In vitro evaluation of electrospun gelatin‐bioactive glass hybrid scaffolds for bone regeneration

Organic–inorganic hybrid materials, composed of phases that interact on a nanoscale and a microstructure that mimics the extracellular matrix, can potentially provide attractive scaffolds for bone regeneration. In the present study, hybrid scaffolds of gelatin and bioactive glass (BG) with a fibrous microstructure were prepared by a combined sol–gel and electrospinning technique and evaluated in vitro. Structural and chemical analyses showed that the fibers consisted of gelatin and BG that were covalently linked by 3‐glycidoxypropyltrimethoxysilane to form a homogeneous phase. Immersion of the gelatin–BG hybrid scaffolds in a simulated body fluid (SBF) at 37°C resulted in the formation of a hydroxyapatite (HA)‐like material on the surface of the fibers within 12 h, showing the bioactivity of the scaffolds. After 5 days in SBF, the surface of the hybrid scaffolds was completely covered with an HA‐like layer. The gelatin–BG hybrid scaffolds had a tensile strength of 4.3 ± 1.2 MPa and an elongation to failure of 168 ± 14%, compared to values of 0.5 ± 0.2 MPa and 63 ± 2% for gelatin scaffolds with a similar microstructure. The hybrid scaffolds supported the proliferation of osteoblastic MC3T3‐E1 cells, alkaline phosphatase activity, and mineralization during in vitro culture, showing their biocompatibility. The results indicate that these gelatin–BG hybrid scaffolds prepared by a combination of sol–gel processing and electrospinning have potential for application in bone regeneration. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Modulating stability and mechanical properties of silica–gelatin hybrid by incorporating epoxy‐terminated polydimethylsiloxane oligomer

Silica‐gelatin hybrids, particularly GT‐G hybrids prepared by crosslinking gelatin (G) with γ‐glycidoxypropyltrimethoxysilane (GT), have attracted much attention in tissue engineering for diverse applications in hard or soft tissue regeneration; however, scaffolds with tunable properties are needed to meet specific requirements. In this work, a silica‐gelatin hybrid (ES/GT‐G) was synthesized by incorporating epoxy‐terminated polydimethylsiloxane oligomer (ES) to modulate the properties of GT‐G hybrid. The ES/GT‐G hybrid sponge presented a 3D network structure with porosity 86.4% ± 0.9%, determined by the liquid displacement method, and average pore size 340 ± 36 μm, determined by SEM observation. Compared with GT‐G hybrid material, the prepared ES/GT‐G hybrid wet film showed a decrease of tensile strength from 2.79 ± 0.04 MPa to 1.87 ± 0.12 MPa, with an increase of elongation at break from 19.96 ± 0.66% to 29.86 ± 0.87%, and the ES/GT‐G hybrid sponge exhibited a decline of compressive yield strength from 1.21 ± 0.04 MPa to 0.72 ± 0.06 MPa, based on the tensile and compression tests respectively. The introduction of ES enhanced the thermal denaturing temperature of GT‐G by 5°C as determined by a DSC study, and increased in vitro biodegradation slightly, without significantly changing surface wettability and swelling behavior. These findings suggest that silica‐gelatin hybrids with tunable properties are promising for applications from hard to soft tissue regeneration. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43059.     

Isothiocyanate derivatives of soybean oil triglycerides: Synthesis,characterization, and polymerization with polyols and polyamines

In this article, a novel two step synthesis of soy oil based isothiocyanate is described. Allylicaly brominated soybean oil (ABSO) was reacted first with ammonium thiocyanate in tetrahydro furan to form allylic thiocyanates. These compounds were then converted to isothiocyanated soybean oil (ITSO) by a thermal rearrangement. Conversion was found to be 70%. The structure of the ITSO was characterized by IR and ¹ H‐NMR techniques. Then ITSO was reacted with ethylene glycol, glycerol, and castor oil to produce polythiourethanes and ethylene diamine and triethylene tetra amine to produce polythioureas. Thermal properties of the products were determined by DSC and TGA techniques. DSC traces showed T_g's for ethylene glycol polythiourethane at ?39 and 58°C, for glycerol polythiourethane at ?39 and 126°C, for castor oil polythiourethane at ?38°C and ?17°C, for ethylene diamine polythiourea at ?45°C, and for triethylene tetra amine poly thiourea at ?39°C. Additionally, DSC analysis of polythioureas showed an endotherm at around 100°C. All of the polymers started to decompose around 200°C. Tensile properties of the polymers were determined. Polythiourethanes showed higher tensile strength and lower elongation when compared with their urea analogs. Stress at break values of the polymers were 1.2 MPa for glycerol polythiourethane, 0.6 MPa for ethylene glycol polythiourethane, 0.5 MPa for ethylene diamine polythiourea, and 0.9 MPa for triethylene tetra amine polythiourea polymers. Unfortunately, polymers synthesized showed poor solvent resistance. All polymers swelled and disintegrated in CH₂Cl₂ in 5 h. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Electrospun nanobandage for hydrocortisone topical delivery as an antipsoriasis candidate

The aim of the present work was to introduce the novel and convenient nanoapproach for more effective control of psoriasis. In this study, the polyacrylonitrile (PAN)-based electrospun fiber-loaded hydrocortisone was prepared with a topical electrospinning process. The results showed that the nanofibers had a smooth surface with an average diameter of 288.62?±?46.42, 195.96?±?35.60, and 160.11?±?30.11 and the tensile stress of 1.74, 3.77, and 15.35?MPa for PAN, PAN with 1 and 5% Tween 80, respectively. The amorphous dispersion of hydrocortisone in the nanobandage was proved by X-ray diffraction and differential scanning calorimetry study. The presence of Tween 80 increased drug released to completely 100% in investigated period with positive effect. The cytotoxicity study proved the noncytotoxicity of fibers against human umbilical vein endothelial cell line.     

The role of drying methods on enzymatic activity and phenolics content of impregnated dried apple

Infusion of antioxidants into vegetables is a new food strategy managed by matrix processing. Raw and blanched apple were air- or freeze-dried. In the case of freeze-dried samples, different freezing methods were previously applied: conventional (?28°C), blast freezing (?30°C), and liquid N₂ (?196°C). Afterwards, air- and freeze-dried samples at different conditions were impregnated with a concentrated (40°Brix) tea extract and finally, air-dried for their stabilization. Total phenolic content (TPC), antioxidant capacity (AC), enzymatic activity, and microstructure were analyzed. Regardless of pretreatments, the impregnation and the further drying improved the antioxidant potential. Samples with the most porous microstructure free of degradative enzymes provided high AC (78.5?±?0.9?mg Trolox/g dried matter) and TPC (16.7?±?0.2?mg GAE/g dried matter).     

In-situ measurement of solder joint strength in board-mounted chip-scale packages using a quantitative laser spallation technique

A previously developed laser spallation (LS) technique for measuring the interface strengths of planar films is modified to determine the interfacial tensile strengths of solder joints, in situ, in board-mounted chip-scale packages (CSPs). The new technique is demonstrated on packages with bare Cu pads and Pb-free solders. The solder/pad interface strength is determined by first using a laser-generated stress wave to separate the geometrically heterogeneous interface, in situ, and then quantifying the failure stress by a combination of interferometry and wave mechanics simulation. The solder to pad interfacial strengths were found to be 705?±?102, 510?±?71, and 369?±?55?MPa for packages stressed by baking at 150?°C for 0, 48, and 100?h, respectively. The interface strengths were found to be roughly proportional to the critical laser energies for separation of solder joints. Thus, it may suffice to use the critical laser energy as a parameter for the purposes of material selection and solder joint quality inspection during manufacturing. The quantitative capability of the LS test for testing board-level packages now provides an opportunity to enhance the board-level drop test that is widely conducted in the industry today.     

Preparation of a new superhydrophobic nanofiber film by electrospinning polystyrene mixed with ester modified silicone oil

A new superhydrophobic nanofiber membrane with certain mechanical strength was prepared by electrospinning the polystyrene (PS) with ester modified silicone oil (EMSO). To increase the roughness and tensile strength, the EMSO with low energy as hydrophobic macromolecular substance was added into PS precursor solution. Then during the process of electrospinning, some of the ester modified silicone oil was distribution on the surface of substrate (PS) fiber films to generate double structure which leaded to the superhydrophobicity. We probed into the relationship between the surface wettability, morphologies, mechanical property, and the mass ratios of ester modified silicone oil /PS, and with the increasing of EMSO, the water CA value increased from 135 ± 0.5° to 152 ± 0.2°and the tensile strength grown from 0.23 MPa to 0.92 MPa. The film shows a network structure consisting of numerous randomly oriented fibers, the diameters of which changed from 0.5 μm to 2.0 μm belong to relatively big diameter fibers, which has great significance to the research of superhydrophobic membrane with big diameter fibers and also this method is easy, convenient and environment friendly. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40718.     

Conversion of waste plastics to single-cell protein by means of pyrolysis followed by fermentation

Waste plastics (e.g. polyethylene, polystyrene and polypropylene) have been converted to single-cell protein using pyrolysis followed by fermentation. Conversion efficiencies of plastics to pyrolysate were 75–90% for polyethylene, 10–56% for polystyrene and 40–50% for polypropylene. Unpyrolysed residues were formed with polystyrene (6–14%) and polypropylene (14–30%), but not with polyethylene. Polyvinyl chloride produced hydrogen chloride fumes, together with 33–39% unpyrolysed residue, no fermentable pyrolysis products being formed. Polyethylene pyrolysate was fermented by the yeast, Candida tropicalis. Batch fermentation was carried out at 31°C and pH 5.5 on polyethylene pyrolysate in shaken flasks (100 cm³ culture) and in an aerated fermenter (500 cm³ culture). Maximum growth rate was 0.168 h^?1, cell yield was 0.47 ± 0.02 g g^?1 pyrolysate used (n = 3) and doubling time was 4–5 h, after 72 h growth on 1.0g pyrolysate 100 cm^?3 culture. Continuous culture (dilution rate 0.10 h^?1) gave a dry cell yield of 0.39 g g^?1 pyrolysate utilised. Utilisation of pyrolysate was 49.0% in batch culture and 33.0% in continuous culture. The efficiency of conversion of polyethylene to biomass was 34–42% in batch culture. Emulsification and pristane-solubilisation were studied as a means of dispersing waxy pyrolysates in culture media. Pristane did not support growth whereas the emulsifier [lecithin, Tween 85 and sodium glycocholate (1:2:2 by weight)] could support up to 27% of the growth observed on polyethylene pyrolysate. Although growth would occur without either emulsifier or pristane, use of pristane increased both dry cell yield (g g^?1 pyrolysate used) and pyrolysate utilisation by 1.3 times in flask cultures. Crude protein content of cells cultured on polyethylene pyrolysate was 46.7 ± 2.4% (n = 3) for batch culture cells, and 43.8 ± 0.3% (n = 4) for continuous culture cells. The true protein content of Candida cells was about 17%. The protein had a favourable nutritional quality as judged by in-vitro chemical tests.     

Synthesis and characterization of novel poly(phenylene sulfide) containing a chromophore in the main chain

A kind of novel poly(phenylene sulfide)s (PPSs) containing a chromophore group were synthesized by the reaction of dihalogenated monomer and sodium sulfide (Na₂S.xH₂O) via nucleophilic substitution polymerization under high pressure. The polymers were characterized by Fourier transform infrared spectroscopy, ultraviolet spectroscopy, fluorescence spectroscopy, XRD, DSC, TGA, mechanical testing and dissolvability experiments. The intrinsic viscosity of the polymers obtained with optimum synthesis conditions was 0.22 ? 0.38 dl g^?1 (measured in 1‐chloronaphthalene at 208 °C). These polymers were found to have good thermal performance with a glass transition temperature (T_g) of 90.5 ? 94.6 °C and initial degradation temperature (T_d) of 475–489 °C, showing improved thermal properties compared with homo‐PPS. At the same time the resultant resins had a high tensile strength of 67.5 ? 74.1 MPa and compressive strength of 70.7 ? 85.4 MPa. Additionally, these polymers exhibited a weak UV ? visible reflectivity minimum at 450–570 nm, and the fluorescence spectra of the polymers showed maximum emission around nearly 370 nm. Also they showed excellent chemical resistance and another special property ? bright shiny colors changed into different colors in acid solution. © 2014 Society of Chemical Industry     

The shear bond strength of repaired high-viscosity bulk-fill resin composites with different adhesive systems and resin composite types

This study compared the effect of different adhesive systems and composite resins on the shear bond strength (SBS) of repaired high-viscosity bulk-fill composites(Tetric EvoCeram Bulk Fill) and investigated failure modes. One hundred twenty cylindrical bulk-fill composite blocks (diameter 5?mm) were fabricated and thermocycled for 5000 cycles (5–55?°C). Specimens were roughened by diamond bur and divided into 8 groups (n?=?15). Bulk-fill blocks were repaired with the same material or nanohybrid composite resin(Tetric EvoCeram Nanohybrid) (diameter 3?mm) using different adhesive systems:Tetric N-Bond Universal (TSE);37% phosphoric acid etching?+?Tetric N-Bond Universal (TER); Clearfil SE Bond (CSE); 37% phosphoric acid etching?+?Adper^TMSingle Bond 2(SB). After repair procedures, all specimens were thermocycled again. The shear bond strengths were measured for all specimens using a universal test machine (crosshead speed of 1?mm/min). Cohesive strengths of bulk-fill composites were measured and described as control group. Debonded surfaces were observed with a stereomicroscope under 10x magnification to determine mode of failure. The SBS data of all groups was statistically analyzed by two-way ANOVA and Bonferroni correction test (p?<?0.05). The specimens repaired with bulk-fill composites showed significantly higher SBS values (25.86?±?5.74, 27.05?±?4.93, 24.49?±?6.95MPa) than those with nanohybrid composites (20.41?±?3.70, 22.08?±?6.37, 18.74?±?6.40?MPa) for TER,CSE,SB, respectively (p?<?0.05). There were no significant differences in SBS according to the type of adhesive systems for both repair materials (p?>?0.05). The predominant mode of failure was a mixed type in the restorative material except for the ones repaired with nanohybrid composites using Adper^TMSingle Bond 2. High-viscosity bulk-fill composites could be successfully repaired with the same materials. SBS of repaired bulk-fill composites reached cohesive strength for all tested groups.     

Dense and strong ZrO2 ceramics fully densified in <15 min

ABSTRACT

Crack-free zirconia ceramics were consolidated via sintering by intense thermal radiation (SITR) approach at 1600–1700°C for 3–5?min. The resulted ceramic bulks can achieve a relative density up to 99.6% with a grain size of 300–1200?nm. Their bending strength, Vickers hardness and indentation toughness values are up to 1244?±?139?MPa, 13.3?±?0.3?GPa and 5.5?±?0.1?MPa?m^1/2, respectively. Quantitative Raman and XRD analysis show the presence of minor m phase on the natural surface (<7%), fracture surface (<10%) and indentation areas (<15%). It reveals that the SITR method is efficient for rapidly manufacturing zirconia ceramics with desired density, fine grained microstructure and good mechanical properties that are strongly demanded in dental applications.     

Electrospun Poly(ε-Caprolactone)/Silk Fibroin Coaxial Core-Sheath Nanofibers Applied to Scaffolds and Drug Carriers

Developing biologically mimetic nanofibers (NFs) is crucial for their applications as scaffolds in tissue engineering and drug carriers. Herein, we present a strategy to facilely fabricate core-sheath NFs using coaxial electrospinning technique. Poly(ε-caprolactone) (PCL) and silk fibroin (SF) were employed as component materials to construct PCL/SF NFs with PCL cores uniformly encapsulated by SF sheaths. Scanning electron microscopy and transmission electron microscopy demonstrate a uniform core-sheath structure of the coaxial NFs. The engineered core-sheath structure confers the composite NFs with greatly improved properties including surface hydrophilicity and mechanical properties. In vitro cell culture validates that the core-sheath NFs are favorable to the cultured rat pheochromocytoma cells (PC 12) attachment. To further demonstrate the advantage of the coupled structural integrity, the PCL/SF core-sheath NFs were compared with the NFs produced from PCL and SF blend. Results showed that the PCL/SF NFs possessed a tensile strength of ~6.93 ± 0.52 MPa and an elongation at break of ~294.31 ± 24.17%, whereas the blend NFs possessed ~5.55 ± 0.50 MPa and ~88.05 ± 13.98%, respectively. Dexamethasone-phosphate sodium (DEX) was employed as a model drug, whereby the in vitro release study indicates that the NFs exhibit an ideal releasing profile, capable of releasing DEX continuously over a period of 450 h. The constructed PCL/SF core-sheath NFs are promising candidates for biomedical applications. POLYM. ENG. SCI., 60:802–809, 2020. © 2020 Society of Plastics Engineers     

Adhesion of resin cement to contemporary hybrid ceramic and polymeric CAD/CAM materials: effect of conditioning methods and ageing

This study assessed the effect of different surface conditioning methods and ageing protocols on adhesion of resin cement to hybrid ceramic and polymeric CAD/CAM materials. CAD/CAM materials (n?=?360, n?=?30 per group), namely (a) Lithium disilicate (IPS e.max CAD-LIS), (b) Zirconia (IPS e.max ZirCAD-ZIR), (c) Polymer (Lava Ultimate-LAV), (d) Polymer infiltrated ceramic network (Enamic-ENA), (e) Polymer infiltrated ceramic (Experimental-1-CS1), (f) Polymer infiltrated ceramic (Experimental-2-CS2), (g) Lithium disilicate reinforced alumina (n!ce-NIC) were cut into slices (3?×?6 × 8?mm³) and conditioned: (a) Method 1: 5% hydrofluoric acid etching (H)+silane and (b) Method 2: Silica coating (CoJet (A)+silane). Group LIS was conditioned with only Method 1 and Group ZIR only with Method 2 (control). Resin cement (Variolink Esthetic II) was bonded onto the conditioned specimens and photopolymerized. One-half of the specimens was subjected to ageing (thermocycling 5–55°, 5000 cycles) and the other half was stored in distilled water (37?°C, 24?h). The resin-substrate interface was loaded under shear forces in a Universal Testing Machine (1?mm/min). Data (MPa) were analyzed using two-way ANOVA and Tukey`s tests (α?=?0.05). Substrate type, conditioning method and ageing had a significant effect on adhesion values (p?<?.05). In aged conditions, ENA-H, ENA-A, LAV-H, LAV-A, CS2-A (15?±?4 – 11.6?±?5) showed no significant difference (p?>?.05), with the CS2-A (15?±?4) showing the least reduction (5.5%) compared to all other groups (5.8–62.6%). CS1-A (100%) followed by ENA-H, ENA-A (93%), CS2-A (80%) presented the highest incidence of cohesive failures after ageing.     

Aqueous tape casting of B4C ceramics

B₄C green tapes are prepared by aqueous tape casting and a spark plasma sintering (SPS) process using polyethylenimine (PEI) as dispersant, hydroxypropyl methyl cellulose (HPMC) as binder and polyethylene glycol (PEG) as plasticiser. The influences of solid content, dispersant content, mass ratio of plasticiser to binder (R value) and milling time on the slurry viscosity are studied. The samples are characterised by means of hardness tester, universal testing machine and scanning electron microscopy. The results indicate that the solid content of B₄C slurry achieves 47.5?wt-% with milling time of 12?h when the content of PEI, HPMC and PEG is 1.5, 5 and 5?wt-%, respectively. The relative density of B₄C ceramics subject to SPS at 1600°C and 50?MPa for 8?min is up to 97.2%. The Vickers hardness, flexural strength and fracture toughness of B₄C ceramics reach 36.5?±?0.7?GPa, 510.3?±?19.4?MPa and 5.04?±?0.29?MPa?m^?1/2, respectively.     

Polydimethylsiloxane‐modified polyurethane–poly(ɛ‐caprolactone) nanofibrous membranes for waterproof,breathable applications

In this study, we prepared polydimethylsiloxane (PDMS)‐modified polyurethane–poly(?‐caprolactone) nanofibrous membranes with excellent waterproof, breathable performances via an electrospinning technique. Field emission scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and mechanical testing were used to characterize the morphologies and properties of the composite nanofibers. The fiber diameter and porous structure of the membranes were regulated by the adjustment of the temperatures of thermal treatment and the PDMS concentrations. The fibrous membranes obtained at a typical temperature of 70 °C possessed an optimized fibrous structure with a diameter of 514 ± 2 nm, a pore size of 0.55–0.65 µm, and a porosity of 77.7%. The resulting nanofibrous membranes modified with 5 wt % PDMS were endowed with good waterproof properties (water contact angle = 141 ± 1°, hydrostatic pressure = 73.6 kPa) and a high breathability (air permeability rate = 6.57 L m^?2 s^?1, water vapor transmission rate = 9.03 kg m^?2 day^?1). Meanwhile, the membranes exhibited robust mechanical properties with a high strength (breakage stress = 11.7 MPa) and excellent thermal stability. This suggests that they would be promising candidates for waterproof, breathable applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46360.     

Synthesis and characterization of polymers from soybean oil and p‐dinitrosobenzene

In this study, rubbery, bio‐based thermoset polymers were synthesized from soybean oil (SO) and p‐dinitrosobenzene (DNB) via an ene reaction. Polymeric p‐dinitrosobenzene (PDNB) was synthesized from p‐quinone dioxime and was thermally depolymerized in the presence of SO. SO/PDNB polymers were synthesized by a two‐stage polymerization. During the reaction, the role of different parameters such as mol ratio of SO and PDNB, preheating temperature of SO, polymerization time, and temperature were examined. Polymerization was followed by IR spectroscopy, and the polymers obtained were characterized by dynamic mechanical analysis, thermogravimetric analysis, and differential scanning calorimetry. The polymers have glass transition temperature ranging from ?51.5°C to ?46.3°C, whereas their storage moduli are between 430 and 210 MPa at ?60°C. Thermogravimetric analysis reveals that all of the polymers have temperatures of maximum degradation around 500°C. The crosslinked network structure of the polymers was investigated by swelling behavior and surface hardness test. Methyl oleate was used as a model compound to examine the chemical structure of the products. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Oleic acid-modified superhydrophobic ZnO nanostructures via double hydrothermal method

Superhydrophobic ZnO nanostructures (ZNs) are synthesized via double hydrothermal method without any surface chemical modification. The water contact angle (CA) was approximately ～150?±?2°. A subsequent chemical treatment with oleic acid (OA) contributed to a superhydrophobic surface with a water CA of 162?±?2°. X-ray diffraction pattern revealed high crystalline quality ZNs with hexagonal wurtzite phase. The crystallite size was approximately ～23?nm. Field-emission scanning electron microscopy images display nanosheet formations assembled in flower-, cauliflower-, and nanorod-like ZNs. The CA of ZNs surfaces increased steadily from 152?±?2° to 162?±?2° when the OA weight percentage increased from 2?mg to 10?mg. Furthermore, UV–Vis spectra of ZNs indicated that the absorption band of all samples is distinguished in the ultraviolet region. All ZnO samples were maintained at room temperature for 1?h to 5 months to examine the stability of the structure surface.     

Fabrication of transparent Y2O3 ceramics with record-high thermal shock resistance

Sintering-additive-free fine-grained highly transparent Y₂O₃ ceramics featuring record-high thermal shock resistance were fabricated using commercial powders via vacuum pre-sintering (1375–1550?°C) followed by hot-isostatic pressing (1450?°C). The sample pre-sintered at 1450?°C provides the optimum microstructure for post HIPing, which resulted in a grain size of 0.64?μm. The transmittance, microhardness and fracture toughness of the thus HIPed sample are 80.8% at 1100?nm and 65.5% at 400?nm (1.2?mm thick), 8.0?±?0.02?GPa and 1.00?±?0.06?MPa?m^1/2, respectively. The thermal conductivity increases from 13.1 to 16.5?W/m/K with increasing vacuum pre-sinterin Proc. SPIE-Int. Soc. Opt g temperature from 1450 to 1550?°C. This hybrid sintering method realized high thermal conductivity and high strength simultaneously. Consequently, the thermal shock resistance of the HIPed specimen vacuum pre-sintered at 1450?°C in this work is the highest ever reported to the best of our knowledge, which makes the developed material a promising candidate for high-power laser host and IR dome.     

Biaxial flexural strength and Weilbull characteristics of adhesively luted hybrid and reinforced CAD/CAM materials to dentin: effect of self-etching ceramic primer versus hydrofluoric acid etching

Abstract

This study evaluated the influence of the surface treatment and aging on the biaxial flexural strength of ceramic materials cemented to a dentin analogue. One hundred twenty disc-shaped specimens were allocated into 12 groups considering three study factors: ceramic material (lithium disilicate, leucite-based ceramic and hybrid ceramic), surface treatment (10% hydrofluoric acid etching?+?silane or self-etching glass-ceramic primer) and Aging (with 10,000 thermocycles of 5–37–55?°C or without). A tri-layer assembly was designed to mimic a cemented restoration (Variolink N) into a dentin analogue. All samples were submitted to the biaxial flexural strength assay. The flexural strength in MPa was calculated using the finite element method for each sample considering thickness, material properties, and the load to fracture during the in vitro test. Fractographic analysis was also performed. The data was evaluated using three-way ANOVA and Tukey test (α?=?5%). ANOVA showed influence for the Material*Treatment*Aging interaction on the flexural strength (p?=?0.011). The highest strength was calculated for lithium disilicate ceramic?+?self-etching ceramic primer without aging (499?±?17?MPa)^A and the lowest value for hybrid ceramic material?+?acid etching with aging (424?±?48?MPa)^E. According to the Weibull modulus, the most predictable strength was calculated for lithium disilicate?+?acid etching after aging. Acid etching or self-etching ceramic primer promotes similar immediate biaxial flexural strength for each evaluated ceramic. In the long-term, superior strength was observed using acid etching for lithium disilicate and the self-etching ceramic primer for the hybrid ceramic while no difference was observed for leucite-based ceramic.

Clinical implications: Some protocols combining the CAD/CAM ceramic material and the surface treatment could present suitable and stable flexural strength.     

Synthesis and Characterization of Novel Polyamides Containing Purine Moiety

A series of new polyamides (inherent viscosities between 0.61 and 1.84?dL?g^?1) were prepared directly by low-temperature polycondensation of a new purine-moiety-containing diamines, 7,10-bis(4-aminopheny) adenine, with various acyl dichlorides in N-methyl-2-pyrrolidinone. The resultant polymers showed glass transition temperatures between 312–339°C and 5% weight loss temperatures ranging from 405 to 513 and 378 to 485°C in nitrogen and air atmosphere, respectively. Some polymers were amorphous and could be cast into transparent, light-colored, and flexible films with tensile strengths of 84–110?MPa, elongations at break of 8.4–16.5%, and tensile modulus of 3.3–5.5?GPa.