Flexural Properties of Heat-Polymerized PMMA Denture Base Resins Reinforced with Fibers with Different Characteristics.

Polymethylmethacrylate (PMMA) has been the most-widely used denture base material in prosthetic dentistry for the last 80 years. It is still one of the best alternatives when new methods are inapplicable. Due to the lack of some physical inadequacies occurring during cyclic use and accidental situations, various reinforcement strategies such as using nanoparticles, wires, fibers, and meshes have been investigated and reported. In this study, it was aimed to conduct a comparative investigation of the effect of fiber additives with different characteristics on the flexural properties of heat-cured PMMA denture base resins. Glass fibers (GFs), polypropylene fibers (PPFs), and carbon fibers (CFs) having 3, 6, and 12 mm lengths and 0.25, 0.50, and 1.0% concentrations (v/v) were used for the reinforcement of PMMA denture base resins. The flexural properties (flexural strength, flexural modulus, and maximum deformation) were determined using a three-point bending test, and three-way ANOVA analyses with Bonferroni corrections were performed on the test results. The morphologies of the fracture surfaces were analyzed using scanning electron microscopy. All three fibers exhibited reinforcement in the flexural strength (p < 0.001) and flexural modulus (p < 0.001) regardless of their length and concentration. The group with 1.0% 12 mm CF-reinforced PMMA exhibited the greatest flexural strength (94.8 ± 8.8 MPa), and that with 1.0% 3 mm GFs displayed the lowest flexural strength (66.9 ± 10.4 MPa) among the fiber-reinforced groups. The greatest value of the flexural modulus was displayed by the 1.0% 3 mm CF-reinforced resin (3288.3 ± 402.1 MPa). Although the CF-reinforced groups exhibited better flexural properties, CFs are not favorable for use as reinforcement in practice due to the dark gray discoloration of the denture base resin. It was concluded that PPF is a promising material for the reinforcement of heat-cured PMMA denture base resins.

Caffeic Acid Phenethyl Ester Loaded Electrospun Nanofibers for Wound Dressing Application.

Electrospinning is an advantageous method with a wide usage area, which enables the production of materials consisting of nano-thickness fibers. In this study, caffeic acid phenethyl ester (CAPE) molecule was loaded onto the poly(lactic-co-glycolic acid) (PLGA) nanofibers and obtained nanofibers were physicochemically and biologically investigated for the first time in the literature. The existence of CAPE molecules, loaded on PLGA membranes by dropping and spraying methods, was evaluated by a comparative investigation of Fourier-transform infrared (FTIR) spectra and X-Ray diffraction (XRD) patterns. Fiber morphology of the membranes was investigated by scanning electron microscope (SEM). CAPE release and swelling behaviors of the membranes were studied in vitro. The radical scavenging activity of CAPE-loaded wound dressing materials was determined by using an antioxidant assay. The antimicrobial properties of PLGA and CAPE-loaded PLGA membranes were evaluated against S. aureus, P. aeruginosa and C. albicans strains by the time-kill method. The biocompatibility study of the obtained CAPE-loaded fibers conducted on human fibroblast cell line and wound healing promoting effect of the fibers was investigated in vitro scratch assay. The results show that CAPE-loaded PLGA membranes are highly antimicrobial against all strains used in the experiment. Additionally, the results show that they are biocompatible and have wound healing properties on human fibroblasts.

Production of Hypericum perforatum oil-loaded membranes for wound dressing material and in vitro tests.

Hypericum perforatum oil loaded electrospun polymeric wound dressing material was produced in order to be used in wound therapy. H. perforatum oil is known to have curative effect on wound-healing process. Wound dressing material was produced in two layers, upper layer of which was made of electrospun PCL nanofibres in order to maintain membrane integrity and mechanical strength, and bottom layer that is designed to be in contact with the wound was formed by electrospraying and electrospining of PEG/H. perforatum oil and PCL polymer solutions from opposite directions (concurrently). Methods such as FTIR, optical and electron microscopy, tensile tests, gas permeability tests, contact angle and swelling tests, in vitro release tests were utilized for material characterization. Encapsulation of H. perforatum oil in PEG capsules which were hold by PEG fibres among PCL fibres was confirmed. H. perforatum oil was released in controlled manner. Antimicrobial activity tests on Staphylococcus aureus and Escherichia coli revealed that H. perforatum content exhibited antimicrobial activity on both. Material was found to be biocompatible and suitable for use as wound dressing according to the results of in vitro tests, in which L929 mouse fibroblast cell line incubated with materials for investigation of biocompatibility (WST-1) and cell-material interactions (proliferation, apoptosis/necrosis).

Fabrication and characterization of novel starch-grafted poly l-lactic acid/montmorillonite organoclay nanocomposites.

In this work, poly(L-lactic acid)-g-starch layered silicate nanocomposites (NCs) (PLLA-g-starch/MMT) were fabricated by intercalative bulk graft copolymerization of LA with starch, in the presence of either stannous octoate acting as a catalyst or LA-MMT organoclay acting as a cocatalyst-nanofiller. This procedure was performed inside a custom vacuum micro-reactor. To better understand the graft copolymerization mechanism, in situ processing types, interfacial interactions and nanostructure formation of PLLA-g-starch/MMT NCs, methods such as FT-IR, XRD, (1)H NMR, (13)C CP/MAS-NMR, DSC/TGA, TEM and SEM were utilized. The morphology and thermal behaviors of nanocomposites were found to be strongly dependent on the loading mass fraction of LA-MMT within the nanocomposite structure and the type of in situ processing such as interfacial, physical and chemical interactions. Preintercalated LA-MMT organoclay exhibited dual functions. It demonstrated the ability to act as a catalyst, essentially accelerating in situ graft copolymerization via esterification of LA carboxyl groups with hydroxyl groups of starch macromolecules, whilst also acting as a nananofiller-compatibilizer.