Methacrylate Research Articles

Synthesis of Hybrid Epoxy Methacrylate Resin Based on Diglycidyl Ethers and Coatings Preparation via Cationic and Free-Radical Photopolymerization

A series of difunctional epoxy methacrylate resins (EAs) containing at least one epoxy and at least one methacrylate group were synthesized by means of an addition reaction between epoxy-terminated diglycidyl ethers and methacrylic acid. In order to investigate the impact of polymer architecture on the course of addition reactions and further coating properties, several different types of diglycidyl ethers, i.e., linear, containing aliphatic or aromatic rings, with a short or polymeric backbone, were employed in the synthesis. The carboxyl-epoxide addition esterification reactions have been found to, in a relatively straightforward manner, control the extent of acrylation depending on the substrate feed ratio and reaction time. The structure of obtained pre-polymers was evaluated by FT-IR and NMR methods. At the same time, the extent of addition reactions was validated via quantitative analysis, including non-volatile matter content (NV), acid value (PAVs), and epoxy equivalent value (EE) analysis. The modification was carried out in a manner likely to create a compound with one epoxy and one carbon-carbon pendant group. Hence, due to the presence of both functionalities, it is possible to crosslink compositions based on synthesized EAs via two distinct mechanisms: (i) cationic polymerization or (ii) free-radical polymerization. Synthesized epoxy methacrylate pre-polymers were further employed for use in formulate photocurable coating compositions by the cationic or radical process. Furthermore, the photopolymerization behavior and properties of cured coatings were explored regarding some structural factors and parameters. The investigated polymeric materials cure in a short time to obtain coatings with good properties, which is why they can be successfully used to produce protective and decorative coatings for many industries.

Polymethyl methacrylate resin containing ε-poly-L-lysine and 2-methacryloyloxyethyl phosphorylcholine with antimicrobial effects

Statement of problemPolymethyl methacrylate (PMMA) is commonly used in dentistry, including as a denture base material. However, the colonization of a PMMA surface by microbial microorganisms could increase the risk of oral diseases such as denture stomatitis and gingivitis. The development of PMMA with antibacterial properties should improve its clinical application, but whether adding ε-poly-L-lysine (ε-PL) and 2-methacryloyloxyethyl phosphorylcholine (MPC) provides antimicrobial effects is unclear. PurposeThis in vitro study aimed to develop a novel antibacterial PMMA resin containing the natural nontoxic antibacterial agent ε-PL and the protein repellent agent MPC. The mechanical properties, protein repellency, and antimicrobial activities of the resin were then evaluated. Material and methodsDifferent mass fractions of ε-PL and MPC were mixed into PMMA as the experimental groups, with unaltered PMMA as the control group. The flexural strength (n=10) and surface roughness (n=6) of the resulting mixtures were measured to determine their mechanical properties. The antiprotein properties were measured by using the micro bicinchoninic acid method (n=6). The antimicrobial effect of the resin was assessed using live/dead staining (n=6) and methyltransferase (MTT) assays (n=10). According to the variance homogeneity and normal distribution results, 1-way analysis of variance followed by the Tukey honestly significant difference test or the Welch test and the Games-Howell test were used (α=.05 for all tests). ResultsNo significant differences were found in the flexural strength values and surface roughness of the specimens containing 1.5% MPC and 1.5% ε-PL compared with those of the control (P>.05). The addition of ε-PL to the PMMA resin alone significantly increased its bactericidal properties (P<.05). Adding both ε-PL and MPC further increased the antibacterial activity of the PMMA resin without increasing protein adhesion more than in the control group. ConclusionsThe incorporation of both ε-PL and MPC into PMMA improved its antibacterial capacity without affecting its mechanical properties and did not increase protein adhesion. Therefore, the novel PMMA fabricated in this study shows promise for dental applications.

Antibacterial Effect of Zirconia Nanoparticles on Polyethyl Methacrylate Resin for Provisional Crowns.

Mid-to-long term use of provisional crowns in the oral cavity is associated with bacterial adhesion and biofilm formation, thus necessitating provisional crowns exhibiting antibacterial properties to prevent the occurrence of gingivitis and periodontal disease. This study aimed to evaluate the antibacterial effect of zirconia nanoparticle-containing polyethyl methacrylate (PEMA) resin for provisional restorations. Zirconia nanoparticles were added to the monomer of PEMA resin for provisional restorations, and the mixture was stirred for 2 h using a magnetic stirrer. Disk-shaped specimens were prepared by mixing the polymer with the nanoparticle solution. The control group contained pure PEMA resin samples, and the experimental groups Group Z2, Group Z4, and Group Z8 included PEMA resin specimens containing 2, 4, and 8% w/v zirconia nanoparticles, respectively. After analyzing the sample surfaces, the antibacterial effect of the specimens was evaluated using Streptococcus mutans. Statistical analysis was performed using Tukey's test and Mann-Whitney U-test, according to the normality result in the Shapiro-Wilk test. FE-SEM and EDX analyses revealed the successful addition of zirconia nanoparticles. Results showed no significant difference in the measured values for surface roughness and contact angle between the experimental and control groups; however, adhesion and biofilm thickness of S. mutans were significantly decreased in Group Z2, Group Z4, and Group Z8 compared to the control group (P < 0.05, P < 0.01, P < 0.01, respectively). The addition of zirconia nanoparticles can lower the incidence of adhesion and biofilm thickness of S. mutans on PEMA resin used for provisional crowns. Thus, incorporating zirconia nanoparticles in repair materials for provisional crowns and PEMA resin can produce an antibacterial effect and prevent gingivitis, periodontal disease, and dental caries.

Tuning of Dielectric Properties of Polymers by Composite Formation: The Effect of Inorganic Fillers Addition

Polymer blend or composite, which is a combination of two or more polymers and fillers such as semiconductors, metals, metal oxides, salts and ceramics, are a synthesized product facilitating improved, augmented or customized properties, and have widespread applications for the achievement of functional materials. Polymer materials with embedded inorganic fillers are significantly appealing for challenging and outstanding electric, dielectric, optical and mechanical applications involving magnetic features. In particular, a polymer matrix exhibiting large values of dielectric constant (ε′) with suitable thermal stability and low dielectric constant values of polymer blend, having lesser thermal stability, together offer significant advantages in electronic packaging and other such applications in different fields. In this review paper, we focused on the key factors affecting the dielectric properties and its strength in thin film of inorganic materials loaded poly methyl meth acrylate (PMMA) based polymer blend (single phase) or composites (multiple phase), and its consequences at low and high frequencies are explored. A wide range of different types of PMMA based polymer blends or composites, which are doped with different fillers, have been synthesized with specific tailoring of their dielectric behavior and properties. A few of them are discussed in this manuscript, with their different preparation techniques, and exploring new ideas for modified materials.

Antibacterial Effect of Polymethyl Methacrylate Resin Base Containing TiO2 Nanoparticles

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.

Effect Of Vaccinium Macrocarpon On Candida Albicans Adhesion To Denture Base Resin

Objective&#x0D; This study aimed to assess the effectivenessof Vaccinium macrocarpon (cranberry)extract on Candida albicans adhesion tocranberry added denture base biomaterial.&#x0D; Method&#x0D; Different proportions of cranberryextract were incorporated into polymer of polymethyl methacrylate (PMMA) self - cure resin material forfabricationfifty of 4 mm x 4mm x 2mm samples. Group I contained 0 wt/wt% cranberry was used as control group. 0.5wt/wt%, 1.0 wt/wt%, 1.5 wt/wt% and 2 wt/wt% was graded as Group II to V in order.Addition of 0.1mL of Candida albicans suspension was done in each well of tissue culture plate and incubated for 48 hours. 2% cranberrywasused as disinfectant solution in four serial dilutions at undiluted, 1:10, 1:100, 1:1000 ratio. Immersion of resin samples in disinfectant solution was done for 10 minutes. A colony forming unit was measuredafter 0.1mL of the solution was plated on as sabouraud dextrose agar (SDA) plate and cultured for 72 hours. Data were subjected to statistical analysis.&#x0D; Results&#x0D; The mean colony forming units (CFU) per mL showed that there were severalconfluent colonieswith all proportions of cranberry extract added poly methyl methacrylate (CA-PMMA) resin samplesin undiluted and 1:10 dilution state with both distilled water and cranberry disinfectants. While immersion indistilled waterat 1 :100 dilution, mean CFU/mL was 2.99 0.29in all groups of CA-PMMA. In 1 :1000 dilution state, the mean SD was 117 0.42.Immersion in cranberry solution at 1:100 and 1:1000 showed 2.65 0.66 and 1.26 0.59 for all groups of CA-PMMA. On comparison between distilled water and cranberry as disinfectants, a statistically significant difference was noted with all groups as p &lt; 0.043. Insignificant variation was observed within the groups with both disinfectants as p &gt; 0.05.&#x0D; Conclusion&#x0D; Adherence of Candida albicans to cranberry added self-cure poly methyl methacrylate biomaterial was evidenced to be less irrespective of extract proportions of 1%, 1.5% and 2% in PMMA.Cranberry’s effectiveness as disinfectant showed lesscandida growth when compared to distilled water immersion. This infers that cranberry has anti-adherence property when used both as a polymer constituent material as well as disinfectant solution.

Comparison of the marginal accuracy of metal copings fabricated by 3D-printed resin and milled polymethyl methacrylate - An in vitro study.

Computer-aided design/computer-aided manufacturing (CAD/CAM) systems have gained popularity over the traditional laboratory procedures in dentistry. In the conventional metal casting technique by burnout of a pattern, instead of using a wax pattern (which has several disadvantages), milled polymethyl methacrylate (PMMA) and 3D-printed resin patterns can also be used. The objective of the study was to assess and compare the marginal accuracy of single-crown cobalt-chromium (Co-Cr) metal copings fabricated using milled PMMA and 3D-printed resin patterns. Digital designing was done for metal coping on a prepared typodont mandibular molar using 3Shape Dental Design software. Standard Tessellation Language document of CAD design was used to fabricate 3D-printed resin patterns (Sprintray 3D printer) and milled PMMA patterns (CAD/CAM milling machine CoriTEC). A total of ten Co-Cr copings were casted, of which five belonged to Group A: 3D-printed resin and the other five to Group B: milled PMMA. The copings were assessed for marginal fit at eight different points using a stereomicroscope. Statistical analysis was done using an independent t-test. The t-test revealed a significant difference between the mean marginal gap values of the two groups, with the marginal gap values for the 3D-printed resin group (82.21 ± 15.26 μm) being lesser than that of the milled PMMA group (106.75 ± 12.76 μm). The marginal accuracy of copings fabricated using 3D-printed resin patterns was superior to that of copings fabricated from milled PMMA patterns.

The Medical Study of Denture Base Resin Poly(Methyl Methacrylate) Reinforced by ZnO and TCP Nanoparticles

Denture base poly (methyl methacrylate (PMMA) resin is one of the most frequently used materials in denture base synthesis, but due to its poor mechanical properties, PMMA can be considered a medium for the attachment and growth of a variety of pathogenic bacteria and fungi, particularly due to PMMA's pores and rough surface. The porosity percentage and surface roughness of the PMMA resin sample was lowered in this study, which resulted in a reduction in microorganisms' surface adhesion by varying the ratios of additives such as zinc oxide (ZnO) and tri-calcium phosphate (TCP) nanoparticles with (1, 2, 3, and 10% wt percent) for each additive separately, and 3% as a combination of ZnO and TCP nanoparticles in an equal ratio. Additionally, mechanical features such as surface hardness are developed, which is a critical attribute for polishing and easy finishing, as well as offering great scratch resistance during denture base cleaning. These results indicated that when compared to the other groups, PMMA (ZnO wt. 1%) and TCP-wt. 1%) reinforced composite resins demonstrated the best optimum properties. Additionally, it was discovered that adding 1% of NPs improved the mechanical qualities, which benefited the biological properties by reducing bacterial adherence to the PMMA composite resin.

To evaluate allergic effects of the residual monomer by using auto polymerised acrylic resins amongst dentists.

Objective: To evaluate the allergic effects of the residual monomer by using auto polymerised acrylic resins amongst dentists. Study Design: Cross Sectional study. Setting: Department of Prosthdontics, Isra Dental College, Hyderabad. Period: June 2019 to October 2019. Material &amp; Methods: The study consists of 50 participants included Prosthodontist specialists, general dental practitioners and dental students. All contributors that filled a questionnaire regarding the allergic effects after using auto polymerised poly methyl methacrylate resin, identity of all participants will be kept private after taking consent. In questionnaire asked the questions from the contributors regarding the designation, qualification, usage duration, organs affected by allergy by using poly methyl meth acrylate resin, any medical treatment acquired for allergy and what kind of precautions used for prevention of allergy. Data was analyzed thru SPSS version 21. Descriptive statistics such as frequency distribution, percentage were included in Data analysis. The level of significance was set at &lt;0.05%. Results: This current study discovered that out of 50 participants, 64% were students, 25% general dentists and 10% specialists. Out of 50 participants, maximum participants 45% found the skin allergic reaction and minimum 8% found respiratory tract. Only 10 participants acquired the treatment and consults the doctor for allergic reactions and 25 participants did not acquired any treatment. Conclusion: Conclusion of this study was that the maximum contributors had allergic effects to the skin while many participants did not acquired or followed any therapeutic service to avoid surplus effects.

Calculation model of the stressed state of the tooth contact zone of surface-hardened gears

Stress state of the surface layer in the contact zone of mating teeth of cylindrical gears has been studied. It is established that stressed state of contact surfaces in the meshing pole of mating teeth is characterized not only by surface contact stresses, but also by deep equivalent stresses. It is shown that under contact loading the stressed state of surface layer is heterogeneous and changes with distance from the surface. Analysis and substantiation of calculation model for stressed state of diffusion layer in contact zone of mating teeth of surface-hardened gears are performed. Value of coefficient, which takes into account influence of normal stresses on efficiency of tangential ones, is specified. Reliability and validity of model of calculation of stressed condition of surface layer in contact zone of mating teeth of surface-hardened gears were estimated according to results of full-scale bench tests of the gears made of cemented steel 20ХГНР. The values of contact stresses in tooth meshing pole were corrected considering the load concentration across the width of cogged ring gear. Spalling depth of damaged teeth was determined by measuring impressions taken from the teeth of each examined gear with methacrylic resin. It is established that the nucleation zone of deep contact pitting for gears with 6.5 mm module is on the depth of occurrence of calculated maximum equivalent shear stresses. The consistency of the calculation results with the experimental data shows the validity of the calculated stress-strain model for involute gears.

Biological Evaluation of the Effect of Root Canal Sealers Using a Rat Model.

Gutta-percha points and root canal sealers have been used for decades in endodontics for root canal obturation. With techniques such as single cone methods, the amount of sealer is larger, making their properties more critical. However, relatively few reports have comprehensively evaluated their biological effects. To this end, we evaluated three types of sealers, zinc oxide-fatty acid-, bio-glass- and methacrylate resin-containing sealers were considered. Their biological effects were evaluated using a rat subcutaneous implantation model. Each sealer was loaded inside a Teflon tube and implanted subcutaneously in the backs of rats. Inflammatory cells were observed around all samples 7 days after implantation and reduced after 28 days. Our results revealed that all samples were in contact with the subcutaneous tissue surrounding the sealer. Additionally, Ca and P accumulation was observed in only the bio-glass-containing sealer. Furthermore, each of the three sealers exhibited unique immune and inflammatory modulatory effects. In particular, bio-glass and methacrylate resin sealers were found to induce variable gene expression in adjacent subcutaneous tissues related to angiogenesis, wound healing, muscle tissue, and surrounding subcutaneous tissue. These results may help to understand the biological impacts of root canal sealers on surrounding biological tissues, guiding future research and comparisons with new generations of materials.

Preparation of Molecularly Imprinted Polymer Microspheres for Selective Solid-Phase Extraction of Capecitabine in Urine Samples.

Molecularly imprinted solid-phase extraction to treat biological samples has attracted considerable attention. Herein, molecularly imprinted polymer (MIP) microspheres with porous structures were prepared by a combined suspension-iniferter polymerization method using capecitabine (CAP) as a template molecule. This material was subsequently used as a solid-phase extraction agent to separate and enrich drug molecules in urine samples. UV analysis revealed that methacrylate (MAA) was an ideal functional monomer, and 1H Nuclear Magnetic Resonance (1H NMR), Ultraviolet (UV), and Fourier transform-infrared (FT-IR) spectroscopic analyses were used to study the interaction forces between MAA and CAP, demonstrating that hydrogen bonding was the primary interaction force. MIPs with outstanding selectivity were successfully prepared, and the analysis of their surface morphology and chemical structure revealed a spherical morphology with small holes distributed across a rough surface. This surface morphology significantly reduced the mass transfer resistance of template molecules, providing an ideal template recognition effect. Using the molecularly imprinted solid-phase extraction method, CAP and the structural analog cytidine (CYT) were pretreated in urine samples and quantified by HPLC. The results showed that CAP and CYT recoveries reached 97.2% and 39.8%, respectively, with a limit of detection of 10.0–50.0 µg·mL−1. This study provides a novel approach to drug molecule pretreatment that can be applied in drug separation and functional materials science fields.

The Mechanical and Antibacterial Properties of Boron Nitride/Silver Nanocomposite Enhanced Polymethyl Methacrylate Resin for Application in Oral Denture Bases.

The introduction of nanomaterials into polymethyl methacrylate (PMMA) resin has been effective for mechanically reinforcing PMMA for application in oral denture bases. However, these methods cannot simultaneously improve the mechanical and antibacterial properties, which limits widespread clinical application. Here, we self-assembled binary nanocomposites of boron nitride nanosheets (h-BNNs) and silver nanoparticles (AgNPs) as nanofillers and incorporated the nanofillers into PMMA. The aim of this study was to achieve antibacterial effects while significantly improving the mechanical properties of PMMA and provide a theoretical basis for further clinical application. We employed scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy (Raman), Ultraviolet visible spectrum (UV) and atomic force microscopy (AFM) to investigate the microscopic morphology and composition of PMMA containing nanocomposites with different mass fraction. In addition, the content of the h-BNNs/AgNPs was 1 wt%, and the compressive strength and flexural strength of pure PMMA were improved by 53.5% and 56.7%, respectively. When the concentration of the nanocomposite in the PMMA resin was 1.4 wt%, the antibacterial rate was 92.1%. Overall, synergistically reinforcing PMMA composite resin with a multi-dimensional nanocomposite structure provided a new perspective for expanding not only the application of resins in clinical settings but also the research and development of new composite resins.

Marginal and Internal Gap of Metal Copings Fabricated Using Three Types of Resin Patterns with Subtractive and Additive Technology: An In Vitro Comparison.

This study analyzes the evidence of the marginal discrepancy and internal adaptation of copings fabricated using three types of resin patterns with subtractive (milling) and additive technology (3D printing), as it is not widely reported. Working casts (n = 15) were scanned and patterns were completed using computer-aided designing (CAD). Resin patterns were fabricated using the designed data and divided into three groups according to the method of fabrication of patterns: subtractive technology–CAD milled polymethyl methacrylate resin (Group-PMMA), additive technology [digital light processing (DLP) technique]–acrylonitrile–butadiene–styrene (ABS) patterns (Group-ABS), and polylactic acid (PLA) patterns (Group-PLA). Resin patterns were casted with Cobalt–Chromium (Co–Cr) alloy (lost wax technique). Internal and marginal gaps of the metal copings were analyzed with the replica technique under optical microscope. The Kruskal–Wallis test was used to compare values among the groups, and post hoc multiple tests confirmed the specific differences within the groups. The median marginal gap was least for CAD milled resin patterns, followed by PLA printed resin patterns and ABS printed resin patterns. There were significant differences between Group-PMMA and Group-PLA and Group-ABS (p = 0.0001). There was no significant difference between Group-PLA and Group-ABS (p = 0.899). The median internal gap was least for metal copings fabricated from Group-PLA, followed by Group-ABS and Group-PMMA. The differences were not statistically significant (p = 0.638) for the internal gap. Full metal Co–Cr copings fabricated from the milled PMMA group had a better marginal fit, followed by the PLA and ABS printed groups. Copings fabricated with the PLA printed group had the best internal fit, though the values were statistically insignificant between the groups.

Semi-interpenetrating Network-Coated Silica Gel Based on Green Resources for the Efficient Adsorption of Aromatic Pollutants from Waters

In the framework of the development of green analytical chemistry, a silica gel (SG) coated with a semi-penetrating network based on the partially biosourced poly(ethersulfone) is studied for a greener extraction process of aromatic organic pollutants. An optimized composition of the semi-penetrating network (80% of the linear polymer (LP): isosorbide-based poly(ethersulfone) and 20% cross-linking agent (XP) type bismaleimide) leads to a total adsorption of the selected aromatic pollutants, whatever their hydrophilicity. Adsorption characteristic, kinetics and isotherms of the SG-semi-INP LP80/XP20 for p-hydroxybenzoic acid and for toluic acid were studied. Langmuir model led to a better fitting of the adsorption isotherms; the adsorption of toluic acid is easier than that of p-hydroxybenzoic acid. 1/n values of benzoic acid was lower for SG-semi-INP LP80/XP20 compared to biochar and to cross-linked methacrylate resin, showing a higher adsorption efficiency.

Effects of cross-linking agents and radiopacifying fillers on degree of conversion and volumetric shrinkage of denture based methacrylic resins

"Development of experimental dental prostheses formulations based on methacrylic resins. The effect Study, on the degree of conversion (DC) and volumetric shrinkage (VS), of four crosslinking agents: DEDGMA, TEGDMA, TETRAEGDA and TMPTA and four radiopacifying mineral fillers: ZrO2, TiO2, SrO and BaO2. The experimental resins are compared to commercial products. The (DC) determination of the experimental and commercial resins was carried out by FTIR in ATR mode. The (VS) was determined experimentally by the Archimed’s method. Chemical structure and weight content of crosslinking agents affected (DC) and (VS). (DC) and (VS) increased with the crosslinking agent chain length and weight contents. Additionally, whatever filler contents and metal nature, (DC) values remains ≥ 99.5%, in accordance with the standards required for residual monomers level tolerated in dental prostheses (&lt;0.45%). (VS) values varied between 4,8 and 10,8%. For two commercial resins, (DC) values were less than 99% while (VS) was in accordance with the standards (5-6%): 6.2% for Major base and 4.3% for Hiflex H."

Comparison analysis of poly ether ketone and poly methyl metha acrylate used in prosthodontia for dentures

Introduction- Several materials have been introduced in dentistry for dentures for over last century. Poly Ether Ether Ketone (PEEK) has adequate flexural strength as a denture base and thereby prolonging its clinical longevity and also overcoming the most common reason for failure of Poly Methyl Metha Acrylate (PMMA) denture base that frequently results in the fracture. Aim- The aim and objective of the present study is to evaluate and compare the flexural strength and hardness of heat-cured PMMA denture base with PEEK. Material and methods- The sample size comprised of 60 samples of PMMA and PEEK which were prepared and divided into two groups i.e.; group I and group II respectively, of 30 each. Both the groups were further divided into subgroups consisting of 15 samples of PMMA and PEEK. The flexural strength was test in group I specimens by universal testing machine (UTM), and group II samples was subjected to hardness test using Vickers microhardness tester. The values were analysed statistically. The unpaired t-test was done for comparison of flexural strength and hardness of PEEK and PMMA.Result-The flexural strength of PEEK was 185 MPa, while that of PMMA was 85 MPa.

Histopathological evaluation of a retinoic acid eluting stent in a rabbit iliac artery model

This study aimed to evaluate the safety and efficacy of innovative retinoic acid (RA) eluting stents with bioabsorbable polymer. Sixty stents divided in ten groups were implanted in the iliac arteries of 30 rabbits. Two polymers (“A”, poly (lactic-co-glycolic acid) and “B”, polylactic acid), and three doses (“Low”, “Medium” and “High”) of RA (groups: AL, AM, AH, BL, BM, BH) were used on cobalt chromium stents (Rontis Corporation), one group of bare stent (C), one group (D) of Everolimus eluting stent (Xience-Pro, Abbot Vascular), and two groups of Rontis Everolimus eluting stents coated with polymer A (EA) and B (EB). Treated arteries were explanted after 4 weeks, processed by methyl methacrylate resin and evaluated by histopathology. None of the implanted stents was related with thrombus formation or extensive inflammation. Image analysis showed limited differences between groups regarding area stenosis (BH, D and EB groups had the lower values). Group BH had lower intimal mean thickness than AH (105.1 vs 75.3 μm, p = 0.024). Stents eluting RA, a non-cytotoxic drug, were not related with thrombus formation and had an acceptable degree of stenosis 4 weeks post implantation. RA dose and type of polymer may play role in the biocompatibility of the stents.

Influence of Block Copolymer Concentration and Resin Crosslink Density on the Properties of UV‐Curable Methacrylate Resin Systems

AbstractAdditive manufacturing is on the verge of replacing established processes in dentistry, as it offers the possibility of manufacturing individual parts simply and cost‐effectively. Due to its suitability for a wide variety of materials and, above all, its high precision, the focus is currently on stereolithographic processes. Intrinsic brittleness of the used multifunctional acrylic monomers remains however one of the major challenges. One promising concept is the use of block copolymers (BCPs) guaranteeing minor effects on 3D‐printing processing and UV‐curing due to initially at least partial solubility, and hence low viscosity impact. A polycaprolactone‐polysiloxane (PCL‐PDMS‐PCL) triblock copolymer is synthesized via ring‐opening polymerization of caprolactone and used in radical UV‐cured methacrylic resin systems. Small angle X‐ray scattering measurements reveal the self‐assembly of the BCPs to objects of around 20 nm prior to curing. Subsequently, thermo‐mechanical characterization is carried out by dynamic mechanical analysis, flexural testing, and fracture toughness measurements (KIC). Transmission electron microscopy and scanning electron microscopy micrographs show a homogenous distribution of the BCPs and effective toughening via cavitation and shear yielding. The influence of the crosslink density on the toughness and the high effectiveness of block copolymers for improving fracture toughness is clearly shown.

Tailoring of Optical Properties of Methacrylate Resins Enriched by HPHT Microdiamond Particles.

Diamond particles have great potential to enhance the mechanical, optical, and thermal properties of diamond–polymer composites. However, the improved properties of diamond–polymer composites depend on the size, dispersibility, and concentration of diamond particles. In the present study, diamond–polymer composites were prepared by adding the microdiamond particles (MDPs) with different concentrations (0.2–1 wt.%) into polymers (acrylate resins) and then subjected to a photocuring process. The surface morphology and topography of the MDPs–polymer composites demonstrated a uniform high-density distribution of MDPs for one wt.% MPDs. Thermogravimetric analysis was employed to investigate the thermal stability of the MDPs–polymer composites. The addition of MDPs has significantly influenced the polymers’ thermal degradation. Absorption and emission spectra of thin layers were recorded through UV/Vis spectrophotometry and spectrofluorimetry. The obtained results revealed a significant increase in the fluorescence intensity of MDPs–polymer composites (at 1 wt.% of MDPs, a 1.5×, 2×, and 5× increase in fluorescence was observed for MDPs–green, MDPs–amber daylight, and MDPs–red resin, respectively) compared with the reference polymer resins. The obtained results of this work show the new pathways in producing effective and active 3D-printed optical elements.