Effect of EDTA, Sodium Hypochlorite, and Chlorhexidine Gluconate with or without Surface Modifiers on Dentin Microhardness

Comparative Analysis of Fracture Resistance of Endodontic Sealer Types and Filling Methods

With the advent of bioceramic sealers, sealers have become a more important filling material for endodontic treatment. When a solid sealer, rather than an elastic gutta-percha, occupies a significant portion of the root canal, it is unclear whether the tooth structure will be strengthened to withstand stress or whether the increased stiffness will transmit the load directly to the entire root, potentially causing root fracture. This study compared the fracture resistance and fracture patterns of roots filled with various root canal sealers, including bioceramic sealers, and each corresponding filling technique. Five groups (n = 10) were tested, including no endodontic treatment, no canal obturation, resin-based sealers with continuous-wave compaction, bioceramic sealers with single-cone technique, and mineral trioxide aggregate (MTA) orthograde obturation. The specimens were radiographed to assess the filling quality. After embedding the specimens in acrylic resin, fracture resistance was tested by a universal testing machine, and fracture features were examined microscopically. The results showed that the bioceramic sealer group using the single-cone technique had the highest fracture strength. Radiographic analysis revealed that achieving void-free filling was more difficult with MTA orthograde obturation compared to resin-based and bioceramic sealer groups. No significant variation in fracture features was observed across the groups.

Effect of final irrigation protocols on the structural integrity and mechanical properties of the root dentine

This study compared the effects of different final irrigation protocols on the mechanical properties and structural integrity of root dentine. One-hundred eight teeth were instrumented and irrigated with sodium hypochlorite (NaOCl) using conventional irrigation (CI). Teeth were distributed into four groups based on final irrigation protocols: Control Group (CG): 17%EDTA/CI + H2O; G1: 2.5%NaOCl/Passive Ultrasonic Irrigation (PUI) + EDTA/PUI + NaOCl/PUI (60s each); G2: EDTA/PUI + NaOCl/PUI (30s each); G3: EDTA/PUI + NaOCl/PUI + H2O/PUI + CHX/PUI (30s each). Four tests were conducted: three-point flexural strength test, Scanning Electron Microscopy analysis, microhardness assessment, and the push-out bond strength (POBS) of the filling material to the root dentine. Data were analyzed using ANOVA and Tukey tests (Flexural strength), and Student t-test (Microhardness). Erosion scores and POBS were analyzed by Kruskal-Wallis and Dunn tests (α = 0.05). Results indicated no significant differences in flexural strength (p > 0.05) among groups. CG exhibited the lowest erosion scores in the cervical third. In the middle third, CG had lower scores than G1 and G2, while in the apical third, CG had lower scores than G1 (p < 0.05). Microhardness values decreased following the protocols (p < 0.05), except for the CG (p > 0.05). G2 displayed higher POBS values in the middle and apical thirds (p < 0.05). The protocols did not significantly influence the flexural strength of root dentine. However, they did affect microhardness and promoted greater erosion. The best results for POBS were observed when the final irrigation involved the sequential use of EDTA and NaOCl employing PUI for 30 seconds in each solution.

Push-out Bond Strength of Two Bioceramic Sealers after Using Various Final Irrigation Solutions: An In Vitro Study

AIM

This study assessed how different final irrigation solutions impact the push-out bond strength (PBS) of EndoSequence Bioceramic (BC) and cerafill BC sealers.

METHODS

Eighty single-root lower premolars were selected and decoronated. The root canals were then cleaned and shaped chemo-mechanically using ProTaper files up to F5, with 5.25% sodium hypochlorite applied between each file for rinsing. Subsequently, the teeth were categorized into four primary groups of 20 each, distinguished by their final irrigation solution. Group A utilized 17% glycolic acid (GA), group B used a 5% apple vinegar solution, group C employed 17% ethylenediamine tetraacetic acid (EDTA), and group D used saline. Each group was further divided into two subgroups of 10 teeth each, based on the type of BC sealer applied-Cerafill BC sealer for subgroup a, and EndoSequence BC sealer for subgroup b. Two dentin disks were then obtained from the middle third of each root (n = 20) and subjected to the PBS test. Upon completion of this test, the dentin disks were scrutinized under a stereomicroscope to determine the mode of failure for each disk.

RESULTS

The use of EndoSequence BC sealer in obturation led to the apple vinegar final irrigation group exhibiting significantly higher PBS than the GA and saline solution groups. Furthermore, when implemented with cerafill BC sealer, the EDTA final irrigation solution group displayed the greatest PBS, showing a significant difference compared with the GA and saline solution groups.

CONCLUSION

Apple vinegar solution could be a potential alternative to EDTA as a chelating agent during root canal treatment, though further research is required.

CLINICAL SIGNIFICANCE

The EDTA and apple vinegar are effective at removing smear layers, which improves sealer penetration and prevents obturation materials dislodgment. How to cite this article: Alnoury AS, Abdalwassie MK, Alawbthani MW, et al. Push-out Bond Strength of Two Bioceramic Sealers after Using Various Final Irrigation Solutions: An In Vitro Study. J Contemp Dent Pract 2024;25(12):1092-1098.

Comparative Evaluation of the Effect of Different Irrigation Regimens With and Without Ultrasonic Activation on Root Dentin Microhardness: An In Vitro Study

Background The structural properties of dentin, including its microhardness, can be affected by exposure to endodontic irrigating solutions and ultrasonic activation. Aim The current study aimed to assess the effect of three different irrigation regimens, with and without ultrasonic activation, on the microhardness of the dentin. Methodology The research was conducted on 120 mandibular premolars randomly divided into four groups (n=30) based on the irrigation regimen, with each group further divided into two subgroups (n=15). Subgroups 'a" were subjected to respective irrigation regimens without ultrasonic activation. Subgroups 'b' were subjected to ultrasonic activation. The Vickers microhardness test was conducted on the samples, and the data underwent statistical analysis using the independent sample t-test, ANOVA, and the Tukey test. Results The observations of the study unveiled that the microhardness of the root dentin was decreased by all the irrigation regimens. Microhardness values of dentin showed higher reduction with ultrasonic activation than without ultrasonic for all groups. Conclusions The dentin microhardness was significantly reduced when 3% and 5% sodium hypochlorite were used with 17% ethylenediaminetetraacetic acid (EDTA) as irrigation solutions. Ultrasonic activation of the irrigants had an adverse effect on the microhardness of dentin.

Effectiveness of chitosan nanoparticles, and novel chemical irrigants with surfactant on smear layer removal and microhardness alteration

Objective

This current study was designed to compare and correlate between smear layer eradication and reduction in microhardness by natural 0.2%chitosan nanoparticles and novel chemical irrigants with surfactant at the apical root third.

Materials and method

One hundred and twenty straight single-rooted extracted lower premolars were decoronated and working length obtained with #10 K-file. Pro-taper rotary files were used till apical size F3. The canals were simultaneously flushed with assigned irrigant containing surfactant [(ChX-Ultra, NaOCl-Extra, Pro-EDTA, 0.2%chitosan nanoparticles, Biopure MTAD]. The samples were randomly divided into two equal groups (n = 60). InGroup S (n = 60), the residual smear layer was examined by scanning electron microscope and in Group M(n = 60) microhardness was determined by Vickers Microhardness Tester. Further both groups were divided into six equal groups (n = 10 each) according to assigned irrigating solutions.For smear layer removal; Kruskal-Wallis tests followed by pair wise comparison using Mann Whitney U test was done. For change in microhardness ANOVA and post hoc Tukey tests was done.

Results

Maximum smear layer removal was recorded in Biopure MTAD (1.8 ± 0.63), followed by pro-EDTA (2.2 0 ± 0.63) then 0.2%chitosan (2.6 ± 0.51), then NaOCL Extra (3.5 ± 0.53)and least in CHX-Ultra (4.4 ± 0.52) and saline (5.0 ± 0.00). Pro-EDTA group (12.8 ± 2.47) revealed significant highest reduction in microhardness followed by Biopure MTAD (8.01 ± 3.06), 0.2%chitosan nanoparticles (5.48 ± 2.87), NaOCl-Extra (5.44 ± 1.62) and least recorded in CHX-Ultra (4.94 ± 1.43) and saline (3.04 ± 0.63).

Conclusion

The elimination of the smear layer is always accompanied by a reduction in microhardness. Moreover, irrigant with surfactant and chelators enhanced smear layer removal, with best perceived in Biopure MTAD.

Investigating the Effects of Various Root Canal Irrigation Solutions on Tissue Dissolution and Microbial Control

Background

Both the mechanical cleansing effect and the irrigants' capacity to disintegrate tissue are necessary for irrigation to be successful. Strong antibacterial but not poisonous to the periapical tissues and increased pulp tissue dissolution irrigant are all desirable qualities in an irrigant.

Aim

To assess and compare the antibacterial properties and pulp tissue dissolving activity of various irrigation solutions.

Methods and Materials

A total of 240 human mandibular permanent premolar teeth that were extracted recently for periodontal or orthodontic reasons were used in this investigation. Following irrigation, blood agar plates were used to conduct colony-forming unit (CFU) counts of the microorganism breeding colonies. Next, log CFU was computed. Before evaluating the ability of the five distinct irrigants utilized in this investigation to dissolve the frozen pulp tissues, the tissues were first smashed into smaller pieces using a mallet.

Results

The bacterial count after irrigation in category 1 (normal saline), category 2 (aqueous ozone), category 3 (ethylenediaminetetraacetic acid (EDTA)), category 4 (chlorhexidine gluconate (CHX)), category 5 (super-oxidized water), and category 6 (sodium hypochlorite (NaOCl)) was 6.08 ± 0.87 log CFU mL-1, 0.92 ± 0.89 log CFU mL-1, 4.15 ± 0.20 log CFU mL-1, 3.34 ± 0.46 log CFU mL-1, 0.21 ± 0.52 log CFU mL-1, and 0.00 ± 0.00 log CFU mL-1, respectively.

Conclusion

NaOCl has maximum antimicrobial reduction and pulp tissue dissolution property.

In vitro evaluation of the impact of a bioceramic root canal sealer on the mechanical properties of tooth roots

Bacground/purpose

Endodontically treated teeth are more prone to vertical root fracture with the mechanical property changes to some extent during root canal treatment. This study aimed to investigate the effects of a bioceramic sealer on the mechanical properties of tooth roots.

Materials and methods

Dentin discs were dried by two different methods (ethanol drying and paper points drying) and then filled with a BC sealer named iRoot SP. SEM and EDS were used to analyze the newly formed minerals in dentin tubules. Elastic modulus and hardness of the secondary dentin in areas proximal to the primary dentin (PD-SD) and areas proximal to canal or iRoot SP (SD-C/SD-iRoot SP) were measured using nanoindentation technique. The compressive strength of roots filled with iRoot SP were tested by compressive loading test.

Results

(1) Penetration and mineralization: Paper points drying was more conducive to iRoot SP adhesion, spreading and penetration into the dentin tubules than 95% ethanol drying. (2) Micromechanical properties: After filling root canal with iRoot SP, the elastic modulus and hardness of SD-iRoot SP were higher than those of PD-SD (P = 0.001 and P = 0.000). (3) Fracture resistance: The compressive strength of the roots filled with iRoot SP was not significantly different from that of the roots unprepared and unfilled (P = 0.957), but was higher than that of the roots prepared and unfilled (P = 0.009).

Conclusion

Excessive drying (95% ethanol drying method) is not conducive to the penetration and mineralization of the BC sealer iRoot SP into dentin tubules. The good bioactivity of iRoot SP was responsible for increasing the elastic modulus and hardness of dentin, which strengthened the prepared roots.

Effect of Different Irrigating Solutions on Root Canal Dentin Microhardness-A Systematic Review with Meta-Analysis

The aim of this study was to evaluate the effect of different irrigating solutions as well as their combination and activation modes on root canal dentin microhardness. The protocol was registered in PROSPERO and PRISMA guidelines were followed. The structured question was as follows: "Which type of irrigating solution used in endodontic treatment causes more change in dentin microhardness?" The literature was screened via PubMed, Google Scholar, Scopus, and Science Direct. The last search was carried out in February 2023 with English language restriction. Two reviewers independently performed screening and evaluation of articles. A total of 470 articles were retrieved from all the databases, whereas only 114 articles were selected for full-text analysis. After applying eligibility criteria, 44 studies were evaluated and included in this review. The results showed that with increased contact time with irrigants, dentin microhardness decreases. Increased contact time with sodium hypochlorite (NaOCl) was associated with more reduction in dentin microhardness compared with other irrigants. Other irrigants, with the exception of distilled water, including EDTA, citric acid, herbal irrigants, glycolic acid, phytic acid, etc., in this study significantly decreased dentin microhardness. The maximum reduction in dentin microhardness was seen with 2.5% NaOCl after 15 min of contact time. The use of irrigating solutions alters the chemical composition of dentin, thereby decreasing its microhardness, which affects the clinical performance of endodontically treated teeth.

The effect of sealer type and obturation technique on the fracture resistance of endodontically treated roots

OBJECTIVE

This study evaluated the effect of sealer type with various obturation techniques on the fracture resistance of root filled teeth.

MATERIALS AND METHODS

Eighty mandibular premolars were collected, and root canals of 70 of them were prepared by Mtwo system up to 40/04. Thirty teeth were obturated using TotalFill BC sealer, and 30 using AH Plus sealer, with one of the obturation techniques (N = 10), namely cold lateral compaction (CLC), warm vertical compaction (WVC), and single cone (SC). Ten teeth were left without obturation as a positive control, and the other 10 teeth were not prepared serving as a negative control. Teeth were stored for 3 weeks, and the crowns were separated and the roots were subjected to fracture test using a universal testing machine.

RESULTS

Data was analyzed by ANOVA followed by Tukey's test. Fracture resistance of the TotalFill groups was significantly higher than the AH Plus groups in each obturation technique, and SC had the highest fracture resistance regardless of sealer used (P < 0.05). Obturation of the root canal by TotaFill BC sealer increased the calcium/phosphorous ratio in the dentin of the root.

CONCLUSIONS

Obturation with TotalFill BC sealer improved the fracture resistance of the roots more than AH Plus sealer, and obturation with SC resulted in higher fracture resistance than CLC and WVC.

CLINICAL RELEVANCE

Obturation of the root canal with Bioceramic sealer with single cone obturation technique could reduce the incidence of vertical root fracture.

The effect of nanobased irrigants on the root canal dentin microhardness: an ex-vivo study

BACKGROUND

Given the favorable antimicrobial properties of zinc oxide (ZnONPs), standard silver (AgNPs), and imidazolium-based silver (Im-AgNPs) nanoparticles, this study aimed to evaluate their influence on the microhardness of root canal dentin.

METHODS

In this experimental study, 40 mandibular premolars were decoronated at the cementoenamel junction and longitudinally sectioned into halves to create 80 specimens. They were randomly allocated to 5 groups (n = 16) and irrigated with ZnONPs, AgNPs, Im-AgNPs, NaOCl, or normal saline (as the negative control) for 15 min. The Vickers Hardness Number (VHN) was measured on each root canal third before and after being soaked in irrigants. Statistical analysis was performed using paired t-test, one-way ANOVA, and post hoc Tukey's test (α = 0.05).

RESULTS

Im-AgNPs and ZnONPs irrigants improved the microhardness of root dentin, whereas, AgNPs and NaOCl decreased it. ZnONPs yielded the highest VHN at the coronal third (P˂0.001), while the Im-AgNPs provided the highest VHN at the middle and apical thirds (P˂0.001). The AgNPs group showed the lowest VHN at the apical third.

CONCLUSIONS

The irrigants containing Im-AgNPs and ZnONPs significantly enhanced the root dentin microhardness. However, the use of AgNPs resulted in decreased microhardness.

Systematic review fracture resistance of endodontically treated posterior teeth restored with fiber reinforced composites- a systematic review

BACKGROUND

Large cavity designs and access cavities impair endodontically treated tooth fracture resistance. As the tooth's strength is known to reduce significantly after the root canal treatment, occlusal loading as a result of functions such as chewing, biting and certain parafunctional tendencies makes the endodontically treated tooth vulnerable to fracture. Hence, after endodontic treatment, it is vital to give adequate and appropriate restorative material to avoid tooth fractures. Accordingly, the choice of such restorative material should be dictated by the property of fracture resistance.

OBJECTIVE

The goal of this study was to conduct a systematic review and critical analysis of available data from in vitro studies examining the fracture resistance of endodontically treated posterior teeth restored with fiber-reinforced composites.

METHODOLOGY

The Preferred Reporting Items for Systematic Review and Meta-Analysis (PRIS-MA) Statement was used to guide the reporting of this systematic review A comprehensive literature search was performed using MEDLINE (via PubMed), Scopus, ScienceDirect, Google Scholar, and LILACS. A manual search of the reference lists of the articles was also performed. The databases provided a total of 796 studies from the electronic systematic search. The databases provided a total of 796 studies from the electronic systematic search. Two reviewers scrutinized the papers for eligibility based on inclusion/exclusion criteria and extracted data. The studies were assessed for their potential risk of bias. Based on modified JBI & CRIS (checklist for reporting in vitro studies) guidelines, along with the methodology and treatment objective, we have formulated 13 parameters specifically to assess the risk of bias. A total of 18 studies met the inclusion criteria and were included for qualitative analysis. Considering the high heterogeneity of the studies included, a meta-analysis could not be performed.

RESULTS

The majority of the included studies had a moderate or high risk of bias. When compared to traditional hybrid composites, fiber-reinforced composites showed increased fracture resistance of endodontically treated teeth in the majority of investigations. On the other hand, limited evidence was found for the bulk fill composites. Moreover, moderate evidence was found for the fracture resistance of inlays and fiber posts with fiber-reinforced composites for core build-up in endodontically treated teeth. No evidence could be found comparing the fracture resistance of endo crowns and fiber-reinforced composites in endodontically treated teeth.

CONCLUSION

According to the research, using fiber-reinforced composites instead of conventional hybrid composites improves the fracture resistance of endodontically treated teeth. However, there was a high risk of bias in the research considered. No judgments could be reached about the superiority of one material over another based-on comparisons between other core restorations.

Evaluation of Antibacterial Efficacy of High-Intensity Focused Ultrasound Versus Photodynamic Therapy Against Enterococcus faecalis-Infected Root Canals

OBJECTIVE

The high incidence of endodontic failure is associated with the remnants of Enterococcus faecalis present within the intricate anatomies of the root canal system (RCS), often inaccessible by the current endodontic practices. This study was aimed at evaluating the effect of high-intensity focused ultrasound (HIFU) and photodynamic therapy (PDT) on E. faecalis biofilms in artificially infected root canals for the potential application in current endodontic practices.

METHODS

Forty-five single-rooted extracted teeth were instrumented using hand files, sterilized in an autoclave, infected with E. faecalis and incubated for 4 wk. The specimens were treated and identified as follows: Control, 4% sodium hypochlorite (NaOCl); riboflavin (1 mg/mL); light only; HIFU (250 kHz, 20 W, 60s); PDT; riboflavin/HIFU; light/HIFU; and riboflavin/HIFU/light. Bactericidal efficacy was determined by colony-forming units (CFU), (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) (MTT) assay, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM).

RESULTS

Enterococcus faecalis biofilm exhibited significantly lower metabolic activity when treated with HIFU (250 kHz, 20 W, 60 s) compared with the control (4% NaOCl) and PDT groups. A similar phenomenon was observed with the CFU assay. HIFU remained the most effective treatment modality, with consistent results in CLSM and SEM.

CONCLUSION

This study highlighted the potential application of HIFU as an adjunct drug-free, non-destructive root canal disinfection method for endodontic treatment, suggesting an alternative to the current gold standard of 4% NaOCl and PDT.

Flexural strength and microhardness of human radicular dentin sticks after conditioning with different endodontic chelating agents

Introduction

The objective of this in vitro study was to examine the impact of different endodontic chelating agents on the flexural strength and microhardness of root dentin.

Materials and Methods

Fourty dentin sticks of (1 mm × 1 mm × 12 mm) were obtained from 10 single-rooted premolars and divided into four groups (n = 10). One stick from each tooth was assigned to one of the experimental groups and was soaked in one of the experimental chelating solutions for 5 min 17% ethylenediaminetetraacetic acid (EDTA), 2.5% phytic acid (PA), 18% etidronic acid, or saline (control group). Following the 5-min soak, the sticks' flexural strength was evaluated using a 3-point loading test using the universal testing machine, and the surface microhardness was tested using a Vickers's microhardness tester.

Results

PA (2.5%) and etidronic acid (18%) showed no significant detrimental effect on either the flexural strength or the surface microhardness of radicular dentin compared to the control. EDTA (17%) exhibited a significant drop in the flexural strength and microhardness of radicular dentin compared to the other groups.

Conclusions

PA and etidronic acid chelators do not compromise the surface and bulk mechanical properties of radicular dentin.

Effect of irrigation protocols on root canal wall after post preparation: a micro-CT and microhardness study

The aim of this study was to investigate the effects of different post space irrigation protocols for removing residual filling material from dentin walls, by using microcomputed tomography (micro-CT), and the influence of these protocols on dentin microhardness. Bovine incisors (n = 35) were filled with the single-cone technique and MTA Fillapex (Angelus, Londrina, PR, Brazil). Post space preparation (PSP) was performed 7 days after filling, using the Odous Touch electrical system (Odous De Deus Ind. e Com., Belo Horizonte, MG, Brazil), followed by post space irrigation using manual irrigation, passive ultrasonic irrigation, or Easy Clean, together with 2.5% sodium hypochlorite (NaOCl), or with 2.5% NaOCl and 17% EDTA (NaOCl/EDTA). Micro-CT scans were performed at three time points. The residual filling material was evaluated at three levels: cervical, middle and apical. The Knoop test was measured with four indentations around the canal lumen at three dentin depths: X (100 μm), Y (200 μm) and Z (400 μm). Statistical analysis was performed using ANOVA (p < 0.05). The effects of the activation method (p < 0.001), and the root level (p = 0.013), as well as the interaction between the irrigant and the activation method (p = 0.041), led to different percentages of residual filling material. Lower amounts of residual filling material were observed at the cervical versus the middle and apical levels (p < 0.05). No significant differences were observed in dentin microhardness (p > 0.05). The best removal of the residual filling material was performed using the Easy Clean tip and NaOCl/EDTA, regardless of the activation methods.

Cytotoxicity of different concentrations of glycolic acid and its effects on root dentin microhardness - An in vitro study

The aim of the study was to evaluate the cytotoxicity of different glycolic acid concentrations (GA) and its effects on dentinal microhardness. Cytotoxicity was evaluated after inoculation of test irrigants in the lymphocyte primary culture for 3 min. The tested substances were distilled water(DW); 17% EDTA; QMix; 10% GA; 17% GA; and 25% GA. Counting of total, live and dead cells was performed, obtaining the average percentage of dead cells of each group. For microhardness evaluation, 60 root dentin samples were divided into the same tested groups (n = 10) and immersed in test irrigants for 3 min. Dentin microhardness was evaluated by Vicker test. Specific statistical analysis was made in both tests. Results showed significant lower cytotoxicity for QMix and 10% GA (P < 0.05). Moreover, all test irrigants presented similar values of microhardness than the control group (P > 0.05). In conclusion, lower GA concentration can be an alternative for final irrigation on endodontics.

Influence of volume of endodontic irrigants used in different irrigation techniques on root canal dentin microhardness

Introduction

Overzealous application of endodontic irrigants affects the root canal dentin mechanical properties. The effect of volume of endodontic irrigants on the microhardness of root canal dentin has not been studied.

Aim

This study assessed the effect of volume of endodontic irrigants used in different final irrigation activation techniques on root canal dentin microhardness (RCDM).

Methodology

Sixty human maxillary central incisors were embedded in acrylic resin in Kuttler's endodontic cube to the level of cementoenamel junction. The root samples were randomly divided into 4 experimental groups (n = 15): Group-NI-needle irrigation, Group-PUI-continuous passive ultrasonic irrigation, Group-EndoVac-apical negative pressure system, Group combination- EndoVac + PUI irrigation. Root canals were instrumented up to size 40 (F4). The resin mounted specimens were sectioned longitudinally into two halves and were reassembled in Kuttler's kube to carry out final irrigation activation. A predetermined standardized volume of irrigants was used in each group. The RCDM was measured after root canal instrumentation and after final irrigation using Vicker microhardness tester (coronal, middle, and apical third). The reduction in RCDM values (p < 0.0086) were analyzed using Kruskal Wallis and Mann Whitney-U tests.

Results

Reduction in RCDM was observed with all the endodontic irrigating techniques tested. EndoVac and combination irrigation techniques showed maximum reduction in RCDM in all thirds of root canal.

Conclusion

It is concluded that the volume of irrigants and agitation plays a role in reducing RCDM. The overall volume of irrigants to cause maximum reduction was 25 ml, beyond which neither volume nor agitation affects RCDM.

Vertical Load and Torque during Postspace Preparation and Their Influence on Microcrack Development

PURPOSE

To investigate, in vitro, the magnitudes of vertical load and torque generated during post space preparation of root canal treated teeth and their influence on microcrack development.

MATERIALS AND METHODS

Forty extracted premolars with single canals were decoronated. The roots were prepared using ProTaper Next system (Dentsply Sirona) to X3 file, obturated, and provisionalized. After a 3-week incubation period, the roots were distributed into 2 groups according to the post drill system used (ParaPost fiber post and RelyX fiber post). During post space preparation, the vertical load, torque, and preparation time were recorded. Before and after the post space preparation, the roots were imaged with micro-computed tomography (SkyScan 1172; Bruker micro-CT) to detect new microcracks. The data were analyzed using the Mann-Whitney U-test and chi-square test.

RESULTS

In ParaPost and RelyX, the post space was prepared in 48.31 ±25.28 and 47.71 ±13.36 seconds, respectively (p = 0.360). The peak vertical load generated with ParaPost (20.23 ±7.80 N) was significantly lower than that of RelyX (29.43 ±5.82 N) (p = 0.010). The maximum torque attained with ParaPost (1.42 ±0.61 N.cm) was found to be significantly lower than that of RelyX (3.23 ±1.58 N.cm) (p = 0.000). No post drill fracture or visible deformation was noticed throughout the experiment. New microcracks were found in three ParaPost samples only.

CONCLUSIONS

The choice of postdrill influenced the loads and torques generated during postspace preparation. The ParaPost system showed favorably lower load and torque values during the postspace preparation compared with the RelyX system.

Microtensile Bond Strength of Fiber-Reinforced and Particulate Filler Composite to Coronal and Pulp Chamber Floor Dentin

This ex vivo study aimed to compare the microtensile bond strength of fiber-reinforced and particulate filler composite to coronal and pulp chamber floor dentin using a self-etching adhesive system. Coronal dentin of 40 human molar teeth was exposed by cutting occlusal enamel with a low-speed saw. Teeth were then randomly divided into two groups (n = 20). The first group was left as is, while in the second group, pulp chamber floor dentin was exposed by trepanation. After placement of a self-etching adhesive system (G-aenial Bond, GC, Tokyo, Japan), groups were further divided into two sub-groups (n = 10) according to the type of composite: fiber-reinforced composite (EP, everX Posterior, GC, Tokyo, Japan) and particulate filler composite (GP, G-aenial Posterior, GC, Tokyo, Japan). Then, composite blocks were built up. Sticks (1.0 × 1.0 mm2) were obtained from each specimen by sectioning, then microtensile bond strength (μTBS) test was performed. Statistical analysis included one-way ANOVA test and Student's t-test (p < 0.05). μTBS values were 22.91 ± 14.66 and 24.44 ± 13.72 MPa on coronal dentin, 14.00 ± 5.83 and 12.10 ± 8.89 MPa on pulp chamber floor dentin for EP and GP, respectively. Coronal dentin yielded significantly higher μTBS than pulp chamber floor dentin (p < 0.05), independently from the tested composites.

Effect of Nd:YAG, Er,Cr:YSGG Laser Irradiation, and Adjunctive Photodynamic Therapy on Push-Out Bond Strength of Zirconia Posts to Radicular Dentin

This study is aimed at assessing the influence of Nd:YAG, Er,Cr:YSGG laser irradiation, and adjunctive photodynamic therapy (aPDT) on the bond strength of zirconia posts to radicular dentin. Eighty extracted anterior teeth were randomly categorized into 4 groups (n = 20) based on varying laser irradiation treatments, i.e., conventional cleaning and shaping (CCS), Nd:YAG, Er,Cr:YSGG, and aPDT group, respectively. Using a cutting machine, the samples were prepared for push-out bond strength analysis; 4 sections (2 on each apical and cervical) of around 1 mm thickness were sectioned for all roots at a right angle to the long axis of the post. After making the space for the post, they were incorporated into the root system and were subjected to different laser treatments. The universal testing machine was utilized to assess the push-out bond strength, which had a defined 1 mm/minute crosshead speed until the failure was encountered. Specimens in the aPDT group (8.20 ± 2.14 MPa) demonstrated the highest mean push-out bond strength, whereas the lowest was shown by samples in the CCS group (7.08 ± 1.11 MPa). According to the independent t-test, the mean push-out bond strength scores of the cervical segments were higher as compared to the apical segments in research groups (p < 0.05). Overall, the adhesive type was the most frequently encountered failure mode in all of the experimental groups, with the least number of failures observed in aPDT treated teeth samples. In conclusion, the push-out bond strength to radicular dentin was not much influenced by Nd:YAG, Er,Cr:YSGG laser, and aPDT in comparison with CCS. Although statistically not significant, however, the application of aPDT provided better outcomes as compared to other research groups.

Influence of ultrasonic activation on antimicrobial activity of a new final irrigant containing glycolic acid: An in vitro study

This study evaluated the influence of ultrasonic activation (US) on the antimicrobial activity of a new final irrigant containing glycolic acid (GA). Extracted teeth were used, being 70 to counting of colony-forming units (CFUs) and 35 to confocal laser scanning microscopy. Samples were inoculated with Enterococcus faecalis and divided into 7 groups: distilled water + US; 17% EDTA; Qmix; 17% GA; 17% EDTA + US; QMix + US; and 17% GA + US and kept in contact with test solution for 1 min in the groups with or no US. In the CFUs, the highest bacterial reduction was observed in QMix + US group, followed by QMix and GA + US. In the confocal evaluation, the lowest number of viable cells was observed in EDTA + US, with no statistical difference from QMix, QMix + US and GA + US (P > 0.05). The use of US improves the antimicrobial activity of EDTA and GA, being statistically different from the isolated use of these final irrigants in both evaluation tests.

Quercetin as an Auxiliary Endodontic Irrigant for Root Canal Treatment: Anti-Biofilm and Dentin Collagen-Stabilizing Effects In Vitro

Bacterial reinfection and root fracture are the main culprits related to root canal treatment failure. This study aimed to assess the utility of quercetin solution as an adjunctive endodontic irrigant that does not weaken root canal dentin with commitment anti-biofilm activity and bio-safety. Based on a noninvasive dentin infection model, dentin tubules infected with Enterococcus faecalis (E. faecalis) were irrigated with sterile water (control group), and 0, 1, 2, 4 wt% quercetin-containing ethanol solutions. Live and dead bacteria percentages in E. faecalis biofilms were analyzed by confocal laser scanning microscopy (CLSM). Elastic modulus, hydroxyproline release and X-ray photoelectron spectroscopy (XPS) characterization were tested to evaluate the irrigants’ collagen-stabilizing effect. The cytotoxicity was tested by CCK-8 assay. Quercetin increased the proportion of dead bacteria volumes within E. faecalis and improved the flexural strength of dentin compared to control group (p < 0.05). Quercetin-treated dentin matrix had less elasticity loss and hydroxyproline release after collagenase degradation (p < 0.05). Moreover, quercetin solutions revealed an increase in the C-O peak area under both C1s and O1s narrow-scan spectra of XPS characterization, and no cytotoxicity (p > 0.05). Quercetin exhibited anti-biofilm activity, a collagen-stabilizing effect with cytocompatibility, supporting quercetin as a potential candidate for endodontic irrigant.

Influence of a glycolic acid-based final irrigant for photosensitizer removal of photodynamic therapy on the microhardness and colour change of the dentin structure

INTRODUCTION

This study aimed to evaluate the influence of glycolic acid-based final irrigant for photosensitizer removal of photodynamic therapy on the microhardness and colour change of the dentin structure.

METHODS

Eighty extracted single-rooted human incisors were used. Sample preparation and root split resulted in 160 samples, 80 samples being used for microhardness and 80 samples for colour change evaluation. In the first, PDT protocol was performed and 80 samples were randomly divided into 4 groups (n = 20), according to the final irrigation protocol: distilled water (DW); 17 % ethylenediaminetetraacetic acid (EDTA); QMix; 17 % glycolic acid (GA). Microhardness was evaluated using the Vicker tester, before and after, PDT and final irrigation protocols, calculating the percentage of microhardness reduction. In the second evaluation, PDT and final irrigation protocols were performed in the same way. Colour change was evaluated using digital spectrophotometer before and after these protocols, calculating the ΔE colour change using the CIELAB system (L*a*b* values). Specific statistical analysis was performed for both evaluations (α = 5%).

RESULTS

The highest percentage of microhardness reduction was observed in 17 % EDTA, QMix and 17 % GA groups, with no significant difference among them (p > 0.05). Furthermore, none of these protocols was effective in photosensitizer removal, and all final irrigation protocols were statically similar to control group (p > 0.05).

CONCLUSIONS

GA promotes microhardness reduction and also contributes to the colourization of dentin structure during the photosensitizer removal process, followingPDT .

Effect of different irrigation protocols for applications in regenerative endodontics on mechanical properties of root dentin

The objective of this study was to evaluate the effect of different concentrations of NaOCl with and without passive ultrasonic irrigation (PUI) on mechanical properties of human dentin for applications in regenerative endodontics (RE). Sixty single-rooted teeth were sectioned into 2 halves (n = 120). Dentin bars were produced from one half for flexural strength and the other half was used for microhardness. Specimens were randomly assigned into 10 groups: G1 and G2 (control): distilled water for 30 and 60 min, respectively; G3: 1.5%NaOCl for 30 min; G4:1.5%NaOCl for 60 min; G5: 1.5%NaOCl + PUI for 30 min; G6: 1.5%NaOCl + PUI for 60 min; G7: 5.25%NaOCl for 30 min; G8: 5.25%NaOCl for 60 min; G9: 5.25%NaOCl + PUI for 30 min; G10: 5.25%NaOCl + PUI for 60 min. An increase in NaOCl concentration showed highly significant reduction in mechanical properties. There was no significant difference between 1.5% NaOCl and control group except for specimens treated with PUI for 60 min. NaOCl in concentrations recommended for RE did not have a significant effect on mechanical properties of dentin. However, PUI with increased irrigation time might have an effect even with low NaOCl concentration.

Assessment of sodium thiosulfate neutralizing effect on micro-hardness of dentin treated with sodium hypochlorite

Background

This study aims to evaluate the ability of sodium thiosulfate (STS) to neutralize the adverse effect of sodium hypochlorite (NaOCl) on dentin micro-hardness.

Methods

Fifty single-rooted teeth were longitudinally sectioned. The samples divided into a control and four sample groups (n = 20). All the samples were immersed in different solutions as follows, Control: Normal saline for 15 min, G1and G2: 2.5% NaOCl for 15 min, G3: 2.5% NaOCl for 15 min, followed by 5% STS for 10 min, G4: Normal saline for 15 min followed by 5% STS for 10 min. All groups except G1 incubated for one week before the test. The micro-hardness of samples was measured. Data were analyzed using the Kruskal–Wallis test for pairwise comparisons. A p value < 0.05 was considered significant.

Results

All groups showed a significant decrease in the micro-hardness value compared with the control group. NaOCl for one week (G2) reduced the micro-hardness of dentine compared with samples, tested immediately after immersion in NaOCl (G1) (p < 0.05). NaOCl alone (G2) or treated with STS (G3) resulted in a significant decrease in micro-hardness compared with the STS group (G4) (p < 0.05).

Conclusions

STS as a neutralizing agent could not prevent the dentin micro-hardness downturn caused by NaOCl.

Effect of different irrigating solutions with surfactants on the microhardness and smear layer removal of root canal dentin: An in vitro study

Aim:

The present in vitro study was undertaken to check the effect of the different irrigating solutions with surfactants, i.e., sodium hypochlorite-(Naocl)-Extra, chlorhexidine (CHX)-Ultra, ethylenediaminetetraacetic acid (EDTA), QMix, and BioPure MTAD on the microhardness and smear layer removal of root canal dentin.

Materials and Methods:

A total of 120 straight rooted lower premolars were collected and were randomly divided into 2 equal groups of 60 each (n = 60). The microhardness of the samples was evaluated by Vickers hardness tester and the removal of smear layer by scanning electron microscope after irrigation of the samples with the tested solutions.

Results:

CHX-Ultra showed the least microhardness reduction, and EDTA showed the maximum microhardness reduction in all the tested groups. BioPure MTAD showed the maximum removal of smear layer in the apical third, and CHX-Ultra showed the minimal smear layer removal in the apical third.

Conclusion:

During smear layer removal, irrigating solutions cause alterations in the chemical composition of dentin, which may decrease the microhardness of the root dentin causing erosion and affecting the clinical performance of the endodontically treated teeth. Irrigating solution with maximum smear layer removal with minimum changes in microhardness should be used.

Effect of Root Canal Irrigants on the Mechanical Properties of Endodontically Treated Teeth: A Scoping Review

INTRODUCTION

The aim of this study was to identify through a scoping review whether root canal irrigants influence the mechanical properties of endodontically treated teeth, and which properties could be affected. The protocol of this study, available online (https://osf.io/yc9nb/), followed the Joana Briggs Institute guidelines. Reporting was based on PRISMA Extension for Scoping Reviews.

METHODS

We selected studies written in English that evaluated the effect of at least one irrigant on the mechanical properties of endodontically treated teeth. The search and study screening were performed in PubMed and Scopus databases by 2 independent researchers. A descriptive analysis was performed to consider the study design, the characteristics of the irrigants, and the properties tested.

RESULTS

The initial search yielded 608 citations, of which 66 were included. On the basis of the collected data, the most commonly used solutions were 17% EDTA, 2.5% or 5% sodium hypochlorite, and 2% chlorhexidine, and the most common tested properties were hardness and strength. Alterations in the modulus of elasticity, stress and strain concentration during preparation, and roughness were also assessed.

CONCLUSIONS

The majority of studies corroborated a negative effect of all solutions on the mechanical properties of endodontically treated teeth. Furthermore, increases in the concentration of the solution and in the time of exposure were found to intensify deleterious effects. However, disinfection of the canal is also a crucial factor in endodontic success. Thus, clinicians should consider these factors to mitigate the effects without interfering with antibacterial properties, customizing the choice of the solution to the case in hand.

The antibiofilm and collagen-stabilizing effects of proanthocyanidin as an auxiliary endodontic irrigant

AIM

To evaluate the antibiofilm effect of proanthocyanidin (PA) solution as an irrigant against Enterococcus faecalis (E. faecalis) and its influence on the mechanical properties and biodegradation resistance of demineralized root dentine.

METHODOLOGY

Enterococcus faecalis were introduced into human root dentine tubules by a serial centrifugation method and grown for 1 week. Dentine blocks infected with 1-week-old E. faecalis biofilms were treated with the following irrigants: sterile water (control), 2% chlorhexidine (CHX), 2% PA, 5% PA and 10% PA. After treatment, the live and dead bacteria proportions within E. faecalis biofilms were analysed using confocal laser scanning microscopy. To evaluate the biostability of fully demineralized dentine treated by the aforementioned irrigants, the elastic modulus and hydroxyproline release of human dentine incubated in collagenase solution were tested at baseline, after irrigant treatment and after biodegradation, respectively. Furthermore, the surface chemical bond of demineralized dentine collagen treated by various irrigants was characterized by X-ray photoelectron spectroscopy (XPS). Statistical analysis was performed using one-way anova and Tukey's post hoc multiple comparisons with the significance level at 5%.

RESULTS

The proportion of dead E. faecalis volume was significantly higher in the PA and CHX groups than that in the control group (P < 0.05). PA irrigation significantly increased the mechanical properties of demineralized dentine (P < 0.05), and the effect was enhanced with increasing PA concentration. CHX and PA groups had significantly less elasticity loss and hydroxyproline release (P < 0.05). The biomodification of dentine collagen by PA was verified by increased C-O/C-N peak percentage under C1s and C-O peak percentage under O1s narrow-scan XPS spectra.

CONCLUSIONS

Proanthocyanidin killed E. faecalis within biofilms and enhanced the biostability of the collagen matrix of demineralized root dentine. It might be used as an auxiliary endodontic irrigant with antibiofilm and collagen-stabilizing effects.

Novel Bioactive and Therapeutic Root Canal Sealers with Antibacterial and Remineralization Properties

According to the American Dental Association Survey of Dental Services Rendered (published in 2007), 15 million root canal treatment procedures are performed annually. Endodontic therapy relies mainly on biomechanical preparation, chemical irrigation and intracanal medicaments which play an important role in eliminating bacteria in the root canal. Furthermore, adequate obturation is essential to confine any residual bacteria within the root canal and deprive them of nutrients. However, numerous studies have shown that complete elimination of bacteria is not achieved due to the complex anatomy of the root canal system. There are several conventional antibiotic materials available in the market for endodontic use. However, the majority of these antibiotics and antiseptics provide short-term antibacterial effects, and they impose a risk of developing antibacterial resistance. The root canal is a dynamic environment, and antibacterial and antibiofilm materials with long-term effects and nonspecific mechanisms of action are highly desirable in such environments. In addition, the application of acidic solutions to the root canal wall can alter the dentin structure, resulting in a weaker and more brittle dentin. Root canal sealers with bioactive properties come in direct contact with the dentin wall and can play a positive role in bacterial elimination and strengthening of the root structure. The new generation of nanostructured, bioactive, antibacterial and remineralizing additives into polymeric resin-based root canal sealers are discussed in this review. The effects of these novel bioactive additives on the physical and sealing properties, as well as their biocompatibility, are all important factors that are presented in this article.

Effect of different laser types on bonding strength of CAD/CAM-customized zirconia post to root canal dentin: an experimental study

In clinical dentistry, the strength of bonding zirconia posts to root canal dentinal walls currently needs enhancement, and laser application can be an important contribution owing to its features that accommodate adjustable modifications on dental materials. Herein, the effect of different laser treatments applied to dentin surfaces on the strength of bonding zirconia posts to root canal dentinal walls is evaluated by using the pull-out bond strength test in a laboratory setting. A total of 40 single-rooted permanent mandibular premolar teeth that were freshly extracted were used here. The root canal preparation steps were performed using the crown-down technique. Custom-made zirconia posts were produced using CAD/CAM technology. Prior to the application of resin cement, the internal surfaces of the root canals were irradiated using Nd:YAG, Er:YAG, and KTP lasers. Pull-out tests were performed on each specimen by using a universal testing machine. One-way analysis of variance and Tukey post hoc tests were used to compare the pull-out bond strength data. The bond strengths of the laser-treated specimens were greater than those of the untreated controls (p < 0.05). While the value of the pull-out bond strength after Nd:YAG laser treatment was significantly higher than the values obtained after the applications of the Er:YAG and KTP lasers (p < 0.05), the pull-out bond strength after Er:YAG laser treatment was considerably greater than that after KTP laser treatment (p < 0.05). The bond strength between the root canal dentin and the CAD/CAM custom-made zirconia post was improved upon using all the laser modalities in current laboratory settings, among which, application of the Nd:YAG laser was the most successful.

Peracetic acid as a single endodontic irrigant: effects on microhardness, roughness and erosion of root canal dentin

The aim was to assess the effects of 1% peracetic acid (PAA) as a single endodontic irrigant on microhardness, roughness, and erosion of root canal dentin, compared with 2.5% sodium hypochlorite (NaOCl) and with 2.5% NaOCl combined with 17% EDTA. Forty human, single-rooted tooth hemisections were submitted to Knoop microhardness test, before and after the following irrigation protocols: PAA = 1% PAA; NaOCl = 2.5% NaOCl; NaOCl-EDTA-NaOCl = 2.5% NaOCl +17% EDTA +2.5% NaOCl; and SS = saline. Another 40 roots were instrumented, irrigated with the same protocols, and sectioned longitudinally. The roughness analysis was performed on the mesial section using a confocal laser scanning microscope, whereas erosion was analyzed on each third of the distal section, using a scanning electron microscope. The data were analyzed using ANOVA and Tukey post-tests, and Kruskal-Wallis and Dunn post-tests (α = .05). The PAA and NaOCl-EDTA-NaOCl groups showed no significant differences (p > .05); both promoted reduction in microhardness and increase in roughness, compared with the NaOCl and SS groups (p < .05). NaOCl-EDTA-NaOCl promoted higher erosion in the cervical and middle thirds than the other groups (p < .05); there was no difference among PAA, NaOCl, and SS (p > .05). There was also no difference among the groups regarding the apical third (p > .05). PAA used as a single endodontic irrigant caused reduction in root canal dentin microhardness and increase in roughness in a similar way to NaOCl-EDTA-NaOCl; however, PAA caused less erosion than NaOCl-EDTA-NaOCl.

Influence of silver nanoparticle solution on the mechanical properties of resin cements and intrarradicular dentin

This study evaluated the influence of silver nanoparticle on mechanical properties of the components of underlying dentin and resin cement in different regions of intraradicular dentin. Ninety extracted single-rooted human teeth were used in this study. After endodontic preparation, the teeth were divided into five groups, according to the irrigating agents: distilled water, 5.25% sodium hypochlorite, 25% polyacrylic acid, 2% chlorhexidine and 23 ppm silver nanoparticles dispersion. Then, the groups were divided in 3 subgroups (n = 6) according to the technique adopted for adhesive cementation: SUA group: Scotchbond Universal Adhesive + RelyX ARC; U200 group: RelyX U200; and MCE group: MaxCem Elite. The mechanical properties of hardness and elastic modulus were measured in resin cement and underlying dentin in ultra-micro hardness tester in different thirds of radicular dentin surface. Data were subjected to ANOVA and Fisher’s test (p = 0.05). In the underlying dentin, in general, there was no statistically significant difference in different thirds of intraradicular dentin according to the different solutions used. In the resin cements, higher hardness values were found, in general, for the cervical third. When silver nanoparticle solution was used, higher mechanical properties were generally obtained for resin cement for the SBU and U200 groups, with little or no changes in mechanical properties for the dentin. Silver nanoparticle application is a viable option for irrigation the intraradicular dentin previously through the cementation process of glass fiber posts. The mechanical properties are influenced by irrigant solutions used and the depth intraradical analyzed area.

PLGA submicron particles containing chlorhexidine, calcium and phosphorus inhibit Enterococcus faecalis infection and improve the microhardness of dentin

Enterococcus faecalis (E. faecalis), a Gram-positive facultative anaerobe, is reported to take responsibility for a large portion of refractory root canal infections and root canal re-infections of human teeth. Chlorhexidine is a strong bactericide against E. faecalis but cannot infiltrate into dentinal tubules. On the other hand, a common negative effect of root canal medicaments is the decrease of dentin microhardness. In this study, poly(D,L-lactic-co-glycolide) (PLGA) submicron particles were applied as delivery carriers to load and release the chlorhexidine as well as calcium and phosphorus. The release profiles, antibacterial ability against E. faecalis, infiltration ability into dentinal tubules, biocompatibility and effects on dentin microhardness of these particles were investigated. Results revealed that encapsulated chemicals could be released in a sustained manner from the particles. The particles also exhibited excellent biocompatibility on MC3T3-E1 cells and significant antimicrobial property against E. faecalis. On dentin slices, the particles could be driven into dentinal tubules by ultrasonic activiation and inhibit E. faecalis colonization. Besides, dentin slices medicated with the particles displayed an increase in microhardness. In conclusion, PLGA submicron particles carrying chlorhexidine, calcium and phosphorus could be developed into a new intra-canal disinfectant for dental treatments.

Do endodontic retreatment techniques influence the fracture strength of endodontically treated teeth? A systematic review and meta-analysis

One of the major concerns about endodontically retreated teeth (ERT) is undoubtedly its loss of remnant structure, which could lead to consequently greater fracture risk. Therefore, the objective of this systematic review is to assess the influence of endodontic retreatment on the fracture strength of the dental tooth remnant. In vitro studies assessing the influence of mechanical retreatment on the mechanical properties (static or under fatigue) of restored teeth were searched in PubMed and SCOPUS databases. Three independent reviewers screened titles/abstracts of articles and the full-text of potentially eligible studies. The risk of bias was independently assessed by one researcher and verified by another two. Comparison between the mean load to fracture of teeth after endodontic treatment and after endodontic retreatment were estimated using pairwise random effects meta-analysis to calculate pooled mean differences. Three studies were included for the systematic review and 2 for the meta-analysis. The pooled effect indicated a statistical difference (Mean difference: -121.03 95%CI: -183.02, -59.05) between conditions favoring the endodontically treated teeth. However, the low number of studies combined with their heterogeneity made it difficult to prove such phenomenon. ERT might present lower fracture strength than endodontically treated teeth. However, more coherent laboratory tests may provide better evidence and quantitative parameters on how much reliability can be attributed to an endodontic retreatment, in addition to which technique can provide more predictable results in this conservative approach.

Evaluation of the effects of the solution used for electrochemical dissolution of nickel-titanium endodontic files on dentine structure, microhardness and cell viability

AIM

To evaluate the effects of the [NaF 12 g L^-1  + NaCl 1 g L^-1 ] solution used in the electrochemical dissolution process of fractured endodontic files, as well as its NiTi-containing product, on dentine hardness, topography and human fibroblast viability.

METHODOLOGY

Sixty single-rooted human teeth were evaluated for dentine microhardness using the Vickers hardness test and the area and number of dentinal tubules by scanning electron microscopy. The samples were divided according to the dentine surface treatment: distilled water; 17% EDTA; [NaF 12 g L^-1  + NaCl 1 g L^-1 ]; and 17% EDTA + [NaF 12 g L^-1  + NaCl 1 g L^-1 ]. Thirty-six single-rooted human teeth were divided according to the irrigation protocol: Dulbecco's Modified Eagle's Medium + 10% foetal bovine serum; 5.25% NaOCl; [NaF 12 g L^-1  + NaCl 1 g L^-1 ]; and [NaF 12 g L^-1  + NaCl 1 g L^-1  + NiTi]. The extracts in contact with the apical foramen were used in the MTT assay to evaluate human fibroblast viability, with dilutions of 100%, 50%, 25% and 12.5%. Statistical tests used were paired t-tests, one-way anova, Tukey's test, Kruskal-Wallis test and Dunn's post-test.

RESULTS

The [NaF 12 g L^-1  + NaCl 1 g L^-1 ] solution did not modify dentine microhardness or the average dentinal tubule area. However, EDTA induced changes in dentine structure and microhardness (P < 0.05). The [NaF 12 g L^-1  + NaCl 1 g L^-1 ] solution, and its NiTi-containing product had lower cytotoxicity than NaOCl at dilutions of 25% and 50% (P < 0.01).

CONCLUSIONS

The [NaF 12 g L^-1  + NaCl 1 g L^-1 ] solution did not alter dentine microhardness or damage the dentine structure. It also demonstrated lower cytotoxicity than NaOCl.

Cytotoxicity Evaluation of Combination Irrigant Regimens with MTAD on Two Different Cell Lines

Background:

Effective management of smear layer ensures adequate clinical success. Use of sodium hypochlorite (NaOCl)/ethylenediaminetetraacetic acid regimen has been the gold standard with limitations. Commercial irrigants incorporate surface modifiers to address these drawbacks. The aim of this study was to evaluate the cytotoxicity of combination regimens on target and nontarget cell lines by trypan blue assay.

Materials and Methods:

Nonsurfactant combination regimen of chlorhexidine (CHX) and NaOCl (2% CHX + 2.5% NaOCl) and surfactant regimens of CHX with cetrimide (CTR) (2% CHX + 0.5% CTR) and CHX with sodium dodecyl sulfate (2% CHX + 1% SDS) were prepared. 0.9% normal saline (NS) and Biopure MTAD (100%) served as control. Cytotoxicity was evaluated on human gingival fibroblast (HGF) and Henrietta Lacks (HeLa) cell lines by trypan blue assay. Thirty microliter of the cell suspension was treated with 20 μl of irrigants. The cell suspension was loaded into Neubauer chamber after 5 min and cell count was performed under inverted microscope and expressed as viability percentage.

Results:

Nonsurfactant combination comprising of 2% CHX + 2.5% NaOCl formed a brownish precipitate while surfactant combination regimes were stable without any precipitate formation. NS and 2% CHX + 0.5% CTR had greater viability scores on both cell lines. Two percent CHX + 1% SDS had better viability on HeLa but were severely cytotoxic on HGF. Two percent CHX + 2.5% NaOCl and MTAD were found to be severely cytotoxic on HeLa with limited viability on HGF.

Conclusion:

The variation in data obtained could be possibly attributed to the difference in the cellular membrane composition and mechanism of action of combination regimens. Experimental surfactant regimen 2% CHX + 0.5% CTR shows lower cytotoxicity than MTAD.

EDTA Treatment for Sodium Hypochlorite-treated Dentin Recovers Disturbed Attachment and Induces Differentiation of Mouse Dental Papilla Cells

INTRODUCTION

The disturbance of cellular attachment to dentin by sodium hypochlorite (NaOCl) may hamper pulp tissue regeneration. The aims of this study were to examine the recovering effect of EDTA on the attachment/differentiation of stemlike cells and to address the mechanisms of EDTA-induced recovery under the hypothesis that attachment to the exposed dentin matrix and the subsequent activation of integrin/phosphatidylinositol 3-kinase (PI3K) signaling play a crucial role.

METHODS

Mouse dental papilla (MDP) cells were cultured on bovine dentin disks treated with NaOCl (0%, 1.5%, or 6%) followed by EDTA (0%, 3%, or 17%). Cell attachment was evaluated by cell density, viability, and scanning and transmission electron microscopy. Odonto-/osteoblastic gene expression in attached MDP cells was analyzed with or without a pan-PI3K inhibitor (LY294002) using real-time polymerase chain reaction.

RESULTS

NaOCl treatment (1.5%, 10 minutes) significantly diminished attached MDP cells (P < .00001), but EDTA treatment (3% and 17%, ≥10 minutes) of NaOCl-pretreated dentin induced a significant increase in attached cells (P < .05). Ultrastructurally, MDP cells on EDTA-treated dentin showed attachment to exposed collagen fibers. MDP cells cultured on EDTA-treated disks (with or without 1.5% NaOCl pretreatment) showed significant up-regulation of alkaline phosphatase, dentin matrix protein 1, and dentin sialophosphoprotein messenger RNAs (P < .05). Alkaline phosphatase expression was down-regulated by LY294002 (P < .05).

CONCLUSIONS

Under the present experimental conditions, 10 minutes of EDTA treatment was sufficient to recover attachment/differentiation of MDP cells on 1.5% NaOCl-pretreated dentin. EDTA-induced exposure of collagen fibers and subsequent activation of integrin/PI3K signaling may contribute, at least partly, to the recovery.

Primum non nocere - The effects of sodium hypochlorite on dentin as used in endodontics

The medical literature is replete with the maxim 'primum non nocere', cautioning health care providers to avoid doing any harm to human subjects in their delivery of medical care. Sodium hypochlorite (NaOCl) is a well-established irrigant for root canal treatment because of its antimicrobial and organic tissue remnant dissolution capability. However, little is known about the deleterious effect of this strong oxidizing agent on the integrity of human mineralized dentin. Iatrogenically-induced loss of dentin integrity may precipitate post-treatment root fracture and has potential medico-legal complications. In the present work, transmission electron microscopy provided evidence for collagen destruction in the surface/subsurface of dentin treated with high NaOCl concentrations and long contact times. Size exclusion chromatography showed that the hypochlorite anion, because of its small size, penetrated the water compartments of apatite-encapsulated collagen fibrils, degraded the collagen molecules and produced a 25-35µm thick, non-uniform "ghost mineral layer" with enlarged, coalesced dentinal tubules and their lateral branches. Fourier transform-infrared spectroscopy identified increases in apatite/collagen ratio in NaOCl-treated dentin. The apatite-rich, collagen-sparse dentin matrix that remained after NaOCl treatment is more brittle, as shown by the reductions in flexural strength. Understanding the deleterious effects of NaOCl on mineralized dentin enables one to balance the risks and benefits in using high NaOCl concentrations for lengthy periods in root canal debridement. Delineating the mechanism responsible for such a phenomenon enables high molecular weight, polymeric antimicrobial and tissue dissolution irrigants to be designed that abides by the maxim of 'primum non nocere' in contemporary medical practices.

STATEMENT OF SIGNIFICANCE

The antimicrobial and tissue-dissolution capacities of NaOCl render it a well-accepted agent for root canal debridement. These highly desirable properties, however, appear to be intertwined with the untoward effect of collagen matrix degradation within mineralized dentin. Because of its small size, the hypochlorite anion is capable of infiltrating mineralized collagen and destroying the collagen fibrils, producing a mineral-rich, collagen sparse ghost mineral matrix with reduced flexural strength. Findings from the present work challenge the biosafety of NaOCl when it is used in high concentrations and for lengthy time periods during root canal treatment, and laid the background work for future biomaterials design in debridement of the canal space.

Evaluating the Effect of CPP-ACP as a Final Irrigant in Improving the Micro-Hardness of Erosive Root Dentin and its Influence on the Bond Strength of Self Etch Resin Sealer - An In-vitro Study

INTRODUCTION

Smear layer removal from the root canal wall involves the use of 17% EDTA and 5.25% sodium hypochlorite, which thereby improves the adhesion of obturating materials to root dentin. But these chemical irrigants have shown to decrease micro hardness, increase roughness, cause erosion and reduce the root dentin fracture toughness. To combat these adverse effects, studies can be focussed on the remineralisation of the erosive root dentin and this novel idea has been utilized in the present study.

AIM

To evaluate the micro hardness of erosive root dentin when Casein Phosphopeptide-Amorphous Calcium Phosphate (CPP-ACP) was used as a final irrigant and its influence on resin sealer bonding tested by push-out bond strength method.

MATERIALS AND METHODS

Sixty extracted maxillary incisors were divided into three groups based on the final irrigation protocol. Group 1-normal saline, Group 2-17% EDTA (Ethylene Diamine Tetraacetic Acid) + 5.25% NaOCl (Sodium Hypochlorite), Group 3 - 17% EDTA + 5.25% NaOCl + CPP-ACP; each group was divided into two subgroups. Half the specimens of each group were evaluated for Vicker's micro hardness test after the treatment. In continuation with the above methodology the remaining specimens were tested for push-out bond strength after obturation of the specimens with self etch adhesive resin sealer and conventional 6% gutta percha cones.

RESULTS

Micro hardness was statistically analysed using Kruskal Wallis test and push-out bond strength was evaluated using Mann Whitney test and paired t-test. CPP-ACP treated group showed increased micro hardness (p<0.05). There was no statistically significant difference between the push-out bond strength values between group EDTA + NaOCl group and EDTA + NaOCl + CPP-ACP group.

CONCLUSION

Within the limitations of this study it can be concluded that, CPP-ACP improved the micro hardness of erosive root dentin and is not affecting its bond strength. Therefore, CPP-ACP may be used before bonding procedures for promoting remineralization of root dentin.