1. Effect of sucrose concentration on streptococcus mutans adhesion to dental material surfacesAnamarija Zore, Franc Rojko, Nives Matijaković Mlinarić, Jona Veber, Aleksander Učakar, Roman Štukelj, Andreja Pondelak, Andrijana Sever Škapin, Klemen Bohinc, 2024, izvirni znanstveni članek Povzetek: Enamel demineralization, known as dental caries, is instigated by the bacterium Streptococcus mutans, which generates acid during carbohydrate metabolism. Among carbohydrates, sucrose is the most cariogenic and capable of biofilm formation. This study aimed to explore and comprehend Streptococcus mutans’ adherence to two prevalent dental material surfaces, i.e., a cobalt–chromium(Co-Cr) alloy and a resin-based composite, under the influence of various sucrose concentrations. To understand bacterial adhesion, the surfaces were characterized using profilometry, tensiometry, and surface charge measurements. Bacterial adhesion was evaluated using scanning electron microscopy and crystal violet dye methods. Results revealed that the composite surface exhibited greater rough-ness compared with the Co-Cr alloy surface. Both surfaces displayed hydrophilic properties and a negative surface charge. Bacterial adhesion experiments indicated lower bacterial adherence to the Co-Cr alloy than to the composite surface before the addition of sucrose. However, the introduction of sucrose resulted in biofilm development on both surfaces, showcasing a similar increase in bacterial adhesion, with the highest levels being observed at a 5% sucrose concentration in the bacterial suspension. In conclusion, the findings suggest sucrose-rich foods could facilitate bacterial adaptation despite less favorable surface characteristics, thereby promoting biofilm formation.
Ključne besede: bacterial adhesion, streptococcus mutans, dental material surfaces, sucrose concentration
Objavljeno v DiRROS: 31.01.2024; Ogledov: 171; Prenosov: 63
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2. Antibacterial effect of polymethyl methacrylate resin base containing TiO2 nanoparticlesAnamarija Zore, Anže Abram, Aleksander Učakar, Ivo Godina, Franc Rojko, Roman Štukelj, Andrijana Sever Škapin, Rajko Vidrih, Olivera Dolić, Valentina Veselinović, Klemen Bohinc, 2022, izvirni znanstveni članek Povzetek: Restorations in dentistry must reproduce the aspect of the patient’s natural teeth and require non-toxicity, biocompatibility, and good mechanical properties in order to last longer. Restorations are permanently in contact with microbes that can adhere to and form biofilms. The purpose of this study was to determine the adhesion extent of Streptococcus mutans to polymethyl methacrylate (PMMA) resin base containing TiO2 nanoparticles. To understand the adhesion of Streptococcus mutans on the modified resin-based surfaces, the following surface properties were measured: the roughness, contact angle, zeta potential and CIE color parameters. Evaluation of tensile stress performance in TiO2 modified PMMA showed that the maximum tensile stress of the modified PMMA resin decreases with an increasing amount of TiO2 nanoparticles. The increasing amount of TiO2 decreases the roughness and causes contact angles in the border between hydrophilic and hydrophobic surfaces. All the studied surfaces are negatively charged and added TiO2 tends to increase the zeta potential. The addition of TiO2 nanoparticles increases the lightness and decreases the intensity of the red and yellow color. The increasing addition of TiO2 nanoparticles into PMMA increases the morphological change of bacterial cells.
Ključne besede: bacterial adhesion, Streptococcus mutans, polymethyl methacrylate resin, TiO2, surface properties
Objavljeno v DiRROS: 20.12.2023; Ogledov: 145; Prenosov: 76
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3. Polypropylene blends with m-EPR copolymers : mechanical and rheological propertiesIztok Švab, Anđela Pustak, Matjaž Denac, Andrijana Sever Škapin, Mirela Leskovac, Vojko Musil, Ivan Šmit, 2018, izvirni znanstveni članek Povzetek: The effects of two metallocene ethylene-propylene-based elastomers (m-EPR1 and m-EPR2) differing in molecular mass and viscosity on mechanical, rheological and interfacial properties were compared. The m-EPR elastomers were added to iPP in 2.5, 5, 10, 15, and 20 vol.%. Torque values, elongation at break and impact strength measured of the iPP/m-EPR1 blends were higher than the iPP/m-EPR2 blends due to higher molten viscosity of m-EPR1 than m-EPR2 copolymer. Slight differences in Young moduli as well as in tensile strength at yield and at break might indicate that tensile properties of iPP/m-EPR blends were not significantly affected by difference in viscosity or molecular mass, miscibility and spherulite size. Optimization diagrams indicated the metallocene m-EPR copolymers are efficient impact modifiers for polypropylene and showed good balancing of mechanical properties in iPP/m-EPR blends.
Ključne besede: isotactic polypropylene, metallocene ethylene-propylene-based elastomers, blend, mechanical properties, adhesion parameters
Objavljeno v DiRROS: 13.12.2023; Ogledov: 184; Prenosov: 85
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4. Antifungal effect of polymethyl methacrylate resin base with embedded Au nanoparticlesIvan Marić, Anamarija Zore, Franc Rojko, Andrijana Sever Škapin, Roman Štukelj, Aleksander Učakar, Rajko Vidrih, Valentina Veselinović, Marijan Gotić, Klemen Bohinc, 2023, izvirni znanstveni članek Povzetek: Full and partial restorations in dentistry must replicate the characteristics of the patient’s natural teeth. Materials must have good mechanical properties and be non-toxic and biocompatible. Microbes, which can form biofilms, are constantly in contact with restorations. In this study, we investigate how well Candida albicans adheres to a polymethyl methacrylate (PMMA) resin base with gold (Au) nanoparticles. We synthesized Au nanoparticles and characterized them. The average size of Au nanoparticles embedded in PMMA was 11 nm. The color difference ∆E between PMMA and PMMA/Au composites was 2.7 and was still esthetically acceptable to patients. PMMA/Au surfaces are rougher and more hydrophilic than pure PMMA surfaces, and the isoelectric point of both types of surfaces was 4.3. Above the isoelectric point, PMMA/Au surfaces are more negatively charged than PMMA surfaces. The added Au nanoparticles decreased the tensile strength, while the hardness did not change significantly. Adhesion measurements showed that PMMA surfaces modified with Au nanoparticles reduced the extent of microbial adhesion of Candida albicans.
Ključne besede: fungal adhesión, C. albicans, polymethyl methacrylate resin, Au, surface properties, composites
Objavljeno v DiRROS: 24.07.2023; Ogledov: 346; Prenosov: 137
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5. Biophysical properties of foamed and solid polymers used in orthotics and prostheticsKlemen Bohinc, Anže Abram, Anamarija Zore, Roman Štukelj, Ana Lenarčič, Rajko Vidrih, Andrijana Sever Škapin, 2021, izvirni znanstveni članek Povzetek: Orthotic and prosthetic materials should have good mechanical and antibacterial properties. Therefore, in our study, we consider four common foamed closed-cells and two solid polymeric materials regarding their mechanical behaviour and tendency for bacterial adhesion. For all materials, the surface roughness, hydrophobicity, zeta potential, tensile properties, hardness and CIE color parameters were measured. We found that foamed polymeric materials have higher roughness, higher hydrophobicity, lower Young's modulus, lower maximum tensile strength and lower hardness than solid materials. Bacterial adhesion test measurements based on observation by scanning electron microscopy show much a lower adhesion extent of S. aureus on solid materials than on foamed materials. The measured biophysical properties could be the key data for users to select the optimal materials.
Ključne besede: surface characterization, bacterial adhesion, foamed materials, prosthetic and orthotic material, surfaces
Objavljeno v DiRROS: 22.05.2023; Ogledov: 253; Prenosov: 164
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6. Deposition of chitosan on plasma-treated polymers : a reviewAlenka Vesel, 2023, pregledni znanstveni članek Povzetek: Materials for biomedical applications often need to be coated to enhance their performance, such as their biocompatibility, antibacterial, antioxidant, and anti-inflammatory properties, or to assist the regeneration process and influence cell adhesion. Among naturally available substances, chitosan meets the above criteria. Most synthetic polymer materials do not enable the immobilization of the chitosan film. Therefore, their surface should be altered to ensure the interaction between the surface functional groups and the amino or hydroxyl groups in the chitosan chain. Plasma treatment can provide an effective solution to this problem. This work aims to review plasma methods for surface modification of polymers for improved chitosan immobilization. The obtained surface finish is explained in view of the different mechanisms involved in treating polymers with reactive plasma species. The reviewed literature showed that researchers usually use two different approaches: direct immobilization of chitosan on the plasma-treated surface or indirect immobilization by additional chemistry and coupling agents, which are also reviewed. Although plasma treatment leads to remarkably improved surface wettability, this was not the case for chitosan-coated samples, where a wide range of wettability was reported ranging from almost superhydrophilic to hydrophobic, which may have a negative effect on the formation of chitosan-based hydrogels.
Ključne besede: polymer surfaces, chitosan, coatings, plasma-surface modification, adhesion
Objavljeno v DiRROS: 24.02.2023; Ogledov: 388; Prenosov: 212
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7. A method for the immobilization of chitosan onto urinary cathetersAlenka Vesel, Nina Recek, Rok Zaplotnik, Albert Kurinčič, Katja Kuzmič, Lidija Fras Zemljič, 2022, izvirni znanstveni članek Povzetek: A method for the immobilization of an antibacterial chitosan coating to polymeric urinary medical catheters is presented. The method comprises a two-step plasma-treatment procedure, followed by the deposition of chitosan from the water solution. In the first plasma step, the urinary catheter is treated with vacuum-ultraviolet radiation to break bonds in the polymer surface film and create dangling bonds, which are occupied by hydrogen atoms. In the second plasma step, polymeric catheters are treated with atomic oxygen to form oxygen-containing surface functional groups acting as binding sites for chitosan. The presence of oxygen functional groups also causes a transformation of the hydrophobic polymer surface to hydrophilic, thus enabling uniform wetting and improved adsorption of the chitosan coating. The wettability was measured by the sessile-drop method, while the surface composition and structure were measured by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. Non-treated samples did not exhibit successful chitosan immobilization. The effect of plasma treatment on immobilization was explained by noncovalent interactions such as electrostatic interactions and hydrogen bonds.
Ključne besede: polymer, chitosan immobilization, adhesion, plasma-surface modification, biopolymers
Objavljeno v DiRROS: 05.12.2022; Ogledov: 461; Prenosov: 282
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