Effects of endodontic root canal irrigants on tooth dentin revealed by infrared spectroscopy: a systematic literature review

BACKGROUND

Root canal irrigation endodontic solutions have effects on the chemistry of dentin. Infrared spectroscopy is a non-destructive chemical characterization method where the strength of absorption often correlates with mineral or organic composition.

OBJECTIVES

To survey effects of commonly used irrigation solutions on the composition of root dentin as detected by widely-available Fourier transform infrared spectroscopy (FTIR) methods.

METHODS

Electronic databases were searched for articles published between 1983 to 2023. After risk of bias assessments (OHAT), studies were grouped according to effects per irrigation solution. Inclusion criteria comprised in vitro studies that used extracted human or bovine teeth, treated by irrigation solutions characterized using FTIR spectroscopy and presenting spectral data. Publications that did not present spectra were excluded.

RESULTS

A wide range of concentrations, durations, and treatment protocols have been tested but only 30 out of 3452 studies met our inclusion criteria. Different FTIR methods were used with Attenuated Total Reflection (ATR) variant being the most common (21 studies). Investigated solutions included sodium hypochlorite (NaOCl), ethylenediaminetetraacetic-acid (EDTA), 1-hydroxyethylidene-1-1-diphosphonic-acid (HEDP), peracetic-acid (PAA), glycolic-acid (GA), and citric-acid (CA) though most focused on NaOCl and EDTA. All solutions had detectable effects in the FTIR signature of dentin. NaOCl mainly affects the organics, revealing reduced amide/phosphate ratios with increasing concentrations. EDTA mainly effects the inorganic component, with the effects increasing with time and concentration, yet glycolic acid has stronger effects than EDTA on dentin. Beyond the type of irrigant and dentin exposure durations, concentration and protocol of application had strong effects. There is a lack of studies comparing similar irrigants under conditions that mimic clinical scenarios analyzing bulk sample because FTIR of powder dentin differs from FTIR of bulk dentin.

SIGNIFICANCE

The ideal root-canal irrigant should combine local disinfection properties with minimal compositional effects on healthy dentin. FTIR methods appear reliable to identify important changes in root dentin chemical composition. Such information can help understand when endodontic irrigation might lead to root degradation or possibly contribute to long term failures such as vertical fractures. Awareness of chemical damage from irrigation procedures may help clinicians select procedures that reduce deleterious effects on the root canal structures.

Calcium hydroxide-loaded nanoparticles dispersed in thermosensitive gel as a novel intracanal medicament

AIM

Design, produce and assess the viability of a novel nanotechnological antibacterial thermo-sensible intracanal medicament This involves encapsulating calcium hydroxide (Ca(OH)2) within polylactic-co-glycolic acid (PLGA) nanoparticles (NPs) and dispersing them in a thermosensitive gel (Ca(OH)2-NPs-gel). In addition, perform in vitro and ex vivo assessments to evaluate tissue irritation and penetration capacity into dentinal tubules in comparison to free Ca(OH)2.

METHODOLOGY

Reproducibility of Ca(OH)₂-NPs was confirmed by obtaining the average size of the NPs, their polydispersity index, zeta potential and entrapment efficiency. Moreover, rheological studies of Ca(OH)2-NPs-gel were carried out with a rheometer, studying the oscillatory stress sweep, the mean viscosity value, frequency and temperature sweeps. Tolerance was assessed using the membrane of an embryonated chicken egg. In vitro Ca(OH)2 release was studied by direct dialysis in an aqueous media monitoring the amount of Ca(OH)2 released. Six extracted human teeth were used to study the depth of penetration of fluorescently labelled Ca(OH)2-NPs-gel into the dentinal tubules and significant differences against free Ca(OH)2 were calculated using one-way anova.

RESULTS

Ca(OH)2-NPs-gel demonstrated to be highly reproducible with an average size below 200 nm, a homogeneous NPs population, negative surface charge and high entrapment efficiency. The analysis of the thermosensitive gel allowed us to determine its rheological characteristics, showing that at 10°C gels owned a fluid-like behaviour meanwhile at 37°C they owned an elastic-like behaviour. Ca(OH)2-NPs-gel showed a prolonged drug release and the depth of penetration inside the dentinal tubules increased in the most apical areas. In addition, it was found that this drug did not produce irritation when applied to tissues such as eggs' chorialantoidonic membrane.

CONCLUSION

Calcium hydroxide-loaded PLGA NPs dispersed in a thermosensitive gel may constitute a suitable alternative as an intracanal antibacterial medicament.

Glycolic acid on push-out bond strength of fiber post and smear removal: an in vitro study

This study aims to investigate glycolic acid (GA) as a final irrigant on push-out bond strength of fiber post and smear removal. Ninety mandibular premolars were stabilized with a silicone key and photographed, and canal cross-section was calculated by image processing software. Round canal morphology was selected. The specimens were divided into five groups (n = 18); 10%GA, 17%EDTA, NaOCl + 10%GA, NaOCl + 17%EDTA, and the control. Fifteen specimens were used for the push-out. Three specimens were evaluated using a scanning electron microscope after post space preparation. Two-way ANOVA and Chi-square were used for statistics. GA presented higher strength than EDTA (p < 0.05). The NaOCl + GA showed higher strength than the NaOCl + EDTA (p < 0.05). The highest values were observed in cervical and lowest in apical thirds (p < 0.05). The most failure type was between dentin and resin (p < 0.05). GA removed the smear in the post space including the apical third. The NaOCl + GA has superiority to NaOCl + EDTA on push-out strength. Glycolic acid improved the bond strength of fiber post when used as a final post space irrigant. The combination of NaOCl and glycolic acid did not negatively affect the bond strength and was more effective compared to the combination with EDTA. Glycolic acid improved the bond strength of fiber post when used as a final post space irrigant. The combination of NaOCl and glycolic acid did not negatively affect the bond strength and was more effective compared to the combination with EDTA.

Dual- or single rinse? The tubular sealer penetration of endodontic chelating agents

INTRODUCTION

In this study, we aimed to compare the effectiveness of various chelating agents, ethilenediaminetetraacetic acid (EDTA), citric acid (CA), and etidronic acid (HEDP) mixed in two different forms, in removing the smear layer and promoting the penetration of an endodontic sealer into the dentinal tubules of extracted single-rooted teeth.

METHODS

The study used 75 teeth divided into five groups: 17% EDTA, 10% CA, 9% HEDP + NaOCl, 9% HEDP + distilled water (DW), and a control (DW) group. Scanning electron microscopy was used to assess smear layer removal and confocal laser microscopy was used to evaluate tubular sealer penetration at different depths from the apical tip.

RESULTS

Sealer penetration was highest with 17% EDTA and 10% CA as compared with the other agents (p<0.001). At the cervical third, the sealer penetration for EDTA, HEDP + NaOCl, and HEDP + DW groups were significantly different than those in DW (p = 0.020). For the middle third, EDTA, CA, and HEDP + NaOCl groups were significantly higher than those of the DW group (p<0.001). Cervical-level values were significantly higher than apical-level values for HEDP + NaOCl, HEDP + DW, and DW (p<0.001). Smear layer removal was lower with 9% HEDP + DW than with 17% EDTA and 10% CA at all depths (p<0.001). A significancy in smear layer removal was observed between 10% CA and control (p = 0.015) in middle depth.

CONCLUSION

Within the limitations of this study, highest values were seen in EDTA and CA in terms of sealer penetration and smear layer removal. In the light of these findings, the use of strong chelating agents highlights better clinical efficiency than dual-rinse or single HEDP irrigation.

Photodynamic and nitric oxide therapy-based synergistic antimicrobial nanoplatform: an advanced root canal irrigation system for endodontic bacterial infections

BACKGROUND

The main issues faced during the treatment of apical periodontitis are the management of bacterial infection and the facilitation of the repair of alveolar bone defects to shorten disease duration. Conventional root canal irrigants are limited in their efficacy and are associated with several side effects. This study introduces a synergistic therapy based on nitric oxide (NO) and antimicrobial photodynamic therapy (aPDT) for the treatment of apical periodontitis.

RESULTS

This research developed a multifunctional nanoparticle, CGP, utilizing guanidinylated poly (ethylene glycol)-poly (ε-Caprolactone) polymer as a carrier, internally loaded with the photosensitizer chlorin e6. During root canal irrigation, the guanidino groups on the surface of CGP enabled effective biofilm penetration. These groups undergo oxidation by hydrogen peroxide in the aPDT process, triggering the release of NO without hindering the production of singlet oxygen. The generated NO significantly enhanced the antimicrobial capability and biofilm eradication efficacy of aPDT. Furthermore, CGP not only outperforms conventional aPDT in eradicating biofilms but also effectively promotes the repair of alveolar bone defects post-eradication. Importantly, our findings reveal that CGP exhibits significantly higher biosafety compared to sodium hypochlorite, alongside superior therapeutic efficacy in a rat model of apical periodontitis.

CONCLUSIONS

This study demonstrates that CGP, an effective root irrigation system based on aPDT and NO, has a promising application in root canal therapy.

Did in-between rinsing and agitating with distilled water prevents precipitate formation by the interaction between sodium hypochlorite and chlorhexidine canal irrigants?

The interaction of sodium hypochlorite (NaOCl) and chlorhexidine gluconate (CHX) produces an orange-brown precipitate. The present study evaluated the influence of distilled water (H2 O) in different irrigation protocols designed to prevent the formation of precipitate with NaOCl and CHX. Fifty canine teeth were instrumented and split longitudinally. The canal was examined with a stereomicroscope and photographed by canal-thirds. The tooth halves were repositioned and distributed randomly into five groups, according to the final irrigation protocol (n = 10): G1 (control)-Ethylenediaminetetraacetic acid (EDTA) + NaOCl + CHX, conventional irrigation (CI); G2-EDTA + NaOCl + CHX, activated with passive ultrasonic irrigation (PUI); G3-EDTA (PUI) + NaOCl (PUI) + H2 O (CI) + CHX (PUI); G4-EDTA + NaOCl + H2 O + CHX (PUI); G5-EDTA (PUI) + NaOCl (PUI) + H2 O (continuous ultrasonic irrigation [CUI]) + CHX (PUI). The specimens were evaluated with a stereomicroscope and scanning electron microscope (SEM). Energy dispersive x-ray spectroscopy analysis was performed to identify the elemental profile of the irrigated canal walls. The images were scored according to the extensiveness of precipitate. Data were analyzed (Kruskal-Wallis test, α = 5%). Under the stereomicroscope, G1 had significantly higher scores than all the other groups in all canal-thirds (p < .05). All four experimental groups showed similar scores (p > .05). There were no significant differences in precipitate formation among root-thirds in intragroup analysis (p > .05). Upon SEM examination, overall, only G5 had lower scores than G1 (p < .05). Analysis by canal-thirds showed no significant difference among groups and among canal-thirds in the intragroup analysis (p > .05). G1 showed high Cl peaks. In-between irrigation with H2 O activated by CUI is effective in preventing precipitate formation during canal debridement with NaOCl and CHX. RESEARCH HIGHLIGHTS: Continuous ultrasonic irrigation with distilled water was capable to prevent the precipitate formation. The precipitate can be classified as a chemical smear layer.

Push out bond strength of fiber post to radicular dentin using Q-mix, lemon/garlic extract, and riboflavin activated by photodynamic therapy as a final canal irrigant

OBJECTIVE

The aim of this study was to assess the extrusion bond values of fiber post to radicular dentin when disinfected using different final irrigants lemon garlic extract (LGE), riboflavin (RFP) activated by PDT (photodynamic therapy), and Q-mix 2-in-1.

MATERIALS AND METHODS

Forty single-rooted mandibular premolar teeth were decoronated. Endodontic treatment was performed, and the canals were continually irrigated with normal saline, dried with paper points, and obturated. Post space was prepared by removing gutta-percha using peso-reamers. All specimens were randomly allocated into four groups based on the final irrigant used. Specimens in Group 1 irrigated with: 5.25% NaOCl+17% EDTA, group 2: 5.25% NaOCl+Q-mix 2-in-1, group 3: 5.25% NaOCl+RFP, and group 4: 5.25% NaOCl+LGE. Following final irrigation, a fiber post was placed in the canal space and luted. Samples were sectioned and each section was placed in a universal testing machine to assess bond values. Debonded samples were assessed for failure modes, EBS and modes of failure. For comparisons among groups, the one-way analysis of variance (ANOVA) test and the Post-Hoc Tukey HSD test were used keeping the level of significance at p=0.05.

RESULTS

The cervical section of samples in group 2 (NaOCL+Qmix) (7.11±0.81 MPa) exhibited the maximum value of EBS. However, the apical section of samples in group 3 (5.25% NaOCl+RFP) (3.33±0.26 MPa) displayed minimum extrusion bond values. Group 3 specimens in which final irrigation was performed with RFP established significantly lower bond integrity values than all the other investigated groups coronal (3.77±0.13 MPa), middle (3.60±0.41 MPa), and apical (3.33±0.26 MPa) (p<0.05). Intragroup comparison analysis, the coronal and middle root sections of all the experimental groups displayed comparable outcomes of EBS (p>0.05). However, near the apical section of the root, the bond strength of all the groups declined considerably.

CONCLUSIONS

Q-mix 2-in-1 as the final irrigant displayed the highest extrusion bond strength of fiber-reinforced composite to canal dentin at all three levels coronal, middle and apical. Lemon garlic extract has the potential to be used alternative to ethylene diamine tetra acetic acid as a final irrigant.

Evaluation of structural integrity effect on adhesion strength of root dentin with a multi-functional irrigation strategy

OBJECTIVES

To evaluate effects of a novel auxiliary irrigation strategy, proanthocyanidin (PA) + carboxymethyl chitosan/amorphous calcium phosphate (CMC/ACP) nanocomplexes, on maintaining the organic-inorganic structural integrity and hence optimizing the adhesion strength of root dentin.

MATERIALS AND METHODS

Dentin specimens (n = 150) were prepared and subjected to the classical irrigating strategy with or without PA and CMC/ACP. The ultrastructure and biomechanical behaviour of dentin were characterized by scanning electron microscopy and atomic force microscope, respectively. Forty single root-canal premolars were employed for push-out bond strength testing. Besides, the antibacterial effects against Enterococcus faecalis were evaluated with confocal laser scanning microscopy. Statistical differences were verified with one-way ANOVA and Tukey's post-tests.

RESULTS

The organic-inorganic structural integrity of root dentin was repaired with the synergetic use of PA and CMC/ACP. Correspondingly, the bond stability between the root canal wall and the AH-Plus sealer was significantly reinforced (P < 0.05). Meanwhile, the tissue biomechanical properties and antibacterial behaviour were enhanced compared to that of control group (P < 0.05).

CONCLUSIONS

The synergistic utilization of PA and CMC/ACP can preserve the structural integrity of root dentin, contributing to optimizing the sealing effects of root canal. Moreover, the novel irrigation strategy demonstrated a favourable antimicrobial activity.

CLINICAL RELEVANCE

The combination of PA and CMC/ACP can serve as a promising auxiliary irrigation strategy to optimize the outcomes of chemical preparation, enhance the sealing effects of root canal and hence improve the success rate of treatment.

Human root dentin microhardness and degradation by triple antibiotic paste and calcium hydroxide

PURPOSE

To investigate and compare the effects of the two widely used regenerative endodontics medicaments: Triple antibiotic paste (ciprofloxacine-metronidazole-clindamycin) and calcium hydroxide on the microhardness and degradation of human root dentin.

METHODS

Following ethical approval and subject consent to use teeth in this research study, 60 singled-rooted permanent human teeth were randomly divided into six groups:(1) Tri-antibiotic paste with distilled water, or with (2) propylene glycol, (3) calcium hydroxide with distilled water, (4) calcium hydroxide propylene glycol, (5) untreated extracted teeth as negative controls, or (6) teeth instrumented and filled with calcium hydroxide or tri-antibiotic paste as positive controls. The microhardness tests were conducted after 1 and 2 months of exposure to the medicaments using a Vickers microhardness tester. Raman spectroscopy and energy dispersive x-ray spectroscopy were used to evaluate the chemistry and structure of the root dentin.

RESULTS

There were differences in the dentin microhardness following treatment with the medicaments or controls (P< 0.05). The time of root dentin exposure to the medicaments was similar (P> 0.05). The root dentin microhardness was lower in the teeth treated with the triple antibiotic paste or calcium hydroxide when combined with propylene glycol. The root dentin collagen in these treated teeth were also significantly degraded when viewed with Raman spectroscopy and energy dispersive x-ray spectroscopy, whereas the inorganic phase (dentin) remained unaltered. Samples exposed to the antimicrobial agents with water as a vehicle exhibited stronger microhardness and less degradation.

CLINICAL SIGNIFICANCE

These ex vivo results suggest that the triple antibiotic paste and calcium hydroxide should be used with propylene glycol if a fast diffusion is desired or with water to avoid degrading the collagen and weakening the microhardness of the teeth. Clinical trials are needed of new formulations of medicaments with propylene glycol to disinfect teeth for regenerative endodontic procedures, to help strengthen the teeth to prevent the loss of children's permanent immature teeth by fracture following caries or trauma.

Impact of dentin conditioning and sealer modification with chitosan-hydroxyapatite nanocomplexes on the antibacterial and mechanical characteristics of root dentin

INTRODUCTION

This study aimed to characterize the effectiveness of dentin-conditioning with bio-mineralizable chitosan-hydroxyapatite precursor (CS-HA) nanocomplexes alone or associated with tricalcium silicate sealer (TCS/CS-HA) on the mechanical property and antibiofilm efficacy in root dentin.

METHODS

Flow tests were performed following ISO6876:2012-specifications. Solubility was measured. Micromorphology was assessed using Scanning Electron Microscopy (SEM). Nanohardness/elastic modulus were also determined. Fracture resistance was determined on lower premolars that were prepared, and randomly distributed among 7-groups (n=8/group), including the control, CS-HA dentin-conditioning and root canal filled groups. Similar canal preparation/distribution procedure was followed to test the antibacterial effect on Enterococcus faecalis-infected roots. Descriptive statistic was used to report SEM findings. Flowability results were analyzed using Paired t-test. Multiple comparisons from solubility, fracture and antibacterial assays were assessed by one-way ANOVA-Tukey's tests.

RESULTS

TCS/CS-HA showed optimal flow and no effect on solubility after immersion for 4 weeks (p>.05). TCS/CS-HA significantly increased nanohardness and elastic modulus (210±11.3MPa, 7.9±0.9GPa) compared to TCS (44.5±7.8MPa, 2.1±0.3GPa,p<.05). SEM revealed needle-shaped mineralized structures resulting in fewer voids and a well-adapted sealer-dentin interface in the TCS/CS-HA groups. NaOCl-EDTA irrigation resulted in reduced fracture resistance (444.34N) while CS-HA dentin-conditioning alone (928.28N, p<.05) and CS-HA dentin-conditioning plus CS-HA/TCS resulted in higher fracture resistance (1134.06N, p<.05). CS-HA dentin-conditioning also reduced bacteria by 2.04 log (4.50±0.43) from the initial bacterial load (6.54±0.07, p<.05). There was further bacterial reduction when CS-HA-conditioned root canals were filled with TCS or TCS/CS-HA (0.00 to 0.98±0.57, p>.05).

CONCLUSION

Dentin modification with CS-HA increased the fracture resistance of root dentin, and decreased the residual bacterial burden. TCS/CS-HA potentiated the nanomechanical and physical properties of TCS.

Evaluation of Free Available Chlorine of Sodium Hypochlorite When Admixed with 0.2% Chitosan: A Preliminary Study

AIM AND OBJECTIVE

The aim of the study was to evaluate the changes in free available chlorine (FAC) when 6% sodium hypochlorite (NaOCl) is admixed with irrigants 17% ethylenediaminetetraacetic acid (EDTA), 2% chlorhexidine (CHX), and 0.2% chitosan in varying proportions of 90:10, 80:20, and 50:50.

MATERIALS AND METHODS

The 25 mL aliquots of 6% NaOCl were admixed in varying proportions of 90:10, 80:20, and 50:50 with secondary irrigation solutions: (a) 17% EDTA, (b) 2% CHX, (c) 0.2% chitosan. Iodometric titration was done to evaluate the change in FAC.

STATISTICAL ANALYSIS USED

Kruskal-Wallis and Mann-Whitney tests.

RESULTS

On titration, the mean FAC value of NaOCl at baseline was 1.99 g%. On mixing NaOCl with EDTA, the FAC decreased in all the three proportions and the values were 0.17 g%, 0.17 g%, and 0.06 g% at 90:10, 80:20, and 50:50 ratios, respectively. pH obtained was 9.55 at 50:50 ratio. On mixing NaOCl with CHX, FAC reduced and the values were 1.84 g%, 1.72 g%, and 0.27 g% at 90:10, 80:20, and 50:50 ratios, respectively. pH obtained was 10.87 at 50:50 ratio. On mixing NaOCl and chitosan, the FAC remained unaltered in all the three proportions and the values were 1.64 g%, 1.51 g%, and 1.63 g% at 90:10, 80:20, and 50:50 ratios, respectively. pH obtained was 11 at 50:50 ratio.

CONCLUSION

Combination of NaOCl and chitosan did not lead to a reduction in FAC and the pH of the solution remained unaltered, suggesting that tissue-dissolving property of NaOCl might be preserved.

CLINICAL SIGNIFICANCE

The combination of chitosan with NaOCl is advantageous in two ways. Firstly, FAC remained unaltered and the pH of the solution was also maintained at 11.05 indicating that the tissue-dissolving property of NaOCl prevailed. Secondly, chitosan is known for its chelating property and is effective in smear layer removal. With further in vivo and in vitro studies, a combination of chitosan and NaOCl can be proposed as a novel irrigant.

Chemical aspect of sodium hypochlorite activation in obtaining favorable outcomes of endodontic treatment: An in-vitro study

BACKGROUND

Endodontic treatment is one of the most widely performed procedures in a dental office. New techniques for enhancing the effectiveness of irrigants are being introduced into the dental market. It is crucial to choose a proper method to obtain the highest possible long-term success of performed endodontic treatment. Sodium hypochlorite (NaOCl) appears to be one of the most common and profitable solutions for root canal irrigation. The activation of a solution may be analyzed in 2 fields, physical - turbulence of flow, and chemical - disintegration of irrigant molecules into very active radicals that improve its activity. While the physical alternations of irrigant flow with different techniques are widely studied, there are not many attempts to approach the subject in chemical terms.

OBJECTIVES

The aim of the study was to compare the chemical effectiveness of 2 methods of NaOCl activation: ultrasonics vs the Self-Adjusting File system (SAF) as an adjunct to increase the efficacy of the irrigant.

MATERIAL AND METHODS

The level of activation was evaluated via a reaction of the activated NaOCl samples, with 9-fluorenol as the starting organic material. The model reaction is based on the oxidation of 9-fluorenol to 9-fluorenon. The evaluation was performed using 1H nuclear magnetic resonance (NMR) spectroscopy, comparing the spectra obtained for the examined mixtures.

RESULTS

Nuclear magnetic resonance studies show that the use of ultrasonics resulted in increased chemical degradation of NaOCl as compared to the SAF system and non-agitated samples. The prevalence of chemical activation in the ultrasonic group over the SAF group was almost 3 times higher, 3.11 to 1.20, respectively. The Kruskal-Wallis rank sum test revealed there is a statistically significant difference in distributions between the groups.

CONCLUSIONS

Both SAF and ultrasonics activate NaOCl. Ultrasonic agitation provided higher chemical activation of NaOCl solution than the SAF. The use of ultrasonic agitation of NaOCl in endodontic treatment will allow us to obtain better long-term clinical results.

Effect of previous irrigation with chlorhexidine on the push-out bond strength of a calcium silicate-based material

This study evaluated the effect of previous irrigation with chlorhexidine (CHX) on the bond strength of a calcium silicate-based material, Biodentine, when used for furcal repair. Furcal perforations were produced in 30 extracted mandibular molars. Teeth were divided into 3 groups according to the irrigant used: distilled water (DW), CHX followed by DW (CHX), and CHX followed by ethylenediaminetetraacetic acid (EDTA) and DW (CHX/EDTA). Biodentine was used to repair the perforations. A push-out bond strength test was performed after 7 days, and data were statistically analyzed using Kruskal-Wallis and Dunn tests (P < 0.05). The CHX/EDTA group showed significantly lower values than the DW and CHX groups (P < 0.05). The failure mode of the DW group was mainly mixed, while that of the CHX group was cohesive. The CHX/EDTA group exhibited adhesive and mixed failures. Irrigation with CHX prior to furcation repair did not result in a statistically significant difference, compared to the use of DW, in the push-out bond strength of Biodentine.

Effects of Final Irrigation with SmearOFF on the Surface of Dentin Using Surface Analytical Methods

INTRODUCTION

SmearOFF (Vista Dental Products, Racine, WI) is an irrigation solution containing chlorhexidine (CHX), EDTA, and a surfactant. This study examined the chemical interaction of SmearOFF with sodium hypochlorite (NaOCl) on the dentin surface, specifically the formation of precipitate and/or parachloroanaline (PCA).

METHODS

Dentin blocks prepared from human maxillary molars were mounted in resin. Dentinal tubules were exposed in a perpendicular orientation using an ultracryomicrotome. The blocks were divided into 2 groups: the CHX group, irrigation with 6% NaOCl, 17% EDTA, 6% NaOCl, and 2% CHX, and the SmearOFF group, irrigation with 6% NaOCl and SmearOFF. The dentin surface was analyzed with time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy to determine the formation of precipitate or/and PCA on the surface of dentin.

RESULTS

Precipitation with PCA and occlusion of the dentinal tubules were noted on the dentin surface in the CHX group. No precipitate and no PCA were detected on the surface of dentin in the SmearOFF group.

CONCLUSIONS

Interaction of SmearOFF with NaOCl on the dentin surface did not result in the formation of precipitate or PCA.

Development of techniques for determination of primary components of dental medicament paste mixtures for root canal treatment

AIMS

The purpose of the present study was to develop techniques to evaluate and quantify the primary components of dental medicament paste mixtures for root canal treatment, and to evaluate if degradation of the primary components occurred during storage.

METHODS

The first part of the study developed a mass spectrometry (MS) method for determination of best recovery process. For this process, analytical grades of triamcinolone acetonide, clindamycin HCl, and doxycycline hyclate were sourced and analyzed. This was followed by solid-phase extraction (SPE) and an analysis of active components in dental pastes.

RESULTS

By utilizing the targeted analytical properties of multiple reaction monitoring MS methods, coupled with SPE technique, the active components of endodontic dental pastes could be quantified and compared. The developed methods showed consistency over multiple runs, with a high level of reproducibility. None of the active components of the tested pastes degraded over the periods of product life tested.

CONCLUSION

The inactivation or destruction of any of the primary components of endodontic medicaments in storage, or when mixed with other pastes, could affect treatment outcomes. The present study provides a reliable technique for the analysis of the active components of root canal medicaments.

Demetallization of Enterococcus faecalis biofilm: a preliminary study

Objectives To determine the concentration of calcium, iron, manganese and zinc ions after the application of chelator to Enterococcus faecalis biofilms. Material and Methods Fifty bovine maxillary central incisors were prepared and inoculated with E. faecalis for 60 days. The following were used as irrigation solutions: 17% EDTA (pH 3, 7 and 10), 2.5% sodium hypochlorite (NaOCl) combined with 17% EDTA (pH 3, 7 and 10), distilled water (pH 3, 7 and 10), and 2.5% NaOCl. Each solution was kept in the root canal for five minutes. Fifteen uncontaminated root canals were irrigated with 17% EDTA (pH 3, 7 and 10). Six teeth were used as bacterial control. The number of calcium, iron, manganese and zinc ions was determined using flame atomic absorption spectrometry. Mean ± standard deviation (SD) values were used for descriptive statistics. Results Calcium chelation using 17% EDTA at pH 7 was higher than at pH 3 and 10, regardless of whether bacterial biofilm was present. The highest concentration of iron occurred at pH 3 in the presence of bacterial biofilm. The highest concentration of manganese found was 2.5% NaOCl and 17% EDTA at pH 7 in the presence of bacterial biofilm. Zinc levels were not detectable. Conclusions The pH of chelating agents affected the removal of calcium, iron, and manganese ions. The concentration of iron ions in root canals with bacterial biofilm was higher after the use of 17% EDTA at pH 3 than after the use of the other solutions at all pH levels.

Influence of Mixed Additives on the Physicochemical Properties of a 5.25% Sodium Hypochlorite Solution: An Unsupervised Multivariate Statistical Approach

INTRODUCTION

This article reports for the first time the effects of multiple additives (polyethylene glycol 400, Triton X-100, benzalkonium chloride, and ethyl formate) on the surface tension, pH, and viscosity of 5.25% sodium hypochlorite (NaOCl) irrigant solution. Advanced statistical approaches based on unsupervised multivariate analysis (cluster analysis and principal component analysis) were used to quantify the variability of the physicochemical properties of the modified NaOCl solution for the first time in dentistry.

METHODS

Solutions of 5.25% NaOCl were modified with multiple additives in various concentrations, physicochemical parameters were measured at 22°C and 37°C, and the results were statistically analyzed to group the solutions and reveal the effects of additives.

RESULTS

Cluster analysis and principal component analysis revealed that pH and surface tension were the significant parameters (P < .05) for grouping the modified solutions. Four principal components, accounting for 90.6% of the total variance, were associated with flow characteristics (37.3%) determined by polyethylene glycol; the wetting property (22.5% and 10.5%), which was dependent on cationic and nonionic surfactant; and the antimicrobial effect (20.3%) influenced by ethyl formate. Varimax rotation of the principal components showed that the cationic surfactant (benzalkonium chloride) had significantly decreased surface tension compared with the nonionic surfactant (Triton-X). Although ethyl formate was introduced as an odor modifier, it had a significant effect on pH decrease and the occurrence of effervescence with O₂ and hypochlorous acid release.

CONCLUSIONS

The statistical results revealed that the 5.25% NaOCl irrigant solution should be modified with a mixture of 0.1% benzalkonium chloride, 1% ethyl formate, and 7% polyethylene glycol for obtaining a low pH and low surface tension.

Intracanal use of heated rinsing solutions: A pilot study

OBJECTIVE

The tissue-dissolving and bactericidal activity of sodium hypochlorite (NaOCl) can be increased by warming the NaOCl solution without concurrently increasing its toxicity. The present study was set up to determine if and to what extent a heated liquid reaches the apical region.

METHOD AND MATERIALS

A temperature sensor was introduced from the apical aspect into a human canine 22 mm in length prepared to size 40.04. At 37°C in the incubator the canal was irrigated with water 10 times each at temperatures of 10°C, 21°C, 45°C, 60°C, and 37°C (control group). The apical temperature curve was recorded with a one-second resolution from the time the irrigation started until at least 2 minutes after its end.

RESULTS

None of the measurements yielded the same temperature in the apical region as that of the coronally introduced liquid. At 60°C, a maximum value of 52.2°C ± 1.39°C, and at 10°C, a minimum value of 16.09°C ± 0.39°C, was achieved apically. At 1 minute after the end of active rinse cycle, the temperature at the apical probe differed only 4.8°C to 0.9°C ± 1.41°C from the initial value (about 37°C). Only with the cold 10°C solution was the temperature difference higher, at 7.5°C ± 2.14°C.

CONCLUSION

The benefit of heating irrigants accrues primarily during the period of active rinsing; immediately after the end of the rinsing cycle, body temperature is reached again. A positive aspect to be noted is that an irrigant stored at room temperature is quickly warmed to 37°C in the root canal by the temperature of the body.

Effectiveness of XP-endo Finisher, EndoActivator, and File agitation on debris and smear layer removal in curved root canals: a comparative study

The purpose of this study was to assess the efficacy of the XP-endo Finisher (FKG Dentaire SA, La Chaux-de-Fonds, Switzerland) file on debris and smear layer removal in curved root canals in comparison to different irrigation regimens. Seventy-five freshly extracted human mandibular molar teeth with mesial root curved more than 20° were used in this study. The mesial root canals were mechanically prepared using the BT-Race rotary system (FKG Dentaire) and divided into five groups (n = 15) according to the following irrigation techniques: positive control, non-agitated, File agitation, XP-endo Finisher, and EndoActivator (Dentsply Tulsa Dental Specialities, Tulsa, OK, USA). Root canals were split longitudinally and evaluated by scanning electron microscopy. Five-grade scoring system was used to assess the presence of debris and smear layer at the coronal, middle, and apical regions. The XP-endo Finisher and EndoActivator groups revealed significantly lower debris and smear layer scores than the other groups at the coronal, middle, and apical regions (P < 0.05). There was no significant difference between XP-endo Finisher and EndoActivator groups (P > 0.05). The apical region had higher debris and smear layer scores compared with the coronal regions in all groups (P < 0.05), except for the positive control group; there was no significant difference between the three regions of the root canal (P > 0.05). Irrigation of curved root canals using XP-endo Finisher and EndoActivator methods appears to be more effective on debris and smear layer removal than the other tested groups.

Effect of Different Antioxidants on the Microtensile Bond Strength of an Adhesive System to Sodium Hypochlorite-treated Dentin

PURPOSE

To evaluate the effects of different antioxidant treatments on the microtensile bond strength of an adhesive system to sodium hypochlorite (NaOCl)-treated dentin.

MATERIALS AND METHODS

Thirty extracted third molars were sectioned 3 mm below the occlusal surface and divided into six groups according to the antioxidant treatment received: control group: distilled water; NaOCl group: 5.25% NaOCl and distilled water; proanthocyanidin (PA) group: 5.25% NaOCl, 5% PA and distilled water; 1-week storage group: 5.25% NaOCl and storage for 1 week in distilled water; Accel group: 5.25% NaOCl, Accel, and distilled water; noni group: 5.25% NaOCl, noni fruit juice, and distilled water. NaOCl, PA, Accel, noni, and distilled water were administered for 30 s, 10 min, 30 s, 10 min, and 30 s, respectively. A self-etching adhesive system (Single Bond Universal Adhesive) was applied to each specimen and a resin composite (Filtek Z550) was built up to a height of 5 mm on the dentin surface. Each specimen was serially sectioned to obtain sticks with a cross-sectional area of 1 mm2, and their microtensile bond strength was determined. Statistical differences between groups were analyzed using one-way ANOVA and Tamhane's T2 test.

RESULTS

Microtensile bond strength in the NaOCl group was significantly lower than in all other groups. However, there were no significant differences in the bond strength between the groups treated with different antioxidants.

CONCLUSIONS

NaOCl significantly reduced the microtensile bond strength of the adhesive system. The application of PA, Accel, and noni fruit juice to NaOCl-treated dentin significantly improved the microtensile bond strength.

Influence of Concentration and Agitation of Sodium Hypochlorite and Peracetic Acid Solutions on Tissue Dissolution

AIM AND OBJECTIVE

To evaluated the tissue dissolution of sodium hypochlorite (NaOCl) and peracetic acid (PA) solutions at different concentrations, with or without ultrasonic agitation.

MATERIALS AND METHODS

The following solutions were analyzed: 2.5% NaOCl, 0.5, 1 and 2% PA, 1% PA associated with 6.5% hydrogen peroxide (HP) and saline. Fragments of bovine pulp tissue with 25 ± 2g mg were immersed into test tubes containing 4 mL of the solutions for 10 minutes. In the groups with agitation, pulp tissues were submitted to 2 cycles of 1 minute of ultrasonic agitation. The specimens were weighed after the removal from the solutions. The percentage of mass loss was calculated according to the difference of mass before and after exposure to solutions. Data were submitted to ANOVA and Tukey tests (p < 0.05).

RESULTS

A total of 2.5% NaOCl with or without agitation showed the higher tissue dissolution (between 64.5 and 67% of mass reduction) (p < 0.005). By comparing the PA solutions, the concentrations of 1 and 2% with or without agitation and the concentration of 0.5% with agitation showed similar dissolution activity (between 35.4 and 44% of mass reduction). The use of the ultrasonic agitation promoted an increase of the dissolution ability only for 0.5% PA.

CONCLUSION

Peracetic acid solution has pulp tissue dissolution. However, this ability is lower than 2.5% NaOCl solution.

CLINICAL SIGNIFICANCE

The sodium hypochlorite solution shows higher ability to dissolve tissue than PA.

Comparative Evaluation of Two Final Irrigation Techniques for the Removal of Precipitate Formed by the Interaction between Sodium Hypochlorite and Chlorhexidine

AIM

To evaluate the effectiveness of two final irrigation techniques for the removal of precipitate formed by the interaction between sodium hypochlorite (NaOCl) and chlorhexidine (CHX).

MATERIALS AND METHODS

Sixty freshly extracted human maxillary incisor teeth were taken and randomly divided into three groups, containing 20 teeth each. Group 1 (control group), were irrigated with 5 ml of 2.5% NaOCl and a final flush with 5 ml of 2% chlorhexidine. Group 2 were irrigated with 5 ml of 2.5% NaOCl and 5 ml of 2% chlorhexidine followed by 5 ml of saline and agitated with F-files. Group 3 were irrigated with 5 ml of 2.5% NaOCl and 5 ml of 2% chlorhexidine followed by 5 ml of 15% citric acid and passively agitated with ultrasonics. A thin longitudinal groove was made along the buccal and lingual aspect of the root using diamond disks and split with chisel and mallet. Both halves of the split tooth will be examined under stereomicroscope. Results were tabulated and analyzed statistically using analysis of variance (ANOVA) and Mann-Whitney U test.

RESULT

There was a significant difference between the mean values (p < 0.05) in groups 2 and 3 compared to group 1 at each level.

CONCLUSION

Passive ultrasonic irrigation is more effective than the F-file agitation technique to remove the precipitate at all three levels measured.

CLINICAL SIGNIFICANCE

Combination of sodium hypochlorite and chlorhexidine irrigation protocol has been practiced since from many years to achieve good results. However, it has adverse effect in the form of precipitate and which is considered to be a carcinogenic in nature, hence this precipitate should be removed.

Bioactivity Studies of β-Lactam Derived Polycyclic Fused Pyrroli-Dine/Pyrrolizidine Derivatives in Dentistry: In Vitro, In Vivo and In Silico Studies

The antibacterial activity of β-lactam derived polycyclic fused pyrrolidine/pyrrolizidine derivatives synthesized by 1, 3-dipolar cycloaddition reaction was evaluated against microbes involved in dental infection. Fifteen compounds were screened; among them compound 3 showed efficient antibacterial activity in an ex vivo dentinal tubule model and in vivo mice infectious model. In silico docking studies showed greater affinity to penicillin binding protein. Cell damage was observed under Scanning Electron Microscopy (SEM) which was further proved by Confocal Laser Scanning Microscope (CLSM) and quantified using Flow Cytometry by PI up-take. Compound 3 treated E. faecalis showed ROS generation and loss of membrane integrity was quantified by flow cytometry. Compound 3 was also found to be active against resistant E. faecalis strains isolated from failed root canal treatment cases. Further, compound 3 was found to be hemocompatible, not cytotoxic to normal mammalian NIH 3T3 cells and non mutagenic. It was concluded that β-lactam compound 3 exhibited promising antibacterial activity against E. faecalis involved in root canal infections and the mechanism of action was deciphered. The results of this research can be further implicated in the development of potent antibacterial medicaments with applications in dentistry.

Effect of Chlorhexidine and Ethanol Application on Long-term Push-out Bond Strength of Fiber Posts to Dentin

AIM

The aim of this study was to evaluate the effect of chlorhexidine and ethanol application on the push-out bond strength and bond durability of fiber posts cemented with an etch-and-rinse adhesive system/resin cement to intraradicular dentin.

MATERIALS AND METHODS

Fifty-four bovine roots were shaped for the cementation of a fiberglass post and received the application of 37% phosphoric acid. They were then randomly divided into three groups, according to the type of dentin treatment (n = 18) performed: no treatment (control group), 100% ethanol, or 2% chlorhexidine. Next, the adhesive system (Adper Scotch Bond Multipurpose Plus, 3M ESPE) was applied to the dentin, according to the manufacturer's instructions. Glass fiber posts were cemented with dual resin cement (Rely X ARC, 3M ESPE). After 48 hours, the specimens were serially sectioned for push-out test analysis, providing two slices from each root third (cervical, medium and apical), one of which was tested immediately and the other stored in distilled water for 180 days. The data were analyzed with three-way analysis of variance (ANOVA) for repeated measures and Tukey's test at a 5% significance level.

RESULTS

Intraradicular treatment with chlorhexidine yielded the highest bond strength means, followed by ethanol treatment. The control group presented the lowest bond strength means. Water storage exerted no effect on bond strength values.

CONCLUSION

Both chlorhexidine and ethanol improved push-out bond strength to intraradicular dentin, with the former providing the best results, regardless of the storage time.

CLINICAL SIGNIFICANCE

The application of 2% chlorhexidine or 100% ethanol may be an important step that can be taken to enhance bond strength of fiber posts to intraradicular dentin, when dual resin cements are used.

Bond strength of self-adhesive resin cement to root dentin. Comparison of photon-initiated photoacoustic streaming technique with needle and ultrasonic irrigation

OBJECTIVE

The aim of this study was to investigate the effects of photon-initiated photoacoustic streaming (PIPS) with various irrigating solutions on the bond strength of a self-adhesive resin cement to root dentin.

MATERIALS AND METHODS

Seventy-two mandibular premolar roots were divided into six groups after post space preparation and treated with a needle irrigation with distilled water and NaOCl, ultrasonic irrigation with NaOCl, PIPS with NaOCl, PIPS with EDTA and PIPS with distilled water at 0.3 W, 15 Hz and 20 mJ per pulse for 60 s. Fiber posts were cemented with a newly marketed, self-adhesive resin cement. The data obtained from the push-out tests were analyzed using analysis of variance (ANOVA) and LSD post-hoc tests (p = 0.05).

RESULTS

PIPS with distilled water resulted in higher push-out values than those of needle (with both distilled water and NaOCl) and ultrasonic irrigation (p < 0.05).

CONCLUSIONS

The use of PIPS may provide higher bond strength of self-adhesive resin cement to root dentin than needle and ultrasonic irrigation techniques.