Effects of four Ni-Ti preparation techniques on root canal geometry assessed by micro computed tomography

Root dentine thickness in C-shaped lower second molars after instrumentation: A CBCT and micro-CT study

Stripping perforation is a possible complication in instrumentation of C-shaped canals. This study evaluated the minimum thickness of the root canal wall in C-shaped teeth after instrumentation. Twelve extracted C-shaped mandibular second molars (four teeth of type I, II and III each) were examined by CBCT (voxel size 90 μm) before and after instrumentation with WOG primary file. Micro-CT scans (voxel size 30 μm) were obtained after instrumentation. Percentage of canal wall area touched by the file and minimum thickness of dentine were measured and compared between CBCT and micro-CT. In type I C-shape canals, less than 10% of the canal wall area was touched by the instrument. In ten teeth, the shortest distance to root surface was from the instrumented area; no perforations occurred. CBCT and micro-CT measurements were in good agreement in ten cases; in two teeth, micro-CT revealed considerably shorter distance to root surface. The two shortest distances were 0.27 and 0.41 mm.

Effects of heat in the properties of NaOCl alone and mixed with etidronate and alkaline tetrasodium EDTA

AIM

To assess the free available chlorine concentration (FAC), organic tissue dissolution and smear layer removal capacity of sodium hypochlorite (NaOCl) alone and when mixtured with etidronate (HEDP) and tetrasodium EDTA (Na₄ EDTA), and heated to different temperatures.

METHODOLOGY

Mixtures at 1 : 1 ratio of 5% NaOCl with distilled water (considered NaOCl alone), 18% HEDP or 10% Na₄ EDTA were heated to 25 °C, 37 °C, 48 °C and 60 °C. The FAC in the mixtures was assessed at 5, 10, 20, 30, 60 and 120 min. Samples of bovine muscle tissue (n = 10) were prepared with similar size and weighed before and after 5, 10 and 15 min of immersion in the mixtures heated to the different temperatures to verify organic matter dissolution. The intergroup results were compared statistically using one-way analysis of variance (anova) and intragroup by two-way analysis of variance (anova), both followed by Tukey's multiple-comparison test (α < 0.01). Bovine dentine blocks (n = 10) were analysed by scanning electron microscopy before and after immersion in the mixtures, and the time taken to remove the smear layer from the surfaces of the samples was determined. The Friedman test was used to compare the scores of the same group (α < 0.01), and the Kruskal-Wallis test with Dunn's post hoc was used to compare the different groups (α < 0.01). Saline solution was used as a control in the experiments of tissue dissolution and smear layer removal, RESULTS: Heating NaOCl alone did not affect its FAC. The higher the temperature of the mixtures with the chelators, the lower the FAC. Organic tissue dissolution was improved by increases in temperature of NaOCl alone and its mixture with HEDP (P < 0.01); however, the mixture with Na₄ EDTA had no improvement (P > 0.01). Smear layer removal by NaOCl alone was enhanced by heating resulting in lower scores in some samples and became more rapid in the mixtures with the chelators. The saline solution did not promote tissue dissolution nor smear layer removal (P > 0.01).

CONCLUSION

In this laboratory study, heating NaOCl alone or when mixed with HEDP improved its capacity to dissolve organic matter and remove the smear layer. However, the mixture with HEDP required frequent refreshment to retain these effects when heated. Due to the acceleration in the reaction between the irrigants, very rapid reductions in the free available chlorine in the mixtures with Na₄ EDTA heated to the different temperatures occurred.

Bactericidal Effect of a Novel Alkaline EDTA Root Canal Cleaning Solution

Objectives  In this study, we aimed to evaluate the bactericidal effect and cytotoxicity of an ethylenediaminetetra-acetic acid (EDTA)-based root canal irrigant solution capable of efficiently removing both the organic matter and the smear layer. We prepared a strong alkaline EDTA (AE) solution with an acid buffer capacity similar to that of sodium hypochlorite.

Materials and Methods  AE was used at concentrations of 1%, 2%, and 3%. The bactericidal effect of AE on Enterococcus faecalis was evaluated by determining the colony number and biofilm removal rate. Biofilms were visualized using a Live/Dead BacLight bacterial viability kit. Viability of AE-treated cells were determined using a CCK-8 cell counting assay.

Statistical Analysis  One-way analysis of variance followed by a Dunnett’s multiple comparison test were used for comparisons among groups.

Results  Significant reduction in cell viability and biofilm formation were observed in case of 3% and 2% AE. AE exerted bactericidal effects in a concentration-dependent manner. Damage of normal human fibroblasts was not observed at any of the AE concentrations.

Conclusions  Our results suggest that the AE solution could be used as an effective canal irrigant for the removal of bacterial biofilm.

Postoperative pain after ultrasonically and laser-activated irrigation during root canal treatment: a randomized clinical trial

AIM

To compare the intensity of postoperative pain after primary root canal treatment of asymptomatic teeth when using ultrasonically (UAI) or laser-activated irrigation (LAI).

METHODOLOGY

In this superiority randomized clinical trial (ClinicalTrials.gov ID: NCT03981237) with parallel design, fifty-six patients with an asymptomatic tooth in need of primary root canal treatment were enrolled. After chemo-mechanical canal preparation using rotary instruments and NaOCl irrigation, teeth were randomly assigned to two groups and patients were blinded to the final irrigation protocol. In the UAI group (n = 28), 60s activation with an Irrisafe tip was done per canal. In the LAI group (n = 28), NaOCl was activated with a pulsed Er:YAG (2940 nm) laser, equipped with a conical tip, with settings of 50 µs, 20 mJ at 15 Hz for 60 s. Patients recorded their pain intensity 6, 24, 48 and 72 h after treatment on a 100 mm visual analogue scale (VAS), as well as their analgesic consumption. Pain levels and incidence were compared across groups using the Mann-Whitney U-test and chi-square test.

RESULTS

Overall, mean postoperative pain intensity was low, with the majority of patients having no or minimal pain 24 h postoperatively. At 6 h postoperatively, pain intensity and incidence were significantly higher in the UAI group compared to the LAI group (P < 0.05). For the other time intervals, no significant differences in postoperative pain incidence or intensity were found. The frequency of analgesic intake did not differ significantly between the two groups. Neither of the activation methods resulted in any adverse effects.

CONCLUSIONS

Ultrasonically and laser-activated irrigation resulted in low and comparable levels of postoperative pain in asymptomatic patients receiving primary root canal treatment.

A Critical Review of Methods for Quantitative Evaluation of Root Canal Transportation

INTRODUCTION

A comparison between root canal transportation studies is nearly impossible because of nonstandardized transportation evaluation methods. The aim of the present review was to search, compare, and critically discuss transportation evaluation methods.

METHODS

A search of PubMed, Web of Science, Scopus, ScienceDirect, and reference lists of articles was conducted up to March 2020 using appropriate key words to identify transportation evaluation methods. The methods in the included articles were extracted, compared, and categorized.

RESULTS

Seventy-four articles using original methods were selected. All studies share 3 main steps: image acquisition, image measurements, and calculation of parameters. Images were acquired by photography, radiography, and computed tomographic imaging. Two types of measurements were used: the amount of removed material and the canal center point distance. The parameters were calculated and reported as distance or ratio. Relationships between the different transportation parameters were found and confirmed with mathematical simulation.

CONCLUSIONS

Although methods were proposed as being novel, similarities between them were found, enabling the classification of the methods and identifying correlations. The canal center point distance is the most suitable for the description of canal transportation because it is comprehensible and it relates to the mathematical concept of translation. Removed material-based measurements are double the value of the canal center point distance. Ratio parameters are not suitable for reporting transportation.

Micro-computed Tomographic Assessment and Comparative Study of the Shaping Ability of 6 Nickel-Titanium Files: An In Vitro Study

INTRODUCTION

This research studies and compares the shaping ability of WaveOne Gold (WG; Dentsply Tulsa Dental Specialties, Tulsa, OK), the Reciproc Blue (RB; VDW, Munich, Germany), TRUShape (TS, Dentsply Tulsa Dental Specialties), XP-endo Shaper (XP; FKG, La Chaux-de-Fonds, Switzerland), iRace (IR, FKG), and TruNatomy (TN; Dentsply Sirona, Ballaigues, Switzerland) in the preparation of moderately curved canals and using micro-computed tomographic technology.

METHODS

Sixty lower molars with 2 mesial canals were randomly distributed into 6 groups of 10 molars and 20 canals per group (n = 20). Specimens were scanned before and after preparation using the SkyScan 1275 (Bruker microCT, Kontich, Belgium). Group 1 was treated with WG, group 2 with RB, group 3 with TS, group 4 with XP, group 5 with IR, and group 6 with TN. After instrumentation, researchers quantified the changes produced in the canal geometry in terms of surface, volume, structure thickness, surface convexity index, structure model index, percentage of surface touched, and centroids. Wilcoxon and analysis of variance tests were performed to compare the values before and after preparation and the differences between groups. The significance level was established at 5%.

RESULTS

There were no significant differences between WG and RB (P > .05) and between TN and XP (P > .05). TN had significant differences with WG, RB, TS, and IR (P < .05). All the files produced similar apical transportation (P > .05).

CONCLUSIONS

WG and RB and TN and XP had similar shaping effectivity. TS and WG touched the highest percentages of canal surfaces (81% and 73%, respectively) but produced the biggest changes in the canal anatomy. TN and XP better kept the canal anatomy, but TN touched the lowest percentage of canal surface (50%). All the files used were able to clean and to shape moderately curved canals with minimal apical transportation.

Clinical efficacy of activated irrigation in endodontics: a focused review

Root canal debridement, which includes the removal of infected tissues and microbial biofilms, is considered the corner stone of root canal treatment. Chemical adjuncts play a multitude of functions in this regard, as tissue solvents, antimicrobial agents and for removing the smear layer. These adjuncts (irrigants) are usually delivered using a syringe and needle. With increasing knowledge of the complexity of root canal anatomy and tenacity of microbial biofilms, the need for strategies that potentiate the action of these irrigants within the root canal system cannot be overemphasized. Several such activated irrigation strategies exist. The aim of this review is to comprehensively discuss the different irrigant activation methods from the context of clinical studies.

Analysis of the Morpho-Geometrical Changes of the Root Canal System Produced by TF Adaptive vs. BioRace: A Micro-Computed Tomography Study

We aimed to analyze the morpho-geometric changes of the root canal system created by two rotary systems (TF Adaptive and BioRace) using micro-CT technology. Two concepts of rotary file system kinematics, continuous rotation and adaptive kinematics, were used in root canal preparation. Twenty mandibular molars (n = 20) were selected with the following criteria: the teeth have mesial roots with a single and continuous isthmus connecting the mesiobuccal and mesiolingual canals (Vertucci’s Type I configuration) and distal roots with independent canals. Teeth were scanned at a resolution of 14 μm. Canals were divided equally into two groups and then enlarged sequentially using the BioRace system and TF Adaptive system according to manufacturer protocol. Co-registered images, before and after preparation, were evaluated for morphometric measurements of canal surface area, volume, structure model index, thickness, straightening, and un-instrumented surface area. Before and after preparation, data were statistically analyzed using a paired sample t-test. After preparation, data were analyzed using an unpaired sample test. The preparation by both systems significantly changed canal surface area, volume, structure model index, and thickness in both systems. There were no significant differences between instrument types with respect to these parameters (p > 0.05). TF Adaptive was associated with less straightening (8% compared with 17% for BioRace in the mesial canal, p > 0.05). Both instrumentation systems produced canal preparations with adequate geometrical changes. BioRace straightened the mesial canals more than TF Adaptive.

Root anatomy and canal configuration of human permanent mandibular second molar: A systematic review

The objective of the study was to review the literature on root anatomy and canal configuration in permanent mandibular second molar based on Vertucci classification. Online electronic databases such as PubMed-Medline, Embase, Scopus, and Cochrane Library were searched using appropriate keywords from the earliest available date till 10^th February 2021 restriction on language. Additional sources such as Google Scholar, major journals, unpublished studies, conference proceedings, and cross-references were explored. Information curated for data extraction included methodology, population, sample size (number of teeth), number of root canals, and type of root canal configuration (RCC). Thirty-seven articles were selected with a total of 12,393 permanent mandibular second molar teeth. In the mesial root, Type IV canal configuration with 37.3% was more frequent, having two canals with 70.4%. In the distal roots, one canal was more prevalent with 77% occurrence, and Type I canal configuration was more frequent with 85.2%. Comprehensive knowledge of tooth anatomy and root canal morphology is crucial to root canal treatment. Therefore, an understanding of the canal configuration and anatomy is necessary for the dentist to enhance successful endodontic treatment. Our systematic review findings reveal a wide variety of possible canal configurations among permanent mandibular second molar, while the number of canals ranged from 1 to 5 in number. The evidence is intended to help dental practitioners to avoid mishaps such as perforation and missing canals and anticipation of potential complications during treatment.

Retrievability of bioceramic-based sealers in comparison with epoxy resin-based sealer assessed using microcomputed tomography: A systematic review of laboratory-based studies

Aim:

The objective was to evaluate the retrievability of bioceramic sealers in comparison with epoxy resin-based sealers assessed using microcomputed tomography.

Materials and Methods:

Four reviewers independently conducted a systematic literature search in four electronic databases. The risk of bias was assessed using modified Joanna Briggs Institute Critical Appraisal tools for Quasi-Experimental Studies.

Results:

Ten articles were included in this review and all had a moderate risk of bias. The results across the included articles were inconsistent with some indicating easier/difficult removal of bioceramic sealers, while others indicate no difference. The studies varied in terms of the type of bioceramic sealer used, root canal anatomy, and retreatment techniques followed. Due to heterogeneity, only a qualitative analysis was performed and no meta-analysis was conducted.

Conclusion:

The quality of evidence is low and no definitive conclusion could be derived regarding the retrievability of bioceramic sealer/AH plus sealer from the root canals during retreatment procedures.

Use of mind maps in dental education: An activity performed in a preclinical endodontic course

PURPOSE/OBJECTIVES

(1) to assess the ability of dental students to use mind maps to express the relationships of endodontic theory and technique; (2) to explore features illustrated from the highest- and lowest-graded mind maps; and (3) to evaluate improvements in successive mind maps from the same student.

METHODS

A total of 31 second-year students were asked to configure a mind map on root canal cleaning-shaping and then 18 weeks later develop a second mind map on root canal obturation. Faculty visually analyzed the mind maps using a qualitative approach: a multilayered process of thematic analysis. Codes and themes were generated to investigate if students were able to express appropriate and evidence-based ideas on the topics (accuracy of relationships and depth of information presented). Two of the highest- and 2 of the lowest-graded mind maps for each activity were directly compared. Improvement by the same student from the first to second mind map was also evaluated based on trend/style and creativity.

RESULTS

The majority of the students accurately expressed the scientific basis for root canal cleaning-shaping and obturation. The highest-graded mind maps displayed the biomedical and humanistic conceptions of critical thinking. In comparing the second mind map to the first, nearly 50% of the students incorporated more detail and artistic expression in the second map.

CONCLUSIONS

using mind maps in dental education can benefit students with different learning styles and help the instructor to identify the level of conceptualization that the student had developed about a topic.

Antimicrobial and physicochemical characterization of endodontic sealers after exposure to chlorhexidine digluconate

OBJECTIVES

Assess the antibacterial, physical and chemical properties of AH Plus, BioRoot RCS and Pulp Canal Sealer (PCS) in contact with 2% chlorhexidine digluconate (CHX) used as final irrigant prior to root canal obturation.

METHODS

The antimicrobial properties were investigated by direct contact tests for planktonic and biofilm growth of E. faecalis, S. mutans, S.epidermidis and S.aureus in vitro. The setting time, wettability, microhardness and surface roughness were also assessed. The sealers were studied in no contact, 1-minute (short-term) and continuous contact (long-term) with CHX. Chemical characterization of sealers was performed by scanning electron microscopy, X-ray diffraction analysis and Fourier-transform infrared spectroscopy after CHX or saline used as the last irrigant in an ex vivo tooth model and in endo training blocks.

RESULTS

CHX increased the antibacterial activity of all the sealers investigated against planktonic bacteria and biofilms with PCS exerting the highest antimicrobial activity with and without the presence of CHX. The setting of AH Plus and BioRoot RCS was retarded, while for PCS accelerated in the presence of CHX. AH Plus and PCS were more hydrophilic after contact with CHX, whilst BioRoot RCS was hydrophobic in a time-dependent manner. The microhardness of sealers was compromised and the surface roughness increased after CHX exposure for AH Plus and BioRoot RCS, and decreased for PCS. CHX did not affect the sealers' chemistry, but PCS that exhibited two extra phases.

SIGNIFICANCE

CHX improved the antibacterial efficacy of endodontic sealers but further evidence is needed to confirm its suitability as a final irrigant prior to root canal obturation.

Effects of a Novel NiTi Thermomechanical Treatment on the Geometric Features of the Prepared Root Canal System

Objectives: This study aimed to compare the ex vivo performance of two rotary nickel–titanium (NiTi) systems with similar designs but manufactured from martensitic and austenitic alloys, the One Curve (OC) and One Shape (OS) rotary endodontic files, respectively. Methods: Forty separate mesial canals of 20 extracted mandibular molars were scanned using micro-computed tomography (CT), which were divided into 2 groups and instrumented with OC and OS, respectively. Post-instrumentation micro-CT scans were evaluated using validated computer algorithms to compare changes in canal thickness, surface area, structure model index (SMI) scores, volume of removed dentin, percentage of untreated canal surface, percentage of curvature straightening, and the amount of canal transportation. Results: Both files led to significant changes in the basic root canal geometry, with no preparation errors and no statistically significant differences. However, OC treatment resulted in significantly less curvature straightening (17.30%; 10.77%) (independent samples t test, p < 0.05) and less apical transportation (55.11 µm; 33.15 µm) (Mann–Whitney U, test p < 0.05) compared to OS treatment. Transportation values in the middle and coronal thirds were statistically similar (independent sample t-test, p > 0.05). OC treatment produced significantly less straightening and less apical transportation than OS.

Determination of Optimal Separation Times for Dual-Pulse SWEEPS Laser-Assisted Irrigation in Different Endodontic Access Cavities

Background and Objectives

The purpose of this ex vivo study is to investigate whether it is possible to pre‐determine and set the optimal separation times for the SWEEPS Er:YAG laser pulses pair during laser‐assisted irrigation of endodontic root canals based on known lateral dimensions of the endodontic access cavities of different types of teeth.

Study Design/Materials and Methods

As the optimal SWEEPS laser pulse pair separation for enhanced shockwave generation depends on the life‐cycle of a single‐pulse bubble, measurements of the oscillation time T_B of the Er:YAG laser‐generated bubble were made in 23 different endodontic access cavities of different types of teeth progressively widened in three different steps, into larger cavities, for a total of 69 cavities of different shapes and sizes. Different fiber‐tip geometries (flat and radial), laser pulse energies (10 mJ and 20 mJ) and depth of fiber‐tip insertion (2 mm and 4 mm) were also investigated. The obtained data were then analyzed using the reported relationship between the bubble oscillation time and the diameter of a cylindrically shaped cavity.

Results

A good fit to the relation analogue for ideal cylindrical cavities was found by taking the characteristic diameter of the access cavity to be represented by the cavity diameter either in the mesiodistal (D_min) or buccolingual (D_max) direction, or alternatively by the average of the two diameters (D_ave). The best fit was obtained for D_min (R² = 0.73) followed in order by D_ave (R² = 0.71) and D_max (R² = 0.63).

Conclusion

In spite of the endodontic cavities being non‐cylindrical and of varied shape and size, the bubble oscillation time T_B and the corresponding optimal SWEEPS separation time can be well predicted using a single characteristic dimension of the access cavity. This finding enables a simple and practical method for determining optimal conditions for shock wave generation and enhanced photodynamic streaming in differently shaped and sized root canals, leading to improved treatment efficacy and safety of root canal irrigation. Lasers Surg. Med. 2020. © 2020 The Authors. Lasers in Surgery and Medicine published by Wiley Periodicals LLC

Contemporary Cleaning of the Root Canal System

This article provides a contemporary synopsis of effective cleaning of the root canal system, an essential stage of root canal treatment. It provides a clinical update on the current state of knowledge on cleaning of the root canal system, and presents an outline of essential theory and practical tips for achieving effective and safe cleaning of the root canal system.

Comparative evaluation of substantivity of two biguanides - 0.2% polyhexanide and 2% chlorhexidine on human dentin

Background:

Substantivity is one of the desirable characteristics of root canal irrigants. Among conventional endodontic irrigants, only chlorhexidine (CHX) is known to exert significant substantivity on root canal dentin. This study explored the substantivity activity of a polymeric biguanide-poly hexamethylene biguanide (PHMB).

Aim:

The aim of this study was to determine the substantivity of a polymeric biguanide - 0.2% PHMB and compare it with that of 2% CHX.

Materials and Methods:

To evaluate and compare the substantivity of 0.2% PHMB and 2% CHX on root canal dentin, dentin disks were prepared and substantivity after 1 h, 24 h, 7 days and 21 days was measured using spectrophotometry.

Statistical Analysis Used:

The data so obtained were analyzed, and the intergroup comparison was made using unpaired t-test.

Results:

The results of this study indicated that 0.2%. PHMB exerts significantly greater substantivity than 2% CHX on human dentin.

Conclusion:

Within the limitations, this study supports the use of 0.2% polyhexanide as an endodontic irrigant based on its property of substantivity.

Chemical and mechanical influence of root canal irrigation on biofilm removal from lateral morphological features of simulated root canals, dentine discs and dentinal tubules

Aim

To investigate the anti‐biofilm efficacy of irrigation using a simulated root canal model, the chemical effect of irrigants against biofilms grown on dentine discs and their impact on biofilm viscoelasticity, the efficacy of the irrigants in decontaminating infected dentinal tubules and the capacity of bacteria to regrow.

Methodology

Biofilm removal, viscoelastic analysis of remaining biofilms and bacterial viability were evaluated using a simulated root canal model with lateral morphological features, dentine discs and a dentinal tubule model, respectively. Experiments were conducted using a two‐phase irrigation protocol. Phase 1: a modified salt solution (RISA) and sodium hypochlorite (NaOCl) were used at a low flow rate to evaluate the chemical action of the irrigants. Ultrasonic activation (US) of a chemically inert solution (buffer) was used to evaluate the mechanical efficacy of irrigation. Phase 2: a final irrigation with buffer at a high flow rate was performed for all groups. Optical coherence tomography (OCT), low load compression testing (LLCT) and confocal scanning laser microscopy analysis were used in the different models. One‐way analysis of variance (anova) was performed for the OCT and LLCT analysis, whilst Kruskal–Wallis and Wilcoxon ranked tests for the dentinal tubule model.

Results

US and high flow rate removed significantly more biofilm from the artificial lateral canal. For biofilm removal from the artificial isthmus, no significant differences were found between the groups. Within‐group analysis revealed significant differences between the steps of the experiment, with the exception of NaOCl. For the dentine discs, no significant differences regarding biofilm removal and viscoelasticity were detected. In the dentinal tubule model, NaOCl exhibited the greatest anti‐biofilm efficacy.

Conclusions

The mechanical effect of irrigation is important for biofilm removal. An extra high flow irrigation rate resulted in greater biofilm removal than US in the artificial isthmus. The mechanical effect of US seemed to be more effective when the surface contact biofilm–irrigant was small. After the irrigation procedures, the remaining biofilm could survive after a 5‐day period. RISA and NaOCl seemed to alter post‐treatment remaining biofilms.

Publication trends in micro-CT endodontic research: a bibliometric analysis over a 25-year period

AIM

To conduct a bibliographic analysis of the research studies published in Endodontics using micro-computed tomography (micro-CT) as an analytical tool over a 25-year period.

METHODOLOGY

The Web of Science electronic database was accessed, and an advanced search using strict criteria was undertaken from January 1995 to June 2020 for studies in the field of Endodontics that used micro-CT as an analytical tool. A further search was conducted between January and August of 2020 for a combination of specific terms and descriptors. For each selected article, the following parameters were recorded: field of the study, analysed specimen, publication title and year, authorship, journal of publication, institution and country of origin, collaborating institutions and countries, and number of citations. The acquired data were analysed using descriptive statistics and graphical mappings.

RESULTS

The screening process identified 877 relevant articles that were classified into 30 thematic categories. The main fields of research were root canal preparation (23.8%), root canal anatomy (17.4%), canal filling (9.2%) and root canal retreatment (7.0%). The most productive half-decade comprised the period of 2015-2019 (n = 513; 58.5%), with the highest number of articles published in 2019 (n = 146; 16.6%). The authors who lead the list as first authors were G De-Deus, A Keleş, F Paqué, MA Versiani and Y Gu, respectively, whilst Versiani was the most productive (n = 51). The leading countries regarding the number of studies were Brazil, China and Turkey with 236, 130 and 65 publications, respectively. The University of São Paulo (n = 90; 10.3%) followed by Wuhan University (n = 37; 4.2%) and the University of Zurich (n = 18; 2.1%) were the prominent contributors by producing the largest number of articles, whilst the University of Zurich was the most-cited institution. The selected studies were published in 140 scientific journals, but the Journal of Endodontics and International Endodontic Journal accounted for almost 50% of the publications.

CONCLUSION

This bibliometric analysis portrayed an original and comprehensive view on the progress and trends of the use of micro-CT technology in endodontic research, and enabled a deep understanding of the development process in this field over the last 25 years.

Root Canal Transportation after Root Canal Preparation with ProTaper Next, WaveOne Gold, and Twisted Files

Background: Root canal preparation during endodontic treatment may be associated with various complications, including a change in the original pathway of the root canal lumen. The aim of our study was to determine whether files of similar sizes that use various movement kinematics (rotary, reciprocal, adaptive motion) cause root canal transportation, and whether the differences between such systems are statistically significant. Methods: The degree of root canal transportation (DT) was calculated with the use of computed tomography scans for 3 groups of teeth (for each group: n = 20) in which the root canals were prepared using either rotary (ProTaper Next—PTN), reciprocal (WaveOne Gold—WOG), or adaptive movement (Twisted Files—TF) instruments. Results: For rotary ProTaper Next instruments, the mean value of the DT index was 0.0795 (SD = 0.0179) for 3 mm from the apex, 0.09 (SD = 0.0262) for 6 mm from the apex, and 0.106 (SD = 0.0221) for 9 mm from the apex. For reciprocal WaveOne Gold Primary instruments, the mean value of the DT index was 0.0355 (SD = 0.015) for 3 mm from the apex, 0.061 (SD = 0.02) for 6 mm from the apex, and 0.08 (SD = 0.25) for 9 mm from the apex. For Twisted Files, the mean value of the DT index was 0.05 (SD = 0.03) for 3 mm from the apex, 0.092 (SD = 0.17) for 6 mm from the apex, and 0.08 (SD = 0.02) for 9 mm from the apex. Conclusions: The use of PTN, WOG, and TF files resulted in root canal transportation to a different degree. The use of rotary PTN files produced the most transported preparation, whereas the use of WOG files produced the conservative root canal preparation that allowed the retention of the original shape of the root canal.

Evaluation of four final irrigation protocols for cleaning root canal walls

The aim of this study was to compare the efficiency of four final irrigation protocols in smear layer removal and bacterial inhibition in root canal systems. Thirty roots inoculated with Enterococcus faecalis were prepared with ProTaper Universal files. The teeth were disinfected by conventional needle irrigation, sonic agitation using the EndoActivator device, passive ultrasonic irrigation, or an M3 Max file. Teeth with no root canal preparation served as blank controls for the establishment of the infection baseline. Teeth with preparation but no final irrigation served as a post-instrumentation baseline. After the final irrigation, the teeth were sectioned in half. One half of each tooth was examined by scanning electron microscopy (SEM) to assess smear layer removal using a five-point scale. The other half was examined by confocal laser scanning microscopy (CLSM) using the LIVE/DEAD BackLight bacterial viability kit to evaluate the depth of bacterial survival in dentinal tubules. SEM analysis revealed no significant difference in smear layer removal throughout the whole canal among the EA, PUI, and M3 Max groups (P > 0.05). CLSM revealed that PUI achieved the greatest bacterial inhibition depth in the coronal ((174.27 ± 31.63) μm), middle ((160.94 ± 37.77) μm), and apical ((119.53 ± 28.49) μm) thirds of the canal (all P < 0.05 vs. other groups). According to this comprehensive SEM and CLSM evaluation, PUI appears to have the best infection control ability in root canal systems.

Selenium intracanal dressing: effects on the periapical immune response

OBJECTIVES

To evaluate the selenium (Se) behavior when used as an endodontic dressing in teeth with pulp necrosis. Additionally, its effects was also compared with the calcium hydroxide (C.H.), which is used globally as a root canal dressing, and the combination of the C.H. with Se (C.H. + Se).

MATERIALS AND METHODS

The sample consisted of 60 patients requiring endodontic treatment who were divided into groups, i.e., without intracanal medication (empty) and with medications as follows: selenium (Se), calcium hydroxide (C.H.), and calcium hydroxide + selenium (C.H. + Se) (n = 15). After the coronary opening, three absorbent paper points were placed in the RCS and maintained for 2 min for microbial evaluation. Following the cleaning and shaping procedures, new paper points were introduced into the root canal system, passing passively through the root apex (2 mm) into the periapical tissues for 2 min, for immune evaluation. The collections were performed again 15 days later. Real-time PCR quantified the expression of the prokaryotic 16S ribosomal RNA. The 16S mRNA was evaluated before the cleaning and shaping procedures and 15 days later in the groups treated with or without medication.

RESULTS

A significant reduction in the microbial load was observed only in the groups that received endodontic dressing (p < 0.05). The cytokines IFN-γ, TNF-α, IL-1α, IL-17A, IL-10, IL-6 and MCP-1, were also quantified by real-time PCR. There was an increase in the gene expression level of the cytokines (T15) TNF-α and IL-10 in the C.H. group compared to the other groups (p < 0.05). The IFN-γ mRNA expression was reduced in the groups treated with the medications (Se, C.H., and C.H. + Se).

CONCLUSIONS

The findings of the present study indicate that in the case of treatment over multiple sessions, the use of root canal dressing is essential to avoid the root canal system (RCS) microbial recolonization. Selenium potentiated the effects of calcium hydroxide inducing an anti-inflammatory response in periapical tissues.

CLINICAL RELEVANCE

Se is a mineral essential for the formation of the amino acid selenocysteine, which is directly involved in the maintenance of the immune response. Selenium has been widely used in the medical field in the treatment of cancer, as an activator of bone metabolism, and as a stimulator of the immune system. In this study, it was shown that the incorporation of Se, whether as intracanal medication alone or in conjunction with other medications, may potentiate periapical tissue repair after RCS cleaning and shaping procedures.

Current status on minimal access cavity preparations: a critical analysis and a proposal for a universal nomenclature

In the last decade, several access cavity designs involveing minimal removal of tooth tissue have been described for gaining entry to pulp chambers during root canal treatment. The premise behind this concept assumes that maximum preservation of as much of the pulp chamber roof as possible during access preparation would maintain the fracture resistance of teeth following root canal treatment. However, the smaller the access cavity, the more difficult it may be to visualize and debride the pulp chamber as well as locate, shape, clean and fill the canals. At the same time, a small access cavity may increase the risk of iatrogenic complications as a result of poor visibility, which may have an impact on treatment outcome. This study aimed to critically analyse the literature on minimal access cavity preparations, propose new nomenclature based on self-explanatory abbreviations and highlight the areas in which more research is required. The search was conducted without restrictions using specifics terms and descriptors in four databases. A complementary screening of the references within the selected studies, as well as a manual search in the highest impact journals in endodontics, namely International Endodontic Journal and Journal of Endodontics, was also performed. The initial search retrieved 1831 publications. The titles and abstracts of these papers were reviewed, and the full text of 94 studies was assessed. Finally, a total of 28 studies were identified as evaluating the influence of minimally invasive access cavity designs on the fracture resistance of teeth and on the different stages of root canal treatment (orifice location, canal shaping, canal cleaning, canal filling and retreatment). Overall, the studies had major methodological drawbacks and reported inadequate and/or inconclusive results on the utility of minimally invasive access preparations. Furthermore, they offered limited scientific evidence to support the use of minimally invasive access cavities to improve the outcome of root canal treatment and retreatment; they also provided little evidence that they preserved the fracture resistance of root filled teeth to a greater extent than traditional access cavity preparations. It was concluded that at present, there is a lack of supporting evidence for the introduction of minimally invasive access cavity preparation into routine clinical practice and/or training of undergraduate and postgraduate students.

Effect of expertise on TF adaptive system instrumentation quality in simulated mandibular molar canals

The aim of the study was to examine the effect of operator experience on the quality of instrumentation of molar canals using the TF Adaptive file system (SybronEndo, Orange, CA) on a 3D-printed molar replica model. Three novice and two expert operators instrumented the root canals of three replicas each and resulting pre- and postinstrumentation 12 micron voxel size-microCT volumes of each replica were digitally registered. Relative modified canal wall surface fraction and canal transportation (1-9 mm from the apex) were calculated and analysed by anova. Instrumentation by expert operators resulted in overall higher (P = 0.002) modified wall surface fraction in the distal but not the mesial and higher (P = 0.002) combined from all canal level transportation in the mesiobuccal canals but not the mesiolingual and distal canals. Instrumentation efficiency but also transportation using the TF Adaptive file system can be higher among expert, compared to novice, operators, depending on the canal type.

Current trends in endodontic irrigation amongst general dental practitioners and dental schools within the United Kingdom and Ireland: a cross-sectional survey

Aims To investigate current trends in endodontic irrigation amongst general dental practitioners (GDPs) and dental schools within UK and Ireland. Secondly, to evaluate if significant differences exist between the irrigant practices of National Health Service (NHS) and private GDPs.Methodology In 2019, an online questionnaire was distributed to the 18 dental schools within the UK and Ireland and 8,568 GDPs. These surveys explored current trends in teaching and usage of endodontic irrigants. Chi-squared tests were performed to make comparisons between NHS and private GDPs (α <0.01).Results All 18 dental schools (100%) and 495 GDPs (6%) returned valid questionnaires. Three hundred and thirty (66.7%) practitioners were NHS and 165 (33.3%) were private. There was strong consensus on irrigation teaching amongst dental schools. These results aligned with GDP responses in terms of irrigant selection (sodium hypochlorite [NaOCl]); NaOCl concentration (≤3%); ethylenediaminetetraacetic acid (EDTA) contact time (>0-5 minutes); final rinse protocols (penultimate EDTA rinse); irrigant temperature (room); and agitation techniques (manual dynamic activation; >0-60 seconds). There was, however, considerable variation in NaOCl contact time and GDPs infrequently used chelating agents or agitation techniques. Compared with private practitioners, NHS GDPs used significantly lower NaOCl contact times and concentrations, less EDTA and activation techniques, and more chlorhexidine (P <0.01).Conclusions Overall, irrigation teaching within the UK and Ireland is consistent and evidence-based. Furthermore, trends in irrigant usage amongst UK GDPs are now more aligned with these teaching practices. Significant differences were, however, observed between NHS and private practitioners.

Working Length Transfer in the Endodontic Clinical Practice: A Comparative Study

The present paper evaluated the accuracy of two different methods for transferring working length (WL) between manual endodontic instruments and nickel–titanium (NiTi) shaping files. Thirty root canals of extracted permanent teeth were used. Root canals were divided according to canal length (CL) and canal curvature (CC). The reference cusp and the root end were flattened to provide reproducible and accurate measurements. During shaping, the WL measurements were obtained with manual k-files (KF) and transferred to WaveOne (W1) NiTi reciprocating files using the traditional method with the endodontic ruler (method I) and an alternative clinical procedure based on the comparison of the instruments side by side from tip to shank (method II). For each file and each tested method, two measures were taken by two examiners using Rhino (ver. 4.0, McNeel, Seattle, WA, USA) software for a total of 360 (30 × 3 × 2 × 2) measures. Analysis of variance was performed by taking the difference in length (Delta WL, DWL) between files used for the same canal. The difference between methods I and II for WL transfer was found to be statistically significant (df = 1; F = 71.52; p < 0.001). The DWL absolute values obtained with method II were found to be closer to 0 mm (i.e., same length as corresponding KF) than those obtained with method I. Both CL (df = 2; F = 1.27; p = 0.300) and CC (df = 1; F = 2.22; p = 0.149) did not significantly influence WL measurements. With respect to WL transfer, method II seemed to better preserve the correct WL transfer between instruments during the clinical endodontic procedures.

Current Trends in the Use of Irrigant Activation Techniques Among Endodontists & Post-Graduate Dental Students in India -A Knowledge, Attitude and Practice Based Survey

Objective:

The aim of this survey was to examine the practice/use of Irrigant Activation Techniques (IAT) among Endodontists and post-graduate dental students in India.

Methods:

An invitation to participate in this survey was sent by electronic mail to 902 members of Indian Endodontic society. A total of 32 questions were finalized for the survey after validation by five endodontic experts. Survey contained 2 demographic questions, 7 knowledge based questions, 11 questions on attitude and 12 questions on practice of IAT. The reliability was checked by randomly asking 10 participants to fill the survey forms again after 15 days. The data was analyzed using chi-square test (P<0.05).

Results:

The overall response rate for the survey was 30.5%. The content validity ratio for the questionnaire was 0.972 & the reliability calculated using Kappa scores was 0.978. Most of the respondents (87.3%) use IAT, while 4.7% do not use IAT. Most commonly used IAT was Manual dynamic agitation (MDA) used by 28.7%, followed by Ultrasonics in 17.2%. Sonic & negative pressure (EndoVac) was used by less than 10% of respondents. Combination of IAT was used by 39%. In 23 (5 on knowledge, 9 on attitude & 9 on practice) out of the 32 questions in this survey, there was a statistically significant difference (P<0.05) in the answers between the groups, with post-graduate dental students opting the correct choices. Sodium hypochlorite (NaOCl) is the preferred choice of irrigant for IAT according to 48.6%, Chlorhexidine (CHX) is used by 4.2% & Ethylene diamine tetra acetic acid (EDTA) by 2.4%. Combination of two irrigants is used by 28.7% and 6% use all the three irrigants.

Conclusion:

Vast majority of the Endodontist in India use some form of IAT to improve the efficacy of irrigation. MDA is the most commonly used IAT.

Measurement of Simulated Debris Removal Rates in an Artificial Root Canal to Optimize Laser-Activated Irrigation Parameters

BACKGROUND AND OBJECTIVES

To compare temporal rates of debris removal from an artificial root canal for three laser-assisted irrigation modalities single-pulse super short pulse (SSP), and two dual-pulse X-SWEEPS and AutoSWEEPS, and for two fiber-tip (FT) geometries flat and radial, and to evaluate the dependence of the debris flushing rate on the delay between the SWEEPS laser pulse pair.

STUDY DESIGN/MATERIALS AND METHODS

Laser-assisted irrigation was performed with a pulsed Er:YAG laser operating in single-pulse SSP and dual-pulse SWEEPS laser modalities. The laser energy was delivered to the water-filled model access cavity through a FT with either a flat or radial ending. The X-SWEEPS modality delivered pairs of laser pulses separated by a fixed adjustable delay, while with the AutoSWEEPS modality the delay was automatically and repeatedly swept between 200 and 600 microseconds. The debris removal rate was determined with the use of a digital camera by measuring the rate at which a simulated debris was being flushed out of the artificial root canal.

RESULTS

The simulated debris removal rate of the AutoSWEEPS modality is almost three times higher compared with that of the SSP modality. Further, the flat FT outperforms the radial FT by a factor of more than five in the case of SSP, and by more than 10 with AutoSWEEPS. The X-SWEEPS flushing rate exhibits strong dependence on the delay between the SWEEPS pulse pair, with the highest removal rate measured to be more than seven times higher in comparison with SSP.

CONCLUSION

Dual-pulse laser irrigation modalities (AutoSWEEPS and X-SWEEPS) exhibit significantly higher simulated debris removal rates in comparison with the standard single-pulse SSP laser-assisted irrigation. As opposed to the previously reported dependence of pressure generation on FT geometry, the flat FT's simulated debris removal rate significantly outperforms the radial FT. © 2020 The Authors. Lasers in Surgery and Medicine published by Wiley Periodicals LLC.

Effect of different laser-assisted irrigation activation techniques on apical debris extrusion

Objective: The aim of this study was to compare apical debris extrusion when neodymium-doped yttrium aluminium garnet (Nd:YAG) lasers, erbium-doped yttrium aluminium garnet (Er:YAG) or photon-induced photoacoustic streaming (PIPS) are used for irrigation activation.Materials and methods: A total of 60 extracted human mandibular premolar teeth have similar dimensions were included and the samples were split into four groups according to the irrigation technique (n = 15): conventional needle irrigation, PIPS, Er:YAG and Nd:YAG. ProTaper Universal system up to F4 was used for root canal instrumentation. Bidistilled water was used as an irrigation solution during instrumentation and irrigation activation. Apically extruded debris was collected into preweighed Eppendorf tubes during instrumentation and irrigation activation procedures. The tubes were then kept in an incubator at 70 °C for 5 days. The initial weight of the tube was subtracted from the final weight and the result was recorded as the weight of dry extruded debris. The data were evaluated statistically using a one-way ANOVA test followed by least significant difference post hoc test (p < .05).Results: Conventional needle irrigation caused significantly less debris extrusion than laser-assisted irrigation activation groups (p < .05). Laser-assisted irrigation activation groups caused statistically similar debris extrusion (p > .05).Conclusion: Laser-assisted irrigation activation techniques caused more debris extrusion when compared to conventional needle irrigation.

Assessment of Mechanical Root Canal Preparation with Centric Reciprocating or Eccentric Rotary Kinematics: A Micro-computed Tomographic Study

INTRODUCTION

The aim of this study was to compare, using micro-computed tomographic imaging, the preparation of mesial canals of mandibular molars with the Reciproc (VDW GmbH, Munich, Germany) and XP-endo Shaper (FKG, La Chaux-de-Fonds, Switzerland) systems, evaluating changes in dentin and canal volume, the percentage of untouched walls, the volume of accumulated hard tissue debris, and root canal deviation in the apical third.

METHODS

Twenty-four mandibular molars with 2 mesial root canals and a single foramen were anatomically paired and divided into 2 experimental groups (n = 12) according to the system used. The specimens were scanned before and after preparation with the SkyScan 1176 microtomographic scanner (Bruker-microCT, Kontich, Belgium) at a resolution of 17.42 μm. The resulting data were statistically compared at a significance level of 5% using the Student t test and the Mann-Whitney test.

RESULTS

A significant difference was observed in the untouched surface area for the total canal and the cervical and middle thirds, with the lowest untouched surface area in the XP-endo Shaper group (P < .05). The volume of accumulated hard tissue debris was significantly higher in the Reciproc group in the total canal as well as in the middle and apical thirds. There was no significant difference between the groups regarding the volume of dentin removed or the increase in canal volume and surface area (P > .05).

CONCLUSIONS

The XP-endo Shaper touched more walls and left less accumulated hard tissue debris in the root canal system than the Reciproc group. Although the XP-endo Shaper showed superior results, neither system was able to fully prepare the root canal.

Evaluation of various irrigation activation systems to eliminate bacteria from the root canal system: A randomized controlled single blinded trial

OBJECTIVE

To evaluate the effect of NaOCl irrigant activation using passive ultrasonic activation, F-files, XP-endo Finisher files and or needle irrigation alone on the reduction of intracanal bacteria from root canals in teeth undergoing root canal treatment.

METHODS

Eighty patients with asymptomatic apical periodontitis were randomly divided into four groups. Access cavities were prepared and pre-treatment samples were taken (S1). Canals were then prepared and post-instrumentation samples (S2) taken. NaOCl was then activated with the various irrigant activation systems and post-irrigation samples (S3) taken. The samples were processed and colony forming units (CFUs) of bacteria were determined. The reduction in CFUs among the experimental groups were analysed using the Kruskal Wallis test and pairwise comparisons with the Mann-Whitney test. The Friedman test was used to compare the differences in the reduction of CFUs within the groups.

RESULTS

Overall, for all groups there was a significant reduction in the CFUs from S1 to S2 (P < 0.05) and from S2 to S3 (P < 0.05). Both XP-endo Finisher and passive ultrasonic activation techniques were associated with the greatest reduction in CFUs with no significant difference between them (P = 0.24). However, both were associated with significantly lower CFUs when compared to F-file activation and needle irrigation (P < 0.05). F-file activation reduced the CFUs significantly more compared to needle irrigation (P = 0.04).

CONCLUSIONS

XP-endo Finisher file activation and passive ultrasonic activation were equivalent in terms of reduction in CFUs. F-file activation did not reduce the CFUs to the same extent as the XP-endo Finisher file and ultrasonic activation but reduced the CFUs more than needle irrigation.

CLINICAL SIGNIFICANCE

The present study highlights the effect of new XP-endo Finisher file and passive ultrasonic activation in reducing the bacterial load from the root canal system which is important for the success of root canal treatment.

Micro-computed tomographic assessment of the shaping ability of the One Curve, One Shape, and ProTaper Next nickel-titanium rotary systems

Objectives

This micro-computed tomographic (CT) study aimed to compare the shaping abilities of ProTaper Next (PTN), One Shape (OS), and One Curve (OC) files in 3-dimensionally (3D)-printed mandibular molars.

Materials and Methods

In order to ensure standardization, 3D-printed mandibular molars with a consistent mesiobuccal canal curvature (45°) were used in the present study (n = 18). Specimens were instrumented with the OC, OS, or PTN files. The teeth were scanned pre- and post-instrumentation using micro-CT to detect changes of the canal volume and surface area, as well as to quantify transportation of the canals after instrumentation. Two-way analysis of variance was used for statistical comparisons.

Results

No statistically significant differences were found between the OC and OS groups in the changes of the canal volume and surface area before and after instrumentation (p > 0.05). The OC files showed significantly less transportation than the OS or PTN systems for the apical section (p < 0.05). In a comparison of the systems, similar values were found at the coronal and middle levels, without any significant differences (p > 0.05).

Conclusions

These 3 instrumentation systems showed similar shaping abilities, although the OC file achieved a lesser extent of transportation in the apical zone than the OS and PTN files. All 3 file systems were confirmed to be safe for use in mandibular mesial canals.

Spatial Cleaning Action of Ultrasonic Irrigation on Enterococcus faecalis Biofilm

This study aimed to examine the spatial cleaning effect of ultrasonic irrigation in simulated root canal with oblong cross section in the absence of antimicrobial agent. A 7-day E. faecalis biofilm was cultivated in a rectangular, simulated canal model and subjected to passive ultrasonic irrigation (PUI) with sterile saline for 5 minutes. After that, the biofilm was examined by confocal microscopy after bacterial viability staining at 58 sites around and beyond the endosonic file. Results showed that, at the vicinity of the file, the amount of viable bacteria ranged from 13.1% (2.75 mm from the tip) to 40.5% (4.5 mm level). Lesser amounts of live bacteria were observed within 1 mm from the vibrating file, which amount increased for sites farther away. At 3 mm distance, the amount of bacteria (35.5 to 64.4%) was significantly greater than areas situated close to the vibrating file (P < 0.01). Sites next to the anti-nodes of file had less bacteria remaining than sites near the nodes (P = 0.050). Apically (0.5 mm or more), the amount of bacteria was significantly greater than that at the file tip (16.4%) (P < 0.05). It was concluded that PUI is able to dislodge a single-species biofilm, provided that they are situated in close vicinity to the vibrating file.

A micro-CT evaluation of the performance of rotary and reciprocating single-file systems in shaping ability of curved root canals

To compare the shaping ability of different single-file systems in the preparation of mesial curved canals of mandibular molars using micro-CT technology. Fifteen mesial roots of mandibular molars with two independent and curved canals (n = 30) were selected, scanned at a resolution of 26.7 μm anatomically matched, and distributed into three groups (n = 10), according to the preparation system: WaveOne 25.08, Reciproc 25.08, and OneShape 25.06. A final micro-CT scanning was performed, data sets were registered with their respective counterparts, and compared regarding the three-dimensional (volume, surface area, and structure model index - SMI) and two-dimensional (perimeter, area, roundness, major and minor diameters) parameters, as well as, canal transportation, using ANOVA and post hoc Tukey tests (α = 5%). Overall, no difference was observed between groups regarding area, perimeter, volume, surface area, and canal transportation (p > 0.05). Within group, no canal transportation was significantly higherobserved in the apical third (0.10 ± 0.05 mm) compared to coronal (0.08±0.040 mm) and middle (0.07 ± 0.03 mm) thirds (p < 0.05). Structure model index (SMI) was statistically higher after preparation with OneShape instrument (0.36 ± 0.26) compared to other systems (p < 0.05). Within the parameters of this study, similar shaping ability was observed in the preparation of mesial curved root canals of mandibular molars with Reciproc, OneShape and WaveOne systems.

Evaluation of Pressure Distribution against Root Canal Walls of NiTi Rotary Instruments by Finite Element Analysis

The aim of this study was to evaluate the contact pressure distribution of two different nickel-titanium (NiTi) endodontic rotary instruments against the root canal walls and to virtually predict their centering ability during shaping with finite element analysis (FEA). Resin blocks simulating root canals were used. One was shaped with ProGlider and ProTaper Next (PTN) X1-X2 and one with ScoutRace and BioRace (BR) 1, 2 and 3. Both resin blocks were virtually replicated with computer-aided design (CAD) software. The endodontic instruments ProTaper Next (PTN) X2 and BioRace BR3 were also replicated with CAD. The NiTi instruments and the shaped blocks geometries were discretized and exported for FEA. The instrument rotation in the root canals was simulated. The finite element simulation was performed by applying an insertion and extraction force of 2.5 N with a constant rotational speed (300 rpm). To highlight possible differences between pressure distributions against the root canal portions outside and inside the canal curvature, the parameter Var was originally defined. Var values were systematically lower for PTN X2, revealing a better centering ability. FEA proved effective for the virtual prediction of the centering ability of NiTi instruments during an early design phase without the use of prototypes.

A micro-computed tomographic assessment of root canal preparation with conventional and different rotary files in primary teeth and young permanent teeth

BACKGROUND

Root canals of primary teeth are commonly prepared with endodontic files that are originally manufactured for permanent teeth.

AIM

This micro-computed tomography (micro-CT) study evaluated and compared the changes in root canal morphology after preparation with different conventional and rotary files in primary teeth and young permanent teeth.

DESIGN

Seventy-two extracted primary and permanent molars were selected and randomly assigned to three subgroups according to the file systems used (n = 12/each). After pre-scanning of teeth with micro-CT, root canals were prepared with One Shape and Revo-S rotary systems and conventional endodontic files. After rescanning procedure, changes in canal volume, surface area, uninstrumented surface area, and apical transportation were evaluated. Mann-Whitney U test, Kruskal-Wallis test, and Conover's multiple comparison test were used for statistical analysis (P = .05).

RESULTS

Instrumentation with rotary files resulted in significantly greater volume and surface area of root canals and less uninstrumented areas (P < .001) than with manual files (P < .001). Primary molars showed significantly less apical transportation than permanent teeth (P < .001).

CONCLUSIONS

Preparation of canals with rotary files could be a viable alternative to conventional files in primary teeth. Regardless of the file system used, uninstrumented areas still exist in both primary teeth and permanent teeth.

Characteristics of Bubble Oscillations During Laser-Activated Irrigation of Root Canals and Method of Improvement

BACKGROUND AND OBJECTIVES

Laser-activated irrigation of dental root canals is being increasingly used as its efficacy has been shown to be superior compared with conventional techniques. The method is based on laser-initiated localized fluid evaporation and subsequent rapid bubble expansions and collapses, inducing microfluid flow throughout the entire volume of the cavity. The irrigation efficacy can be further improved if optimally delayed "SWEEPS" double laser pulses are delivered into the canal. This study aims to show that the irrigation efficacy, as measured by the induced pressure within the canal, is related to the double pulse delay, with the maximal pressure generated at an optimal delay. The second aim is to find a method of determining the optimal delay for different cavity dimensions and/or laser parameters.

STUDY DESIGN/MATERIALS AND METHODS

Experiments were made in transparent models of root canals where Er:YAG laser (λ = 2.94 μm, pulse duration t_p  = 25 or 50 microseconds, and pulse energies up to E_L  = 40 mJ) was used with a combination of cylindrical and conical fiber-tip geometries (diameters 400 and 600 µm). High-speed photography (60,000 fps) and average pressure measurements inside the canal were used for process characterization.

RESULTS

The results show that a pressure amplification of more than 1.5 times occurs if the laser pulse delay approximately coincides with the bubble oscillation time. Correlations between normalized oscillation time and canal diameter for a wide range of laser pulse energies (R²  = 0.96) and between the average pressure within the canal and the bubble oscillation periods (R²  = 0.90) were found. A relationship between the bubble oscillation time and the diameter of the treated cavity was found depending on the bubble oscillation time in an infinite fluid reservoir.

CONCLUSIONS

The bubble oscillation time within a constrained volume can be determined based on the known oscillation time in infinite space, which offers a fast and simple solution for optimization of the laser parameters. These findings enable determination of optimal conditions for shock wave generation, and improvement of root canal irrigation at the same dose of laser energy input, leading to improved treatment efficacy and safety. Lasers Surg. Med. © 2020 The Authors. Lasers in Surgery and Medicine published by Wiley Periodicals, Inc.

Modulation of virulence in Enterococcus faecalis cells surviving antimicrobial photodynamic inactivation with reduced graphene oxide-curcumin: An ex vivo biofilm model

BACKGROUND

Enterococcus faecalis, as a major microorganism in persistent/secondary infections of endodontically treated teeth, is less likely to be eliminated during endodontic therapy. In this study, the effect of root canal disinfection and anti-virulence activities of photodynamic inactivation (PDI) of E. faecalis utilizing reduced graphene oxide-curcumin (rGO-Cur) as a photosensitizing agent following irradiation with light-emitting diode (LED), as well as intracellular ROS production were evaluated on ex vivo biofilms of E. faecalis in comparison with sodium hypochlorite (NaOCl) as the traditional endodontic irrigation solution.

MATERIALS AND METHODS

After formulation and confirmation of synthesized rGO-Cur using scanning electron microscopy (SEM), Fourier transformation infrared (FT-IR), UV-Vis spectra, dynamic light scattering (DLS), and Zeta potential, the minimum biofilm inhibitory concentrations (MBICs) and in vitro anti-biofilm activity of rGO-Cur, light-emitting diode (LED) at the wavelength of 435 ± 20 nm, and rGO-Cur-PDI were determined against 4-week-old pre-formed biofilms of E. faecalis. After preparation of ex vivo biofilm model in root canals, the ex-vivo anti-biofilm potential of rGO-Cur, LED, and rGO-Cur-PDI against E. faecalis were analyzed using the XTT assay and scanning electron microscopy (SEM) in comparison with NaOCl. The effects of sub-MBIC of rGO-Cur and NaOCl, sub-lethal dose of LED, and sub-significant inhibitory (SSI) potential of rGO-Cur-PDI for E. faecalis biofilms on virulence genes (efa, esp, gel, and fsr) expression of E. faecalis were analyzed using real-time polymerase chain reaction (qRT-PCR) assay. Intracellular reactive oxygen species (ROS) level was measured in rGO-Cur-PDI-treated bacterial cells compared to control cells with 2',7'-dichlorfluorescein-diacetate (DCFH-DA) fluorescent probe.

RESULTS

The FTIR, DLS, Zeta potential, SEM, and UV-Vis spectra analysis indicated the successful synthesis of rGO-Cur. The MBIC of rGO-Cur was 250 μg/ml, which inhibited the growth ofE. faecalis. LED showed insignificant anti-biofilm activity against E. faecalis even after treating for a long irradiation time (300 s). According to checkerboard assay, the MBIC value of rGO-Cur-PDI was reduced noticeably compared to the individual MBIC values of rGO-Cur and LED for E. faecalis. The expression levels of efa, esp, gel, and fsr genes in pre-formed E. faecalis biofilms were markedly reduced after rGO-Cur, rGO-Cur-PDI, and NaOCl treatment in comparison with the control group. Conversely, LED revealed no significant change in the expression of the virulence genes. The intracellular ROS assay showed a significant increase (8.3-fold) in rGO-Cur-PDI when compared to the control.

CONCLUSION

Our data support that rGO-Cur-PDI showed dual inhibitory effects on biofilm formation ability and virulence activity of E. faecalis with potential clinical applications for infection control in endodontics.

Comparative Evaluation of the Efficacy of Chlorhexidine, Sodium Hypochlorite, the Diode Laser and Saline in Reducing the Microbial Count in Primary Teeth Root Canals - An In Vivo Study

Introduction: One of the primary goals of pulpectomy is to decrease the sum total of microorganisms and disinfect the tooth root canal system. To achieve this, mechanical preparation, irrigation, disinfection and obturation of the root canal is necessary. The present study was set out to evaluate the difference in the antibacterial efficacy of primary teeth root canals either irrigated with chlorhexidine, saline, and sodium hypochlorite or irradiated with a soft tissue diode laser (980 nm, Photon Plus, Zolar Tech & Mfg Co. Inc, Ontario, Canada). Methods: Sixty primary teeth of children requiring pulpectomy were divided into 4 groups of 15 each, group 1 (2% chlorhexidine), group 2 (1% sodium hypochlorite), group 3 (laser irradiation) and group 4 (saline). Pulp tissue was extirpated from the canals and the samples were collected using sterile absorbent paper points. After cleaning and shaping, the root canals of the teeth in each group were irrigated using sodium hypochlorite, chlorhexidine, and saline or were irradiated with the laser. The samples were obtained again and sent for microbiological examination. Results: The colony-forming unit (CFU) counts from pre-disinfection sample served as a baseline for comparisons throughout the study. The mean bacterial colony counts of all the isolated bacteria reduced after irrigation or irradiation. Intergroup comparisons showed no significant difference when groups 1, 2, and 3 were compared to each other (P > 0.05). However, a significant difference was seen when groups 1, 2, 3 were compared to group 4 (P < 0.05). Conclusion: Two percent chlorhexidine, 1% sodium hypochlorite and laser irradiation succeeded in reducing the root canal infection. Hence, diode laser irradiation may be a possible supplement to existing protocols for disinfecting the root canal system.