Effect of 2% chlorhexidine gluconate cavity disinfectant on microtensile bond strength of tooth-coloured restorative materials to sound and caries-affected dentin

This study evaluated the effect of 2% chlorhexidine gluconate-based cavity disinfectant (CHX) on the microtensile bond strength (μTBS) of glass ionomer, resin-modified glass ionomer and packable resin composite to sound and caries-affected dentin. Sound and occlusal caries-affected human third molars (N?=?36, n?=?3 per group) were randomly divided into three experimental groups to receive one of the following restorative materials. (a) Glass ionomer (Ketac Molar, 3 M ESPE; GI), (b) resin-modified glass ionomer (Vitremer, 3 M ESPE; RMGI) and (c) packable resin composite (Surefil, Dentsply; PRC) with a bonding agent (Prime Bond NT, Dentsply De Trey). Caries was removed using a caries-detecting dye (Caries Detector, Kuraray Medical Ltd.) and flat dentin surfaces were achieved by finishing up to 1200-grit silicon carbide abrasive. Half of the teeth in each group received 2% CHX (Consepsis, Ultradent). Dentin surfaces were built-up with the respective materials incrementally and were sectioned with a slow-speed saw into multiple beams. The beams were subjected to μTBS test (0.5 mm/min) in a Universal Testing Machine. The data were analysed using two-way analysis of variance and Tukey’s tests. For each restorative material, μTBS results were not affected by the application of CHX (p?>?0.05) on both sound and caries-affected dentin (p?>?0.05). PRC in combination with the corresponding bonding agent showed significantly higher results (p?<?0.05) than those of GI and RMGI, on sound and caries-affected teeth, respectively. Cohesive failure in dentin was not observed in any of the groups. The use of 2% chlorhexidine-based cavity disinfectant did not impair the adhesion of the restorative materials tested to either sound or caries-affected dentin.     

Synthesis of bis[(4-hydroxyethoxy)phenyl]sulfone containing urethane acrylates and their applications

UV-curing processes are used in industrial applications because of their advantages such as high speed applications and solvent-free formulations at ambient temperature. UV-curable sulfone containing polyurethane acrylates were synthesized from bis[(4-hydroxyethoxy)phenyl]sulfone (BHEPS), polyols, isophorone diisocyanate (IPDI) and 2-hydroxyethyl methacrylate (HEMA). The polyurethane acrylates characterized with ¹H NMR and FT-IR spectroscopies. The UV-cured coatings and films were formulated with polyurethane acrylates, reactive diluents such as dipropyleneglycol diacrylate (DPGDA), 1,6-hexanediol diacrylate (HDDA) and photoinitiator. The water wettability of the UV-cured films was investigated by measuring contact angle. Sulfone containing polyurethane acrylates increase mechanical properties such as pendulum hardness, pencil hardness, tensile strength, and e-modulus values. These mechanical properties and chemical-solvent resistance may have been strongly dependant on the sulfone content and crosslinking density.     

Boron containing UV-curable epoxy acrylate coatings

In the present work boron acrylate monomer was synthesized by esterification reaction. UV-curable boron containing epoxy acrylate coatings were prepared and applied on plexiglass substrates to obtain thermally and mechanically stable coatings. The physical and mechanical properties of UV-cured coatings were investigated such as gel content, solvent resistance, hardness, flexibility and tensile tests. The thermal behavior of coatings was also evaluated. It was observed that the tensile properties and thermal stabilities of boron modified epoxy coatings mainly depend on the boron content.     

Preparation and electrochemical behavior of dopamine-selective polymeric membrane

Summary o-toluidine was polymerized electrochemically using constant-potential electrolysis at a gold electrode surface. Electrochemical behavior of dopamine and ascorbic acid at the polymer electrode prepared in this manner was examined by cyclic and differential pulse voltammetry techniques. The influence of chemical and electrochemical variables on dopamine selectivity of the polymer electrode was systematically investigated and the optimal values for each parameter were determined. Experimental results showed that optimized polymeric membrane exhibited selectivity for dopamine while blocking ascorbic acid. Therefore, it is claimed that poly (o-toluidine) film can be used as a dopamine-selective polymeric membrane in the presence of ascorbic acid. Key Words: poly (o-toluidine); selective membrane; dopamine Received: 22 November 1999/Revised version: 25 January 2000/Accepted: 10 February 2000     

Understanding the influence of hydrogen bonding and diisocyanate symmetry on the morphology and properties of segmented polyurethanes and polyureas: Computational and experimental study

Quantum mechanical calculations (QMC) and dissipative particle dynamics (DPD) simulations were utilized to understand the nature of the short and long-range hydrogen bonding and its influence on the microphase morphology in segmented polyurethanes and segmented polyureas prepared without chain extenders through the stoichiometric reactions of hydroxy or amine terminated poly(tetramethylene oxide) (PTMO-1000) with 1,4-phenylene diisocyanate (PPDI) and 1,3-phenylene diisocyanate (MPDI). The possibility of long-range connectivity due to a network of well-ordered hydrogen bonds between symmetrical PPDI and kinked MPDI based model urethane and urea compounds were also investigated. Special emphasis was given on the understanding of the influence of diisocyanate symmetry and nature of the hydrogen bonding between hard segments on the morphology development. QMC results obtained clearly indicated the possibility of long-range ordering of hydrogen bonds between PPDI based urethane and urea groups, while MPDI based systems did not display such a behavior. DPD results strongly supported the QMC studies and clearly demonstrated the possibility of long-range connectivity of hydrogen bonds between urethane and urea groups in PPDI based segmented copolymers, leading to the formation of microphase separated morphologies in these systems, which was not observed in the kinked MPDI based segmented urethane and urea copolymers. Computational results obtained strongly supported the experimental observations reported on the morphology and thermal and mechanical properties of these segmented polyurethanes and polyureas based on PPDI and MPDI.     

Multiscale Modeling of the Morphology and Properties of Segmented Silicone-Urea Copolymers

Abstract  

Molecular dynamics and mesoscale dynamics simulation techniques were used to investigate the effect of hydrogen bonding on the microphase separation, morphology and various physicochemical properties of segmented silicone-urea copolymers. Model silicone-urea copolymers investigated were based on the stoichiometric combinations of α,ω-aminopropyl terminated polydimethylsiloxane (PDMS) oligomers with number average molecular weights ranging from 700 to 15,000 g/mole and bis(4-isocyanatocyclohexyl)methane (HMDI). Urea hard segment contents of the copolymers, which were determined by the PDMS molecular weight, were in 1.7–34% by weight range. Since no chain extenders were used, urea hard segments in all copolymers were of uniform length. Simulation results clearly demonstrated the presence of very good microphase separation in all silicone-urea copolymers, even for the copolymer with 1.7% by weight hard segment content. Experimentally reported enhanced properties of these materials were shown to stem from strong hydrogen bond interactions which leads to the aggregation of urea hard segments and reinforcement of the PDMS.     

Synthesis of cyclohexanone formaldehyde resin‐methylmethacrylate block‐graft copolymers via ATRP

Well defined block‐graft copolymers of cyclohexanone‐formaldehyde resin (CFR) and methylmethacrylate (MMA) were prepared via atom transfer radical polymerization (ATRP). In the first step, cyclohexanone formaldehyde resin (CFR) containing hydroxyl groups were modified with 2‐bromopropionyl bromide. Resulting multifunctional macroinitiator was used in the ATRP of MMA using copper bromide (CuBr) and N,N,N′,N″,N″‐pentamethyl‐diethylenetriamine (PMDETA) as catalyst system at 90°C. The chemical composition and structure of the copolymers were characterized by nuclear magnetic resonance (¹H‐NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and molecular weight measurement. Molecular weight distributions of the CFR graft copolymers were measured by gel permeation chromatography (GPC). M_n values up to 19,000 associated with narrow molecular weight distributions (polydispersity index (PDI) < 1.6) were obtained with conversions up to 49%. Coating properties of synthesized graft copolymers such as adhesion and gloss values were measured. They exhibited good adhesion properties on Plexiglas substrate. The thermal behaviors of all polymers were conducted using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Influence of laser parameters in surface texturing of polyphenylene sulfide composites

Creating dimples at the ideal geometries to enhance the tribological properties of the polyphenylene sulfide (PPS) composite surface is the principal purpose of this study. In this manner, the effects of focus position (FP), pulse number (PN), and energy used for the making dimple geometry were investigated. In the ablation process, Nd:YAG laser with 1064 nm wavelength was used. Optimum laser process parameters were intended to obtain the largest ratio of dimple depth to width, circular dimples with a minimum ratio of molten zone diameter to spot size. The most effective parameters for obtaining dimple of desired properties are pulse energy (PE) with 60.64%, pulse duration (PD) with 55.61%, and FP with 55.94% for aspect ratio, circularity, and ratio of the diameter of the dimple to the spot size, respectively. In order to achieve a high aspect ratio or good circularity or minimum molten zone-to-spot size ratio, Taguchi optimization predicted the laser parameters. In the confirmation experiment with the proposed parameters, the highest aspect ratio was obtained as 2.05, the best circularity was obtained as 1.05, and minimum molten zone-to-spot size ratio was obtained as 1.073. Using the Taguchi method, accurate results were found with less experimentation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47976.