramatically changed clinical endodontics over the last few decades. Before NiTi, it was necessary to use more instruments to create an ideal root canal shape, and many approaches, sequences and techniques were developed over the years. Recently, NiTi endodontic instruments have undergone a series of changes brought about by modifications in design, surface treatments, and thermal treatments to improve their root canal preparation outcomes and reduce associated canal preparation risks during root canal treatment. Heat treatment is one of the most fundamental approaches to improving the fatigue resistance and flexibility of NiTi endodontic instruments. In addition, new kinematics have been developed to offer greater safety and efficiency. This narrative review describes the general properties and manufacturing of NiTi instruments, and the mechanical system evolution of NiTi instruments.

Effect of glide path instruments in cyclic fatigue resistance of reciprocating instruments after three uses

The present study aims to evaluate the effect of different glide path instruments on the cyclic fatigue resistance of reciprocating endodontic instruments after three uses in mandibular molars. Eighteen Wave One Gold Primary reciprocating instruments were selected and randomly divided into three groups according to the glide path instrument: G1 - manual file K #15, G2 - Wave One Glider reciprocating instrument, and G3 (control group) - glide path was not performed. The reciprocating instruments were tested on mandibular molars and subdivided into three other groups: a new instrument, an instrument with a previous single-use, and an instrument with two previous uses. After the endodontic instrumentation, the instruments were subjected to the cyclic fatigue resistance test using an appropriate tool. The data were submitted to the Shapiro-Wilk test, and subsequently the Kruskal-Wallis test with a significance level of 5%. The results showed no statistical difference between the groups. Thus, it was concluded that the creation of a glide path did not affect the cyclic fatigue resistance of the reciprocating instrument. In addition, the reuse of final preparation instruments up to two times proved to be safe since no fractures were observed in the tested instruments.

Special Issue "Recent Advances in Biomaterials and Dental Disease" Part I

Oral cavities provide an entry point for food and nutrients [...].

Physicochemical and Mechanical Properties of Premixed Calcium Silicate and Resin Sealers

The aim of the present in vitro study was to evaluate specific mechanical and physicochemical properties of two calcium silicate based sealers, (AH Plus Bioceramic “AHPB”; Well-Root ST “WRST”), and a conventional resin sealer (AH Plus “AHP”). These aims were accomplished by assessing the porosity, pH, compression strength, roughness, wettability and cell attachment of the tested materials. The results were compared statistically using the one-way ANOVA test. Higher pH values were obtained in both AHPB and WRST compared to AHP at 3, 24 and 72 h (p < 0.05). A greater level of porosity and wettability was detected for both AHPB and WRST compared to the resin sealer AHP (p < 0.05). Evident cell growth characterized by elongated morphology was observed on the surface of AHPB and WRST, while only a thin layer of cells was seen on the surface of AHP. A significant lower compression strength and modulus were obtained in the specimens created using AHPB compared to those made with AHP and WRST (p < 0.05). The removal of calcium silicates may be quite tricky during endodontic retreatment. In conclusion, considering the limitations of the present in vitro study, both calcium silicate sealers demonstrated good physicochemical properties. However, the lower compression strength and modulus of AHPB may facilitate its removal and make the retreatment procedures considerably easier.

Update in the Diagnosis and Treatment of Root Canal Therapy in Temporary Dentition through Different Rotatory Systems: A Systematic Review

The need to perform fast, effective and efficient pulpectomies has led to the development of numerous valid rotary systems. Its technical features allow the clinician to obtain good results in less working time. The objective of this study is to compare the characteristics of the different current rotary systems to favor a correct diagnosis and subsequent treatment. A systematic review of the literature has been carried out in accordance with the PRISMA recommendations. A search was carried out in PubMed, Embase Scopus, Cochrane and Web of Science databases, and was completed with a manual search. The following variables were extracted from the selected studies: author, year, sample, rotary systems used (length, diameter, taper, speed), obturation material and irrigant. From the initial electronic search of the five databases, 315 articles were identified. Once the duplicate articles were eliminated, a total of 233 remained. After reading both title and abstract, 200 articles were eliminated, leaving 33. On account of reading the full text, 22 were eliminated for not answering the research question or the inclusion criteria, leaving a total of 11 articles for the systematic review. Rotary systems which are able to adapt to the root anatomy of primary teeth and allow rapid and simple instrumentation, without producing excessive extrusion of debris at the root apex, will be the ones that provide the best results to the pediatric dentist during the performance of pulp treatment in primary teeth. Clinical success will only be achieved through proper prior diagnosis.