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

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 share FTIR spectra were excluded.

RESULTS

A wide range of concentrations, durations, and methodologies have been tested but only 30 out of 3452 studies met our inclusion criteria. Different FTIR methods were used with the 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 on the FTIR signature of dentin. NaOCl mainly affects the organic signatures, revealing reduced amide/phosphate ratios with increasing concentrations. EDTA mainly effects the inorganic component, 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 bulk measurements.

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 final irrigation protocols with chitosan nanoparticle and genipin on dentine against collagenase degradation: An ex-vivo study

AIM

Endodontic irrigants may affect the mechanical and chemical properties of dentine. This study evaluated the effects of various final irrigation protocols including the use of chitosan nanoparticle (CSnp) and cross-linking with genipin on the (1) mechanical and (2) chemical properties of dentine against enzymatic degradation.

METHODOLOGY

CSnp was synthesized and characterized considering physiochemical parameters and stability. The root canals of 90 single-rooted teeth were prepared and irrigated with NaOCl. Dentine discs were obtained and divided into groups according to the following irrigation protocols: Group NaOCl+EDTA, Group NaOCl+CSnp, Group NaOCl+EDTA+CSnp, Group NaOCl+CSnp+Genipin, Group NaOCl+EDTA+CSnp+Genipin and Group distilled water. (1) Mechanical changes were determined by microhardness analysis using Vickers-tester. (2) Chemical changes were determined by evaluating molecular and elemental compositions of dentine using Fourier transform infrared spectroscopy (FTIR) analysis and scanning electron microscope (SEM)/energy dispersive X-ray spectroscopy (EDS) analysis, respectively. All analyses were repeated after the discs were kept in collagenase for 24 h. Data were analysed with repeated measures analysis of variance and Bonferroni correction for microhardness analysis, and Kruskal-Wallis and Wilcoxon tests for FTIR and SEM/EDS analyses (p = .05).

RESULTS

(1) Collagenase application did not have a negative effect on microhardness only in Group NaOCl+EDTA+CSnp+Genipin when compared with the post-irrigation values (p > .05). Post-collagenase microhardness of Group NaOCl+EDTA+CSnp and Group NaOCl+CSnp+Genipin was similar to the initial microhardness (p > .05). (2) After collagenase, Amide III/PO 4 3 - ratio presented no change in Group NaOCl+EDTA+CSnp, Group NaOCl+CSnp+Genipin and Group NaOCl+EDTA+CSnp+Genipin (p > .05), while decreased in other groups (p < .05). Collagenase did not affectCO 3 2 - /PO 4 3 - ratio in the groups (p > .05). There were no changes in the groups in terms of elemental level before and after collagenase application (p > .05).

CONCLUSIONS

CSnp and genipin positively affected the microhardness and molecular composition of dentine. This effect was more pronounced when CSnp was used after 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.

Multispecies oral biofilm and identification of components as treatment target

Endodontic infections involve a multispecies biofilm, making it difficult to choose an antimicrobial treatment. Characteristics such as the pathogens involved and number of microorganisms, nutrients, material surface to develop the biofilm, flow and oxygenation conditions are important for biofilm development using in vitro models.

OBJECTIVE

To develop a standardized biofilm model, which replicates the main features (chemical, microbiological, and topographical) of an infected root canal tooth to detect components as treatment target.

DESIGN

Clinical strains of Enterococcus faecalis, Candida albicans, and Actinomyces israelii were isolated, and a multispecies biofilm was developed using continuous laminar flow reactors under anaerobic conditions in human dental roots. The microbiological composition was determined by counting colony-forming units and scanning electron microscope micrographs. In addition, the chemical composition of the exopolymeric matrix was determined by vibrational Raman spectroscopy and liquid chromatography of biofilm supernatant treated with enzyme.

RESULTS

E. faecalis turned out to be the main microorganism in mature biofilm, this was related to the presence of β-galactosidase detected by vibrational Raman spectroscopy. After the enzymatic treatment of the extracellular polymeric substance, the presence of mannose and glucose was established.

CONCLUSIONS

The present work contributes to better understanding of standard conditions to develop a multispecies biofilm in human dental roots, which could have an impact on the generation of new root canal disinfection techniques in endodontic pathologies.

Use of a Cellulase from Trichoderma reesei as an Adjuvant for Enterococcus faecalis Biofilm Disruption in Combination with Antibiotics as an Alternative Treatment in Secondary Endodontic Infection

Apical periodontitis is an inflammation leading to the injury and destruction of periradicular tissues. It is a sequence of events that starts from root canal infection, endodontic treatment, caries, or other dental interventions. Enterococcus faecalis is a ubiquitous oral pathogen that is challenging to eradicate because of biofilm formation during tooth infection. This study evaluated a hydrolase (CEL) from the fungus Trichoderma reesei combined with amoxicillin/clavulanic acid as a treatment against a clinical E. faecalis strain. Electron microscopy was used to visualize the structure modification of the extracellular polymeric substances. Biofilms were developed on human dental apices using standardized bioreactors to evaluate the antibiofilm activity of the treatment. Calcein and ethidium homodimer assays were used to evaluate the cytotoxic activity in human fibroblasts. In contrast, the human-derived monocytic cell line (THP-1) was used to evaluate the immunological response of CEL. In addition, the secretion of the pro-inflammatory cytokines IL-6 and TNF-α and the anti-inflammatory cytokine IL-10 were measured by ELISA. The results demonstrated that CEL did not induce the secretion of IL-6 and TNF-α when compared with lipopolysaccharide used as a positive control. Furthermore, the treatment combining CEL with amoxicillin/clavulanic acid showed excellent antibiofilm activity, with a 91.4% reduction in CFU on apical biofilms and a 97.6% reduction in the microcolonies. The results of this study could be used to develop a treatment to help eradicate persistent E. faecalis in apical periodontitis.

A novel peptide isolated from Catla skin collagen acts as a self-assembling scaffold promoting nucleation of calcium-deficient hydroxyapatite nanocrystals

Catla collagen hydrolysate (CH) was fractionated by chromatography and each fraction was subjected to HA nucleation, with the resultant HA-fraction composites being scored based on the structural and functional group of the HA formed. The process was repeated till a single peptide with augmented HA nucleation capacity was obtained. The peptide (4.6 kDa), exhibited high solubility, existed in polyproline-II conformation and displayed a dynamic yet stable hierarchical self-assembling property. The 3D modelling of the peptide revealed multiple calcium and phosphate binding sites and a high propensity to self-assemble. Structural analysis of the peptide-HA crystals revealed characteristic diffraction planes of HA with mineralization following the (002) plane, retention of the self-assembled hierarchy of the peptide and intense ionic interactions between carboxyl groups and calcium. The peptide-HA composite crystals were mostly of 25-40 nm dimensions and displayed 79% mineralization, 92% crystallinity, 39.25% porosity, 12GPa Young's modulus and enhanced stability in physiological pH. Cells grown on peptide-HA depicted faster proliferation rates and higher levels of osteogenic markers. It was concluded that the prerequisite for HA nucleation by a peptide included: a conserved sequence with a unique charge topology allowing calcium chelation and its ability to form a dynamic self-assembled hierarchy for crystal propagation.

Changes to dentin extracellular matrix following treatment with plant-based polyphenols

This study investigated whether treatment with plant-based polyphenols (PB-P) affected the biochemical and/or biomechanical properties of dentin extracellular matrix (ECM). Three PB-Ps were evaluated: luteolin (LT), galangin (GL), and proanthocyanidin (PAC). Because dentin ECM requires demineralization before treatment, this study also assessed the effect of these PB-Ps on dentin demineralized by two different chemicals. Dentin samples from extracted third molars were obtained, sectioned, and randomly assigned for demineralization with either phosphoric acid (PA) or ethylenediaminetetraacetic acid (EDTA). Following demineralization, baseline infrared (IR) spectra and apparent elastic modulus (AE) of each specimen were independently acquired. Based upon these initial tests, samples were randomly assigned to one of the PB-P treatments to ensure that distribution of baseline AE was similar across treatment groups. IR and AE specimens were individually immersed in either 0.2% LT, 0.4% GL or 1% PAC for 2 min. IR spectra of treated samples were compared to baseline IR spectra, looking for any interaction of PB-Ps with the demineralized dentin. The IR spectrum and AE of each PB-P-treated specimen were compared with their own correspondent baseline measurement. The ability of PB-Ps to inhibit proteolytic activity of dentin ECM was assessed by the hydroxyproline assay. Finally, the effect of PB-Ps on immediate bond strength of a dental adhesive to PA- or EDTA-etched dentin was also evaluated. PB-Ps exhibited distinctively binding affinity to dentin ECM and promoted significant increase in AE. PB-P treatment reduced the degradation rate of dentin ECM without causing detrimental effect on immediate bond strength to dentin. Our work represents the first-time that LT and GL have been assessed as dentin ECM biomodifiers.

Effect of guided conservative endodontic access and different file kinematics on debris extrusion in mesial root of the mandibular molars: An in vitro study

Background

Guided conservative endodontic access is a novel technique and the influence of such access cavities on apical debris extrusion (ADE) can have a significant effect on postoperative pain.

Objective

This study compared ADE and preparation time (PT) in the mesial canals of the mandibular first permanent molars in different access cavity designs and the amount of sodium hypochlorite in the extruded debris using attenuated total reflection-Fourier transform infrared spectrometer (ATR-FTIR).

Materials and Methods

Human mandibular first permanent molars (N = 72) were selected and randomly divided into six groups (n = 12) based on type of cavity design and files used: Group 1, Conservative Access Cavity [ConsAC])-WaveOne Gold; Group 2, ConsAC-Mtwo; Group 3, ConsAC-XP-endo shaper; Group 4, Traditional Access Cavity [TradAC])-WaveOne; Group 5, TradAC-Mtwo; and Group 6, TradAC-XP-endo shaper. All the ConsAC were prepared with a customized template fabricated using cone beam computed tomography. ADE evaluation was done using the Myers and Montgomery set up. All the instruments were used according to the manufacturers' instructions, followed by a final irrigation using Endoactivator. The time taken for preparation was calculated using a digital watch. Five samples in each group was taken and subjected to ATR-FTIR analysis.

Results

There was no significant difference between the groups with respect to ADE (P > 0.05). Whereas, a statistically significant difference was seen in PT between the TradAC and ConsAC (P < 0.05). Using ATR-FTIR, it was found that all the samples of extruded debris had the presence of sodium hypochlorite.

Conclusions

All instrumentation systems produced ADE irrespective of access cavity design. The time taken for preparation of canals in ConsAC was significantly longer compared to TradAC.

Clinical Relevance

ADE can translate clinically as postoperative pain. Assessing the ADE in ConsAC could shed light on the type of file systems that can be used in such cavities in order to minimize postoperative pain clinically.

Experimental Solution of Chitosan and Nanochitosan on Wettability in Root Dentine: In Vitro Model Prior Regenerative Endodontics

Aims

To compare the effect of CS and CSnp on the wettability in root dentine with other irrigation protocols with an experimental in vitro model prior regenerative endodontics. Methods and Material. An in vitro experimental study that included eighty hemisected human root distributed into 8 groups: G1- distilled water; G2- 1% NaOCl/17% EDTA; G3- hypochlorous acid 0.025% HOCl, G4- 1% NaOCl/0.025% HOCl/17% EDTA, G5- 0.2 g/100 mL CS, G6- 1% NaOCl/0.2 g/100 mL CS, G7- CSnp, and G8- 1% NaOCl/CSnp. The wettability analysis calculated the contact angle (θ) between a drop of a blood-like and root dentinal surface; topographic characterization with scanning electron microscopy (SEM) quantified the diameter and number of tubules per area; spectroscopy infrared analyses (IR-S) identified chemical changes in the inorganic (phosphate/carbonate) and organic phase (amide/methyl). Statistical analysis: a linear mixed model, Kruskal–Wallis, and Holm–Bonferroni correction (P < 0.05) were used.

Results

Significantly higher wettability for G2 (27.1 (P = 0.0001)) was found. A mean value of 67°±°for experimental groups (P = 0.07) was found, and we did not identify differences between them. The SEM identified greater tubular opening and erosion for G4 and greater dentinal permeability per area for NaOCl/CS. IR-S identified dentinal organic integrity with NaOCl-CS/CSnp compared to organic reduction promoted for NaOCl/EDTA.

Conclusions

This in vitro dentin determined an indirect association between the wettability and organic contents. The oxidative effect of NaOCl could be neutralized by CS-CSnp, and consequently, the wettability of the substrate decreases.

Evaluation of Stabilized Chlorine Dioxide in Terms of Antimicrobial Activity and Dentin Bond Strength

BACKGROUND

Antimicrobial agents are recommended for disinfection of the cavity following mechanical dental caries removal prior to application of restorative material. There is limited information about stabilized chlorine dioxide (ClO2) as a cavity disinfectant.

OBJECTIVE

The objective of this study is to determine the antimicrobial activity and effect on dentin bond strength of ClO2 compared to chlorhexidine digluconate (CHX), sodium hypochlorite (NaOCl) and ethanolic propolis extract (EPE).

METHODS

Antimicrobial activities of agents against oral pathogens (Staphylococcus aureus, Enterococcus faecalis, Streptococcus mutans, Lactobacillus acidophilus, Lactobacillus casei, Candida albicans, and Saccharomyces cerevisiae) and analyses of EPE were examined. Seventy-five mandibular third molars were sectioned, prepared and divided into five subgroups (n=15/group). Cavity disinfectants (2% CHX, 2.5% NaOCl, 30% EPE, 0.3% ClO2) were applied to etched dentin prior to adhesive and composite build-up. Shear bond strength (SBS) was evaluated with a universal testing machine at a crosshead speed of 0.5 mm/min. The SBS data were analyzed with one-way analysis of variance (ANOVA) and Tukey's post-hoc test (p <0.05). The failure modes were evaluated with a stereomicroscope.

RESULTS

It was determined that the compared disinfectants were showed different inhibition zone values against oral pathogens. ClO2 exhibited the highest antimicrobial activity, followed by CHX, NaOCI and EPE, respectively. No statistically significant difference was observed in the SBS values between the disinfectant treated groups and control group. The failure modes were predominantly mixed.

CONCLUSION

The use of 0.3% stabilized ClO2 as a cavity disinfectant agent exhibited high antimicrobial activity against oral pathogens and no adverse effects on SBS to etched dentin.

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.

Surface and structural changes in root dentine by various chelating solutions used in regenerative endodontics

AIM

To evaluate the effects of the prolonged use of various irrigant solutions used during regenerative endodontic procedures on the physical and chemical structure of root canal dentine in extracted human teeth.

METHODOLOGY

Sixtyroot dentine samples from extracted, single-rooted, human teeth were assigned to 10 groups. Eight groups were irrigated with 1.5% NaOCl for 5 min, followed by 3%, 10%, 17% EDTA or 10% citric acid (CA) for 5 or 10 min. One group received only NaOCl irrigation, and samples with only distilled water irrigation were used as a control group. The changes in microhardness and flexural strength were determined using Vickers and 3-point flexural tester, respectively. Molecular and elemental compositions were recorded using FTIR and EDS spectroscopy. Data were analysed using one-way anova, Kruskal-Wallis and Mann-Whitney U tests.

RESULTS

The application of 1.5% NaOCl for 5 min did not affect the mineral content or microhardness of dentine (P > 0.05). However, it significantly decreased the dentine collagen peak values (P < 0.05), which was similar to the control group after the use of chelating agents (EDTA and 10% of CA) (P > 0.05). The effect of EDTA on the inorganic content was not concentration and time dependent (P > 0.05). CA resulted in a significantly greater reduction in the inorganic contents compared with the control and EDTA groups (P < 0.05). Regardless of the time, EDTA and CA significantly decreased dentine microhardness compared to the control (P < 0.05) with the greatest reduction in the CA groups (P < 0.05). NaOCl alone was associated with the lowest flexural strength, while none of the other irrigation regimens significantly decreased the flexural strength compared to the control group (P> 0.05).

CONCLUSIONS

Use of 1.5% NaOCl for 5 min decreased the collagen content of samples of human dentine from extracted teeth while EDTA and 10% citric acid mostly affected the inorganic content and microhardness of dentine surfaces. None of the irrigant solutions significantly decreased the mechanical properties of the entire dentine specimen.

The effect of NaOCl and heat treatment on static and dynamic mechanical properties and chemical changes of dentine

OBJECTIVES

To determine the effect of heat on flexural strength (FS), maximum strain (MS), storage modulus (SM), tan delta (TD) and chemical changes through micro-Raman spectroscopy of dentine exposed to 2.5% NaOCl or saline.

METHOD

ology: Dentine bars were randomly allocated to 8 test groups. Half (groups 2,4,6,8) were treated with NaOCl for 20 min; the rest (groups 1,3,5,7) remained in saline. FS/MS were measured in groups 1-4 (n = 15) (3/4 were also heated to 200 °C & re-hydrated in saline). Micro-Raman spectroscopy was performed on bars from groups 1-4. SM/TD were measured in 5-8: in 5/6 (n = 10), repeated after heating (200 °C), then following re-hydration; in 7/8 (n = 3) after heating to 25-185 °C.

RESULTS

Increase in MS on heat and FS/MS on heat + NaOCl was not significant (P > 0.05). SM increased (P = 0.06) after heat treatment but reduced to initial state after rehydration (P = 0.03). TD did not change (P = 0.4) after heat (200 °C) treatment but rehydration increased it compared with pre-treatment state (P = 0.001). For dentine bars pre-treated with NaOCl, SM did not change (P = 0.6) after heat (200 °C) treatment or rehydration but TD significantly increased (P = 0.02) upon re-hydration compared with pre- (P=0.007), or post- (P = 0.03) heat-treatment states. SM and TD varied between 25-185 °C with no consistent trend amongst the NaOCl pre-treated bars. Micro-Raman only detected chemical changes following NaOCl treatment in the mineral phase.

CONCLUSIONS

Exposure of dentine bars to heat and NaOCl produced only moderate changes to quasi-static but marked changes to viscoelastic properties, which may be explained by chemical alterations.