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

OBJECTIVE: The high incidence of endodontic failure is associated with the remnants of Enterococcus faecalis present within the intricate anatomies of the root canal system (RCS), often inaccessible by the current endodontic practices. This study was aimed at evaluating the effect of high-intensity focused ultrasound (HIFU) and photodynamic therapy (PDT) on E. faecalis biofilms in artificially infected root canals for the potential application in current endodontic practices. METHODS: Forty-five single-rooted extracted teeth were instrumented using hand files, sterilized in an autoclave, infected with E. faecalis and incubated for 4 wk. The specimens were treated and identified as follows: Control, 4% sodium hypochlorite (NaOCl); riboflavin (1 mg/mL); light only; HIFU (250 kHz, 20 W, 60s); PDT; riboflavin/HIFU; light/HIFU; and riboflavin/HIFU/light. Bactericidal efficacy was determined by colony-forming units (CFU), (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) (MTT) assay, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). RESULTS: Enterococcus faecalis biofilm exhibited significantly lower metabolic activity when treated with HIFU (250 kHz, 20 W, 60 s) compared with the control (4% NaOCl) and PDT groups. A similar phenomenon was observed with the CFU assay. HIFU remained the most effective treatment modality, with consistent results in CLSM and SEM. CONCLUSION: This study highlighted the potential application of HIFU as an adjunct drug-free, non-destructive root canal disinfection method for endodontic treatment, suggesting an alternative to the current gold standard of 4% NaOCl and PDT.

"No-Primer" Resin Cementation of Lithium Disilicate Ceramic: A Microtensile Bond Strength Evaluation.

OBJECTIVE: The objective of this study was to evaluate the resin-ceramic adhesion of a long-carbon-chain silane (LCSI)-containing resin cement. METHODS: Polished lithium disilicate ceramic discs were etched with hydrofluoric acid and randomly assigned into four groups; (PSAP), cemented using a silane-free resin cement with no prior priming; (PSAP-S), primed using a silane-containing primer before cementation using a silane-free resin cement; (PSAU), cemented using a LCSI-containing resin cement with no prior priming; (PSAU-S), primed as for the group (PSAP-S) and cemented using a LCSI-containing resin cement. The cemented blocks were sectioned into microbeams. The resin-ceramic microtensile bond strength (µTBS) was measured at 1 week and after thermocycling. The failure modes of the tested microbeams were evaluated. RESULTS: The µTBS of the LCSI-containing and silane-free resin cements, either with or without a prior priming step, did not significantly differ. The adhesion of the LCSI-containing resin cement to lithium disilicate ceramic, either with or without a prior priming step, did not significantly deteriorate after artificial aging. CONCLUSIONS: The long-carbon-chain silane (LCSI) monomer incorporated in the resin cement eliminated the need for a silane priming step of a hydrofluoric acid-etched lithium disilicate ceramic.

Formulation of nano-graphene doped with nano silver modified dentin bonding agents with enhanced interfacial stability and antibiofilm properties.

OBJECTIVE: The aim of this study was to synthesize and characterize reduced nano graphene oxide (RGO) and graphene nanoplatelets (GNPs) doped with silver nanoparticles (nAg) and to prepare an experimental dentin adhesive modified with RGO/nAg and GNP/nAg nanofillers for studying various biological and mechanical properties after bonding to tooth dentin. METHODS: Nanoparticles were characterized for their morphology and chemical structure using electron microscopy and infrared spectroscopy. Experimental dentin adhesive was modified using two weight percentage (0.25% and 0.5%) of RGO/nAg and GNP/nAg to study its degree of conversion (DC), antimicrobial potential, and cytotoxicity. The effect and significance of these modified bonding agents on resin-dentin bonded interface were investigated by evaluating interfacial nanoleakage, micropermeability, nanodynamic mechanical analysis, micro-tensile bond strength (µTBS), and four-point bending strength (BS), RESULTS: Both 0.25% and 0.5% GNP/nAg graphene-modified adhesives showed comparable DC values to the commercial and experimental adhesive (range: 42-46%). The bacterial viability of the groups 0.25% and 0.5% GNP-Ag remained very low under 25% compared to RGO/nAg groups with low cytotoxicity profiles (cell viability>85%). Resin-bonded dentin interface created with GNP/nAg showed homogenous, well-defined hybrid layer and regularly formed long resin tags devoid of any microporosity as evidenced by SEM and confocal microscopy. The lowest nanoleakage and highest bending strength and µTBS was recorded for 0.25% GNP/nAg after 12 months of ageing. A significantly increased nanoelasticity was seen for all experimental groups except for control groups. SIGNIFICANCE: The addition of 0.25% GNP/nAg showed optimized anti-biofilm properties without affecting the standard adhesion characteristics.

Characterization of multiscale interactions between high intensity focused ultrasound (HIFU) and tooth dentin: the effect on matrix-metalloproteinases, bacterial biofilms and biological properties.

The aim of this study was to characterize multiscale interactions between high intensity focused ultrasound (HIFU) and dentin collagen and associated matrix-metalloproteinases, in addition to the analysis of the effect of HIFU on bacterial biofilms and biological properties. Dentin specimens were subjected to 5, 10 or 20 s HIFU. XPS spectra were acquired and TEM was performed on dentin slabs. Collagen orientation was performed using Raman spectroscopy. Calcium measurements in human dental pulpal cells (hDPCs) were carried out after 7 and 14 days. For macrophages, CD36+ and CD163+ were analysed. Biofilms were analyzed using CLSM. Tandem mass spectroscopy was performed for the detection of hydroxyproline sequences along with human MMP-2 quantification. Phosphorus, calcium, and nitrogen were detected in HIFU specimens. TEM images demonstrated the collagen network appearing to be fused together in the HIFU 10 and 20 s specimens. The band associated with 960 cm-1 corresponds to the stretching ν1 PO43-. The control specimens showed intensive calcium staining followed by HIFU 20 s > HIFU 10 s > HIFU 5 s specimens. Macrophages in the HIFU specimens co-expressed CD80+ and CD163+ cells. CLSM images showed the HIFU treatment inhibiting bacterial growth. SiteScore propensity determined the effect of HIFU on the binding site with a higher DScore representing better site exposure on MMPs. Multiscale mapping of dentin collagen after HIFU treatment showed no deleterious alterations on the organic structure of dentin.

Development of 3D printed resin reinforced with modified ZrO2 nanoparticles for long-term provisional dental restorations.

OBJECTIVE: To characterize and investigate efficacy of loading functionalized ZrO2 nanoparticles in 3-dimensional (3D) printed acrylate ester-based resin subjected to accelerated aging in artificial saliva. As well as to evaluate the effect of ZrO2 nanoparticle volume fraction addition on mechanical and physical properties of printed composite. METHODS: Functionalized ZrO2 nanoparticles were characterized using TEM and Raman spectroscopy. 3D printed dental resin was reinforced, with ZrO2 nanoparticles, in the concentration range (0-5wt.%). The resulted nanocomposites, in term of structure and physical/mechanical properties were evaluated using different mechanical testing, microscopic and spectroscopic techniques. RESULTS: ZrO2 based nanocomposite was successful and formed composites were more ductile. Degree of conversion was significant at the highest level with blank resin and 1wt.%. Sorption revealed reduction associated with volume fraction significant to neat resin, however solubility indicated neat and 4wt.% had the lowest significant dissolution. Vickers represented critical positive correlation with filler content, while nanohardness and elasticity behaved symmetrically and had the maximum strength at 3wt.% addition. In addition, 3wt.% showed the highest fracture toughness and modulus. Improvement of flexural strength was significantly linked to filler concentration. Overall properties dramatically were enhanced after 3 months aging in artificial saliva, especially degree of conversion, microhardness, nanoindentation/elasticity, and flexural modulus. However, significant reduction was observed with flexural modulus and fracture toughness. SIGNIFICANCE: The outcomes suggest that the newly developed 3D printed nanocomposites modified with ZrO2 nanoparticle have the superior potential and efficacy as long-term provisional dental restoration materials.

Formulation of pH-sensitive chlorhexidine-loaded/mesoporous silica nanoparticles modified experimental dentin adhesive.

We formulated a pH-sensitive chlorhexidine-loaded mesoporous silica nanoparticles (MSN) modified with poly-(lactic-co-glycolic acid) (CHX-loaded/MSN-PLGA) and incorporated into experimental resin-based dentin adhesives at 5 and 10 wt%. Nanocarriers were characterized in terms of morphology, physicochemical features, spectral analyses, drug-release kinetics at varying pH and its effect on dentin-bound proteases was investigated. The modified dentin adhesives were characterized for cytotoxicity, antimicrobial activity, degree of conversion (DC) along with CHX release, micro-tensile bond strength (µTBS) and nano-leakage expression were studied at different pH values and storage time. CHX-loaded/MSN-PLGA nanocarriers exhibited a significant pH-dependent drug release behavior than CHX-loaded/MSN nanocarriers without PLGA modification. The highest percentage of CHX release was seen with 10 wt% CHX-loaded/MSN-PLGA doped adhesive at a pH of 5.0. CHX-loaded/MSN-PLGA modified adhesives exhibited more profound antibiofilm characteristics against S. mutans and more sustained CHX-release which was pH dependent. After 6 months in artificial saliva at varying pH, the 5 wt% CHX-loaded/MSN-PLGA doped adhesive showed excellent bonding under SEM/TEM, higher µTBS, and least nano-leakage expression. The pH-sensitive CHX-loaded/MSN-PLGA could be of crucial advantage for resin-dentin bonding applications especially in reduced pH microenvironment resulting from biofilm formation; and the activation of dentin-bound proteases as a consequence of acid etching and acidic content of bonding resin monomers.

Effect of Propolis Nanoparticles against Enterococcus faecalis Biofilm in the Root Canal.

To determine the antibacterial effect of propolis nanoparticles (PNs) as an endodontic irrigant against Enterococcus faecalis biofilm inside the endodontic root canal system. Two-hundred-ten extracted human teeth were sectioned to obtain 6 mm of the middle third of the root. The root canal was enlarged to an internal diameter of 0.9 mm. The specimens were inoculated with E. faecalis for 21 days. Following this, specimens were randomly divided into seven groups, with 30 dentinal blocks in each group including: group I-saline; group II-propolis 100 µg/mL; group III-propolis 300 µg/mL; group IV-propolis nanoparticle 100 µg/mL; group V-propolis nanoparticle 300µg/mL; group VI-6% sodium hypochlorite; group VII-2% chlorhexidine. Dentin shavings were collected at 200 and 400 µm depths, and total numbers of CFUs were determined at the end of one, five, and ten minutes. The non-parametric Kruskal-Wallis and Mann-Whitney tests were used to compare the differences in reduction in CFUs between all groups, and probability values of p < 0.05 were set as the reference for statistically significant results. The antibacterial effect of PNs as an endodontic irrigant was also assessed against E. faecalis isolates from patients with failed root canal treatment. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were also performed after exposure to PNs. A Raman spectroscope, equipped with a Leica microscope and lenses with curve-fitting Raman software, was used for analysis. The molecular interactions between bioactive compounds of propolis (Pinocembrin, Kaempferol, and Quercetin) and the proteins Sortase A and ß-galactosidase were also understood by computational molecular docking studies. PN300 was significantly more effective in reducing CFUs compared to all other groups (p < 0.05) except 6% NaOCl and 2% CHX (p > 0.05) at all time intervals and both depths. At five minutes, 6% NaOCl and 2% CHX were the most effective in reducing CFUs (p < 0.05). However, no significant difference was found between PN300, 6% NaOCl, and 2% CHX at 10 min (p > 0.05). SEM images also showed the maximum reduction in E. faecalis with PN300, 6% NaOCl, and 2% CHX at five and ten minutes. CLSM images showed the number of dead cells in dentin were highest with PN300 compared to PN100 and saline. There was a reduction in the 484 cm-1 band and an increase in the 870 cm-1 band in the PN300 group. The detailed observations of the docking poses of bioactive compounds and their interactions with key residues of the binding site in all the three docking protocols revealed that the interactions were consistent with reasonable docking and IFD docking scores. PN300 was equally as effective as 6% NaOCl and 2% CHX in reducing the E. faecalis biofilms.

Correction to: the Effect of Cross-Linking Efficiency of Drug-Loaded Novel Freeze Gelated Chitosan Templates for Periodontal Tissue Regeneration.

The correct spelling of the second author's name is Liebert Parreiras Nogueira.

New antimicrobial and collagen crosslinking formulated dentin adhesive with improved bond durability.

OBJECTIVE: Here we describe a novel formulation, based on quaternary ammonium (QA) and riboflavin (RF), which combines antimicrobial activities and protease inhibitory properties with collagen crosslinking without interference to bonding capabilities, was investigated. METHODS: Experimental adhesives modified with different fractions of dioctadecyldimethyl ammonium bromide quaternary ammonium and riboflavin (QARF) were formulated. Dentine specimens were bonded to resincomposites with control or the experimental adhesives to be evaluated for bond strength, interfacial morphology, micro-Raman analysis, nano-CT and nano-leakage expression. In addition, the antibacterial and biocompatibilities of the experimental adhesives were investigated. The endogenous proteases activities and their molecular binding-sites were studied. RESULTS: Modifying the experimental adhesives with QARF did not adversely affect micro-tensile bond strength or the degree of conversion along with the demonstration of anti-proteases and antibacterial abilities with acceptable biocompatibilities. In general, all experimental adhesives demonstrated favourable bond strength with increased and improved values in 1% QARF adhesive at 24 h (39.2 ± 3.0 MPa) and following thermocycling (34.8 ± 4.3 MPa). SIGNIFICANCE: It is possible to conclude that the use of QARF with defined concentration can maintain bond strength values when an appropriate protocol is used and have contributed in ensuring a significant decrease in microbial growth of biofilms. Incorporation of 1% QARF in the experimental adhesive lead to simultaneous antimicrobial and anti-proteolytic effects with low cytotoxic effects, acceptable bond strength and interfacial morphology.

A quaternary ammonium silane antimicrobial triggers bacterial membrane and biofilm destruction.

To study the antimicrobial effects of quaternary ammonium silane (QAS) exposure on Streptococcus mutans and Lactobacillus acidophilus bacterial biofilms at different concentrations. Streptococcus mutans and Lactobacillus acidophilus biofilms were cultured on dentine disks, and incubated for bacterial adhesion for 3-days. Disks were treated with disinfectant (experimental QAS or control) and returned to culture for four days. Small-molecule drug discovery-suite was used to analyze QAS/Sortase-A active site. Cleavage of a synthetic fluorescent peptide substrate, was used to analyze inhibition of Sortase-A. Raman spectroscopy was performed and biofilms stained for confocal laser scanning microscopy (CLSM). Dentine disks that contained treated dual-species biofilms were examined using scanning electron microscopy (SEM). Analysis of DAPI within biofilms was performed using CLSM. Fatty acids in bacterial membranes were assessed with succinic-dehydrogenase assay along with time-kill assay. Sortase-A protein underwent conformational change due to QAS molecule during simulation, showing fluctuating alpha and beta strands. Spectroscopy revealed low carbohydrate intensities in 1% and 2% QAS. SEM images demonstrated absence of bacterial colonies after treatment. DAPI staining decreased with 1% QAS (p < 0.05). Fatty acid compositions of dual specie biofilm increased in both 1% and 2% QAS specimens (p < 0.05). Quaternary ammonium silane demonstrated to be a potent antibacterial cavity disinfectant and a plaque inhibitor and can be of potential significance in eliminating caries-forming bacteria.

The Effect of Cross-linking Efficiency of Drug-Loaded Novel Freeze Gelated Chitosan Templates for Periodontal Tissue Regeneration.

Innovative strategies for periodontal regeneration have been the focus of research clusters across the globe for decades. In order to overcome the drawbacks of currently available options, investigators have suggested a novel concept of functionally graded membrane (FGM) templates with different structural and morphological gradients. Chitosan (CH) has been used in the past for similar purpose. However, the composite formulation of composite and tetracycline when cross-linked with glutaraldehyde have received little attention. Therefore, the purpose of the study was to investigate the drug loading and release characteristics of novel freeze gelated chitosan templates at different percentages of glutaraldehyde. These were cross-linked with 0.1 and 1% glutaraldehyde and loaded with doxycycline hyclate. The electron micrographs depicted porous morphology of neat templates. After cross-linking, these templates showed compressed ultrastructures. Computerized tomography analysis showed that the templates had 88 to 92% porosity with average pore diameter decreased from 78 to 44.9 µm with increasing concentration. Fourier transform infrared spectroscopy showed alterations in the glycosidic segment of chitosan fingerprint region which after drug loading showed a dominant doxycycline spectral composite profile. Interestingly, swelling profile was not affected by cross-linking either at 0.1 and 1% glutaraldehyde and template showed a swelling ratio of 80%, which gained equilibrium after 15 min. The drug release pattern also showed a 40 µg/mL of release after 24 h. These doxycycline-loaded templates show their tendency to be used in a functionally graded membrane facing the defect site.

Effect of photoactivated riboflavin on the biodegradation-resistance of root-dentin collagen.

This study was conducted to evaluate the effect of UVA-activated 1% riboflavin solution on structural integrity; mechanical properties and stability; and collagenase-mediated collagen solubilisation resistance of demineralized root dentin collagen matrix. Root dentin specimens demineralized with 17% EDTA for 7days were treated with 1% RF for 1min followed by UVA photo-activation at intensity 7mW/cm2 for 1min. Control specimens were completely devoid of riboflavin and/or UVA treatments. Specimens were challenged with bacterial collagenase type-I solution for different time-periods at 37°C. Collagen solubilisation resistance was evaluated in terms of hydroxyproline (HYP) liberation. Mechanical characterization of dentin specimens before and after 24h of exposure to collagenase solution was done in terms of apparent-elastic modulus (Eappr) and ultimate tensile strength (UTS). Variations in dentin collagen-network structure with exposure time in collagenase were visualized by TEM. Crosslinking dentin with UVA-activated riboflavin significantly decreased HYP release and increased Eappr and UTS compared to control specimens with storage time in collagenase. Moreover, crosslinked specimens showed higher structural resistance to collagenase effect reflected from dense, well-formed collagen fibrils-network with characteristic collagen cross-banding. UVA-activated riboflavin treatment increased collagenase-mediated collagen degradation resistance and enhanced mechanical stability against collagenase challenges of root dentin after EDTA demineralization.

Characterization of Chlorhexidine-Loaded Calcium-Hydroxide Microparticles as a Potential Dental Pulp-Capping Material.

This study explores the delivery of novel calcium hydroxide [Ca(OH)2] microparticles loaded with chlorhexidine (CHX) for potential dental therapeutic and preventive applications. Herein, we introduce a new approach for drug-delivery to deep dentin-surfaces in the form of drug-loaded microparticles. Unloaded Ca(OH)2 [Ca(OH)2/Blank] and CHX-loaded/Ca(OH)2 microparticles were fabricated by aqueous chemical-precipitation technique. The synthesized-microparticles were characterized in vitro for determination of surface-morphology, crystalline-features and thermal-properties examined by energy-dispersive X-ray scanning and transmission electron-microscopy (EDX-SEM/TEM), Fourier-transform infrared-spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential scanning-calorimetry (DSC). Time-related pH changes, initial antibacterial/biofilm-abilities and cytotoxicity of CHX-loaded/Ca(OH)2 microparticles were evaluated. Microparticles were delivered to dentin-surfaces with subsequent SEM examination of treated dentin-substrates. The in vitro and ex vivo CHX-release profiles were characterized. Ca(OH)2/Blank were hexagonal-shaped with highest z-average diameter whereas CHX-inclusion evidenced micro-metric spheres with distinguishable surface "rounded deposits" and a negative-shift in diameter. CHX:Ca(OH)2/50 mg exhibited maximum encapsulation-efficiency with good antibacterial and cytocompatible properties. SEM examination revealed an intact layer of microparticles on exposed dentin-surfaces with retention of spherical shape and smooth texture. Microparticles loaded on dentin-surfaces showed prolonged release of CHX indicating substantial retention on dentin-substrates. This study validated the inherent-applicability of this novel drug-delivery approach to dentin-surfaces using micro-metric CHX-loaded/Ca(OH)2 microparticles.

PLGA nanoparticles as chlorhexidine-delivery carrier to resin-dentin adhesive interface.

OBJECTIVE: To characterize and deliver fabricated CHX-loaded PLGA-nanoparticles inside micron-sized dentinal-tubules of demineralized dentin-substrates and resin-dentin interface. METHODS: Nanoparticles fabricated by emulsion evaporation were assessed in-vitro by different techniques. Delivery of drug-loaded nanoparticles to demineralized dentin substrates, interaction with collagen matrix, and ex-vivo CHX-release profiles using extracted teeth connected to experimental setup simulating pulpal hydrostatic pressure were investigated. Furthermore, nanoparticles association/interaction with a commercial dentin-adhesive applied to demineralized dentin substrates were examined. RESULTS: The results showed that the formulated nanoparticles demonstrated attractive physicochemical properties, low cytotoxicity, potent antibacterial efficacy, and slow degradation and gradual CHX release profiles. Nanoparticles delivered efficiently inside dentinal-tubules structure to sufficient depth (>10µm) against the simulated upward pulpal hydrostatic-pressure, even after bonding-resins infiltration and were attached/retained on collagen-fibrils. These results verified the potential significance of this newly introduced drug-delivery therapeutic strategy for future clinical applications and promote for a new era of future dental research. SIGNIFICANCE: This innovative drug-delivery strategy has proven to be a reliable method for delivering treatments that could be elaborated for other clinical applications in adhesive and restorative dentistry.

Characterization of Chitosan/TiO2 Nano-Powder Modified Glass-Ionomer Cement for Restorative Dental Applications.

OBJECTIVES: We are introducing novel glass-ionomer cement (GIC) dually-modified with chitosan (CH) in the liquid phase and titanium-dioxide nano-powder (TiO2 /NP) in the powder phase. The aim was to investigate the effect of this dual-modification on the antibacterial properties against S. mutans biofilms and on the bulk and surface mechanical properties. METHODS: Commercially available powder/liquid restorative GIC was used in this study. The GIC specimens were modified with 3% (w/w) TiO2 /NP, 10% (v/v) CH solution, or dually-modified with TiO2 /CH. The non-modified GIC was used as a control. The biofilms formations were characterized by SEM, live/dead assay using confocal-microscopy, colony-forming unit counts, and MTS assay. The bulk and surface mechanical properties were characterized in terms of flexural and compressive strengths and surface hardness, respectively. RESULTS: With the dual-modification, a significant improvement in the antibacterial properties was found both qualitatively and quantitatively. The synergetic effect of the dual-modification was also reflected on the enhancement of the flexural and compressive strengths. However, no difference was found in surface hardness. CONCLUSIONS: The modification of GIC powder with TiO2 /NP showed to be more effective in enhancing the mechanical properties. However, the enhancement in the antibacterial properties was more evident with CH incorporation in GIC liquid. CLINICAL SIGNIFICANCE: This study introduced novel glass ionomer cement dually-modified with TiO2 NP and chitosan with superior mechanical and antibacterial properties for potential applications in restorative and preventive dentistry. The modification of GIC powder with TiO2 NP showed to be more effective in enhancing the mechanical properties. However, the enhancement in the antibacterial properties was more evident with CH incorporation in GIC liquid. Although of the promising synergetic effect of the dual-modification of GIC with TiO2 NP/CH, further clinically-related studies are recommended. (J Esthet Restor Dent 29:146-156, 2017).

Fabrication and evaluation of electrohydrodynamic jet 3D printed polycaprolactone/chitosan cell carriers using human embryonic stem cell-derived fibroblasts.

Biological function of adherent cells depends on the cell-cell and cell-matrix interactions in three-dimensional space. To understand the behavior of cells in 3D environment and their interactions with neighboring cells and matrix requires 3D culture systems. Here, we present a novel 3D cell carrier scaffold that provides an environment for routine 3D cell growth in vitro We have developed thin, mechanically stable electrohydrodynamic jet (E-jet) 3D printed polycaprolactone and polycaprolactone/Chitosan macroporous scaffolds with precise fiber orientation for basic 3D cell culture application. We have evaluated the application of this technology by growing human embryonic stem cell-derived fibroblasts within these 3D scaffolds. Assessment of cell viability and proliferation of cells seeded on polycaprolactone and polycaprolactone/Chitosan 3D-scaffolds show that the human embryonic stem cell-derived fibroblasts could adhere and proliferate on the scaffolds over time. Further, using confocal microscopy we demonstrate the ability to use fluorescence-labelled cells that could be microscopically monitored in real-time. Hence, these 3D printed polycaprolactone and polycaprolactone/Chitosan scaffolds could be used as a cell carrier for in vitro 3D cell culture-, bioreactor- and tissue engineering-related applications in the future.

Characterization of antibacterial and adhesion properties of chitosan-modified glass ionomer cement.

OBJECTIVES: The aim is to investigate the effect of modifying the liquid phase of a conventional glass ionomer restorative material with different chitosan volume contents on the antibacterial properties and adhesion to dentin. METHODS: The liquids of commercially available restorative glass ionomer cements (GIC) were modified with chitosan (CH) solutions at different volume contents (5%, 10%, 25%, and 50%). The GIC powders were mixed with the unmodified and the CH-modified liquids at the desired powder/liquid (P/L) ratio. For the characterization of the antibacterial properties, Streptococcus mutans biofilms were formed on GIC discs and characterized by scanning electron microscope (SEM), confocal microscopy, colony forming unit (CFU) count, and cell viability assay (MTS). The unmodified and CH-modified GICs were bonded to dentin surfaces and the micro-tensile bond strength (µTBs) was evaluated and the interface was investigated by SEM. RESULTS: Modification with CH solutions enhanced the antibacterial properties against S. mutans in terms of resistance to biofilm formation, CFU count, and MTS assay. Generally, significant improvement in the antibacterial properties was found with the increase in the CH volume content. Modification with 25% and 50% CH adversely affected the µTBs with predominant cohesive failure in the GIC. However, no difference was found between the control and the 5% and 10% CH-modified specimens. CONCLUSION: Incorporation of acidic solutions of chitosan in the polyacrylic acid liquid of GIC at v/v ratios of 5-10% improved the antibacterial properties of conventional glass ionomer cement against S. mutans without adversely affecting its bonding to dentin surface.

In vitro analysis of riboflavin-modified, experimental, two-step etch-and-rinse dentin adhesive: Fourier transform infrared spectroscopy and micro-Raman studies.

To modify two-step experimental etch-and-rinse dentin adhesive with different concentrations of riboflavin and to study its effect on the bond strength, degree of conversion, along with resin infiltration within the demineralized dentin substrate, an experimental adhesive-system was modified with different concentrations of riboflavin (m/m, 0, 1%, 3%, 5% and 10%). Dentin surfaces were etched with 37% phosphoric acid, bonded with respective adhesives, restored with restorative composite-resin, and sectioned into resin-dentin slabs and beams to be stored for 24 h or 9 months in artificial saliva. Micro-tensile bond testing was performed with scanning electron microscopy to analyse the failure of debonded beams. The degree of conversion was evaluated with Fourier transform infrared spectroscopy (FTIR) at different time points along with micro-Raman spectroscopy analysis. Data was analyzed with one-way and two-way analysis of variance followed by Tukey's for pair-wise comparison. Modification with 1% and 3% riboflavin increased the micro-tensile bond strength compared to the control at 24 h and 9-month storage with no significant differences in degree of conversion (P<0.05). The most predominant failure mode was the mixed fracture among all specimens except 10% riboflavin-modified adhesive specimens where cohesive failure was predominant. Raman analysis revealed that 1% and 3% riboflavin adhesives specimens showed relatively higher resin infiltration. The incorporation of riboflavin in the experimental two-step etch-and-rinse adhesive at 3% (m/m) improved the immediate bond strengths and bond durability after 9-month storage in artificial saliva without adversely affecting the degree of conversion of the adhesive monomers and resin infiltration.

Effect of high-intensity focused ultrasound on Enterococcus faecalis planktonic suspensions and biofilms.

In this study, the effect of high-intensity focused ultrasound (HIFU) on Enterococcus faecalis on both planktonic suspensions and biofilms was investigated. E. faecalis persist in secondary dental infections as biofilms. Glass-bottom Petri dishes with biofilms were centered at the focal point of the HIFU wave generated by a 250-kHz transducer. Specimens were subjected to HIFU exposure at different periods of 30, 60 and 120 s. The viable bacteria, removal effect and bacterial viability of biofilms attached to the Petri dish surface were studied by colony-forming units (CFUs), scanning electron microscopy and confocal microscopy, respectively. The removal and bactericidal effects of HIFU are dependent on the exposure time. A significant reduction in biofilm thickness and CFU was found with the increase in HIFU exposure. The removal or bactericidal effect of HIFU was more significant starting from 60 s of exposure. This study highlighted the potential application of HIFU as a novel method for root canal disinfection.

Chitosan/Riboflavin-modified demineralized dentin as a potential substrate for bonding.

Previous studies have suggested different approaches to modify dentin collagen for potential improvement in bonding to dentin. Here, we are proposing a new approach to reinforce dentin collagen fibrils network by chitosan as a reinforcement phase and UVA-activated riboflavin as crosslinking agent within clinically acceptable time-frame as potential substrate for bonding. The effect of modifying demineralized dentin substrates with chitosan/riboflavin, with a gradual increase in chitosan content, was investigated by SEM, nano-indentation, conventional-mechanical testing and hydroxyproline (HYP) release at collagenolytic and/or hydrolytic challenges. The resin/dentin interface morphology, immediate bond strength and short-term bond durability were also investigated using etch-and-rinse dentin adhesive. Modification with chitosan/riboflavin increased the mechanical properties, enhanced the mechanical stability of demineralized dentin substrates against hydrolytic and/or collagenolytic degradation challenges and decreased HYP release with collagenase exposure. When chitosan was added to riboflavin at 20%v/v ratio, significant improvement in bond strength at 24 h and 6 months in distilled water was found indicating the positive dual effect on bonding to dentin. With the gradual increase in chitosan content, obliteration of interfibrillar-spaces that might adversely affect bonding to dentin was found. Although it has a synergetic effect, chitosan content is crucial for any subsequent application in adhesive dentistry.