Antimicrobial activity,effects on Streptococcus mutans biofilm and interfacial bonding of adhesive systems with and without antibacterial agent

ObjectivesThis study evaluated the antimicrobial activity (by agar disk diffusion test, AD), viability of S. mutans biofilm (VB), and effect on resin-dentin interface (RDI) of six adhesive systems.MethodsThree adhesives containing antibacterial components (Gluma 2Bond (G2B)/glutaraldehyde, Clearfil SE Protect (CSP)/MDPB and Peak Universal Bond (PUB)/chlorhexidine) and the corresponding adhesives with similar composition, but without antibacterial agents (Gluma Comfort Bond, GCB; Clearfil SE Bond, CSB and Peak LC Bond, PLB) were evaluated. AD was determined measuring the extent of halo formation following application of adhesives and control groups (light cured or not) to cultures of four strict anaerobic and four facultative bacteria. For VB, a UA159 biofilm was grown on adhesive-coated hydroxyapatite discs for five days, collected and processed to count the number of viable cells. For RDI analysis, adhesives were applied according to manufacturers' recommendations and teeth were restored with resin composite, sectioned to obtain bonded slices and visualized by SEM.ResultsAn inhibition halo was observed for G2B (strict anaerobic/light cured and not light cured), CSP (strict anaerobic and facultative/light cured and not light cured) and PUB (strict anaerobic and facultative/not light cured). PUB when light cured produced an inhibition halo on L. casei and S. mutans only. G2B and CSP significantly reduced the viability of S. mutans. Adhesives containing antimicrobial compounds had no detectable effect on RDI.ConclusionThe MDPB-containing bonding agent showed better results of inhibition for all oral pathogens tested and a decrease of viability of Streptococcus mutans biofilm, among the adhesives tested.     

The effect of functional monomer chain spacer length on the bond strength of an experimental dental adhesive

The study evaluated the effect of the carbon-chain spacer of monomers on the bonding effectiveness of two-step self-etching adhesive systems (SES). We investigated three acrylamidophosphonic acid monomers which vary only by the length of the carbon chain, 2-(N-methylmethacrylamido)ethylphosphonic acid, 6-(N-methylmethacrylamido)hexylphosphonic acid and 10-(N-methylmethacrylamido)decylphosphonic acid, on their effect in bonding performance while formulated in a self-etching primer with dentin and enamel. The results correlated well with those obtained from Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM).It is concluded that there are no significant differences in terms of immediate Shear Bond Strength (SBS) on either enamel or dentin by using experimental self-etching primer (SEP) of different spacer chain length.     

Biodegradation of caries-affected dentin bonding interface of fluoride and MDPB-containing adhesive system

The aim of this study was to evaluate the effect of a fluoride/MDPB (12-methacryloyloxydodecylpyridinium bromide)-containing adhesive system on the durability of a bond to permanent artificially induced caries-affected dentin (CAD) exposed to Streptococcus mutans culture and water storage. Twelve third molars were selected. Flat dentin surfaces were submitted to artificial caries development in S. mutans and Broth heart infusion (BHI). Caries-infected dentin was removed with burs according to clinical criteria and CAD cavities were restored with Adper Scotchbond Multi-Purpose (SBM) and Clearfil Protect Bond (CPB). Nontrimmed resin–dentin bonded interfaces (1 mm²) were stored in S. mutans+BHI for 3 days, in deionized water for 3 months, and afterwards subjected to microtensile bond strength test (μTBS). The control group was not submitted to storage and immediate μTBS testing was performed. Fractographic analysis was performed after μTBS testing. Four molars were restored as described, and morphological evaluation hybrid layer (HL) was performed by scanning electron microscopy (SEM). Two-way ANOVA with split-plot design and Tukey′s tests were performed. No difference was found between μTBS values of SBM and CPB irrespective of groups. Significant decrease was observed in μTBS values after S. mutans culture and water storage, but without difference between them. CPB had more homogenous hybrid layer than SBM. Fluoride/MDPB-containing adhesive system did not prevent degradation of CAD bond strength in both degradation methods.     

Effect of self-etching dual-curing universal adhesive system application on bond strength of dentin resinous liners dentin

Purpose: The aim of this study was to evaluate the influence of previous application of an adhesive system on bond strength of resinous liner materials to dentin. Methods: Ninety bovine incisors crowns had a 6 × 6 mm area of dentin exposed, with minimum of 2 mm thickness. They were embedded in acrylic resin, and the dentin was polished with P600 SiC sandpaper for 30 s to standardize the smear layer. The specimens were divided into 6 groups (n = 15) according to the application or not of a self-etching system (Futurabond U – Voco) and the type of resinous liner used: A+Ionoseal (adhesive and Ionoseal – Voco); Ionoseal (Ionoseal only); A+Vitrebond (adhesive and Vitrebond – 3M/ESPE); Vitrebond (Vitrebond only); A+Ionosit (adhesive and Ionosit – DMG) and Ionosit (Ionosit only). Adhesives were used following manufacturer’s instructions, and the liner materials were applied inside a 2-mm-depth matrix and light-cured for 20 s. The bond strength was measured by microtensile test, using a universal testing machine with a cross-speed of 1 mm/min. Data were analyzed using one-way ANOVA and Tukey’s test (p < 0.05). Results: The adhesive system application increased bond strength of all liners tested. Ionoseal presented the highest bond strength when the adhesive system was used and exhibited similar performance to Vitrebond without adhesive. Ionosit without adhesive showed the smallest bond strength compared with the other liners tested. Conclusion: The application of an adhesive system prior to the use of the resinous liners improved the bond strength to dentin and should be preconized.     

Synthesis of polyurethane acrylates by hydrogenated castor oil and dimer‐based polyester diol and study on pressure‐sensitive adhesive

Synthesis of polyurethane acrylate (PUA) and preparation of the UV‐cured pressure‐sensitive adhesives (PSA) are reported. Molecular weight (M_w) (by gel permeation chromatography) and viscosity (η*) of PUA were measured. Characterization of PUA and PSA before and after UV‐curing was made by FTIR. Increase of the hydroxyls from hydrogenated castor oil/hydroxyls from dimer‐based polyester diol (OH_HCO/OH_Diol) ratio decreased the M_w and η* value of PUA. Dynamic viscoelastic properties (by dynamic rheological spectrometer) and performance of the UV‐cured PSA were also studied. Increase of the OH_HCO/OH_Diol ratio increased the storage modulus (G′), the loss modulus (G″), and complex viscosity (Eta*) of the UV‐cured PSA, which, in turn, enhanced holding power and shear adhesion failure temperature (SAFT) and yet decreased peeling strength. Substitution of OB for DBTDL depressed the M_w and η* value of PUA, while the G″ and Eta* values of the UV‐cured PSA were elevated, which, in turn, increased the holding power and SAFT and yet depressed the peeling strength. Elevation of the tackifying resin content depressed the G′, G″, and Eta* values of the cured PSA and yet increased glass transition temperatures (T_g) of PSA, measured by differential scanning calorimetry. Peeling strength of PSA elevated as increasing the tackifying resin, while the holding power and SAFT fell. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1814–1821, 2005     

Influence of radiant exposure on degree of conversion,water sorption and solubility of self-etch adhesives

The purpose of this study was to investigate the influence of the radiant exposure on the degree of C=C conversion (DC), water sorption (WS), and solubility (S) of the Clearfil SE Bond (CSE) and Filtek LS (LS) self-etch adhesive systems. The primer of the LS (LSP), and bond agents of the CSE (CSEB) and LS (LSB) were tested. Specimens were light-cured using a light-emitting diode (LED) at different radiant exposures (6.1, 12.2, 13.9, and 27.8 J/cm²). DC (n=10) was measured using Fourier-transform infrared spectroscopy (FT-IR). WS and S were determined according to ISO 4049. Data were subjected to two-way ANOVA and Tukey's test at pre-set alpha of 0.05. The highest DC was exhibited by LSP, followed by CSEB and LSB, all with statistical difference (p<0.001). The DC was increased with higher radiant exposure and extended light-curing time (p<0.001). LSB and CSEB showed the lower WS followed by LSP, all with statistical difference (p<0.001). CSEB and LSB presented no significance difference on the S values (p>0.05) and were lower than LSP (p≤0.05). The WS and S were not influenced by the different radiant exposures evaluated (p=0.9548 and p>0.05, respectively). The monomer conversion is related to improvement on the mechanical properties of resinous material, but these properties also depend on the polymer network structure formed.     

The interaction of water with an epoxide adhesive based on the diglycidylether of bisphenol-A and triethylene tetramine

The adhesive made by curing the diglycidylether of bisphenol-A and triethylenetetramine demonstrates Fickian uptake from liquid water at temperatures between 4°C and 85°C. Uptake from water vapour at 50°C shows that the diffusion coefficient decreases slightly with concentration. The vapour uptake equilibria are examined using the Zimm clustering theory and the Flory-Huggins lattice model and these support the view that the water absorbed by the adhesive forms clusters.     

Synthesis,Characterization and Cytotoxicity Evaluation of an Oleic Acid Derived Novel Bicephalous Dianionic Surfactant

A novel oleic acid derived bicephalous dianionic surfactant disodium (Z) 3,3′‐(oleoylazanediyl)dipropanoate containing one hydrophobic carbon chain and two hydrophilic head groups was synthesized, characterized and evaluated for cytotoxicity for the purpose of introducing a new biocompatible surfactant. The head group 3,3′‐azanediyldipropanoate was synthesized through Michael addition of methyl acrylate to benzylamine and subsequent reductive debenzylation with Pd/C, H₂ and was condensed with an oleic acid moiety via amide bond formation. Ester groups at the periphery were hydrolyzed using acetyl chloride‐water and the diacid formed was neutralized with sodium bicarbonate to obtain the desired surfactant. The CMC was determined by conductometry, log P_{octanol/water} by ChemSW software and the hydrophilic‐lipophilic balance (HLB) by the Davies method and ChemSW. In vitro cytotoxicity study was performed using sulforhodamine B assay and the in vivo skin irritation study was performed on male New Zealand white rabbits as per OECD guideline 404. The CMC was found to be 1.9 mm/l which was almost half of the CMC of sodium oleate. The Log P_{octanol/water} value of ?3.87 and the HLB values of 35.22 and 34.46 by the Davies method and ChemSW software respectively revealed the hydrophilic nature of the surfactant. The surfactant did not exhibit any cytotoxicity at any of the concentrations tested and was found to be non‐irritating by in vivo skin irritation studies. The findings of the present work suggest that the synthesized novel bicephalous dianionic surfactant is a safe and biocompatible excipient. It has the potential to be an attractive alternative to linear and gemini surfactants for applications in biological studies and pharmaceutical drug delivery systems.     

Mechanical properties,water absorption and adhesive properties of diepoxy aliphatic diluent-modified DGEBA/Cycloaliphatic amine networks on 316 L stainless steel

In this study, the mechanical behaviors, adhesive properties and water absorption of networks based on diglycidyl ether of bisphenol A (DGEBA) modified with diepoxy aliphatic diluent (1,4-butanediol diglycidyl ether, DGEBD) cured with cycloaliphatic amine were studied. The mechanical behaviors and adhesive properties were evaluated by compression testing and single lap-shear using 316 L stainless steel as the adherend, respectively. Water absorption was evaluated by water immersion at 37±0.2 °C. The fracture mechanisms of the networks were determined by optical microscopy. Decreases in the glass transition temperature (T_g) and the yield stress (σ) were noted with increased additive concentrations. The best mechanical performance, accompanied by slight increased adhesive strength, was obtained with 30 phr of additive. The DGEBA/4MPip network modified with 30 phr of diluent shows the best compressive behavior, adhesive strength, and lower water absorption. This behavior may relate to the lower crosslinking density resulting from the reaction mechanism, of stepwise and addition polymerization. Greater participation of cohesive fracture mechanisms was observed in the epoxy networks modified with 30 phr of additive.     

Effect of hydroxyapatite morphology and quaternary ammonium polymer co-inclusion on bond strength,cytotoxicity, and cell morphology of self-etching adhesive

This study aimed to obtain and evaluate hydroxyapatites (HAp) as nanoparticles and nanorods for use in self-etching adhesive. The effect of co-inclusion of a multifunctional quaternary ammonium methacrylate polymer (QAMP) on their mechanical, cell viability, and morphological properties was also investigated. Hydroxyapatite nanoparticles (HApP24 and HApP36) and nanorod-shaped hydroxyapatite (HApR14) were characterized by XRPD, SEM-FEG, and FTIR spectroscopy. HApP24, HApP36, HApR14, and HApR14 + QAMP were added to Clearfil™ SE Bond. Microtensile bond strength (μTBS), cell viability (MTT method), and cell morphology (SEM) of these adhesives were studied. Characterization data confirmed that hydroxyapatites were successfully synthesized. Significant decrease μTBS was achieved for Clearfil™ SE Bond + HApP24 (p = 0.031) and Clearfil™ SE Bond + HApP36 (p = 0.008) when immediate (IM) and 12 months (12 M) were compared. No statistical difference (p > 0.05) was achieved when six months (6 M) and 12 M results of μTBS were compared for Clearfil™ SE Bond + HApR14. Clearfil™ SE Bond + QAMP, Clearfil™ SE Bond + HApR14 + QAMP, and Clearfil™ SE Bond presented no significant difference comparing storage periods. Lower cell viability was achieved when HApP24 and HApP36 were included to Clearfil™ SE Bond. Co-inclusion of QAMP + HApR14 into Clearfil™ SE Bond improved (p = 0.049) the viability of cells when compared to Clearfil™ SE Bond. SEM micrographs of fibroblast-like cells demonstrated consistent results with cell viability. This is the first report that hydrothermal nanorods of HAp and QAMP are co-included into adhesive system for providing remineralizing and antimicrobial properties at the same time as they kept bond stability.     

Effect of loading chemically and mechanically pre-treated fumed silica as filler on an etch & rinse model dental adhesive

Fumed silica is one of the most commonly used fillers for dental resin adhesives. However, fumed silica produced by flame hydrolysis of chlorosilanes are typically agglomerated aggregates instead of isolated primary particles. The fumed silica aggregates may affect the dispersion of fillers in the resin matrix, thus affect the bonding performance of the dental adhesives. In this study, fumed silica fillers chemically treated with methacrylsilane were loaded into an etch & rinse model dental adhesive. Filler 1 was only chemically pre-treated, while Filler 2 was combined chemically and mechanically pre-treated to break the agglomerated aggregates. The experiment result indicated that Filler 1 has faster rheology control effect than Filler 2 on the handling property of the filled resin adhesive showing as the rapid increased viscosity, which may due to the fast inorganic phase growing in the Filler 1 filled resin matrix. As for the mechanical properties, neither Filler 1 nor Filler 2 has an positive effect on the micro-tensile bond strength in short term and long term, despite of the fact that lower weight percent of Filler 2 loading is favourable to the penetration of the experimental adhesive into dentin substrate. In conclusion, mechanically pre-treatment to break the agglomerated fumed silica is helpful to increase the limit of filler loading percent while maintaining appropriate handling property, but the chemically and mechanically pre-treatment cannot provide positive effect on bonding performance within the range of this study.     

Effect of natural antioxidants in virgin olive oil on oxidative stability of refined,bleached, and deodorized olive oil

The factors influencing the oxidative stability of different commercial olive oils were evaluated. Comparisons were made of (i) the oxidative stability of commercial olive oils with that of a refined, bleached, and deodorized (RBD) olive oil, and (ii) the antioxidant activity of a mixture of phenolic compounds extracted from virgin olive oil with that of pure compounds andα-tocopherol added to RBD olive oil. The progress of oxidation at 60°C was followed by measuring both the formation (peroxide value, PV) and the decomposition (hexanal and volatiles) of hydroperoxides. The trends in antioxidant activity were different according to whether PV or hexanal were measured. Although the virgin olive oils contained higher levels of phenolic compounds than did the refined and RBD oils, their oxidative stability was significantly decreased by their high initial PV. Phenolic compounds extracted from virgin olive oils increased the oxidative stability of RBD olive oil. On the basis of PV, the phenol extract had the best antioxidant activity at 50 ppm, as gallic acid equivalents, but on the basis of hexanal formation, better antioxidant activity was observed at 100 and 200 ppm.α-Tocopherol behaved as a prooxidant at high concentrations (>250 ppm) on the basis of PV, but was more effective than the other antioxidants in inhibiting hexanal formation in RBD olive oil.o-Diphenols (caffeic acid) and, to a lesser extent, substitutedo-diphenols (ferulic and vanillic acids), showed better antioxidant activity than monophenols (p- ando-coumaric), based on both PV and hexanal formation. This study emphasizes the need to measure at least two oxidation parameters to better evaluate antioxidants and the oxidative stability of olive oils. The antioxidant effectiveness of phenolic compounds in virgin olive oils can be significantly diminished in oils if their initial PV are too high.     

Effect of Nanoclay on the Mechanical,Thermal, and Water Absorption Properties of an UP-toughened Epoxy Network

Unsaturated polyester (UP)-toughened epoxy nanocomposites were prepared, and their effective mechanical and thermal properties were studied. Two types of organo-modified montmorillonite (OMMT) clays were used to prepare the nanocomposites. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis showed the formation of exfoliated silicate layers in the UP-toughened epoxy matrix. Mechanical tests revealed that nanocomposites (containing 1 wt% OMMT clay) showed an increase in tensile strength to 13.8%, flexural strength to 10%, and impact strength to 4% compared with an UP-toughened epoxy blend. The effect of different heating rates on the curing behavior of UP-toughened epoxy nanocomposites was investigated using non-isothermal differential scanning calorimetry. The data were interpreted using the Kissinger and Flynn–Wall–Ozawa models to find the curing reaction parameter. The water uptake behavior for nanocomposites increased with the addition of OMMTs. Scanning electron microscopy micrographs indicated morphological changes in the impact fractured samples of UP-toughened epoxy nanocomposites.     

Experimental investigation of fuel properties, engine performance, combustion and emissions of blends containing croton oil, butanol, and diesel on a CI engine

Emission problems associated with the use of fossil fuels have led to numerous research projects on the use of renewable fuels. The aim of this study is to evaluate the effects of blends containing croton mogalocarpus oil (CRO)-Butanol (BU) alcohol-diesel (D2) on engine performance, combustion, and emission characteristics. Samples investigated were 15%CRO-5%BU-80%D2, 10%CRO-10%BU-80%D2, and diesel fuel (D2) as a baseline. The density, viscosity, cetane number CN, and contents of carbon, hydrogen, and oxygen were measured according to ASTM standards. A four cylinder turbocharged direct injection (TDI) diesel engine was used for the tests. It was observed that brake specific energy consumption (BSEC) of blends was found to be high when compared with that of D2 fuel. Butanol containing blends show peak cylinder pressure and heat release rate comparable to that of D2 on higher engine loads. Carbon dioxide (CO₂) and smoke emissions of the BU blends were lower in comparison to D2 fuel.     

Effects of palm oil fatty acid on curing characteristics,reversion and fatigue life of various natural rubber compounds

The effects of palm oil fatty acid concentration (0, 1, 3, 5, 7 phr) and epoxidation on curing characteristics, reversion and fatigue life of carbon black filled natural rubber compounds have been studied. Three different types of natural rubber, SMR L, ENR 25 and ENR 50 having 0, 25 and 50 mol% of epoxidation and conventional sulphur vulcanization were used. The cure time t₉₀, scorch time t₂, M_HR − M_L (maximum torque − minimum torque) and fatigue life of all rubbers were found to increase with increasing palm oil fatty acid concentration. However, the reversion of all rubbers decreases with increasing palm oil fatty acid concentration. At similar concentrations of palm oil fatty acid, ENR 50 compounds exhibit the shortest scorch and cure times followed by ENR 25 and SMR L compounds. For reversion, SMR L compounds show the lowest value followed by ENR 50 and ENR 25 compounds, whereas for fatigue life, the highest value is obtained with ENR 50 compounds followed by ENR 25 and SMR L compounds. © 1999 Society of Chemical Industry     

The effect of carotene extraction system on crude palm oil quality, carotene composition, and carotene stability during storage

Palm carotene was successfully concentrated from crude palm oil (CPO) by an adsorption process using a synthetic adsorbent followed by solvent extraction. Evaluation of feed CPO and CPO which underwent the carotene extraction process was conducted. The quality of CPO after the extraction process was slightly deteriorated in terms of free fatty acid, moisture content, impurities, peroxide value, anisidine value, discriminant function, and deterioration of bleachability index. However, the CPO still can be refined to produce refined, bleached, deodorized palm oil that meets the Palm Oil Refiners Association of Malaysia specifications. No extra cost was incurred by refining this CPO as the dosage of bleaching earth used was very similar to the refining of standard CPO. The triglyceride carbon number and fatty acid composition of CPO after going through the carotene extraction process were almost the same as CPO data. The major components of the carotene fraction were similar to CPO, which contains mainly α- and β-carotene. The carotene could be stored for at least 3 mon.     

Comparison between the adherence of a rigid axisymmetrical cone and a truncated one,in adhesive contact on an elastic half-space

We compare the equilibrium contacts and the kinetics of adherence of an axisymmetrical rigid cone and a flat-ended one with the same angle, applied against the flat and smooth surface of a soft elastomer sample (unfilled vulcanized natural rubber, cured with dicumyl peroxide), with the help of fracture mechanics concepts which can easily be introduced in this class of problems by using Sneddon's solution (1965) of Boussinesq's problem extended to all axisymmetric adhesive punches with a convex profile. The kinetics of adherence are measured when an imposed tensile force is applied in order to disturb the size of the contact area. Variations of the strain energy release rate, G, and of the associated dissipation function | =(G m w)/w, where w is the Dupré energy of adhesion, are studied as a function of the parameter, a T ± V, in which V is the crack propagation speed at the interface between a cone and a truncated one made of glossy Plexiglass®, and the rubber sample (the limit of the contact is considered as a crack tip), and a T , is the shift factor of the Williams-Landel-Ferry transformation. As expected, a master curve | (V) is found, confirming the variation of | as the power function V 0.55 , at fixed temperature, as recently established by Barquins et al. in adherence of a flat ended sphere and cone in pull-off/push-on tests, adherence and rolling of cylinders experiments and rebound of balls tests, with the same elastomer. Present results lead to propose one to write | =k ± (a T ± V) 0.55 , k=2520 and V being valued using S.I. units, for the reference temperature θ=25°C, with a quite good accuracy in the order of 1%.     

Catalytic activity of Co,Mo and CoMo supported on NaY zeolite: hydrodesulfurization of gas oil at high pressure

Three series of Co/NaY, Mo/NaY and CoMo/NaY zeolite catalysts with variable metal content, prepared by a conventional impregnation method, were characterized by XRD, IR spectroscopy (oxide state) and acidity measurements (sulfide state), and tested in hydrodesulfurization (HDS) of gas oil at high pressure in the temperature range 275–350°C. The combined results of surface area, XRD and IR showed that in the catalysts with high metal loading a small loss in crystallinity and a partial blockage of the zeolite supercages were produced by Mo oxide species. The number of acid sites, which was lower for the Co/NaY than for the Mo/NaY catalysts, increased with increasing Co or Mo loading, but the strength of the acid sites was stronger for the Co/NaY series. HDS specific activities of the Co/NaY and Mo/NaY monometallic catalysts reached a maximum at very low loadings of Co ( 0.10 at. nm^–2) or Mo ( 0.16 at. nm^–2) by the double action of the metal sulfide species and the strong acid sites generated on the zeolite by the Co or Mo incorporation. In the binary CoMo/NaY catalysts, the synergy between Co and Mo species was significant for high Mo contents only.     

Synthesis of imine bond containing insoluble polymeric ligand and its transition metal complexes,structural characterization and catalytic activity on esterification reaction

In this study, synthesis of insoluble polymeric ligand (L) and its transition metal complexes [Cu(L)Cl₂]·2H₂O (1), [Co(L)Cl₂(H₂O)₂] (2) and [Ni(L)Cl₂(H₂O)₂] (3), having the azomethine groups, were synthesized by the condensation reactions of the diamines and dialdehydes. The structural properties were characterized by the analytical and spectroscopic methods using by elemental analysis, Fourier Transform Infrared, Thermo Gravimetric Analysis, Powder X-ray Diffraction, magnetic susceptibility and Inductively Coupled Plasma. The solubilities of the synthesized polymeric materials were also investigated and found as insoluble some organic and inorganic solvents. Additionally, their catalytic performance was carried out for the esterification reaction of acetic acid and butyl acetate. The highest conversion rate is 75.75% by using catalyst 1. The esterification of butanol gave butyl acetate with 100% selectivity.