The "balanced force" concept for instrumentation of curved canals

Shaping ability of NiTi reciprocating file systems R-motion and waveOne gold in mesial canals of mandibular molars; micro CT study

The preservation of the original configurations of root canals during endodontic preparation is crucial for treatment success. Nickel-titanium (NiTi) rotary systems have been refined to optimize canal shaping while minimizing iatrogenic errors. This study aimed to evaluate and compare the shaping efficacy of the novel R-Motion (RM) and the established WaveOne Gold (WG) systems using micro-computed tomography (micro-CT). Twenty-four mesial canals of 12 double-rooted extracted mandibular first molars were randomly assigned to either the RM or WG groups, with the mesiobuccal (MB) and mesiolingual (ML) canals allocated accordingly. Root canals were prepared following the manufacturer's protocols. In the RM group, crown-down technique up to a 25/0.06 taper was employed. For the WG group, the preparation was completed with a WG primary file (25/0.07 taper). Specimens were scanned using micro-CT scans before and after instrumentation to establish baseline and post-instrumentation datasets. The following parameters were evaluated, and values were calculated to compare the shaping ability of the two files: percentage of untouched canal walls, changes in surface area, canal volume, dentin thickness, canal angulation, structure model index, canal transportation, and centering ability ratio. Data were analyzed using IBM SPSS Statistics for Windows, Version 23.0 (IBM Corp., Armonk, NY), with a statistical significance set at P ≤ 0.05. Micro-CT analysis demonstrated comparable untouched canal surface areas and changes in surface area and volume between both RM and WG systems. Both systems effectively straightened canal curvature without significant differences in canal angulation. The RM files exhibited a statistically lower reduction in dentin thickness, indicating better preservation of structural integrity. Both RM and WG files displayed similar effective shaping abilities. However, RM caused less dentin removal and canal transportation. Thus, RM is recommended for its ability to balance effective canal shaping with structural preservation in a conservative manner.

Comparative Evaluation of Periapical Expulsion Using Manual, Rotary, and Reciprocating Instrumentation With EndoVac Irrigation: An In Vitro Study

Background The present study aimed to assess the efficacy of a heat-treated, FlexiCON nickel-titanium (Ni-Ti) rotary instrumentation system and compare it with existing commonly used instrumentation systems (hand file, ProTaper Universal, and WaveOne) using the EndoVac irrigation system. Methodology A total of 210 single-rooted, human permanent anterior teeth were equally divided into four groups of 50 teeth each (Group I for step-back, group II for ProTaper rotary, Group III for WaveOne reciprocating, and Group IV for FlexiCON rotary instrumentation system), and 10 teeth were used as controls. Canals were irrigated with EndoVac irrigation in each group. Extruded debris, irrigating solution, and Enterococcus faecalis were quantified and statistically analyzed. Results Group IV exhibited the least amount of debris, irrigating solution, and microorganisms than other groups, while Group I presented the most. FlexiCON with EndoVac irrigation demonstrated the least amount of microbe extrusion (14 colony-forming units (CFUs)) among the four instrumentation systems, whereas step-back instrumentation with EndoVac irrigation demonstrated the most (39 CFUs). The control group showed no debris, irrigating solution, or microorganisms. Conclusions FlexiCON Ni-Ti rotary instrumentation showed the least debris, irrigating solution, and bacterial extrusion compared with hand, ProTaper Universal, and WaveOne reciprocating instrumentation systems when EndoVac irrigation methods were used.

Evaluation of Apical Extrusion of Debris with Tactile Controlled Activation Technique Using Controlled Memory Files in Curved Root Canals: An in vitro Study

Background and Objectives

The purpose of the study was to quantify the amount of debris that was extruded apically when single-length and tactile controlled activation (TCA) techniques were used to instrument curved canals.

Materials and Methods

A total of forty mandibular first molars having curved mesial roots of standardized length were subjected to instrumentation, utilizing both single-length and TCA techniques. Pre-weighed Eppendorf tubes were used to collect the extruded debris. The tubes underwent weighing to acquire the final weight of the dry debris. The initial weight was subtracted from the final weight to determine the weight of the extruded debris. The Shapiro-Wilk test was utilized to evaluate the data distribution. The Mann-Whitney U test was utilized to analyze continuous variables with a significance level of P ≤ 0.05.

Results

Either of the techniques tested was associated with apical debris extrusion, but the TCA technique in a crown-down approach resulted in considerably less debris extrusion compared to the single-length technique.

Conclusion

The TCA technique in the crown-down approach demonstrated the least debris extrusion, suggesting the importance of selecting the appropriate technique in curved canal management.

Glide Path in Endodontics: A Literature Review of Current Knowledge

The introduction of nickel-titanium rotary instruments revolutionized shaping procedures as they were able to produce a well-tapered preparation while reducing operator fatigue. The major drawback of rotary instruments was the high risk of fracture due to bending and torsional stress. Thus, the creation of a glide path has been advocated and recommended by most rotary instrument manufacturers. The aim of the present review is to summarize existing knowledge on glide path preparation and identify areas where further research is needed. The primary goal is to provide a comprehensive overview of the techniques and instruments used in glide path preparation, highlighting their advantages and limitations. The secondary goal is to explore the effect of glide path creation on the overall success of endodontic treatment, particularly in terms of reducing procedural errors and improving treatment outcomes. An online search on PubMed, ScienceDirect, UCLA, and Scopus databases was conducted, and 116 articles were identified. Eligible articles were divided into nine categories based on what they researched and compared. The categories included centering ability and/or root canal transportation, cyclic fatigue resistance, glide path and shaping time, tortional stress resistance, apical extrusion of debris and/or bacteria, defects in dentine walls, file separation, postoperative pain assessment, and scouting ability and performance. Establishing a glide path reduces root canal transportation, especially with rotary methods. Reciprocating and heat-treated files offer higher fatigue resistance and shorter preparation time. Instruments with shorter pitch lengths have greater torsional strength. Preparation and coronal preflaring reduce apical debris and bacteria. Glide paths do not affect dentine microcracks, file separation, or defects but reduce immediate postoperative pain and improve cutting ability. Randomized trials are needed to assess their impact on treatment outcomes.

The Impact of Minimum Invasive Access Cavity Design on the Quality of Instrumentation of Root Canals of Maxillary Molars Using Cone-Beam Computed Tomography: An in Vitro Study

Aim Minimally invasive dentistry has been facilitated by advances in instruments and restorative materials. This study aims to compare the change in the shaping ability of the RECIPROC blue rotary system in both traditional and conservative access cavities, using cone beam computed tomography (CBCT). Material and methods Sixty root canals of 20 artificial maxillary molars were assigned into two groups (n=30 root canals) according to the access cavity design used: Group I: traditional access cavity (TAC) and Group II: conservative access cavity (CAC). CBCT scans of samples were made before and after root canal preparation using the RECIPROC blue rotary system. The shaping parameters are evaluated in root canal transportation and the centering ability. Three CBCT sections per tooth were analyzed at 3, 6, and 9 mm from the apex to assess the canal transportation and centering ability at three levels, apical, middle, and coronal thirds. Data were analyzed using the GraphPad Prism (GraphPad Software, San Diego, CA). Results The results of this study showed a significant difference in transportation within the coronal and middle thirds. However, in apical thirds, there were no significant differences. Both groups observed a significant difference in the centering ability in the coronal third. Conclusion Within the limitations of this study, CAC can be recommended with caution as an alternative access to TAC.

Comparative Evaluation of Effectiveness of Rotary and Hand File Systems in Terms of Quality of Obturation and Instrumentation Time among Primary Teeth: A Systematic Review and Meta-analysis of Randomized Controlled Trials

Aim

This systematic review and meta-analysis aimed to answer the following focused question: Are rotary file systems more effective than hand file systems in terms of the quality of obturation and instrumentation time among primary teeth?

Study eligibility criteria participants and interventions

The inclusion criteria comprised studies that compared the effect on quality of obturation and instrumentation time among primary teeth after using rotary and hand file systems for biomechanical preparation of the root canals.

Materials and methods

This review was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The searched databases included Medline (via PubMed), EBSCO, and Google Scholar. Articles published from January 2000 to December 2021, but only in English, were included.

Results

The search resulted in 8,003 published studies. After the removal of duplicate studies and full-text analysis, 9 studies were selected for systematic review, and 8 were selected for meta-analysis. Overall, the results demonstrated the promising effects of rotary file systems in reducing instrumentation time and improving obturation quality compared to hand files.

Conclusion

Within the limitations of this review, it can be asserted that rotary file systems are superior to hand files in primary teeth for pulpectomy procedures.

Clinical significance

Rotary files, a more recent technique, are more efficient than traditional hand files in lowering the time required for instrumentation. Additionally, they provide superior obturation quality in primary molars, making them particularly beneficial for pediatric patients.

How to cite this article

Gala UP, Kalaskar R, Vinay V, et al. Comparative Evaluation of Effectiveness of Rotary and Hand File Systems in Terms of Quality of Obturation and Instrumentation Time among Primary Teeth: A Systematic Review and Meta-analysis of Randomized Controlled Trials. Int J Clin Pediatr Dent 2024;17(8):962-969.

Comparing Warm and Cold Gutta-Percha Techniques for Root Canal Filling: An In Vitro Study

Background

Gutta-percha is commonly used in endodontic therapy for obturating root canals after cleaning and shaping procedures. Warm and cold gutta-percha techniques are two common methods employed for obturation, each with its own advantages and limitations.

Materials and Methods

Twenty extracted human teeth with single-rooted canals were selected and divided into two groups: warm gutta-percha obturation and cold gutta-percha obturation. In the warm gutta-percha group, gutta-percha was heated to a predetermined temperature using a warm gutta-percha heating device and injected into the root canal using a heated carrier. In the cold gutta-percha group, gutta-percha was applied directly to the root canal without prior heating. Root canal obturation quality was assessed using radiographic imaging to evaluate the presence of voids, completeness of obturation, and adaptation to the canal walls. Micro-computed tomography (micro-CT) analysis was also performed to quantify the volume of obturating material and assess the three-dimensional distribution of gutta-percha within the root canal space.

Results

Both warm and cold gutta-percha techniques demonstrated effective obturation of root canals, with comparable outcomes in terms of void formation, completeness of obturation, and adaptation to canal walls. However, micro-CT analysis revealed differences in the volume and distribution of gutta-percha within the root canal space. Warm gutta-percha obturation exhibited more uniform distribution of gutta-percha material and higher volumetric filling compared to cold gutta-percha obturation. Additionally, the warm gutta-percha technique demonstrated superior flowability and adaptation to irregularities within the root canal system.

Conclusion

In this in vitro study, warm gutta-percha obturation demonstrated advantages over cold gutta-percha obturation in terms of volumetric filling, distribution within the root canal space, and adaptation to canal irregularities.

Expert consensus on difficulty assessment of endodontic therapy

Endodontic diseases are a kind of chronic infectious oral disease. Common endodontic treatment concepts are based on the removal of inflamed or necrotic pulp tissue and the replacement by gutta-percha. However, it is very essential for endodontic treatment to debride the root canal system and prevent the root canal system from bacterial reinfection after root canal therapy (RCT). Recent research, encompassing bacterial etiology and advanced imaging techniques, contributes to our understanding of the root canal system's anatomy intricacies and the technique sensitivity of RCT. Success in RCT hinges on factors like patients, infection severity, root canal anatomy, and treatment techniques. Therefore, improving disease management is a key issue to combat endodontic diseases and cure periapical lesions. The clinical difficulty assessment system of RCT is established based on patient conditions, tooth conditions, root canal configuration, and root canal needing retreatment, and emphasizes pre-treatment risk assessment for optimal outcomes. The findings suggest that the presence of risk factors may correlate with the challenge of achieving the high standard required for RCT. These insights contribute not only to improve education but also aid practitioners in treatment planning and referral decision-making within the field of endodontics.

Microscopic Evaluation of Dentinal Defects after Root Canal Preparation with Different Hand and Nickel-Titanium Files; An In Vitro Study

Background

Effective endodontic instrumentation aims to remove microorganisms, debris, and tissue from the root canal while maintaining dentinal integrity. This study compares dentinal defect incidence following canal preparation with different hand files, nickel-titanium rotary files, and reciprocating files.

Materials and Methods

Eighty single-rooted mandibular premolars with mature apices were collected. Four groups (n = 20) were established based on canal patency establishment, canal preparation technique, irrigation solution, and final irrigation. After root sectioning at 3 mm, 6 mm, and 9 mm from the apex, slices were examined under a stereomicroscope, and dentinal defects were recorded. A second examiner reviewed the images.

Results

The results showed significant difference of P = 0.031 among Hand files vs. Rotary ProTaper files: In Hand files vs. Reciprocating WaveOne files significant difference was P = 0.048, and for rotary ProTaper files vs. Reciprocating WaveOne files: No significant difference (P = 0.643). Dentinal defect counts were similar at 3 mm, 6 mm, and 9 mm. Statistically significant variation was observed between hand files and rotary files, as well as hand files and reciprocating files.

Conclusion

Both rotary and reciprocating files showed a statistically significant increase in dentinal defect incidence compared to hand files. However, clinical implications should be considered cautiously. Instrumentation technique selection should be based on clinical context, operator experience, and patient factors. Further clinical studies are needed for validation.

Accuracy of the KontrolFlex AccuFile when used with the Root ZX electronic apex locator in vitro

The aims of this study were to determine the efficacy of the KontrolFlex™ Accufile™ compared to the READY•STEEL™ Flexofile® using an electronic apex locator and to evaluate the instrument's design via scanning electron microscopy. Actual canal lengths of 30 extracted teeth were determined under magnification. An alginate model was used to determine experimental canal lengths with the Root ZX II apex locator (EAL) and size #10 Accufiles and Flexofiles. Differences between actual lengths and experimental lengths were compared with Student's t test. The average experimental lengths were short of the actual length by -0.10 mm (±0.34) and -0.12 mm (±0.16) for the Accufile and Flexofile, respectively with no statistical difference (p > 0.05). SEM images revealed similar non-cutting Batt tips and a square cross-section for the Accufile and triangular for the Flexofile. Both files provided similarly high levels of reliability when used with the Root ZX II EAL.

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.

Anatomical complexities affecting root canal preparation: a narrative review

A fundamental aspect of the Endodontic field is the knowledge of root canal anatomy. Using a variety of techniques, the internal and external anatomy of teeth have been extensively investigated throughout the past century. Recent improvements in three-dimensional computed tomography have enabled more detailed evaluations of root canal morphology in both clinical and laboratory settings. Essentially, researches have unveiled that the root canal constitutes a complex system, comprising not only the main root canal but also lateral components, including isthmuses, fins, accessory canals and apical ramifications. Undoubtedly, this intricate morphology poses a significant challenge when it comes to the process of shaping, cleaning and disinfecting the root canal system. This article aims to explore the anatomical aspects of the root canal system that impact the chemomechanical procedures.

Effectiveness of conservative instrumentation in root canal disinfection

OBJECTIVES

The impact of conservative instrumentation on the disinfection of root canals with different curvatures has not yet been determined. This ex vivo study aimed to evaluate and compare the effect of conservative instrumentation with TruNatomy (TN) and Rotate and a conventional rotary system, ProTaper Gold (PTG), on root canal disinfection during chemomechanical preparation of straight and curved canals.

MATERIALS AND METHODS

Ninety mandibular molars with straight (n = 45) and curved (n = 45) mesiobuccal root canals were contaminated with polymicrobial clinical samples. Teeth were divided into three subgroups (n = 14) according to the file systems and the curvature. Canals were instrumented with TN, Rotate, and PTG, respectively. Sodium hypochlorite and EDTA were used as irrigants. Intracanal samples were taken before (S1) and after (S2) instrumentation. Six uninfected teeth were used as negative controls. The bacterial reduction between S1 and S2 was measured by ATP assay, flow cytometry, and culture methods. Kruskal-Wallis and ANOVA tests were followed by the Duncan post hoc test (p < 0.05).

RESULTS

Bacterial reduction percentages were similar for the three file systems in straight canals (p > 0.05). However, PTG showed a lower reduction percentage of intact membrane cells in flow cytometry than TN and Rotate (p = 0.036). For the curved canals, no significant differences were obtained (p > 0.05).

CONCLUSION

Conservative instrumentation of straight and curved canals using TN and Rotate files resulted in similar bacterial reduction compared to PTG.

CLINICAL RELEVANCE

The disinfection efficacy of conservative instrumentation is similar to conventional instrumentation in straight and curved root canals.

Comparative Evaluation of Extrusion of Apical Debris in Primary Maxillary Anterior Teeth Using Two Different Rotary Systems and Hand Files: An In Vitro Study

Successful outcome of pulp therapy depends on good chemomechanical preparation of the canals. This is completed with the help of various upcoming rotary and hand files. However, during this preparation, there might be an apical extrusion of the debris which may result in postoperative complications. The aim of this study was to evaluate and compare the number of debris apically extruded during canal preparation using two different pediatric rotary file systems and conventional hand file systems in primary teeth. 60 primary maxillary central incisors that were extracted due to trauma or untreated dental caries with no signs of resorption were taken. Canal preparation was executed using three different file systems: Group A: Group A hand K file system, Group B Kedo S Plus, Group C Kedo SG Blue. For each of these files using the Myers and Montgomery model, the pre- and post-weight of the eppendorf tube was assessed to quantify the number of apical debris. The maximum extrusion of apical debris was noticed with the Hand K-file system. The least debris was noticed in the Kedo S Plus file system. Statistical analysis revealed that there were highly significant differences in apical extrusion and debris when comparing hand files and rotary files and also between the two rotary files used. Apical debris collection is an unavoidable outcome of canal instrumentation. Among the file systems compared, rotary files had lesser extrusion when compared to hand files. Among the rotary files, Kedo S plus showed normal extrusion compared to SG Blue.

Effectiveness of endodontic complexity assessment tool (E-CAT) on the undergraduate students in an endodontic training program and its predictive capability on complications

INTRODUCTION

Dental students face a number of challenges when it comes to performing root canal treatments (RCTs). The Endodontic Complexity Assessment Tool (E-CAT) was developed to assist dental practitioners in assessing the complexity of RCTs before beginning treatment.

MATERIALS AND METHODS

The E-CAT was filled out independently by both the educator and the student. To allow educators to record scores and complexity classes, they transferred their and students' forms to the website https://www.e-cat.uk/. Students began endodontic treatment after learning about the complexity level of the case. The educators were responsible for recording any complications encountered in every case from the outset to 1 month after treatment.

RESULTS

A total of 70 students, 33 in fourth and 37 in fifth-grade, were included in the study. In the cases with higher E-CAT scores, complications such as misdiagnosed, faulty access cavity, furca or coronal third perforation, insufficient root canal instrumentation, working length loss, canal blockage, overpreparation, incomplete root canal filling and overfilling were experienced significantly more often compared to the cases with lower E-CAT scores (p < .05). The number of complications (r = .40, p < .001), treatment sessions (r = .44, p < .001), and teacher support (r = .24, p < .001) positively correlated with E-CAT score (p < .05).

CONCLUSION

The E-CAT is an effective tool for assisting dental students in understanding technical challenges, such as complex root canal anatomy and possible complications during treatment. Educators can also use e-CAT to pre-select clinical cases and standardise student training by offering cases of equal complexity.

Exploring a Paradigm Shift in Primary Teeth Root Canal Preparation: An Ex Vivo Micro-CT Study

Traditional hand instrumentation is a commonly used technique to perform pulpectomy in deciduous teeth by most specialists in pedodontics. Lately, dentists have embraced rotary instrumentation as a safe and effective alternative. This study aimed to compare the efficacy of root canal preparation in extracted primary molars between manual and two rotary file systems using micro-CT. Thirty-six extracted human second primary mandibular molars were divided into three groups according to the instrumentation method: (1) Manually instrumented (MI) group (n = 9) in which the teeth were treated using K-files up to size 30; (2) Kedo-Ssystem (KS) group (n = 9); (3) ProTaper Gold system (PTG) group (n = 10) and control group (n-8). Each tooth was scanned before and after the retrograde root canal preparation. Residual dentin volume was calculated using micro-CT scans to evaluate the technique's efficacy. Additionally, the preparation time and procedural errors were recorded for each tooth preparation. A one-way ANOVA test was carried out to compare the groups' dentin volume and preparation time. The mean preparation time using the manual method (13.14 min) was more than two times longer than that of the rotary techniques (4.62 min and 6.45 min). The manual preparation method using a K-file removed almost half the root canal material when compared with the rotor method (p = 0.025). Conclusion: our results suggest that rotary instrumentation is more efficient for root canal preparation in primary teeth than the traditional manual method. This finding may call for a paradigm shift in current clinical practices, where manual instrumentation is still commonly preferred.

Effect of photon-induced photoacoustic streaming and shock-wave enhanced emission photoacoustic streaming technique on the removal of the smear layer after root canal preparation in curved root canals

Background/purpose

The efficiency of root canal irrigation has an important impact on the prognosis of root canal treatment. Photon-induced photoacoustic streaming (PIPS) and shock wave enhanced emission photoacoustic streaming (SWEEPS) are the special modality of Er: YAG laser, whether can they improve the efficiency of root canal irrigation remains to be studied.

Materials and methods

Fifty human teeth with curved root canals were collected and stored in the thymol solution until used in the study. After traditional endodontic cavities preparation, root canals were prepared to size #35 with a 0.04 taper. The final irrigating techniques were as follows: (I) manual dynamic activation (MDA), (II) ultrasonically activated irrigation (UAI), (III) sonically activated irrigation (SAI), (IV) PIPS, and (V) SWEEPS. Fifty teeth were randomly divided into five groups mentioned above. After root canal preparation, the roots were cleaved longitudinally. The dentine surfaces were photographed from the coronal, middle, and apical third of the root by scanning electron microscopy operated at a low vacuum. Two examiners separately graded each image according to the remained smear layer situations.

Results

PIPS and SWEEPS groups showed fewer smear layers remaining than the others in the middle and the apical third (P < 0.05) of the root canal. In contrast, in the coronal third, five groups showed no significant difference (P > 0.05).

Conclusion

PIPS and SWEEPS showed superior smear layer clearing efficiency than traditional irrigating techniques in curved root canals.

Buckling Susceptibility of a K-File during the Initial Negotiations of Narrow and Curved Canals Using Different Manual Techniques

(1) Background: One possible way to investigate the potential impact or susceptibility of buckling on different manual techniques is to measure compressive loads during canal negotiation. The higher their values, the easier and quicker the critical load level to buckling is reached, leading to possible instrument lateral deformation. The objective of the present study was to investigate the impacts of compressive loads on a small K-file manipulated with different techniques for canal negotiation in simulated narrow and curved canals. (2) Methods: The tooth model selected was a plastic double-curved premolar 23 mm long (DRSK Group AB, Kasernvagen 2, SE-281 35, Hassleholm, Sweden) with an extremely narrow canal lumen to mimic a very difficult anatomical scenario. An experienced endodontist performed the negotiation of 90 of these artificial teeth randomly assigned to 3 different groups of 30 blocks each, respectively, using 3 different techniques: Group A: watch winding/pull (WW) motion; Group B: balanced forces (BF) technique; Group C: envelope of motion (EOM). The measurement system was based on the use of a dynamometer, Instron, Ltd. (model 2525-818 2kN f.s.), linked to a data acquisition unit HBM MGC+ to test all the compression and tensile loads, including all the peaks. (3) Results: All data acquired were processed by the CATMAN AP HBM software. Multiple comparisons for the highest compressive loads estimated the mean difference between WW vs. BF techniques of 3.60 [95% confidence interval (CI): 2.85 to 4.35, p < 0.001], WW vs. EOM of −1.76 (95% CI: −2.11 to 1.40, p < 0.001), and BF vs. EOM −5.36 (95% CI: −6.04 to −4.67, p < 0.001). (4) Conclusions: In conclusion, among the tested manual motions, the BF technique (Group B) was the most susceptible to buckling with the highest compressive load. WW motion (Group A) and EOM (Group C) were less susceptible to buckling than the BF technique. Therefore, a pressure-free manipulation of manual files, such as WW motion or EOM, can help reduce the susceptibility to buckling during the negotiation of narrow-curved canals.

Endodontic Rotary Files, What Should an Endodontist Know?

Clinicians should be aware of all the characteristics and capacities of the instruments that are possible to use when conducting a root canal treatment. The wide variety of nickel–titanium (Ni-Ti) rotary systems on the market and the lack of standardisation of this type of instrument makes the choice in each specific case difficult. Therefore, this review is intended to summarize the characteristics that should be taken into account when choosing one instrument over another. It will be essential to know characteristics, of alloy from which the instrument is made. Moreover, the geometry of the instrument will determine its behaviour, being the mass, the one that marks its resistance to a greater extent. The movement performed by the file is another of the fundamental keys to understand rotary instruments. In conclusion, when performing root canal treatment, the characteristics of the instrument and the tooth must be taken into account, and the operator’s own limitations should be known. This paper provides the key points to keep in mind when making this type of treatment.

A Novel Digital Technique to Analyze the Wear of CM-Wire NiTi Alloy Endodontic Reciprocating Files: An In Vitro Study

The present study seeks to describe a novel digital measurement technique for analyzing the wear volume of controlled memory (CM)-wire NiTi alloy endodontic reciprocating files after clinical use. Material and Methods: Ten CM-wire NiTi endodontic reciprocating files were randomly used in ten first upper molar teeth within four root canals. The CM-wire NiTi alloy endodontic reciprocating files were subjected to preoperative and postoperative micro-computed tomography (micro-CT) scans to obtain accurate digital imaging and communication on medicine (DICOM) digital files, which were segmented using intensity-based thresholding and an exclusive OR (XOR) logical operation (Boolean algebra logical operator) to obtain a mask of the location to localize and quantify the wear volume of the CM-wire NiTi alloy endodontic reciprocating files. Gage repeatability and reproducibility statistical analysis was applied to assess the reproducibility and repeatability of this measurement technique. Results: The analysis showed a repeatability and reproducibility of 0.00% for the digital measurement technique used to analyze the wear volume of CM-wire NiTi alloy endodontic reciprocating files after clinical use. Wear was mostly identified at the tip and cutting edges of the CM-wire NiTi alloy endodontic reciprocating files. Conclusions: This novel digital measurement technique is a repeatable, reproducible, and accurate method of quantifying the wear volume of CM-wire NiTi alloy endodontic reciprocating files after clinical use.

Evolution and development: engine-driven endodontic rotary nickel-titanium instruments

Various engine-driven NiTi endodontic files have been indispensable and efficient tools in cleaning and shaping of root canals for practitioners. In this review, we introduce the relative terms and conceptions of NiTi file, including crystal phase composition, the design of the cutting part, types of separation. This review also analysis the main improvement and evolution of different generations of engine-driven nickel-titanium instruments in the past 20 years in the geometric design, manufacturing surface treatment such as electropolishing, thermal treatment, metallurgy. And the variety of motion modes of NiTi files to improve resistance to torsional failure were also discussed. Continuous advancements by the designers, provide better balance between shaping efficiency and resistance to of NiTi systems. In clinical practice an appropriate system should be selected based on the anatomy of the root canal, instrument characteristics, and operators' experience.

Present Status and Future Directions - Canal Shaping

This narrative review will focus on the evolution, present and future of engine‐driven root canal preparation. Root canal preparation changed drastically when Walia in 1988 introduced the use of nickel‐titanium (NiTi) alloys in Endodontics. In 2013, five generations of NiTi endodontic instruments had been established based on their metallurgical, mechanical properties and design features. Since then, manufacturers have been introducing further major changes in instrument design and characteristics that have not been translated in new recognized generations of instruments. In general, those changes have demonstrated enhanced instrument properties, but it is not clear yet if all those improvements are directly translated to an improvement in clinical success. This narrative review attempts to address the present status of engine‐driven instruments in terms of both evidence from laboratory‐based studies and clinical data, to identify potential further generations of instruments, and last to anticipate future directions for research and development.

Present status and future directions -Management of curved and calcified root canals

Root canal curvature and calcification introduce factors that increase the risk of procedural accidents during root canal treatment. The inability to achieve patency to the apical third, asymmetrical dentine removal leading to transportation, perforation and instrument fracture inside the curved trajectories are some of the procedural problems that might jeopardize the management of intraradicular infection and result in poor treatment outcomes. In fact, curved and constricted canals introduce such complexity that total instrumentation concepts and specially designed instruments have been developed to deal with the challenge. This narrative review seeks to provide and consolidate the principles necessary for understanding the dynamics of curved and constricted canal management and to improve the understanding for future developments in this field.

In Vitro Analysis of the Fatigue Resistance of Four Single File Canal Preparation Instruments

Instrument separation during root canal therapy is inevitable in endodontics with several unfavorable clinical consequences. Therefore, examining the cyclic flexural fatigue resistance of commonly used rotary endodontic files is crucial. This study aimed to determine the cyclic flexural fatigue resistance of four nickel–titanium (NiTi) rotary files used as a single canal preparation technique: WaveOne, Reciproc, Protaper F2, and Unicone medium instruments. According to the manufacturer’s instructions, each file was rotated freely within a 1.3 mm deep and 1.3 mm wide V-shaped groove in a stainless-steel block with a 40° and 5 mm radius of curvature. Cyclic fatigue resistance was compared between the NiTi files by verifying the time needed to crack. The data were analyzed using one-way analysis of variance (ANOVA) followed by Scheffé post hoc with a significant level set at p < 0.05. Our results demonstrated that the WaveOne instrument had the highest cyclic flexural fatigue resistance among the tested groups (p ≤ 0.05), while Unicone had the lowest cyclic flexural fatigue resistance. This study concluded that WaveOne size 25/0.08 could illustrate a superior cyclic flexural fatigue resistance when instrumenting root canals with the lowest possibility to cause instrument separation.

Microtomographic Evaluation of Canal Centralization and Dentine Removal after Canal Preparation with Two Rotary Systems: HyFlex EDM and ProTaper Next

OBJECTIVE

 This study compared the ProTaper Next (PTN; Dentsply Sirona, Tulsa, Oklahoma, United States) and HyFlex EDM (HEDM; Coltene/Whaledent AG, Alstätten, Switzerland) systems using micro-computed tomography (CT).

MATERIALS AND METHODS

 Twenty-one mesial roots classified as Vertucci's type IV from extracted mandibular first molars with curvatures between 20 and 40 degrees were selected. The teeth were scanned using a micro-CT before and after root canal preparation by both systems, applied to the same root, in alternating canals. The following parameters were analyzed: canal centering, apical transportation, root canal diameter/root diameter.

RESULTS

 No statistically significant differences between both systems were observed for any of the assessed morphological parameters (p > 0.05). All canals presented diameter enlargement of more than 40% in relation to root diameter in the cervical and middle segments. No statistically significant difference was noted between the HEDM and PTN groups. The wear percentage for the HEDM group in the cervical and middle thirds were 49.66 ± 8.65 and 46.48 ± 14.29, respectively, and 51.02 ± 11.81 and 45.48 ± 10.79 for the PTN group, respectively.

CONCLUSION

 Both systems displayed similar mandibular molar mesial canals preparation, with no differences noted for any of the assessed parameters. Both groups showed increased canal diameter in the cervical and middle thirds by more than 40%.

Quantitative evaluation of apically extruded debris during biomechanical preparation using hand K-file, protaper next, and waveone – An In Vitro study

Background:

The instrumentation technique which produces least amount of apically extruded debris is desirable to use in biomechanical preparation of root canal.

Aim:

To quantitatively evaluate apically extruded debris during instrumentation with hand K-file, ProTaper Next, and WaveOne.

Materials and Methods:

Forty-five extracted human single-rooted mandibular premolars with straight, single canal and single apical foramen were selected after radiographic evaluation and divided equally into three groups. Cleaning and shaping was done using hand K-files in step-back technique, ProTaper Next, and WaveOne single-file system. Debris extruded apically was collected into Eppendorf tubes and stored in an incubator at 37°C temperature for 5 days for drying. Weight of dry debris was measured using electronic microbalance with an accuracy of 10⁻⁵ g.

Statistical Analysis:

Student's t-test, with P value < 0.05 is statistically significant.

Results:

Statistically significant (P < 0.05) amount of debris was extruded by all three instrumentation systems: hand K-file- 1.9220 mg, ProTaper Next- 1.4940 mg, and WaveOne- 0.9940 mg. Least amount of debris produced by WaveOne was statistically significant (P < 0.05) when compared with the other two systems.

Conclusion:

The WaveOne reciprocating system extruded least amount of debris in comparison to hand K-file and ProTaper Next.

Shaping ability of 2Shape and NeoNiTi rotary instruments in preparation of curved canals using micro-computed tomography

Background

Various systems of nickel-titanium (NiTi) instrument have long been commercially available. However, the preparation of narrow and curved root canals has always been challenging. The purpose of this study was to compare the shaping ability of two NiTi systems (2Shape and NeoNiTi) in severely curved root canals with different morphological patterns using micro-computed tomography (Micro-CT).

Methods

A total of 22 human extracted permanent teeth of mandibular first molars, with the exact mesial angle of curvature of 25 and 35 degrees, according to Schneider’s technique, were distributed randomly into two groups (group I: 2Shape, group II: NeoNiTi) based on the rotary system used (n = 22). The groups were subdivided into two subgroups corresponding to the angle of canal curvature (25° and 35°) (n = 11). Canals were scanned using Micro-CT pre- and post-preparation to assess the volume of dentin removed; canal transportation; and canal centering ratio at 3, 6, and 9 mm from the apex. The Mann–Whitney U test was utilized to determine any significant differences between the two systems. The level of statistical significance was set at p < 0.05.

Results

There was no significant difference between the two groups in volume of dentin removed; canal transportation; and centering ability for 25° and 35° canal curvatures at 3, 6, and 9 mm from the apex (coronal, middle, and apical) thirds (p > 0.05). At the middle third, the NeoNiTi group demonstrated a statistically significant increase in volume of dentin removed for 35° canal curvatures compared to the 2Shape group.

Conclusion

Within the limitation of our in vitro study, 2Shape and NeoNiTi systems with severely curved canals were confirmed to be relatively safe in preparation and to respect original canal anatomy. Nevertheless, NeoNiTi instruments produced more centered preparation and minimal canal deviation compared to the 2Shape system.

Canal Transportation and Volumetric Dentin Removal Abilities of Ni-Ti Rotary File Systems in Curved Primary Root Canals: CBCT Study

Current improvements in nickel-titanium (Ni-Ti) rotary file systems have created a paradigm shift in the root canal therapy of primary teeth. Therefore, it is necessary to perform a comprehensive evaluation regarding the efficiencies of newly manufactured instruments for different parameters. The current study was conducted to evaluate the abilities of RaceEvo, R-Motion, ProTaper Gold (PTG) systems in curved primary root canals with regard to the patterns of canal transportation and volumetric dentin removal by using cone-beam computed tomography (CBCT). Two experimental sets were designed following the determination of experimental groups by using pre- and post-operative CBCT data: canal transportation and volumetric dentin removal. The highest amount of canal transportation was significantly detected in the PTG group in comparison to RaceEvo and R-Motion groups. When the mean values of volumetric dentin removal data were analyzed across all groups, the PTG group again exhibited the significantly highest value of dentin removal volumetrically, compared to RaceEvo, R-Motion and manual instrumentation groups. It is possible to state that R-Motion and RaceEvo rotary systems could be used as reliable alternatives without causing adverse mechanical effects and maintaining the original root canal anatomy of curved primary root canal systems compared with PTG rotary systems and manual instrumentation, with a high diagnostic sensitivity of CBCT in pediatric endodontics when the alternative methods are not adequate.

Root canals shaped by nickel-titanium instrumentation with automated computerized numerical control systems

Background

To investigate the efficacy of a nickel-titanium (NiTi) file with an automated computerized numerical control (CNC) system for root canal shaping.

Methods

The movement of the automated device and the insertion angle were investigated. In Experiment 1, simulated resin root canals were randomly divided into four groups (n = 20): manual downward movement using a handpiece (Group 1), vertical downward movement by CNC (Group 2), reciprocating up and down movement by CNC (Group 3), and spiral up and down movement by CNC (Group 4). In Experiment 2, five different insertion angles of the NiTi file were evaluated (n = 20). Four parameters were used to evaluate the shaping ability: change in the working length, central axis offset, curvature variation, and preparation time. Groups were compared using one-way analysis of variance (ANOVA) with significance was set at P < 0.05.

Results

The change in central axis position in the curved part of the root canal was found to be smaller in Group 4 than in other groups (P < 0.05). The curvature changes and preparation time of Groups 1 and 4 were significantly reduced compared with Groups 2 and 3 (P < 0.05). The variation in working length and curvature in the 5° insertion angle group was significantly smaller than in the other groups (P < 0.05).

Conclusions

A spiral up and down movement, controlled by the CNC machine, and 5° insertion angle, maintained original root canal shape more precisely than other methods.

An Update on Root Canal Preparation Techniques and How to Avoid Procedural Errors in Endodontics

Background:

Effective root canal treatment involves cleaning and shaping root canals using a range of instrumentation procedures and techniques. The aim of this review was to provide an update on root canal hand instrumentation techniques and how to overcome iatrogenic errors.

Methods:

A comprehensive search was carried out using multiple databases, PubMed, Medline, Google scholar, and Scopus, to identify relevant studies addressing the objective of this study and to summarize the current evidence to readers. Keywords, i.e., endodontics, root canal preparation, hand instrumentation, techniques and procedural errors, as well as, MeSH terms, i.e. “endodontics”, “instrumentation”, “root canal preparation” were used to conduct our comprehensive search.

Results:

The hybrid technique is a commonly-used approach that combines the benefits of both the crown-down and step-back techniques and was reported to be one of the best techniques to produce an optimal root canal preparation outcome. Hand-instrument manipulation using the balanced forced technique is also favoured as it rapidly and safely permits removal of canal contents allowing irrigants and medications to reach deep inside canal spaces.

Conclusion:

The use of hand files is still recommended for initial canal negotiation and preparation and is essential for the correction of procedural errors. This study provided an update on several hand instrumentation techniques commonly used in endodontics. The correct and safe application of these techniques can prevent iatrogenic procedural errors from occurring which optimizes the quality of treatment outcome.

Micro-CT evaluation of rotary and reciprocating glide path and shaping systems outcomes in maxillary molar curved canals

The shaping outcomes after instrumentation with rotary and reciprocating glide path and shaping systems were evaluated through micro-computed tomography (Micro-CT). Thirty extracted maxillary first molars were selected. Mesio-buccal canals were randomized into two groups (n = 15): rotary system ProGlider and ProTaper Next X1, X2 (PG-PTN) and reciprocating system WaveOne Gold Glider and WaveOne Gold Primary (WOGG-WOG). Specimens were micro-CT scanned before, after glide path and after shaping. Increase in canal volume and surface area, percentage of removed dentin from the inner curvature, centroid shift and canal geometry variation through ratio of diameter ratios (RDR) and ratio of cross-sectional areas (RA) were measured in the apical and coronal levels and at the point of maximum curvature. The number of pecking motions needed to reach the working length (WL) was recorded. One-way ANOVA and post hoc Turkey–Kramer tests were used (p < 0.05). Post-glide path analysis revealed that in the coronal third, RDR was more favorable to PG and centroid shift was lower for WOGG in the apical third. Post-shaping analysis showed a reduced removal of dentin and a more favorable RA for PTN at point of maximum curvature. The number of pecking motions up to WL resulted in different between groups both for glide path and shaping phases. Despite a higher dentin removal for reciprocating instruments at the point of maximum curvature, both systems seemed to produce well-centered glide path and shaping outcomes. Rotary and reciprocating systems seemed able to respect the original canal anatomy.

Comparison of canal transportation and centering ability of manual K-files and reciprocating files in glide path preparation: a micro-computed tomography study of constricted canals

Background

Optimum Glide Path (OGP) is a new reciprocating motion aiming to perform efficient glide path preparation in constricted canals. The aim of this study was to investigate and compare manual and OGP movement in terms of canal transportation and centering ability in glide path preparation of constricted canals.

Methods

Thirty constricted mesial root canals of mandibular molars, with initial apical size no larger than ISO#8, were selected and negotiated with #6–#8 K-files under the microscope. Canals were randomly divided into two experimental groups: Group 1 (MAN, n = 15): Glide path was established by using #10-#15 stainless steel K-files manually; Group 2 (OGP, n = 15): #10-#15 Mechanical Glide Path super-files were used with OGP motion (OGP 90°, 300 rpm). Each instrument was used to prepare only 2 canals (as in one mesial root). Canals were scanned before and after glide path preparation with micro-computed tomography (micro-CT) to evaluate root canal transportation and centering ratio at 1, 3 and 5 mm levels from the root apex. File distortions and separations were recorded. Paired t-test was used to statistically evaluate the data (P < .05).

Results

Group 2 showed a significantly lower transportation value than group 1 at 1-mm and 3-mm levels (P < .05), however the difference at 5-mm level was not significant. There was no significant difference regarding the centering ratio between the groups. Six #10 K-files were severely distorted in group 1, while no file separation or distortion was found in group 2.

Conclusions

OGP motion performed significantly less canal transportation (apical 3 mm) and file distortion during glide path establishment in constricted canals comparing to manual motion, while the centering ability between the two was similar.

Clinical relevance

OGP reciprocating motion provides a safer and efficient clinical approach compared to traditional manual motion in glide path establishment with small files in constricted canals.

The Invasion of Bacterial Biofilms into the Dentinal Tubules of Extracted Teeth Retrofilled with Fluorescently Labeled Retrograde Filling Materials

In this study, we evaluated the invasion of bacteria into the dentinal tubules of retrofilled extracted human teeth, and the influence of different fluorescently labeled retrograde filling materials on the bacterial invasion and viability, by means of confocal laser scanning microscopy (CLSM). The root apices of extracted teeth were cut, prepared, and filled retrogradely using either intermediate restorative material (IRM), mineral trioxide aggregate (MTA), or Biodentine. The roots were filled with Enterococcus faecalis bacteria from their coronal part for 21 days. Then, 3-mm-long apical segments were cut to get root axial slices, and the bacteria were fluorescently stained and evaluated by CLSM. Bacterial penetration into the dentinal tubules favored the bucco-lingual directions. The filling materials penetrated up to 957 µm into the tubuli, and the bacteria, up to 1480 µm (means: 130 and 167 μm, respectively). Biodentine fillings penetrated less and the associated bacteria penetrated deeper into the tubuli compared to MTA or IRM (p = 0.004). Deeper filling penetration was associated with shallower penetration of both dead and live, or live alone, bacteria (p = 0.015). In conclusion, the current study enables better understanding of the microbiological–pathological course after endodontic surgical procedures. It was found that even with retrograde fillings, bacteria invade deep into the dental tubules, where deeper filling penetration prevents deeper penetration of the bacteria and adversely affects the viability of the bacteria.

Apical extrusion of debris with different rotary and reciprocating single-file endodontic instrumentation systems: a systematic review and meta-analysis protocol

INTRODUCTION

Root canal treatment is one of the oldest dental procedures for the treatment of endodontic infection. Extrusion of debris beyond the root apex during root canal instrumentation and subsequent persistence of pain are common complications. A systematic review of the evidence on reciprocating single-file instrumentation systems and their comparison with rotary single-file systems, with apical extrusion of debris as primary outcome, will be done through this study.

METHODS AND ANALYSIS

Published ex vivo and in vitro studies with no language restriction will be included. We will search MEDLINE (Ovid), EMBASE (Ovid), Web of Science, Cochrane and Google Scholar. Strategies will be incorporated to search grey literature also. Thorough evaluation of search results, completion of data abstraction and assessment of quality will be done by two reviewers independent from each other. Assessment of included studies will be done by utilising an evidence model developed on the basis of standards of quality reported in guidelines to document ex vivo and in vitro studies regarding dental materials and pertained for extrusion of debris apically and has been already used in quality assessment of studies involving quantification of debris extrusion apically. We will calculate the standardised mean differences for apically extruded debris, with congruent 95% CIs. We will measure the statistical heterogeneity by applying the Cochrane Q test and quantify using the I² statistic. Existence of covariates and any potential heterogeneity will be explored through prespecified subgroup and sensitivity analyses.

ETHICS AND DISSEMINATION

Approval from an ethical research committee is not required because it will be done using data that have been already published and have no concerns related to the privacy of patients. Extensive dissemination of results from this review will be done through submission to a peer-reviewed journal for publication and conferences.

PROSPERO REGISTRATION NUMBER

CRD42019151804.

Influence of glide path kinematics during endodontic treatment on the occurrence and intensity of intraoperative and postoperative pain: a systematic review of randomized clinical trials

BACKGROUND

Preliminary canal enlargement (glide path preparation) may play a significant role in the development of pain. The aim of this systematic review of randomized clinical trials was to assess the influence of glide path kinematics during endodontic treatment on the occurrence and intensity of intraoperative and postoperative pain.

METHODS

A search was performed in June 2019 in six electronic databases (PubMed, Scopus, LILACS, SciELO, Embase and Web of Science) and two grey literature databases (OpenGrey and OpenThesis). The bibliographic references of the eligible articles were also hand-searched. The included clinical studies assessed the occurrence and intensity of intraoperative and/or postoperative pain after root canal preparation without glide path preparation (WGP) or with glide path preparation using manual (M-GP), continuous rotary (CR-GP), or reciprocating (R-GP) instruments. The primary outcome was the occurrence and intensity of intraoperative and postoperative pain, while analgesic consumption was the secondary outcome. The full texts of the eligible studies were analyzed by two reviewers who performed calibration exercises to verify the risk of bias and quality of the individual studies using the Joanna Briggs Institute Critical Appraisal tool.

RESULTS

From 1283 identified articles, only six studies were included in the qualitative analysis of the results, with a total sample of 884 patients/teeth. Three studies presented a high risk of bias, while three studies presented a moderate risk. Two studies reported that CR-GP causes lower pain levels than M-GP and WGP, and three studies showed no differences between CR-GP and R-GP. Regarding analgesic consumption, two studies found no differences among glide path kinematics, and one study reported lower consumption for CR-GP than for M-GP. Because of the limited number of studies and methodological differences, no statistical analyses were performed for the glide path kinematics comparisons.

CONCLUSIONS

Compelling evidence indicating a significantly different occurrence and intensity of pain among glide path kinematics is lacking. The systematic review protocol was registered in the PROSPERO database [CRD42020139989].

Push-out bond strength of fiberglass posts cemented with adhesive and self-adhesive resin cements according to the root canal surface

Evaluating the bond strength of fiberglass posts cemented with different resin cements.

MATERIALS AND METHODS

Seventy freshly extracted roots of healthy human canines were endodontically treated and prepared to receive fiberglass posts. The roots were randomly divided into seven groups: (G1) RelyX ARC, (G2) Enforce, (G3) BisCem, (G4) Duo-Link, (G5) Cement Post, (G6) Variolink II, and (G7) RelyX U200. After post cementation, the specimens were sectioned perpendicularly to the root axis using a high-speed diamond disc, totaling 340 specimens. The strength values obtained in the push-out test were submitted to two-factor ANOVA and Tukey test (p = 0.05).

RESULTS

The root thirds (p = 0.001) and the type of cement (p = 0.001) influenced the bond strength values. The relation between these two factors was also significant (p = 0.011).

CONCLUSIONS

The bond strength of self-adhesive resin cements was significantly higher as compared to other cements. Besides the cervical third in roots cemented with conventional cements types presented the highest bond strength values (p < 0.05).

A bibliometric analysis of the 103 top-cited articles in endodontics

Objective: The purpose of this study was to identify the 100 top-cited articles in endodontics and analyse their bibliometric characteristics. Material and methods: The Web of Science database was reviewed to identify the relevant articles. Results: One hundred and three articles were included because the last four articles had the same number of citations. The top-cited article received 2115 citations. The articles were published in 28 different journals, with the most popular publication being the Journal of Endodontics (n = 36). The most prolific country was the United States (n = 41), followed by Sweden (n = 17) and Switzerland (n = 8). The most prolific author and institution were M. Torabinejad (n = 12) and Umeå University (n = 9), respectively. The majority of articles were of a basic science nature (n = 55), while endodontic microbiology (n = 24) was the most frequent subspecialty. The most common study design used in clinical articles was non-randomized experimental study (n = 5). Half of the clinical articles (n = 11) had a level III evidence score. Conclusions: The present citation analysis provides insights into the historical progress and current trends in endodontics.

Evaluation of dentinal defects during root canal preparation using thermomechanically processed nickel-titanium files

OBJECTIVE

The aim of this study was to compare the incidence of root cracks after root canal instrumentation with thermomechanically processed nickel-titanium (Ni-Ti) files with different instrumentation kinematics.

MATERIALS AND METHODS

A total of 150 extracted mandibular premolars with mature apices and straight root canals were divided into five groups and used in this study. In Group 1, 30 teeth were prepared using hand K-files and assigned to control group, Group 2 was instrumented using K3XF Rotary files (SybronEndo, Glendora, CA, USA) with continuous rotary motion. The teeth in Group 3 were instrumented by ProTaper Next (Dentsply Maillefer, Ballaigues, Switzerland) rotary files which make asymmetric rotary motion, In Group 4, teeth were instrumented by RECIPROC (VDW, Munich, Germany) with reciprocation motion and in Group 5, teeth were instrumented by Twisted File (TF) Adaptive (SybronEndo, Orange, CA, USA) files that use combination of continuous rotation and reciprocation motion (n = 30/per group). All the roots were horizontally sectioned 3, 6, and 9 mm from the apex with a low speed saw under water cooling. Then, the slices were examined through a stereomicroscope to determine the presence of dentinal microcracks.

RESULTS

For the apical (3-mm) and coronal (9-mm) sections, the ProTaper Next and TF Adaptive produced significantly more cracks than the hand files, RECIPROC, and K3XF (P < 0.05). There was no significant difference between the experimental groups and control group at the 6-mm level (P > 0.05).

CONCLUSIONS

Within the limitations of this in vitro study, all thermal-treated Ni-Ti instruments and hand files caused microcracks in root canal dentin.

Kinematics of a novel reciprocating endodontic handpiece

AIM

To analyse the kinematics of the Reciproc Direct^® contra-angle reciprocating device with different motor sources.

METHODOLOGY

Reciproc Direct contra-angle (VDW GmbH, Munich, Germany) was tested with new micro-motor sources. The micro-motor groups were as follows: a brushless electric micro-motor, a brushed electric micro-motor and an air-driven micro-motor. The electric micro-motor sources were also divided into four subgroups as 10 000, 15 000, 20 000 and 25 000 rpm. The maximum air pressure of the air-driven micro-motor was adjusted to 2 and 3 kgf cm^-2 . A custom target object was attached to the Reciproc Direct, and reciprocating motions were recorded with a high-speed camera at 1200 frames per second. The following kinematic parameters were calculated: duration of each reciprocating motion, engaging and disengaging angles, cycle rotational speeds, engaging and disengaging rotational speeds, net cycle angle, total cycle angle and number of cycles to complete full rotation. One-way anova was used where applicable, followed by Tukey's multiple comparison tests, to compare the kinematic values of reciprocating motion for each micro-motor/Reciproc Direct combination. The Kruskal-Wallis test followed by Dunn's multiple comparison test was used for non-normally distributed data. Statistical analysis was performed (α = 0.05).

RESULTS

For the brushless micro-motor, median engaging angle was 186.5 ° at 10 000 rpm and 188.0 ° at 15 000 rpm which were significantly different than median engaging angles at 20 000 (188.5 °) and 25 000 (189.3 °) rpm (P < 0.05). For the brushless micro-motor, median cycle rotational speed was 372.5 rpm at 10 000 and 459.8 rpm at 15 000 rpm which were significantly different than median cycle rotational speed at 20 000 (576.2 rpm) and 25 000 (677.8 rpm) rpm (P < 0.05). For the brushed micro-motor, median cycle rotational speed was 293.5 rpm at 10 000 and 386.3 rpm at 15 000 rpm which were significantly different than median cycle rotational speed at 20 000 (508.9 rpm) and 25 000 (597.6 rpm) rpm (P < 0.05).

CONCLUSIONS

Rotational speeds were influenced significantly by motor sources even when the Reciproc Direct was used at speeds recommended by the manufacturer. This could indicate that the kinematics of the Reciproc Direct are dependent on the power of the rotating motor.

Effectiveness of rotary and reciprocating systems on microbial reduction: A systematic review

Introduction:

The role of microorganism and their products in the initiation, propagation, and persistence of periradicular periodontitis has been established. One of the major goals of the treatment of infected root canals of teeth with apical periodontitis is to promote maximal reduction in the intracanal bacterial populations. Engine-driven nickel-titanium instruments possess the latest generation of root canal instruments. The possible benefit of rotary instrumentation over other instrumentation techniques regarding cleaning and disinfecting effects would be irrigant warming and/or turbulence caused by the mechanical rotation of instruments. Furthermore, reciprocating instrument has been introduced for root canal preparation. It has been shown that instruments subjected to reciprocation have increased resistance to fatigue and longer usual life when combined with instruments used in continuous rotation motion. The reciprocating system uses single-file instrumentation technique which can shape and clean the canal in a shorter period and together with the lesser amount of antimicrobial agent.

Objective:

The objective of this study is to compare and evaluate the microbial reduction of rotary and reciprocating systems on microbial reduction.

Search Strategy:

A search was performed in Electronic databases (i.e., PubMed, Cochrane library, Science direct, Lilac, Sigle) using following search terms alone and in combination by means of PubMed search builder from January 1985 to December 2017.

Selection Criteria:

Studies were selected if they met the following criteria: In vivo studies comparing rotary and reciprocating system in asymptomatic apical periodontitis patients.

Main Results:

The results showed that the reciprocating system exerted an almost similar antibacterial effect when compared with the rotary system.

Conclusion:

The present systematic review does not provide concrete evidence to show increased antibacterial efficacy of reciprocating system as compared to the rotary system. Furthermore, clinical trials are required to evaluate the efficacy of various instrumentation systems in reducing bacteria from the root canal system.

A microcomputed tomography evaluation of the shaping ability of three thermally-treated nickel-titanium rotary file systems in curved canals

OBJECTIVE

To evaluate the shaping ability of three thermally-treated rotary nickel-titanium (NiTi) systems including ProTaper Next (PTN), HyFlex™ CM (HFCM) and HyFlex™ EDM (HFEDM) during root canal preparation in simulated root canals.

METHODS

A total of 45 simulated root canals were divided into three groups ( n = 15) and prepared with PTN, HFCM or HFEDM files up to size 25. Microcomputed tomography (microCT) was used to scan the specimens before and after instrumentation. Volume and diameter changes, transportations and centring ratios at 11 levels of the simulated root canals were measured and compared.

RESULTS

HFEDM caused significantly greater volume increases than HFCM and PTN in the entire root canal and in the apical and middle thirds. HFCM removed the least amount of resin in the coronal third compared with HFEDM and PTN. Overall, HFCM caused significantly less transportation in the apical 2 mm and was better centred than PTN in the apical 3 mm.

CONCLUSION

Under the conditions of this study, all systems prepared curved canals without significant shaping errors and instrument fracture. PTN and HFCM cut less resin than HFEDM. HFCM stayed centred apically and cut the least material coronally.

Shaping ability of the profile 25/0.06 and protaper F2 in rotary motion, and reciproc in simulated canals

Background

Since the introduction of nickel–titanium (Ni–Ti) instruments to dentistry, a wide variety of Ni–Ti instruments have become commercially available. These Ni–Ti instruments are expensive, which limits their usage in developing countries and forces practitioners to use instruments repeatedly. Another problem is the possible prion cross-contamination associated with the multiple usage of endodontic instruments. In addition, the use of these instruments requires new skills and experience. In this article, the shaping capacities of two conventional rotary file systems, ProFile 25/0.06 and ProTaper F2, were reviewed and compared with the Reciproc single-file system.

Methods

A total of 45 simulated canals with 40° curvature, in clear resin blocks, were prepared using conventional rotary systems consisting of ProFile orifice shaping (OS) #3 and final flaring #25/.06, Reciproc R25, and ProTaper shaping file SX and finishing file F2. Pre-and post-instrumentation images were analyzed at ten different levels, using AutoCAD 2007 software. The measurement positions were defined in 1-mm intervals: positions 0–3 established the apical part, positions 4–6 constituted the middle part, and positions 7–10 established the coronal part of the canal. The amount of removed resin, the transportation, instrumentation time, change in working length (WL), instrumentation fractures, and the presence of ledge were evaluated. Data were analyzed using ANOVA, Kruskal–Wallis and independent t-test (p < 0.001).

Results

ProFile removed the least resin (p < 0.001) and caused less transportation than Reciproc and ProTaper, in total (p < 0.001). ProTaper caused more transportation ProFile and Reciproc in the apical part (p < 0.000). Reciproc caused more transportation than ProTaper and ProFile (p < 0.001), and the transportation tendency toward the inner aspect of the curvature in the middle part. Reciproc caused the less transportation than ProFile and ProTaper in the coronal part. The transportations tended to occur toward the outside of the curvature, except the middle part with Reciproc and at points 5 and 6 with ProTaper. There were no significant differences among the groups in terms of maintaining the original WL. Reciproc was significantly faster than the others group (p < 0.001). Only one instrument fracture (25/0.06 ProFile) was noted. All groups showed one ledge each.

Discussion

The results of the present study showed that both ProFile 25/06 and ProTaper F2, combined with a file used for coronal enlargement (OS3 and SX), have the potential to create satisfactory canal shape in the curved root canals. Further studies using real human teeth are needed to confirm our results.

Unprepared root canal surface areas: causes, clinical implications, and therapeutic strategies

Chemomechanical preparation is intended to clean, disinfect, and shape the root canal. This step is of utmost importance during treatment of infected teeth with apical periodontitis, because treatment outcome depends on how effectively the clinician eliminates bacteria, their products, and necrotic tissue that would serve as substrate for bacterial regrowth. Nonetheless, curvatures and complex internal anatomical variations of the root canal system can pose a high degree of difficulty in reaching these goals. In infected teeth, bacteria may persist not only in difficult-to-reach areas such as isthmuses, ramifications, dentinal tubules, and recesses from C-shaped or oval/flattened canals, but also in areas of the main canal wall that remain untouched by instruments. If bacteria withstand chemomechanical procedures, there is an augmented risk for post-treatment apical periodontitis. This article discloses the reasons why some areas remain unprepared by instruments and discusses strategies to circumvent this issue and enhance infection control during endodontic treatment/retreatment of teeth with apical periodontitis.

Methods for measurement of root canal curvature: a systematic and critical review

The assessment of root canal curvature is essential for clinical and research purposes. This systematic review presents an overview of the published techniques for the measurement of root canal curvature features using imaging and to provide a critique of their clinical application. A database search in PubMed, PubMed Central, Embase, Scopus, EBSCO Dentistry & Oral Sciences Source and Virtual Health Library was conducted, using appropriate key words to identify measurement methods for root canal curvatures. The search strategy retrieved 10594 records in total, and 31 records fulfilled the inclusion criteria. From 2D image acquisitions, eleven studies measured exclusively the angle of curvature, an additional thirteen measured other curvature features (level, height, radius, length and shape). Seven reports described methods from 3D imaging (CBCT, μCT). Root canal curvatures should be measured, for clinical proposes, to facilitate endodontic treatment planning, and in research, to reduce the risk of selection bias. This review has revealed that there are many methods described in the literature; however, no consensus exists on which method should be used. Some of the methodologies have potential clinical translation, whereas others are suitable for research purpose only, as they require a specific software or radiographic exposure in the mesiodistal direction.