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

Effects of phytic acid and etidronic acid using continuous and sequential chelation on the removal of smear layer, dentin microhardness, and push-out bond strength of calcium silicate-based cement

BACKGROUND

This study assessed the effects of sequential and continuous chelation using phytic acid and etidronic acid on smear layer removal, microhardness, and push-out bond strength (PBS) at radicular dentin.

METHODS

One hundred twenty single-rooted teeth were selected. Thirty teeth were split longitudinally, and initial microhardness was measured. The roots were then divided into six groups. In sequential chelation, 2.5% sodium hypochlorite (NaOCl) was used for 20 min, followed by 17% ethylenediaminetetraacetic acid (EDTA), 9% etidronic acid (HEDP), or 2.5% phytic acid (PA) for 2 min, while no chelator was applied in the control group. In continuous chelation, etidronic acid (DR HEDP) or phytic acid (DR PA) was mixed with NaOCl and applied for 20 min. Final microhardness values were measured, and the change was calculated as a percentage. Mid-root sections were obtained from the 60 teeth for the PBS test and divided into six groups. Irrigants were applied as in the microhardness test. Sections obturated with calcium silicate cement. PBS values were measured, and the types of failures were analyzed. Thirty teeth were analyzed using scanning electron microscopy (SEM). In sequential chelation, 2.5% NaOCl irrigation was performed during instrumentation, followed by 17% EDTA, 9% HEDP, or 2.5% PA for 2 min, while no chelator was applied in the control group. In continuous chelation, DR HEDP or DR PA was mixed with NaOCl and used during instrumentation. Images were taken, and smear layer scores were recorded. The PBS data were analyzed using one-way ANOVA, and the alterations in microhardness and remaining smear layer were analyzed using a two-way ANOVA test. The pairwise comparisons were analyzed using Tukey's HSD post hoc test. The failure patterns and smear scores were compared using Pearson's chi-squared test (α = 0.05).

RESULTS

Results showed that DR HEDP (4.02 ± 0.68%) caused the least reduction in microhardness. DR HEDP (10.26 ± 1.74 MPa) exhibited the highest bond strength, followed by PA (7.97 ± 0.92 MPa) and DR PA (7.74 ± 1.16 MPa). Failure patterns did not differ significantly. Lower percentages of the remaining smear layer area were observed in the DR PA (26.7 ± 18%), PA (24.2 ± 9.8%), and DR HEDP (37.1 ± 16.5%) groups compared to the others.

CONCLUSIONS

The use of etidronic acid with the continuous chelation technique and phytic acid with the sequential chelation technique may be an alternative method to sequential EDTA irrigation.

SWEEPS-Assisted Antibacterial Photodynamic Therapy Against Dual-Species Biofilms in Mandibular Molars: An In Vitro Study

Objectives: The synergistic effect of shock wave-enhanced emission photoacoustic streaming (SWEEPS) and antimicrobial photodynamic therapy (aPDT) in mandibular molar root canal disinfection remains underexplored, particularly against dual-species biofilms that better simulate clinical conditions. This study evaluates their combined antimicrobial efficacy against Enterococcus faecalis and Candida albicans biofilms and assesses potential tooth discoloration caused by riboflavin and nano-curcumin. Materials and Methods: The mesiobuccal canals of 57 extracted mandibular molars were inoculated with E. faecalis and C. albicans biofilms. The antimicrobial effects were assessed using riboflavin or nano-curcumin with a 450 nm diode laser (BDL), SWEEPS, or their combinations, compared to 5.25% NaOCl (positive control) and saline (negative control). Biofilm reduction was quantified by colony-forming units (CFUs/mL), and discoloration was evaluated using the ΔE metric in the CIE L*a*b* color space. Results: Both microorganisms showed a significant decrease in colony numbers in all experimental groups compared to the negative control (p < 0.001), except for E. faecalis, where no significant difference was observed between the riboflavin/nano-curcumin groups and the negative control. Combining riboflavin or nano-curcumin with SWEEPS or BDL significantly enhanced antimicrobial efficacy compared to individual treatments (p < 0.001). The combined photodynamic therapy and SWEEPS groups showed the lowest colony counts. The ΔE values were, on average, 1.81 for riboflavin and 1.09 for nano-curcumin. Conclusions: The combination of SWEEPS and aPDT effectively reduces E. faecalis and C. albicans biofilms in molars, supporting its potential as an adjunct in endodontic disinfection. Minimal discoloration further highlights its clinical applicability.

Exploring a new Portland cement-free calcium silicate cement -Part 1: Synthesis of dicalcium and tricalcium silicate

Mineral trioxide aggregate cement is an excellent pulp-capping material; however, its base Portland cement contains highly toxic elements and is expensive. This study aimed to explore the possibility of using calcium silicate cement without Portland cement. Synthesis was attempted via firing using calcium silicate (CS), as the base material, and calcium oxide (CA). According to the chemical reaction, they were weighed and sintered in an electric furnace at a sintering temperature of 1,300ºC based on the results of thermogravimetric differential thermal analysis. The powder composition after firing was examined by X-ray diffraction analyses. Compressive tests were performed using a universal testing machine. The sintered powders were confirmed as dicalcium silicate (CS2) and tricalcium silicate (CS3); however, some peaks were detected and their compressive strengths were lower than that of CS. These results suggest that CS2 and CS3 were successfully synthesized from a mixture of CA and CS.

Advancing Adhesive Strategies for Endodontically Treated Teeth-Part I: Impact of Endodontic Irrigation Protocols on the Chemical Composition and Structural Integrity of Coronal Dentin

OBJECTIVE

To evaluate the effects of four endodontic irrigation protocols on the chemical composition and ultrastructure of coronal dentin.

MATERIALS AND METHODS

Coronal dentin fragments were assigned to five study groups: NaOCl (3% sodium hypochlorite), NaOCl/EDTA (3% NaOCl and 17% ethylenediaminetetraacetic acid), NaOCl/EDTA/CHX (3% NaOCl, 17% EDTA and 2% chlorhexidine), NaOCl/HEDP (mixture of 3% NaOCl and 9% etidronic acid), and control (distilled water). Confocal Raman microscopy was employed to analyze the spatial distribution of organic and inorganic components, while attenuated total reflection Fourier transform infrared spectroscopy and energy-dispersive spectroscopy were used to assess the surface composition of dentin. Ultrastructural evaluation was conducted using scanning electron microscopy (SEM). Statistical analysis was performed using a mixed linear model with a significance level of 0.05.

RESULTS

All NaOCl-treated groups showed reduced amide II (p < 0.001), indicating protein degradation. Exclusive NaOCl irrigation yielded the lowest amide II, highest mineral content, and increased phosphate/amide II and carbonate/phosphate ratios (p < 0.05). Chelators reduced mineral content (p < 0.001), with NaOCl/HEDP and NaOCl/EDTA/CHX producing more mineralized surfaces than NaOCl/EDTA and control groups (p < 0.05). A general decrease in organic (C and N) and an increase in inorganic (O, P, and Ca) components occurred across treatments, particularly in NaOCl and NaOCl/HEDP groups. EDTA disturbed the Ca/P equilibrium (p < 0.05). SEM showed a dense smear layer and mostly obliterated tubules in NaOCl and control samples, while chelators reduced the smear layer, partially opened tubules, and caused erosion.

CONCLUSIONS

Exclusive use of 3% NaOCl produces hypermineralized, collagen-depleted coronal dentinal surfaces, with a dense smear layer. Sequential irrigation with 17% EDTA induces stronger demineralization compared to a continuous chelation protocol with 9% HEDP. Both EDTA- and HEDP-treated coronal dentin display partially opened dentinal tubules, signs of erosion, and substantial smear layer reduction.

CLINICAL SIGNIFICANCE

Clinically recommended endodontic irrigation protocols significantly alter the chemical composition and ultrastructural integrity of coronal dentin, the primary substrate for adhesive restorations. These findings enhance the understanding of post-irrigation coronal dentin conditions and their potential implications on the interaction with adhesive restorative materials.

Antibacterial effect of femtosecond laser against Enterococcus faecalis and Fusobacterium nucleatum biofilms on dentin: an in vitro study

BACKGROUND

Removing infectious bacteria biofilms from the root canal system is crucial for a successful endodontic treatment. This study investigated the antibacterial effect of femtosecond laser (fs-laser) against Enterococcus faecalis (E. faecalis) and Fusobacterium nucleatum (F. nucleatum) biofilms on dentin.

METHODS

The chemical composition of dentin slices from extracted human teeth was analyzed using FTIR and Raman probes. The morphology of fs-laser ablated dentin grooves was evaluated by an optical profiler, and the fs-laser ablation fluence threshold was obtained by a mathematical model. A correlation between dentin chemical composition and ablation threshold was established. The antibacterial effect of different fs-laser irradiation dosages within the safe threshold on E. faecalis and F. nucleatum biofilms was firstly evaluated using the growth curve method. The biofilm removal efficacy on dentin and antimicrobial effect in dentinal tubules was further evaluated by CLSM and SEM analysis. The effect of fs-laser irradiation on the microhardness of dentin surface was also evaluated. The fs-laser irradiation process was observed using a spectrometer.

RESULTS

The peak intensity of phosphate group showed a positive correlation to the fs-laser dentin ablation fluence threshold in both FTIR and Raman spectroscopy. The safe fluence threshold of 1.8 J/cm2 was determined by a prediction model on 20 dentin samples. The antimicrobial effect of fs-laser increased along with the irradiation fluence or time. Both E. faecalis and F. nucleatum biofilms on dentin could be effectively removed by the fs-laser with 1.5 J/cm2 fluence for 20 s without compromising the microhardness of dentin surface. Meanwhile, fs-laser could also eliminate the bacteria in dentinal tubules. The generation of plasma occurred during the fs-laser irradiation process, and the plasma spectra exhibited distinguishable characteristics between the two kinds of biofilms.

CONCLUSIONS

Fs-laser could effectively remove both E. faecalis and F. nucleatum biofilms on dentin, along with a notable antibacterial effect in dentinal tubules.

Stress distribution in restored mandibular molars with external cervical resorption: a finite element analysis

This study evaluates the stress distribution in mandibular molar teeth with external cervical resorption restored using various restorative and biomimetic materials through finite element analysis. A mandibular first molar was scanned to create a 3D model. 'Class 2Bp' external cervical resorption defects were simulated on the buccal aspect and restored with different materials. Composite resin or highly viscous glass ionomer cement restored the coronal portion, while mineral-trioxide-aggregate, Biodentine, BioAggregate, or glass-ionomer cement filled the radicular portion. Models representing unrestored external cervical resorption and intact teeth were also created. Access cavities were restored with composite resin in all models except the intact tooth model. This computational simulation study used finite element analysis (ANSYS) to assess stress distribution in mandibular molars with external cervical resorption. A 300 N oblique force, directed buccally at a 45° angle, was applied to simulate masticatory forces, and von Mises stresses were evaluated in the resorption regions to compare materials' performance in terms of stress concentration and tooth integrity. Similar stress distributions were observed when restoring the coronal portion with composite resin or highly-viscous glass ionomer cement. Stress decreased with mineral-trioxide-aggregate or glass-ionomer cement in the radicular portion compared to Biodentine and BioAggregate. Restored and intact tooth models experienced lower stresses than unrestored tooth. All tested models were considered safe, except the unrestored external cervical resorption model. Restored external cervical resorption models are generally safe; however, using mineral-trioxide-aggregate or glass-ionomer cement in the radicular portion may slightly reduce stress in external cervical resorption regions.

The importance of interdisciplinary collaboration in advanced therapy of odontogenic cysts: A 31 Month follow-up case report

In this case report, we present the treatment of a 39-year-old male patient with a bilateral maxilla cyst diagnosed as an additional finding ont he X-ray. Both conservative dentistry treatments and oral surgical procedures were carried out using state-of-the-art materials and equipment, and in close collaboration with the other dental specialists. Endodontic treatment of the remaining teeth was performed before the oral surgery treatment. The root canal fillings were made using bioceramic-based root canal sealer. Cystectomy was then performed on both sides and the bone cavities were filled with platelet-rich fibrin (PRF). In the 4th month X-ray after the operation, radiological images showed bone regeneration. After 31 months, the periapical region is intact on the X-ray, the function of the root canal treated teeth has been preserved and the patient is free of complaints. With the chosen therapy we achieved a complication-free, long-term successful result in a time-efficient manner.

Navigating the Endodontic Challenge of a 40 mm Canine and Its Technical Adaptations

Aim. The aim of this case report is to present the successful endodontic management of an abnormally long right maxillary canine diagnosed with symptomatic irreversible pulpitis, highlighting the technical adaptations employed during treatment. Summary. Technical adaptations included modifying the handle of the endodontic hand file and utilizing a side-vented microcannula for irrigation using positive and negative pressure technique. Despite the challenges posed by the abnormal tooth length, the procedure achieved a working length of 40.7 mm, and periapical radiography confirmed the master gutta-percha reaching full working length. Notably, the patient remained asymptomatic during the six-month follow-up, highlighting the efficacy of the treatment. This article also reviews the current literature, examining comparable cases and techniques documented in scholarly sources.

Fitting of Different Intraradicular Composite Posts to Oval Tooth Root Canals: A Preliminary Assessment

The purpose of the present study was to perform a preliminary analysis of the fitting of different fiber-reinforced composite (GFRC) posts to tooth root canals and determine the resin cement layer thickness. The following GFRC posts were assessed: bundle posts (Rebilda GTTM, VOCO, Germany), sleeve system (SAPTM, Angelus Ind, Brazil), and accessory posts (ReforpinTM, Angelus, Brazil). Twenty-four freshly extracted mandibular single-rooted pre-molars were endodontically treated and divided into six groups, according to the type of GFRC post and resin cement (self-adhesive or conventional dual-cured). Then, specimens were cross-sectioned and inspected by optical microscopy regarding the cement layer thickness and presence of defects such as pores, voids, or fissures were assessed. Bundle and accessory posts revealed a regular distribution of resin cement with a lower number of voids than found with sleeve systems. The sleeve system posts showed poor fitting at the apical portion of the root canals. The type of resin cement did not affect the thickness of the interface, although both bundle and accessory posts allow a better distribution of resin cement and fibers. The present preliminary study reveals interesting insights on the fitting of bundle and accessory posts to root dentin and resin cement layer thickness in oval-shape root canals. The sleeve system posts showed adequate fitting only at the coronal portion of the canals.

Impact of using XP-endo finisher and nanobubble water during EDTA dentin conditioning on TGF-β1 release in regenerative endodontic procedures

INTRODUCTION

Transforming Growth Factor-Beta 1 (TGF-β1) plays a crucial role in the success of Regenerative Endodontic Procedures (REPs) as they directly impact the proliferation and differentiation of stem cells. TGF-β1 is released by conditioning of the dentin matrix using 17% EDTA. EDTA was found to have deleterious effects on dentin especially in immature teeth with fragile dentin walls. Decreasing the irrigation time was reported to decrease these effects. Accordingly, enhancement and activation of the EDTA solution to maintain its efficiency in TGF-β1 release from dentin and thus compensating the reduction in irrigation time was employed. EDTA solution was enhanced by adding Nanobubble (NB) water which contains oxygen filled cavities less than 200 nm in diameter. Additionally, EDTA was activated with XP-endo Finisher rotary file. The aim of this study was to assess the impact of NB enhancement and/or XP-endo Finisher activation of the EDTA solution on the TGF-β1 release from dentin.

METHODS

Fifty standardized root segments with open apex were allocated to two main groups according to whether EDTA was enhanced with NB water or not, and within each group whether XP-endo Finisher activation was used or not in addition to a Negative Control group. The concentration of the released TGF-β1 in the root canal was measured using enzyme-linked immunosorbent assay (ELISA). The statistical analysis was done using the Shapiro- Wilk, Kolmogorov Smirnov, ANOVA and Post-hoc Tukey tests.

RESULTS

All groups released a considerable amount of TGF-β1 with the highest values in the EDTA/NB/XP group, followed by EDTA/NB, EDTA/DW/XP, EDTA/DW and Negative Control groups respectively.

CONCLUSIONS

The results of this study suggest that NBs can promote the success of REPs since it revealed a significant increase in the TGF-β1 release following its use in the enhancement of the EDTA solution. A comparable effect was obtained by XP-endo finisher activation of the EDTA solution. The combined use of NBs and XP-endo Finisher can be a promising addition in REPs. Accordingly, Enhancement and activation of the EDTA solution may compensate decreasing the EDTA irrigation time attempted to avoid the deleterious effect of EDTA on dentin.

Effects of endodontic irrigation solutions on structural, chemical, and mechanical properties of coronal dentin: A scoping review

OBJECTIVE

This review aims to assess structural, chemical, and mechanical properties of coronal dentin after endodontic irrigation.

MATERIALS AND METHODS

Reporting followed the PRISMA extension for scoping reviews. An electronic search was carried out in PubMed, Embase, and Cochrane Library. Records filtered by language and published up to November 4, 2022 were independently screened by two researchers. Studies evaluating structural, chemical, or mechanical properties of human permanent coronal dentin after irrigation within the scope of nonsurgical root canal treatment were included. Data were extracted regarding study type, sample description and size, experimental groups, outcome, evaluation method, and main findings.

RESULTS

From the initial 1916 studies, and by adding 2 cross-references, 11 in vitro studies were included. Seven studies provide ultrastructural and/or chemical characterization, and six assessed microhardness and/or flexural strength. One percent to 8% sodium hypochlorite (NaOCl) and 1%-17% ethylenediaminetetraacetic acid (EDTA) were the most commonly tested solutions, with contact times of 2-240 min (NaOCl) and 1-1440 min (EDTA) being evaluated.

CONCLUSIONS

Overall, the literature is consensual regarding the inevitable impact of NaOCl and chelating agents on coronal dentin, with both deproteinizing and decalcifying effects being concentration- and time-dependent. The alteration of mechanical parameters further confirmed the surface and subsurface ultrastructural and chemical changes.

CLINICAL SIGNIFICANCE

Endodontic treatment success highly depends on restorative sealing. Understanding the result of exposing coronal dentin, the main substrate for bonding, to irrigants' action is crucial. The deproteinizing and decalcifying effects of NaOCl and chelating agents are both concentration- and time-dependent, causing surface and subsurface ultrastructural, chemical, and mechanical alterations.

Effects of different treatment modalities on biomechanical behavior of maxillary incisors with external invasive cervical resorption at different progression levels

BACKGROUND/AIM

This study aimed to evaluate the biomechanical behavior of maxillary incisors with external invasive cervical resorption (EICR) at different progression levels after receiving different modes of treatment under occlusal forces using finite element analysis (FEA).

MATERIALS AND METHODS

Three-dimensional (3D) models of intact maxillary central incisors were constructed and modified to include EICR cavities with different progression levels in the buccal cervical areas. The EICR cavities confined to dentin were repaired using Biodentine™ (Septodont Ltd., Saint Maur des Fausse ́s, France), resin composite, or glass ionomer cement (GIC) . Additionally, EICR cavities with pulp invasion requiring direct pulp capping were simulated as repaired using Biodentine only or 1 mm thick Biodentine and either resin composite or GIC for the rest of the cavity. Moreover, models with root canal treatment and EICR defects repaired using Biodentine, resin composites, or GIC were also generated. A force of 240 N was applied to the incisal edge. The principal stresses in the dentin were evaluated.

RESULTS

GIC showed more favorable results than the other materials in EICR cavities confined to the dentin. However, Biodentine alone resulted in more favorable minimum principal stresses (Pmin ) compared to other materials in EICR cavities with close pulp proximity. Exceptionally, the models localized in the coronal third of the root with a circumferential extension of the cavity >90° showed more favorable results for GIC. The presence of root canal treatment had no significant effect on stress values.

CONCLUSIONS

Based on this FEA study the use of GIC in EICR lesions confined to the dentin is recommended. However, Biodentine may be a better option for restoring EICR lesions close to the pulp with or without root canal treatment. Except when the circumferential extension of the cavity is >90°, the use of GIC may be more advantageous.

In vitro assessment of antimicrobial potential of low molecular weight chitosan and its ability to mechanically reinforce and control endogenous proteolytic activity of dentine

AIMS

Chitosan-based biomaterials exhibit several properties of biological interest for endodontic treatment. Herein, a low molecular weight chitosan (CH) solution was tested for its antimicrobial activity against Enterococcus faecalis (E. faecalis) and effects on dentine structure.

METHODOLOGY

The root canal of 27 extracted uniradicular teeth were biomechanically prepared, inoculated with a suspension of E. faecalis and randomly assigned to be irrigated with either 5.25% sodium hypochlorite (NaClO), 0.2% CH or sterile ultrapure water (W). Bacteriologic samples were collected from root canals and quantified for of E. faecalis colony-forming units (CFUs). The effectiveness of CH over E. faecalis biofilms was further measured using the MBEC Assay®. Additionally, dentine beams and dentine powder were obtained, respectively, from crowns and roots of 20 extracted third molars. Dentine samples were treated or not with 17% EDTA and immersed in either CH or W for 1 min. The effects of CH on dentine structure were evaluated by assessment of the modulus of elasticity, endogenous proteolytic activity and biochemical modifications.

RESULTS

The number of E. faecalis CFUs was significantly lower for samples irrigated with CH and NaClO. No significant differences were found between CH and NaClO treatments. Higher modulus of elasticity and lower proteolytic activity were reported for dentine CH-treated specimens. Chemical interaction between CH and dentine was observed for samples treated or not with EDTA.

CONCLUSIONS

Present findings suggest that CH could be used as an irrigant during root canal treatment with the triple benefit of reducing bacterial activity, mechanically reinforcing dentine and inhibiting dentine proteolytic activity.

Effect of Different Root Canal Drying Protocols on the Bond Strength of Two Bioceramic Sealers

OBJECTIVES

 This study evaluated in vitro the effect of two different drying protocols on the dentin bond strength of two different bioceramic sealers (Sealer Plus BC [SP] and Bio C Sealer [BCS]). Bond strength and failure mode were evaluated according to the sealer, drying protocol, and root canal third.

MATERIALS AND METHODS

 Sixty extracted human mandibular single-rooted premolars were selected after anatomical standardization. The crowns were sectioned and root canals were prepared. Roots were randomly divided into four groups (n = 15 each). Each group was assigned a combination of one of the evaluated sealers (SP or BCS) and one of the drying protocols: canals dried with paper points (PP) or irrigation with saline followed by aspiration with silicon cannulas (IA). Obturations were performed using a single-cone technique. The teeth were temporized and stored for 7 days (100% humidity, 37°C). Roots were cut to obtain 2 mm thick discs for each third (coronal, middle, and apical). Push-out tests were performed on a universal testing machine, and the bond strength (MPa) of each specimen was calculated by dividing the load (N) by the interface area. Failure type was assessed under ×4 magnification.

STATISTICAL ANALYSIS

 Data were statistically analyzed with a significance set at 5%. An analysis of variance test followed by the Games-Howell post-hoc test was used to compare the mean values between the groups and the interaction of the variables.

RESULTS

 The predominant failure type was cohesive, followed by mixed failure and adhesive in all groups. The apical third presented the highest bond strength (p < 0.05) regardless of the group, followed by the middle and coronal thirds. Overall, the SP PP group had the highest mean bond strength (p < 0.01), but the SP sealer was negatively affected by the IA drying protocol in the coronal and middle thirds. The BCS presented similar results within the third stage, regardless of the drying protocol.

CONCLUSIONS

 Sealer Plus BC had a higher bond strength than Bio C Sealer, but it was negatively affected by the irrigation-aspiration protocol in the coronal and middle thirds. For the apical third, there was no difference between the groups; thus, a similar bond strength was observed regardless of the drying protocol or sealer.

Evaluation of the effects of different chelation agents on root dentin roughness

Successful root canal treatment requires effective irrigation of the entire root canal system. While chelating agents support irrigation, they can also alter physicochemical properties of the root dentin structure. The aim of this study is to evaluate the effect of different chelation agents on root dentin roughness. Twenty-five extracted maxillary incisors were used in this study. Samples were separated longitudinally and divided into five groups: distilled water, NaOCl, ethylenediaminetetraacetic acid (EDTA), phytic acid and citric acid (CA). Atomic force microscope and energy dispersive X-ray spectroscopy analyses were used for analysing. One-way analysis of variance and Turkey tests were used in the statistical analysis of the study. EDTA, CA and phytic acid solutions increased the roughness and phytic acid and CA solutions decreased the Ca/P ratio in dentin tissue. No statistical difference was observed in the other groups. The decrease of Ca/P ratio should be taken under consideration during irrigation. The increase in surface roughness may provide clinical benefit by supporting the adhesion of the root canal filling materials to the dentin surface.

Antimicrobial FiteBac® K21 promotes antimicrobial Potency and wound healing

Objectives

Successful root canal therapy is dependent on the efficacy of complete instrumentation and adequate use of chemical irrigant to eliminate the biofilm from dentin surface. The aim of the study was to examine antibiofilm and antimicrobial effectiveness of newly formulated Quaternary ammonium silane (QAS/also codenamed K21; against Fusobacterium nucleatum (F. nucleatum) and Enterococcus faecalis (E. faecalis) biofilm on radicular dentin with evaluation of the anti-inflammatory consequence in vivo.

Methods

Fourier Transform Infrared Spectroscopy (FTIR) was performed after complete hydrolysis of K21 solution. Human teeth were inoculated with biofilms for 7-days followed by treatment with various irrigants. The irrigant groups were Sodium hypochlorite [NaOCl (6%)], Chlorhexidine [CHX (2%)], K21 (0.5%), K21 (1%) and Saline. Scanning electron microscopy (SEM) was performed for biofilm and resin-dentin penetration. Transmission Electron Microscopy (TEM) of biofilms was done to evaluate application of K21. For in vivo evaluation, Albino wistar rats were injected subcutaneously and sections were stained with haematoxylin/eosin. Macrophage, M1/M2 expression were evaluated along with molecular simulation. Raman measurements were done on dried biofilms.

Results

FTIR K21 specimens demonstrated presence of ethanol/silanol groups. Raman band at 1359 cm-1 resemble to -CH2- wagging displaying 29Si atoms in Nuclear Magnetic Resonance (NMR). 0.5%K21 showed cells exhibiting folded membranes. SEM showed staggering amount of resin tags with 0.5% K21 group. TEM showed membrane disruption in K21-groups. K21 groups were initially irritant, which subsided completely afterwards showing increased CD68. K21 and MMP/collagen complex was thermodynamically favourable.

Conclusion

K21 root canal irrigant was able to penetrate bacterial wall and can serve as a potential irrigant for therapeutic benefits. Expression of M2 polarized subsets showed K21 can serve in resolving inflammation and potentiate tissue repair.

Analysis of Shaping Abilities of Rotary File Systems in Oval Canals with Moderate Root Curvature: A Randomized Controlled Ex Vivo Study

AIM

The purpose of this study was to evaluate and compare the canal transportation tendencies and centering ability of the TruNatomy shaper (TN) and XP-endo shaper (XPS) rotary systems in oval-shaped canals with moderate root curvature (15°-25°), using cone-beam computed tomography (CBCT) imaging.

MATERIALS AND METHODS

Sixty single-rooted permanent human teeth were chosen after considering the inclusion and exclusion criteria. The teeth were divided into two groups (n = 30). The test group was instrumented with TN files and the other with XPS according to manufacturer's instructions. CBCT images were taken before and after instrumentation to record the root canal distances from mesial, distal, buccal, and lingual borders of the root at 3, 5, and 7 mm distances from the root apex using a specific formula. Statistical analysis was done using the Statistical Package for the Social Sciences software program, version 20.0. The data were analyzed using the unpaired t test.

RESULTS

Both TN and XPS were safe for use in oval-shaped canals with moderate root curvature. However, the XPS showed higher buccolingual transportation as compared with TN at 3 mm from the apex and higher mesiodistal transportation at 3 and 5 mm levels from the apex as compared with TN.

CONCLUSION

Canal transportation has been detected in both systems; however, the values obtained were within the safe range (<0.3 mm). Overall, no significant difference was observed between TN and XPS (p > 0.05) in their canal transportation tendencies and centering ability.

CLINICAL SIGNIFICANCE

The study assesses the canal centering and transportation tendencies of the recently launched TN rotary system in extracted teeth with a combination of morphologies. The findings of the study are significant clinically as minimum transportation of the canal, minimal dentin removal, efficient disinfection, and three-dimensional obturation of the root canal are considered important factors in deciding the prognosis of endodontic therapy.

Cauterization of Narrow Root Canals Untouched by Instruments by High-Frequency Current

The mechanical removal of bacteria is fundamental to the treatment of infected root canals, but complete sterilization of biofilms tends not to extend to uninstrumented areas. However, during electrical conduction to a root canal filled with a conductor, the higher impedance where the root canal is narrower generates Joule heat that may result in a large temperature increase and sterilization. The effect of a high-frequency electric current on the wall of a simulated narrow root canal was investigated by scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). Simulated root canals, 0.1 mm in diameter, were prepared in dentine blocks. The root canal wall was treated with Plank-Rychlo solution for 5 min to create a decalcified layer. The simulated root canal was filled with either saline or NaClO, and 150 or 225 V at 520 kHz was applied for 0 s, 1 s, or 5 s. As the conduction time increased, and when the saline was replaced with NaClO, the proportion with a flat decalcified surface decreased, dentinal tubules and a lava-like morphology were significantly more evident on SEM (p < 0.01), and EDS showed significant decreases in carbon and oxygen and increases in calcium (p < 0.01). It was concluded that filling uninstrumented root canals with NaClO and using electrical conduction for 5 s could incinerate and eliminate the organic material of the root canal wall. The application of high-frequency electric current may lead to the cure of many cases of persistent apical periodontitis.

Effect of Endodontic Irrigating Solutions on Radicular Dentine Structure and Matrix Metalloproteinases-A Comprehensive Review

Irrigating solutions play an important role in the eradication of intracanal microbes and debris dissolution during endodontic treatment. Different combinations of solutions and protocols have been advocated, with sodium hypochlorite (NaOCl), ethylenediamine tetra acetic acid (EDTA), and chlorhexidine (CHX) remaining the most widely used ones by many clinicians. Although these solutions provide efficient inorganic dissolution and antimicrobial capacity, their use has also been reported to cause undesired effects on root dentin composition and mechanical and biomechanical properties, such as microhardness, surface roughness, bond strength, and matrix metalloproteinase (MMP) activity. Several corroborating studies attribute these changes in mechanical properties of dentine to the use of irrigating solutions, and there are limited reports on how the solutions affect the expression of MMPs, which may be a correlating link to understanding the role of these enzymes in dentin collagen and changes in the mechanical properties of dentin. Hence, using the basis of several studies from the literature, the objective is to comprehensively review the influence of individual and combined irrigating solutions on root dentine structure and the activity of the MMPs.

In Situ Zymography Analysis of Matrix Metalloproteinases Activity Following Endodontic Irrigation Protocols and Correlation to Root Dentine Bond Strength

The objective was to evaluate the effect of different root canal irrigating solutions on the activity of matrix metalloproteinases (MMPs), and correlation to the push-out bond strength (PBS) and nanoleakage expression (NL) in the root dentin. Seventy-two single-rooted teeth were treated endodontically and distributed into four groups (n = 6 for in-situ zymography, n = 10 for PBS, and n = 2 for NL per group) according to the irrigating solutions used: (I) saline (S); (II) 5.25% sodium hypochlorite (SH); (III) 5.25% SH + 10% citric acid (CA); and (IV) 5.25% SH + 10% CA + 0.2% chlorhexidine (CHX). After root canal obturation, post space was prepared to receive the glass fiber post. Dual-cure resin was used for luting and light polymerization was performed. The root/fiber post assemblies were sectioned and subjected to in situ zymography, and PBS and NL expression analysis tests. The enzymatic activity was quantified and expressed as a percentage of the green fluorescence, while fractographic evaluation was performed after PBS with a stereomicroscope, and data were statistically analyzed at p < 0.05. The zymography analysis shows high expression of MMPs in the middle third of the root in all groups, while the most abundant activity of MMPs following the irrigating solutions is observed in groups I and III, where saline and citric acid are used, respectively. Inversely, group IV, where chlorhexidine is the final rinse, records the lowest MMP activity with the highest PBS, and the statistical analysis of the groups are ranked as: IV > II > III > I (p < 0.05). The combination of SH, CA, and CHX results in lower expression of MMPs and higher push-out bond strength of fiber posts to root dentin, with no difference seen in the nanoleakage expression (p > 0.05); hence, this irrigation regime with chlorhexidine as a final rinse is more favorable than other combinations in ensuring optimal adhesion to root dentine.

Final irrigation protocols affect radicular dentin DMP1-CT expression, microhardness, and biochemical composition

OBJECTIVE

To evaluate the effect of several final irrigation protocols on radicular dentin microhardness, biochemical composition, and DMP1-CT expression.

MATERIALS AND METHODS

A total of 140 single-rooted human teeth were prepared with WaveOne Gold files and randomly distributed into 7 groups (n = 20) according to the final irrigation protocol: distilled water (DW); sodium hypochlorite-EDTA (NaOCl-EDTA); EDTA (EDTA); EDTA-NaOCl (EDTA-NaOCl); EDTA-chlorhexidine (EDTA-CHX); passive ultrasonic irrigation (PUI:NaOCl-EDTA); and PUI:NaOCl-EDTA-NaOCl. Dentin microhardness (n = 10) was evaluated in the root canal lumen using Vickers hardness tester. Immunohistochemical analysis (n = 5) was used to evaluate DMP1-CT expression. Dentin ultrastructure and biochemical composition were evaluated by using Raman and energy dispersive X-ray analysis (EDAX) (n = 5) with a scanning electron microscope (SEM). Analysis of variance (ANOVA) and Tukey test were performed (p˂0.05).

RESULTS

Raman spectra of the organic content and DMP1-CT expression were lower at the lumen canal in EDTA-NaOCl, PUI:NaOCl-EDTA, and PUI:NaOCl-EDTA-NaOCl when compared to control (p < 0.05). EDAX showed reduced values for calcium and phosphorus in EDTA-NaOCl, PUI:NaOCl-EDTA, and PUI:NaOCl-EDTA-NaOCl. SEM microphotography's showed completely cleaned dentin, permeable tubules, and dentin erosion, mainly when PUI was used. NaOCl-EDTA presented significantly higher microhardness values than PUI:NaOCl-EDTA-NaOCl (p < 0.05). PUI:NaOCl-EDTA-NaOCl exhibited the lowest Vickers hardness values of all groups.

CONCLUSION

The final irrigation protocols that used a final rinse with NaOCl and PUI showed a detrimental effect on radicular dentin DMP1-CT expression, biochemical composition, and microhardness.

CLINICAL RELEVANCE

The adequate irrigation protocol could be advantageous to preserve the radicular dentin ultrastructure, promote adequate adhesion, and sustain favorable conditions for biomineralization and regeneration.

A critical analysis of research methods and experimental models to study the load capacity and clinical behavior of the root filled teeth

The prognosis of root‐filled teeth depends not only on a successful root canal treatment but also on the restorative prognosis. This critical review discusses the advantages and limitations of various methodologies used to assess the load capacity or clinical survivability of root‐filled teeth and restorations. These methods include static loading, cyclic loading, finite element analysis and randomized clinical trials. In vitro research is valuable for preclinical screening of new dental materials or restorative modalities. It also can assist investigators or industry to decide whether further clinical trials are justified. It is important that these models present high precision and accuracy, be reproducible, and present adequate outcomes. Although in vitro models can reduce confounding by controlling important variables, the lack of clinical validation (accuracy) is a downside that has not been properly addressed. Most importantly, many in vitro studies did not explore the mechanisms of failure and their results are limited to rank different materials or treatment modalities according to the maximum load capacity. An extensive number of randomized clinical trials have also been published in the last years. These trials have provided valuable insight on the survivability of the root‐filled tooth answering numerous clinical questions. However, trials can also be affected by the selected outcome and by intrinsic and extrinsic biases. For example, selection bias, loss to follow‐up and confounding. In the clinical scenario, hypothesis‐based studies are preferred over observational and retrospective studies. It is recommended that hypothesis‐based studies minimize error and bias during the design phase.

Push-Out Bond Strength of EndoSeal Mineral Trioxide Aggregate and AH Plus Sealers after Using Three Different Irrigation Protocols

OBJECTIVE

 The current study was designed to assess the bonding strength of EndoSeal MTA and AH Plus sealers after using three irrigation protocols as follows: (1) 17% Ethylenediamine tetraacetic acid, (2) 7% maleic acid, and (3) 37% phosphoric acid.

MATERIALS AND METHODS

 Push-out bond strength was evaluated for 60 middle root slices of 1-mm thickness each. They were horizontally cut from freshly extracted single-rooted human teeth. A hole in the root canal was made using a carbide round bur of 1.1 mm in diameter in a middle third root slice. Specimens were dipped in 2.5% NaOCl, and then they were grouped into three groups; G1: 17% EDTA, G2: 7% maleic acid, and G3: 37% phosphoric acid as a final irrigant for 3 minutes. Each group was subdivided into two subgroups, according to the type of sealer, either EndoSeal MTA or AH Plus.

STATISTICAL ANALYSIS

 After the full set of the sealer, the bond strength was evaluated with the push-out test by applying a force to each slice using a plunger with a 1-mm diameter. The one-way Tukey's post hoc test, analysis of variance (ANOVA) test, and Student's t-test were utilized to gather data and statistically evaluate it.

RESULTS

 The irrigation protocol used exhibited significant influence on the bond strength of EndoSeal MTA and AH Plus sealers. AH Plus sealer subgroups showed the highest bond strength with 7% maleic acid, followed by 37% phosphoric acid, and 17% EDTA. While in the EndoSeal MTA sealer subgroups, the highest bond strength was shown with the 17% EDTA followed by 7% maleic acid and 37% phosphoric acid, respectively.

CONCLUSION

 The present study revealed that the type of the final irrigant significantly impacts the bond strength of the sealer used. The AH Plus sealer bond strength was improved by using the 7% maleic acid as a final irrigant. In contrast, the EndoSeal MTA sealer showed the best results with the 17% EDTA as a final irrigant.

The effect of intracanal medication variations on microhardness of simulated immature root dentin

The effect of different medicaments and irrigation solutions on root dentin microhardness (MH) was evaluated depending on time. After initial measurements, MH of 60 maxillary incisors (n = 15 per group) was measured after 3 steps: irrigation with 2.5% sodium hypochlorite, exposure to medicaments [triple antibiotic (TAP) or calcium hydroxide (CH) pastes, 1 week or 1 month)] and final irrigation [20 mL of 17% EDTA or 20 mL 1% phytic acid (PA)]. The percentage of MH reduction was calculated. Data were analysed statistically at P < 0.05. Treatments caused a significant decrease in MH values compared to baseline and pre-measurements (P < 0.05). TAP significantly reduced the MH values of the samples over time (P < 0.05). Removal of TAP after 1 month with PA resulted in a significant reduction in MH compared to removing TAP after 1 week and CH removing after 1 month (P < 0.05). Considering the chemical preparation steps, the most hazardous effect on MH was observed after the first irrigation.

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.

The effect of root canal irrigants on dentin: a focused review

Despite the vast literature on the effects of root canal irrigants on the dentin characteristics, the precise effects of clinically relevant irrigation sequences remain unclear. In this review, we systematically dissect the role of different sequential irrigation approaches that are used in clinical endodontics. Using a systematic search strategy, we attempt to answer the question: ‘Which irrigating sequence has the most deleterious effects on dentin structure and properties?’ The effect of irrigants on the dentin composition and mechanical properties have been reviewed. A wide variety of concentrations, duration and techniques have been employed to characterize the effects of chemicals on dentin properties, thus making it impossible to draw guidelines or recommendations of irrigant sequences to be followed clinically. It was apparent that all the studied irrigation sequences potentially result in some deleterious effects on dentin such as decrease in the flexural strength, microhardness, modulus of elasticity and inorganic content and organic-inorganic ratio of the dentin. However, the literature still lacks comprehensive investigations to compare the deleterious effect of different irrigation sequences, using a wide variety of qualitative and quantitative methods. Such investigations are essential to make clinical recommendations and strategize efforts to minimize chemically-induced damage to dentin characteristics.