The effect of initial irrigation with two different sodium hypochlorite concentrations on the erosion of instrumented radicular dentin

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.

Effect of herbal irrigants on surface roughness of intraradicular dentin using quantitative method of 3D surface texture analysis

Replacing the conventional endodontic irrigants with herbal agents could avoid complications associated with using sodium hypochlorite (NaOCl). Endodontic irrigants alter the surface roughness of the dentinal wall surface, which affects sealer mechanical retention. This study aimed to assess the effect of experimental herbal Moringa oleifera and orange peel extract irrigant on intraradicular dentin (IRD) surface roughness using quantitative 3D surface analysis by scanning electron microscopy (SEM) regarding the smear layer assessment. Sixty human root sections were divided into four groups (n = 15): NaOCl combined with 17% ethylenediaminetetraacetic acid (EDTA); negative control (saline); moringa extract (MO); and orange oil (OO). SEM images were assessed quantitatively for surface roughness (Ra) in the coronal, middle, and apical IRD. The data were analysed by Kruskal-Wallis, Friedman, and Dunn's tests. All groups showed statistically significant differences (P = 0.007). MO exhibited significantly greater Ra values at the coronal, middle, and apical root levels than OO (P = 0.007, 0.009, and 0.046, respectively). There was no significant change in Ra values at various root levels within each group at P = 0.091, 0.819, 0.819, and 0.549 for the EDTA, saline, MO, and OO groups. Considerable (IRD) surface roughness analysis makes Moringa extract a promising herbal endodontic irrigant alternative to the NaOCl plus EDTA regimen.

Effect of continuous vs sequential chelation on the mechanical properties of root dentin: An ex vivo study

OBJECTIVES

To evaluate the mechanical properties of root canal dentin treated with sodium hypochlorite (NaOCl) in combination with hydroxyethylidene diphosphonic acid (HEDP) or ethylenediaminetetraacetic acid (EDTA).

METHODS

For testing fracture resistance, 45 single-rooted teeth were instrumented and irrigated with NaOCl/HEDP, NaOCl/EDTA, or distilled water. Fifteen untreated teeth served as control. After obturation, specimens from the experimental groups were thermocycled, dynamically-loaded, and then statically-loaded in a universal testing machine until failure. For flexural strength analysis, 15 teeth were instrumented and irrigated with NaOCl/HEDP or NaOCl/EDTA. Root segments were sectioned into dentin bars and tested for flexural strength using a universal testing machine. For microhardness evaluation, 20 teeth were instrumented and irrigated with NaOCl/HEDP or NaOCl/EDTA. Dentin disks from the coronal-third of each root segment were prepared, one before and one after irrigation, for microhardness testing with a Knoop hardness tester.

RESULTS

The highest fracture resistance was recorded in the untreated group, and the lowest in the EDTA group. Although the HEDP group had higher fracture resistance than the EDTA group, the distilled water group demonstrated even greater fracture resistance than the HEDP group. Specimens treated with HEDP had significantly higher flexural strength and microhardness values when compared with those treated with EDTA.

CONCLUSION

The fracture resistance, flexural strength, and microhardness of root canal dentin were higher when root canals were irrigated with NaOCl/HEDP, when compared with NaOCl/EDTA.

CLINICAL SIGNIFICANCE

Irrigating root canals with NaOCl combined with HEDP significantly improves the mechanical integrity of root canal dentin compared to the use of NaOCl with EDTA.

Effect of sodium hypochlorite and ethylenediaminotetraacetic acid activated by laser and ultrasonic energy on surface morphology and chemical composition of intracanal dentin

The aim of the study was to evaluate the structural and chemical changes in intracanal dentin after root canal irrigation with sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) using additional activation with a novel Er:YAG Shock Wave-Enhanced Emission Photoacoustic Streaming (SWEEPS), ultrasonic irrigation (UI), and Nd:YAG irradiation. Root canals of extracted human premolars were instrumented with distilled water and distributed into groups according to the irrigation protocol used: Group 1: conventional needle irrigation (CI) with 3% NaOCl; group 2: CI with 15% EDTA; and group 3: CI with NaOCl+EDTA. In group 4, root canals were irrigated with NaOCl+EDTA+NaOCl using the following techniques: CI (group 4A), SWEEPS (group 4B), UI (group 4C). In group 4D, root canals were finally irradiated with Nd:YAG laser. After the irrigation, the intracanal dentin sample was collected and analyzed using spectroscope with a Fourier transformation of infrared spectrum in Attenuated total reflection technique (FTIR-ATR) to calculate apatite/collagen ratio. Scanning electron microscopy (SEM) and energy dispersive x-ray spectrometry (EDS) were used to determine its chemical composition. FTIR-ATR showed no significant difference in the phosphate/amid I ratio between the control and the experimental groups (p > 0.05). SWEEPS and UI of NaOCl+EDTA+NaOCl caused the most pronounced decrease of Ca and P (p < 0.05) value compared to CI and control group, and canal wall erosion. SWEEPS and UI of NaOCl+EDTA+NaOCl caused the most pronounced decrease of Ca and P value and significant canal wall erosion. However, no difference in phosphate/amide ratio was reported among groups. RESEARCH HIGHLIGHTS: SWEEPS and UI of NaOCl+EDTA+NaOCl caused the most pronounced decrease of Ca and P values and significant canal wall erosion. There was no difference in phosphate/amide ratio among the irrigation protocols.

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.

Minimally invasive management of vital teeth requiring root canal therapy

The present study aimed to investigate the possible use of a non-instrumentation technique including blue light irradiation for root canal cleaning. Extracted human single rooted teeth were selected. Nine different groups included distilled water, NaOCl, intra-canal heated NaOCl, and NaOCl + EDTA irrigation after either instrumentation or non-instrumentation, and a laser application group following non-instrumentation technique. The chemical assessment of the root canal dentine was evaluated using energy dispersive spectroscopy (EDS) and Fourier transform infrared (FT-IR) spectroscopy. Surface microstructural analyses were performed by using scanning electron microscopy (SEM). The antimicrobial efficacy of different preparation techniques was evaluated using microbial tests. Light application didn't change the calcium/phosphorus, carbonate/phosphate and amide I/phosphate ratios of the root canal dentin. The root canal dentin preserved its original chemistry and microstructure after light application. The instrumentation decreased the carbonate/phosphate and amide I/phosphate ratios of the root canal dentin regardless of the irrigation solution or technique (p < 0.05). The application of light could not provide antibacterial efficacy to match the NaOCl irrigation. The NaOCl irrigation both in the non-instrumentation and instrumentation groups significantly reduced the number of bacteria (p < 0.05). The use of minimally invasive root canal preparation techniques where the root canal is not instrumented and is disinfected by light followed by obturation with a hydraulic cement sealer reduced the microbial load and preserved the dentin thus may be an attractive treatment option for management of vital teeth needing root canal therapy.

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.

Effects of concentration of sodium hypochlorite as an endodontic irrigant on the mechanical and structural properties of root dentine: A laboratory study

AIM

The use of high-concentration sodium hypochlorite (NaOCl) as an endodontic irrigant remains controversial because of its potential impact on the fracture strength of endodontically-treated teeth. This study evaluated the effects of using different NaOCl concentrations, with 2-min-ethylenediaminetetraacetic acid (EDTA) as the final active irrigant, on the biomechanical and structural properties of root dentine.

METHODOLOGY

A new test method, which is more clinically relevant, was utilized to calculate the fracture strength of root dentine. Bovine incisors were used to obtain root dentine discs. The root canals were enlarged to mean diameter of 2.90 mm with a taper of 0.06. The resulting discs were divided into 5 groups (n=20) and treated with different concentrations of NaOCl (5.25%, 2.5%, and 1.3%) for 30 min plus 17% EDTA for 2 min. The discs were then loaded to fracture by a steel rod with the same taper through the central hole. The fractured specimens were examined by scanning electron microscopy to evaluate changes in the dimensions of the remaining intertubular dentine and the tubular radius. Micro-hardness was also measured with a Knoop diamond indenter along a radius to determine the depth of dentine eroded by the irrigation. Results were analyzed by one-way ANOVA and the Tukey test. The level of significance was set at α = 0.05.

RESULTS

The damage by NaOCl increased with its concentration. 5.25% NaOCl greatly reduced the fracture strength of root dentine from 172.10±30.13 MPa to 114.58±26.74 MPa. The corresponding reduction in micro-hardness at the root canal wall was 34.1%. The damages reached a depth of up to 400 μm (p < 0.05). Structural changes involved degradation of the intratubular wall leading to enlarged dentinal tubules and the loss of intertubular dentine. Changes in the microstructural parameters showed positive linear relationships with the fracture strength.

CONCLUSIONS

With the adjunctive use of EDTA, NaOCl caused destruction to the intratubular surface near the root canal and, consequently, reduced the root dentine's mechanical strength. The higher the concentration of NaOCl, the greater the effect. Therefore, endodontists should avoid using overly high concentration of NaOCl for irrigation to prevent potential root fracture in endodontically-treated teeth.

Antibacterial and antibiofilm efficacy of k21-E in root canal disinfection

OBJECTIVES

The aim of the current project was to study the antimicrobial efficacy of a newly developed irrigant, k21/E against E. faecalis biofilm.

METHODS

Root canals were instrumented and randomly divided into the following groups: irrigation with saline, 6% NaOCl (sodium hypochlorite), 6% NaOCl+2% CHX (Chlorhexidine), 2% CHX, 0.5% k21/E (k21 - quaternary ammonium silane) and 1% k21/E. E. faecalis were grown (3-days) (1×10⁷CFU mL^-1), treated, and further cultured for 11-days. Specimens were subjected to SEM, confocal and Raman analysis and macrophage vesicles characterized along with effect of lipopolysaccharide treatment. 3T3 mouse-fibroblasts were cultured for alizarin-red with Sortase-A active sites and Schrödinger docking was performed. TEM analysis of root dentin substrate with matrix metalloproteinases profilometry was also included. A cytotoxic test analysis for cell viability was measured by absorbance of human dental pulp cells after exposure to different irrigant solutions for 24h. The test percentages have been highlighted in Table 1.

RESULTS

Among experimental groups, irrigation with 0.5% k21/E showed phase separation revealing significant bacterial reduction and lower phenylalanine 1003cm^-1 and Amide III 1245cm^-1 intensities. Damage was observed on bacterial cell membrane after use of k21/E. No difference in exosomes distribution between control and 0.5%k21/E was observed with less TNFα (*p<0.05) and preferential binding of SrtA. TEM images demonstrated integrated collagen fibers in control and 0.5%k21/E specimens and inner bacterial membrane damage after k21/E treatment. The k21 groups appeared to be biocompatible to the dental pulpal cells grown for 24h.

SIGNIFICANCE

Current investigations highlight potential advantages of 0.5% k21/E as irrigation solution for root canal disinfection.

Adjunctive procedure with solvent mixtures in non-surgical endodontic retreatment: does it affect root dentin hardness?

The aim of this study was to compare the effects of new irrigation solvent mixtures with Methyl ethyl ketone (MEK)/Tetrachloroethylene (TCE) and MEK/Orange oil (OOil), and different agitation techniques on dentin hardness. One hundred forty-four mandibular teeth were prepared and standardized, with each root's middle part transversely sectioned. Initial hardness was measured using a Vickers microhardness tester. Specimens were divided into four groups of agitation techniques (n = 36): no agitation; EndoActivator; IrriSafe; and XP-endo Finisher R. Each group was subdivided into six subgroups of irrigation protocols (n = 6): saline solution; NaOCl + EDTA; NaOCl + EDTA + MEK/TCE; MEK/TCE; NaOCl + EDTA + MEK/OOil; MEK/OOil. Final hardness was measured. The irrigation protocols NaOCl + EDTA, NaOCl + EDTA + MEK/TCE, and NaOCl + EDTA + MEK/OOil significantly decreased dentin hardness, while MEK/OOil increased it (p < 0.05). Comparing to NaOCl + EDTA sequence, dentin hardness increased significantly with the additional exposure to MEK/TCE (3%NaOCl + 17%EDTA + MEK/TCE) or MEK/OOil (3%NaOCl + 17%EDTA + MEK/OOil) (p < 0.05). There were no significant differences regarding agitation effects on dentin hardness decrease. The irrigation protocols affected dentin hardness significantly. However, the additional solvent proposals do not seem to address further concerns on dentin's mechanical properties. Agitation did not show any influence on dentin's hardness reduction.

Effects of different irrigation protocols on dentin surfaces as revealed through quantitative 3D surface texture analysis

The combination of ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl) has been advocated as an effective irrigation methodology to remove organic and inorganic matter in root canal therapy. Yet, it was suggested that both solutions might lead to structural changes of the dentinal wall surface, depending on the order of application which might affect sealer mechanical retention. This study aims to evaluate the effect of different irrigating protocols on dentin surface roughness using quantitative 3D surface texture analysis. Data stems from 150 human root dentin sections, divided into five groups, each prepared according to one of the following protocols: Negative control; 17% EDTA; 17% EDTA followed by 5.25% NaOCl; 5.25% NaOCl; and 5.25% NaOCl followed by 17% EDTA. Each dentin sample was examined for its three-dimensional surface texture using a high-resolution confocal disc-scanning measuring system. EDTA 17% and the combined EDTA 17% with NaOCl 5.25% showed considerably higher roughness properties compared to the control and to NaOCl 5.25% alone. However, the irrigation sequence did not affect the dentin roughness properties. Therefore, mechanical retention is probably not dependent upon the selection of irrigation protocol sequence.

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

Background

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

Methods

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

Results

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

Conclusions

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

The effects of sequential and continuous chelation on dentin

OBJECTIVE

Proteolytic and demineralizing agents have a profound influence on the dentin ultrastructure, which plays a key role in the mechanical integrity of the tooth and integrity of dentin-biomaterial interfaces. In-depth characterization of dentin treated with a novel root canal irrigation protocol comprising sodium hypochlorite (NaOCl) and etidronate (HEDP) is lacking. This study comprehensively characterized and compared the effects of the continuous chelation (NaOCl/HEDP) and sequential chelation (NaOCl/EDTA) protocols on dentin.

METHODS

Dentin blocks, dentin powder and root canals of mandibular premolars were distributed into Group 1, Saline (control); Group 2, NaOCl/EDTA; and Group 3, NaOCl/HEDP. Ultrastructural characteristics of the treated dentin were investigated using electron microscopy and light microscopy, while the surface roughness was analyzed using atomic force microscopy. Chemical compositional changes were characterized using Fourier transform infrared spectroscopy (FTIR) and energy-dispersive-X-ray spectroscopy (EDS), while collagen degradation was determined using ninhydrin assay. Data were statistically analyzed using multiple-factor one-way ANOVA and Tukey HSD tests (P = 0.05).

RESULTS

NaOCl/HEDP resulted in partially degraded, yet mineralized collagen fibers, with minimal alteration to the subsurface matrix. Conversely, NaOCl/EDTA dissolved the hydroxyapaptite encapsulation, exposing collagen fibre bundles. There was no significant difference in the surface roughness between the two protocols (P > 0.05). NaOCl/HEDP resulted in homogenous distribution of organic and inorganic components on the treated surface.

SIGNIFICANCE

This study highlighted that continuous chelation (NaOCl/HEDP) resulted in a frail surface collagen layer while sequential chelation (NaOCl/EDTA) exposed bare collagen fibres. These surface and sub-surface effects potentially contribute to structural failures of dentin and/or dentin-biomaterial interfacial failures.

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

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

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.

Effect of benzalkonium chloride addition to EDTA on attachment and proliferation of dental pulp stem cells on dentin and on transforming growth factor-β1 release

To investigate the effect of benzalkonium chloride (BAC) addition to ethylenediaminetetraacetic acid (EDTA) on transforming growth factor-β1 (TGF-β1) release, as well as attachment and proliferation of dental pulp stem cells (DPSCs) on dentin. A total of standard 268 human dentin disks were prepared and immersed in 1.5% sodium hypochlorite (NaOCl) for 5 min. The disks were rinsed with distilled water and randomly divided into seven groups. In control group, the disks received no further treatment. The remaining disks were immersed in following solutions: 17% EDTA or 17% EDTA + 0.008% BAC for 1, 5 or 10 min and rinsed with distilled water. DPSCs were seeded in part of the disks since the TGF-β1 release assay was performed with disks with and without cells. The attachment and proliferation of DPSCs on dentin disks were analyzed using lactate dehydrogenase activity and WST-1 assays, respectively. The cell morphology was observed by scanning electron microscopy. The release of TGF-β1 was quantified using ELISA. Data were analyzed using three- and two-way analysis of variance with Bonferroni corrections. Both EDTA solutions increased the attachment and proliferation of DPSCs (p < .05) while there was no significant difference between them (p > .05). The exposure time of both EDTA solutions had no influence on cell attachment, proliferation and TGF-β1 release (p > .05). There was no significant difference in TGF-β1 release between the control and experimental groups (p > .05). The amount of released TGF-β1 from dentin disks was similar whether or not they were seeded with cells (p > .05). Dentin treatment with either of the EDTA solutions had no effect on the amount of TGF-β1 release while both EDTA solutions improved cell attachment and proliferation on dentin surface regardless of exposure time.

Influence of a propolis-based irrigant solution on gap formation and bond strength of posts bonded to root canal dentin using different resin cements

This study evaluated the influence of an aqueous propolis-based solution (PROP) on gap formation and bond strength of posts bonded to root canal dentin using resin cements. Endodontically-treated bovine incisors received different irrigation protocols: 1) 2.5% sodium hypochlorite (NaOCl)/17% EDTA/NaOCl; 2) saline solution (NaCl)/EDTA/0.12% chlorhexidine (CHX); 3) NaOCl/PROP/NaOCl; 4) NaCl/PROP/CHX; 5) NaCl/PROP/NaCl. Posts were then bonded with cements: RelyX ARC; Panavia F2.0; or RelyX U200 (n=10). The specimens were cross-sectioned. Gaps were assessed and performed the push-out bond strength test. Surface roughness of dentin fragments was also evaluated. Statistical analysis was performed (5%). RelyX U200 exhibited greater gap-free interfaces. Bond strength varied as a function of cements and irrigation protocols. PROP irrigation had no negative effect on the bond strength (p>0.05). Roughness increased significantly after NaOCl/EDTA/NaOCl, but remained unaltered after PROP irrigation protocols. Propolis-based irrigation protocols do not interfere in the bonding performance of posts cemented to root canal dentin.

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

AIM

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

METHODOLOGY

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

RESULTS

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

CONCLUSIONS

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

The influence of irrigation solutions in the inorganic and organic radicular dentine composition

The aim of this study was to analyse changes in radicular dentine composition after different irrigation regimes using attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR). Dentine slices from human single-root teeth were immersed in: (i) 5.25% sodium hypochlorite (NaOCl) for 1, 5 and 20 min; (ii) 17% EDTA for 1 min; and (iii) 5.25% NaOCl for 20 min, and 17% EDTA and 5.25% NaOCl, both for 1 min. Carbonate/mineral, Amide I/mineral and Amide III/CH₂ ratios were determined using ATR-FTIR before and after immersion in the irrigation solutions tested. Results showed that 5.25% NaOCl significantly decreased carbonate/mineral, Amide I/mineral and Amide III/CH₂ ratios (P < 0.05). Application of 17% EDTA produced no change in carbonate/mineral ratio (P = 0.120), while an increase in Amide I/mineral in apical third (P = 0.002) and Amide III/CH₂ (P < 0.001) was observed. The combination of NaOCl, EDTA and NaOCl increased carbonate/mineral ratio in coronal third (P = 0.037), and Amide I/mineral (P = 0.003) and Amide III/CH₂ (P = 0.001) ratios. In conclusion, irrigation solutions tested significantly affected radicular dentine composition.

In Vitro Evaluation of Antibacterial Properties and Smear Layer Removal/Sealer Penetration of a Novel Silver-Citrate Root Canal Irrigant

This study aimed at evaluating the efficacy of a novel silver-citrate root canal irrigation solution (BioAKT) on smear layer removal, sealer penetration after root canal instrumentation and antibacterial activity. Single-root teeth were endodontically treated, sealed with an epoxi-amine resin sealer and irrigated using: Group I: 5.25% sodium hypochlorite (NaOCl); Group II: silver-citrate solution (BioAKT); Group III: phosphate buffer solution (PBS); Group IV: 17% ethylenediaminetetraacetic acid (EDTA). Smear layer removal and silver deposition at the coronal, middle and apical portion of each canal were analyzed using scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). Sealer penetration into dentinal tubules at coronal, middle and apical portion was assessed through dye-assisted confocal microscopy (CSM). Both SEM and CSM micrographs were evaluated by two examiners (κ = 0.86), who were blind to the irrigation regimens; scores were given according to the degree of penetration of the sealer. Data analysis included Pearson’s x² and Sidak’s multiple comparisons. Dentin discs were polished and sterilized. Enterococcus faecalis biofilms were grown using a continuous-flow bioreactor under anaerobic conditions for 72 h. Specimens were irrigated with the tested solutions, and bacterial viability was assessed using a tetrazolium salt assay (MTT). Statistical analysis included one-way ANOVA and Student’s post-hoc t-test (p < 0.05). BioAKT and EDTA were the most efficient solutions both in removing the smear layer and allowing sealer penetration. However, at the apical portion BioAKT performed significantly better compared to EDTA both in smear layer removal and sealer penetration (p < 0.05). BioAKT and NaOCl showed comparable antibacterial effect (p = 0.53). In conclusion, BioAKT represents a suitable smear layer removal agent, which allows for reliable sealer penetration at the apical portion of the root canal system and offers significant antibacterial properties.

Effect of EDTA, sodium, and calcium hypochlorite on the inorganic component of root canal dentin: A SEM analysis

This study evaluated the influence of canal irrigation protocols with 5.25% calcium hypochlorite [Ca(OCl)₂ ], 5.25% sodium hypochlorite (NaOCl) and 17% EDTA solution on the inorganic component of root canal dentin. Sixty roots were randomly divided into six groups (n = 10): Saline solution (SS) (control); Saline solution (SSE) +17% EDTA; CH - 5.25% Ca(OCl)₂ ; CHE - 5.25% Ca(OCl)₂  + 17% EDTA; SH - 5.25% NaOCl; SHE - 5.25% NaOCl +17% EDTA. After canal irrigation, the specimens were longitudinally split and analyzed by scanning electron microscopy (SEM). Dentinal tubules were observed in transverse (middle and apical thirds) direction. The images were classified in scores, according to smear layer removal and peritubular dentin alteration, and data were analyzed by Kruskal-Wallis's test, followed by Dunn's test (α = 0.05). In the middle third, all groups with EDTA presented better removal of the smear layer with higher peritubular dentin alteration (p < .05). In the apical third, this happened only in SHE (p < .05). Ca(OCl)₂ and NaOCl exhibit similar performance to remove smear layer and alteration of the inorganic component in the middle third. In the apical third, NaOCl associated with EDTA showed better performance in smear layer removal.

Proof-of-concept study to establish an in situ method to determine the nature and depth of collagen changes in dentine using Fourier Transform Infra-Red spectroscopy after sodium hypochlorite irrigation

AIM

To establish a method using Fourier Transform Infra-Red spectroscopy (FTIR) to characterize the nature and depth of changes in dentinal collagen following exposure to sodium hypochlorite (NaOCl) during root canal irrigation in an ex vivo model.

METHODOLOGY

Fourier Transform Infra-Red spectroscopy was used to assess the changes in dentinal collagen when the root canal was exposed to NaOCl. The changes in dentinal collagen caused by NaOCl irrigation of root canals in transverse sections of roots, at 0.5 mm from the canal wall and 0.5 mm from the external root surface, were assessed by FTIR. The data were analysed using paired t-test with 5% significance level.

RESULTS

Fourier Transform Infra-Red spectroscopy confirmed that NaOCl exposure caused alterations in the chemistry and structure of collagen in dentine. FTIR spectra obtained from dentine surfaces and dentine adjacent to root canals exposed to NaOCl, all consistently showed degradation and conformational change of the collagen structure. FTIR data from the ex vivo model showed that the depth of effect of NaOCl extended to at least 0.5 mm from the canal wall.

CONCLUSION

In extracted human teeth, NaOCl caused changes in dentinal collagen that were measurable by FTIR. In an ex vivo model, the depth of effect into dentine extended at least 0.5 mm from the canal wall.

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

AIM

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

METHODOLOGY

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

RESULTS

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

CONCLUSIONS

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

Effects of Different Irrigation Solutions and Protocols on Mineral Content and Ultrastructure of Root Canal Dentine

Introduction

The aim of this study was to evaluate the effect of different irrigating solutions and irrigation protocols on the chemical and physical structure of root dentin.

Materials and Methods

Thirty extracted single-rooted human teeth were selected and then distributed into the following treatment groups (n=10): G1, saline solution (0.9% NaCl); G2, 2.5% NaOCl + 17% EDTA + 2.5% NaOCl; G3, 2.5% NaOCl + 9% Etidronate (HEBP) + 2.5% NaOCl; G4, mixture of 5% NaOCl + 18% HEBP; G5, 2.5% NaOCl + 17% EDTA + 0.9% NaCl, and G6, 2.5% NaOCl + 9% HEBP + 0.9% NaCl. The ultrastructure of dentin was characterized through scanning electron microscopy (SEM) and energy dispersive x-ray spectrometry (EDS) determined the chemical composition in terms of the calcium (Ca), phosphorus (P), magnesium (Mg) and potassium (K) content and the Ca/P ratio; and the crystalline phase was analyzed by x-ray diffraction (XRD). A descriptive analysis was performed on the ultrastructure and the crystallography data of dentin. Data analysis included a chemical composition analysis of variance (one-way ANOVA) and a subsequent multiple comparison test (Tukey's test).

Results

Except for the control group, all groups showed morphological changes upon visualization with SEM. For EDS, G2 and G5 showed significant mineral loss and changes in the Ca/P ratio (P<0.05); the highest values of Ca and P were observed in G3, G4 and G6.

Conclusion

All the irrigating solutions and irrigation protocols tested promoted changes in the morphology and physical and chemical composition of the dentin. However, no significant differences were observed crystallographically.

Effect of different irrigations on the bond strength of self-adhesive resin cement to root dentin

Background

Different disinfectant solutions or medications are indicated prior fiber post bonding procedures.The aim was to evaluate the effect of different pretreatments of root canal on the bond strength of a fiber post luted to dentin with self-adhesive resin cement.

Material and Methods

Forty-eight single-rooted mandibular premolars were endodontically treated and prepared to receive fiber posts. Teeth were assigned to four groups (n=12). Root canal walls were subjected to no pretreatment (G1 - control); irrigation with 10 mL of 5% sodium hypochlorite (NaOCl) (G2); 10 mL of 17% ethylenediaminetetraacetic acid (EDTA) associated with 10 mL of 5% NaOCl (G3); or 10 mL of 17% EDTA (G4). Fiber posts were bonded with self-adhesive cement. After the roots were sectioned into slices, a push-out bond strength test was performed using a universal testing machine at crosshead speed of 0.5 mm/min. Bond strength data were recorded and expressed in MPa and analyzed by Anova (5%) and Tukey Test (5%).

Results

It was found that G2 (9.36 MPa) and G4 (6.33 MPa) were significantly different among themselves and statistically inferior to G1 (13.93 MPa) while G3 (14.31 MPa) was statistically similar to G1 (control) and superior to G2 and G4.

Conclusions

Irrigation with 17% EDTA associated with 5% NaOCl showed increased bond strength compared with the same solutions used alone. Key words:Self-adhesive, Dentin, Push-out, Bonding.

Effect of ethanol on the antimicrobial properties of chlorhexidine over oral biofilm

The aim of this study was to evaluate the effect of 95% ethanol irrigation, with 5 or 10 min of action, on the antibacterial properties of 2% chlorhexidine (CHX), on oral biofilm, evaluated with confocal laser scanning microscopy (CLSM). Oral biofilm development was induced in 80 sterilized bovine dentin blocks, distributed in two groups (5 or 10 min) and 4 subgroups, according to time and the solution used: Saline (SALINE5, SALINE10); Saline followed by CHX (SALINE/CHX5, SALINE/CHX10); Ethanol (ETHANOL5, ETHANOL10), Ethanol followed by CHX (ETHANOL/CHX5, ETHANOL/CHX10). The surface of the block was dyed with Live/Dead^® BacLight. Images from different areas were analyzed by BioImage L program. The total biovolum (µm³), biovolum of live cells (green), percentage of live cells of the thickness of the biofilm visualized in CLSM and on surface biofilm were evaluated. Total biovolum and biovolum of living cells showed similar results among the different groups (p > .05). The percentage of living cells in total thickness of the biofilm also was similar among the groups (p > .05), except ETHANOL5, SALINE/CHX10, ETHANOL10, and ETHANOL/CHX10 that showed lower percentage than SALINE5 (p < .05). The ETHANOL10 and ETHANOL/CHX10 also showed lower percentage of living cells than ETHANOL/CHX5 and SALINE10 (p < .05). In relation to biofilm surface, SALINE/CHX5, SALINE/CHX10, ETHANOL5, ETHANOL10, ETHANOL/CHX5, and ETHANOL/CHX10 showed a lower percentage of living cells percentage than SALINE5 and SALINE10 groups (p < .05). Therefore, ethanol has no effect on antimicrobial properties of 2% chlorhexidine, prior when used as endodontic irrigating solution.

Concentration and time-dependent effect of initial sodium hypochlorite on the ability of QMix and ethylenediaminetetraacetic acid to remove smear layer

Aims:

The aim of this study was to compare the ability of 17% ethylenediaminetetraacetic acid (EDTA) and QMix with different concentrations and time exposures of initial sodium hypochlorite (NaOCl) to remove the smear layer from the root canals.

Materials and Methods:

Eighty maxillary central incisors were used. After instrumentation, the teeth were divided into eight experimental groups according to the initial and final rinse. About 2.5% and 5% NaOCl were used during instrumentation and for 1 or 3 min was used as postinstrumentation initial irrigants, and 17% EDTA and QMix used as final irrigants. The apical and middle parts of the specimens were observed by scanning electron microscope.

Statistical Analysis Used:

Data were analyzed using the Kruskal–Wallis, Mann–Whitney, and Friedman's test.

Results:

Regardless of the type of final irrigant, QMix allowed more smear layer removal than EDTA after using 5% initial NaOCl for 3 min. In the apical part of the root canal walls, the smear layer was not completely removed.

Conclusion:

QMix and EDTA were similarly effective in smear layer removal at the middle parts of the root canal regardless of the concentration and time exposure of initial NaOCl, while none of the irrigation protocols was able to remove smear layer at the apical parts.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

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

STATEMENT OF SIGNIFICANCE

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

Final irrigation protocols may affect intraradicular dentin ultrastructure

OBJECTIVES

The aim of this study was to evaluate the effect of different irrigation protocols on the root dentin structure using scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

MATERIALS AND METHODS

Thirty-nine lower bovine incisors were hemisected longitudinally and randomly divided into 13 groups (n = 3). After the root halves were reassembled, it was applied a specific irrigation protocol for each group, as following: G1, distilled water (control); G2, 0.9% saline; G3, saline + 17% EDTA; G4, saline + PUI; G5, saline + PUI + EDTA; G6 to G9 received the same protocol as above replacing 0.9% saline by 2.5% NaOCl; and G10 to G13 by 2% CHX. One-half of each sample was prepared and evaluated using SEM and the other one by TEM observations.

RESULTS

TEM descriptive analysis showed modifications in dentin organic ultrastructure, characterized by the thinning of dentin collagen fibrils, caused by NaOCl, enhanced by EDTA and/or PUI. SEM analysis showed that NaOCl with PUI caused significantly larger erosion of the peritubular dentin than in all the other groups (P < 0.05), followed by NaOCl + EDTA and NaOCl + EDTA + PUI.

CONCLUSIONS

NaOCl caused ultrastructural alterations in the dentin collagen, and enhanced by EDTA and/or PUI, promoted peritubular and intertubular erosion.

CLINICAL RELEVANCE

The effect of irrigating solutions on dentin ultrastructure was still unclear. The acknowledgment about the kind of solution, concentrations, application time, and sequence of use was important to achieve the right sanitization without jeopardizing the dentin ultrastructure quality.

Influence of Intracanal Irrigants on Coronal Fracture Resistance of Endodontically Treated and Bleached Teeth: An In vitro Study

Background:

Irrigation has a key role in the success of endodontic treatment. Intracanal irrigant solutions have adverse effects on the physical properties of dentin.

Aim:

The present study aimed to evaluate the effect of different irrigation protocols on coronal fracture resistance of endodontically treated teeth undergoing bleaching treatment.

Design and Materials and Methods:

Access cavities were prepared in 120 maxillary premolars which were divided into two groups (n = 60) – Group A: nonbleached, Group B: bleached (B). Each group was subdivided into five subgroups based on irrigation protocol (n = 12); G1: normal saline (NS), G2: 2.5% sodium hypochlorite (NaOCl), G3: 10% citric acid (CA), G4: 17% ethylene diamine tetra acetic acid, and G5: NaOCl plus CA. In Group B, the teeth were bleached using 38% hydrogen peroxide and 20% carbamide peroxide gels as in-office and at-home bleaching techniques for 3 weeks. All the teeth were restored with composite resin, thermocycled, and incubated for 24 h. The specimens underwent fracture resistance tests. Data were analyzed with ANOVA, Tukey honestly significant difference test, t-test, and Chi-squared test (α =0.05).

Results:

T-test showed significant differences between each two corresponding subgroups (P < 0.0001). In Group A, NS demonstrated significantly higher fracture resistance compared to others; however, minimum fracture resistance recorded in G2. In Group B, the maximum fracture resistance was recorded in G1, with the minimum being recorded in G5. Samples irrigated with NaOCl and NaOCl plus CA exhibited significantly lower fracture resistance compared to NS subgroup (P < 0.05).

Conclusions:

Within the limitations of this study, it can be concluded that the irrigation protocol used during endodontic treatment with/without bleaching can affect the coronal fracture resistance.

Tissue dissolution and modifications in dentin composition by different sodium hypochlorite concentrations

OBJECTIVES

To determine the organic matter dissolution and changes in dentin chemical composition promoted by different concentrations of NaOCl over time.

MATERIAL AND METHODS

Fragments of bovine muscle tissue were weighed before and after 5, 10, and 15 min of immersion in the groups (n=10): G1- 0.9% saline solution; G2- 1% NaOCl; G3- 2.5% NaOCl; and G4- 5% NaOCl. Bovine dentin fragments were subjected to the same irrigants and absorption spectra were collected by Attenuated Total Reflectance of Fourier Transform Infrared Spectroscopy (ATR-FTIR) before and after 0,5, 1, 2, 3, 5, 8, and 10 min of immersion in the solutions. The ratios of the amide III/phosphate and carbonate/phosphate absorption bands were determined. The tissue dissolution and carbonate/phosphate ratios were submitted to the two-way analysis of variance (ANOVA) with Tukey's multiple-comparison test (α<0.05) and to the one-way analysis of variance with Tukey's (α<0.05). The amide III/phosphate ratio was analyzed by Friedman test (α<0.05) and the Kruskal-Wallis test with Dunn's post-hoc (α<0.05).

RESULTS

The increase in NaOCl concentration and contact time intensified the dissolution of organic matter and dentin collagen with reduction in the amide III/phosphate ratio. Significant differences between all groups (p<0.05) were observed in the dissolution of organic matter at 10 min and in the amide III/phosphate ratio between the saline solution and 5% NaOCl at 5 min. The carbonate/phosphate ratio decreased significantly in G2, G3, and G4 after 0,5 min of immersion (p<0.05), but more alterations did not occur in the subsequent periods (p>0.05). Intergroup differences were not observed in this ratio (p>0.05).

CONCLUSIONS

The increase in the exposure time and in the concentration of NaOCl solution lead to an increase in the tissue dissolution and dentin collagen deproteination. Furthermore, some carbonate ions are removed from the dentin inorganic phase by the NaOCl.

Comparative Analysis of Dentinal Erosion after Passive Ultrasonic Irrigation versus Irrigation with Reciprocating Activation: An Environmental Scanning Electron Study

INTRODUCTION

The aim of this study was to assess ex vivo the erosive effects of passive ultrasonic irrigation versus irrigation with reciprocating activation on the dentinal surface of the root canal at 3 predetermined levels using environmental scanning electron microscopy.

METHODS

Ten roots of mandibular premolars were prepared using the ProTaper Universal system (Dentsply Maillefer, Ballaigues, Switzerland). The specimens were embedded in flasks cleaved longitudinally, and indentations were made 3.0, 6.0, and 9.0 mm from the apex. The specimens in the control group (n = 10) were cleaned in an ultrasonic bath containing 2.5% sodium hypochlorite and 17% EDTA and then dried. Then, environmental scanning electron microscopic images were obtained at magnification × 800. The specimens were then reassembled in their flasks, and the NaOCl and EDTA solutions were activated according to the conditions established for the experimental groups (ie, the passive ultrasonic irrigation group [n = 5] and the EasyClean (Easy Equipamentos Odontológicos, Belo Horizonte, MG, Brazil) group, irrigation with reciprocating activation with the EasyClean instrument [n = 5]). The specimens of both experimental groups were analyzed in the same manner as in the control group. Analysis of the dentinal surface topography was conducted using the 3D Roughness Reconstruction program (Phenom-World BV, Eindhoven, the Netherlands) as a means for assessing erosion. The data were evaluated by means of the Kruskal-Wallis, Student-Newman-Keuls, and Mann-Whitney tests.

RESULTS

In the EasyClean group, the degree of dentinal erosion at 3.0 mm was significantly higher than at 9.0 mm. In the other comparisons, there was no statistically significant difference (P < .05).

CONCLUSIONS

The final irrigation techniques tested were equivalent in relation to the degree of erosion caused to the dentinal surface.

Effects of QMix and ethylenediaminetetraacetic acid on decalcification and erosion of root canal dentin

The aim of this study was to evaluate the effect of initial NaOCl on the decalcification and erosion ability of EDTA and QMix. Sixty-maxillary-incisors were bisected longitudinally and the tooth-halves were used. The experiment was conducted in two-sets. In set-I, 80-tooth halves were treated in the presence or absence of initial NaOCl and EDTA. In set-II, 40-tooth halves were immersed in NaOCl and QMix. After each treatment, calcium-ion release was determined with flame photometry. The erosion was imaged using SEM. Initial NaOCl led to concentration- and time-dependent increase in calcium removal effect of 17% EDTA (p < .05). The rate of calcium removal and root canal wall erosion was considerably more severe with the use of 5% NaOCl for 3 min (p < .05). QMix as a final solution showed less decalcification and erosion than 17% EDTA when used 5% NaOCl as an initial irrigant (p < .05). Optimizing the concentration and application time of NaOCl can decrease the decalcification effect of chelating agents.

Dental Calculus Stimulates Interleukin-1β Secretion by Activating NLRP3 Inflammasome in Human and Mouse Phagocytes

Dental calculus is a mineralized deposit associated with periodontitis. The bacterial components contained in dental calculus can be recognized by host immune sensors, such as Toll-like receptors (TLRs), and induce transcription of proinflammatory cytokines, such as IL-1β. Studies have shown that cellular uptake of crystalline particles may trigger NLRP3 inflammasome activation, leading to the cleavage of the IL-1β precursor to its mature form. Phagocytosis of dental calculus in the periodontal pocket may therefore lead to the secretion of IL-1β, promoting inflammatory responses in periodontal tissues. However, the capacity of dental calculus to induce IL-1β secretion in human phagocytes has not been explored. To study this, we stimulated human polymorphonuclear leukocytes (PMNs) and peripheral blood mononuclear cells (PBMCs) with dental calculus collected from periodontitis patients, and measured IL-1β secretion by ELISA. We found that calculus induced IL-1β secretion in both human PMNs and PBMCs. Calculus also induced IL-1β in macrophages from wild-type mice, but not in macrophages from NLRP3- and ASC-deficient mice, indicating the involvement of NLRP3 and ASC. IL-1β induction was inhibited by polymyxin B, suggesting that LPS is one of the components of calculus that induces pro-IL-1β transcription. To analyze the effect of the inorganic structure, we baked calculus at 250°C for 1 h. This baked calculus failed to induce pro-IL-1β transcription. However, it did induce IL-1β secretion in lipid A-primed cells, indicating that the crystalline structure of calculus induces inflammasome activation. Furthermore, hydroxyapatite crystals, a component of dental calculus, induced IL-1β in mouse macrophages, and baked calculus induced IL-1β in lipid A-primed human PMNs and PBMCs. These results indicate that dental calculus stimulates IL-1β secretion via NLRP3 inflammasome in human and mouse phagocytes, and that the crystalline structure has a partial role in the activation of NLRP3 inflammasome.

Effect of Intracanal Irrigants on Bond Strength of Fiber Posts Cemented With a Self-adhesive Resin Cement

OBJECTIVE

The aim of this study was to evaluate the effect of five intracanal irrigants on bond strength of fiber posts cemented with newer self-adhesive resin cement.

METHODS

A total of 60 extracted, single-rooted human premolars, sectioned at 14 mm, were prepared with the ProTaper Universal system with a size F3 instrument and filled with an F3 master cone and AH Plus. The root canal filling was partially removed, leaving 4 mm of apical gutta-percha. Specimens were randomly assigned to five groups (n=12), according to the solution used for dentin surface treatment before fiber post cementation, as follows: EDTA 17% (EDTA); QMix (QM); SmearClear (SC); 2.5% sodium hypochlorite (NaOCl), and 0.9% saline solution (SS). Ultrasonic activation was performed (three times, 20 seconds each), and root canals were dried with paper points. Fiber posts were cemented with RelyX U200. In one specimen per group, rhodamine B dye was mixed with RelyX U200 to provide adequate fluorescence for confocal laser scanning microscopy (CLSM) assessment. Specimens were transversally sectioned and three slices were obtained, one for each root third. Next, a push-out test was performed. A stereomicroscope and CLSM were used to analyze the failure modes and to illustrate the pattern of infiltration of RelyX U200 into dentinal tubules, respectively. Bond strength means were calculated, and analysis of variance and Bonferroni tests were used for statistical analysis.

RESULTS

SS showed the highest mean bond strength values (11.5±5.3), superior to QM (5.1±3.1) and SC (5.1±3.3). NaOCl presented intermediary bond strength values (9.7±5.0), similar to EDTA (7.7±2.9) and SS. QM and SC showed the lowest mean bond strength (p<0.05). Adhesive failures between cement/dentin were predominant (53.9%).

CONCLUSION

SS and NaOCl associated with ultrasonic activation seem to be adequate solutions for root canal cleaning before fiber post cementation with self-adhesive resin cement, whereas chelating solutions, such as EDTA, QM, and SC, cause a decrease in bond strength.

Effect of Argon Plasma on Root Dentin after Use of 6% NaOCl

Abstract The aim of this study was to evaluate the effect of argon plasma on dentin surface after use of 6% NaOCl. Sixty bovine incisors had their crowns removed, the roots split, and the segments planed. One hundred twenty segments of the cervical third were used. The samples were divided in two groups (n=60): Control group: immersed in 6% NaOCl, washed, dried and then immersed in 17% EDTA, washed and dried and Argon group: after treatment described for the Control group, non-thermal argon plasma was applied for 30 s. Ten samples were evaluated by scanning electron microscopy in each group. Other ten samples were analyzed by Fourier transform infrared spectroscopy (FTIR). Thirty samples were analyzed with a goniometer to measure the contact angle between the dentin surfaces and solutions, to determine the surface free energy. The last ten samples were used to evaluate the wettability of AH Plus sealer. Data were statistically analyzed using Kruskal Wallis and Mann-Whitney tests (p<0.05). The results of this study showed that argon plasma did not modify the surface topography. FTIR analysis showed chemical modifications after plasma treatment. Argon plasma increased the surface free energy of dentin and AH Plus wettability. In conclusion, argon plasma treatment modified chemically the dentin surface. This treatment increased the surface free energy and wettability of an epoxy resin root canal sealer, favoring its bonding to dentin surfaces.

Evaluation of the smear layer removal and erosive capacity of EDTA, boric acid, citric acid and desy clean solutions: an in vitro study

Background

The purpose of this study was to investigate the smear layer removal and erosive capacity of various irrigation solutions with sequential use of NaOCl on instrumented root canal walls.

Methods

The root canals of single-rooted teeth were instrumented with ProTaper rotary instrument. Then, the teeth were randomly divided into five experimental groups. The root canals were irrigated with one of the following solutions (5 mL/1 min): 5 % EDTA, 5 % boric acid (BA), a mixture of BA and CA, 2.5 % citric acid (CA) and 5 % Desy Clean. After irrigating with 2.5 % NaOCl and distilled water, the roots were split into two halves and each half was prepared for SEM examination. Representative photographs were taken from each third at x500 and x1000 magnifications. Double blind scoring was performed by two calibrated observers for smear layer and erosion. The scores were statistically analyzed using Kruskal-Wallis, Dunn’s post hoc and Spearman’s correlation tests (p = 0.05).

Results

There were statistically significant differences among the solutions by means of smear layer and erosion (p < 0.05). While 2.5 % CA solution was the most effective solution in removal of smear layer, it was also the most erosive solution (p < 0.05). 5 % Desy Clean removed smear layer effectively and caused less erosion. There was a negative, but statistically significant correlation between presence of smear layer and erosion (r = −0.684; p < 0.0001).

Conclusion

Desy Clean can be a promising agent as an irrigation solution with optimal smear layer removal capacity and less erosive effects.

Effect of intracanal medicaments used in endodontic regeneration procedures on microhardness and chemical structure of dentin

Objectives

This study was performed to investigate the effects of different intracanal medicaments on chemical structure and microhardness of dentin.

Materials and Methods

Fifty human dentin discs were obtained from intact third molars and randomly assigned into two control groups and three treatment groups. The first control group received no treatment. The second control group (no medicament group) was irrigated with sodium hypochlorite (NaOCl), stored in humid environment for four weeks and then irrigated with ethylenediaminetetraacetic acid (EDTA). The three treatment groups were irrigated with NaOCl, treated for four weeks with either 1 g/mL triple antibiotic paste (TAP), 1 mg/mL methylcellulose-based triple antibiotic paste (DTAP), or calcium hydroxide [Ca(OH)₂] and finally irrigated with EDTA. After treatment, one half of each dentin disc was subjected to Vickers microhardness (n = 10 per group) and the other half was used to evaluate the chemical structure (phosphate/amide I ratio) of treated dentin utilizing attenuated total reflection Fourier transform infrared spectroscopy (n = 5 per group). One-way ANOVA followed by Fisher's least significant difference were used for statistical analyses.

Results

Dentin discs treated with different intracanal medicaments and those treated with NaOCl + EDTA showed significant reduction in microhardness (p < 0.0001) and phosphate/amide I ratio (p < 0.05) compared to no treatment control dentin. Furthermore, dentin discs treated with TAP had significantly lower microhardness (p < 0.0001) and phosphate/amide I ratio (p < 0.0001) compared to all other groups.

Conclusions

The use of DTAP or Ca(OH)₂ medicaments during endodontic regeneration may cause significantly less microhardness reduction and superficial demineralization of dentin compared to the use of TAP.

Quantitative Assessment of Root Canal Roughness with Calcium-Based Hypochlorite Irrigants by 3D CLSM

Chemical solutions play important roles in endodontic treatment and promote ultrastructural changes in dentin surface. The aim of this study was to quantify root canal roughness at different concentrations of calcium hypochlorite (Ca(OCl)2) and sodium hypochlorite (NaOCl) by confocal laser scanning microscopy (CLSM). Fifty-two human mandibular premolars were sectioned and randomly organized into thirteen groups (n=8): saline (control); 1%, 2.5% and 5% NaOCl; 1%, 2.5% and 5% Ca(OCl)2; the hypochlorite groups were further divided into with or without EDTA. The chlorine concentrations of the different solutions were measured by iodine titration (%). The superficial roughness (Sa) was quantified by CLSM. Ca(OCl)2 presented substantial decrease in chlorine concentration that differed from the package indication, but without compromising the dentin ultrastructure changes. There were no significant differences in dentin roughness between Ca(OCl)2 or NaOCl at all studied concentrations. The combination with EDTA provided similar roughness values among the solutions (p>0.05). The 5% Ca(OCl)2 and NaOCl solutions significantly increased dentin roughness and did not differ from the EDTA association (p>0.05). Ca(OCl)2 promoted similar dentin roughness as the NaOCl at the same concentrations and combined with EDTA. It may be concluded that Ca(OCl)2 modified the root canal dentin roughness similarly to NaOCl, at the same concentrations and EDTA combinations used in this study. Ca(OCl)2 and NaOCl, both at 5%, significantly altered dentin roughness, overcoming EDTA association, thus Ca(OCl)2 concentrations ranging from 1% to 2.5% may be suitable solutions for root canal irrigation protocols.