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Effects of Thermal Cycling on Surface Hardness, Diametral Tensile Strength and Porosity of an Organically Modified Ceramic (ORMOCER)-Based Visible Light Cure Dental Restorative Resin
Published in P. Mereena Luke, K. R. Dhanya, Didier Rouxel, Nandakumar Kalarikkal, Sabu Thomas, Advanced Studies in Experimental and Clinical Medicine, 2021
Dental restorative polymer composite materials based on polymerizable bisphenol-A glycidyl methacrylate (Bis-GMA) monomers [1, 2] and quartz/radiopaque glass fillers has been the most popular materials used in dentistry, since Bowen [1, 2] introduced (Bis-GMA) in the 1960s. Though they have good aesthetic and physical properties [3], attempts including few structural variations in the organic matrix of dental composites are going on to improve the clinical performance of restorative materials [4–14]. Among these modifications, urethane dimethacrylates (UDMAs), [4] urethane tetramethacrylates, [5] organically modified ceramics (ORMOCERS) [6,-13], and bioactive materials [14] are included.
Nano-Sized CT Contrast Agents *
Published in Valerio Voliani, Nanomaterials and Neoplasms, 2021
Nohyun Lee, Seung Hong Choi, Taeghwan Hyeon
Smaller radiopaque nanoparticles with higher iodine contents of ~55% were prepared by emulsion polymerization of an iodinated monomer, 2-methacryloyloxyethyl(2,3,5-triidobenzoate) (MAOETIB, Fig. 4.7b) [40]. Later, the colloidal stability of the nanoparticles was improved by copolymerization of MAOETIB and a low concentration of glycidyl methacrylate (GMA) [41]. After intravenous injection of p(MAOETIB-GMA) nanoparticles, signals of blood pool and macrophage-rich organs such as lymph nodes, liver, and spleen were increased. Because the nanoparticles were cleared by healthy liver parenchyma, tumors in the liver were revealed at 4 h after injection (Fig. 4.8). Multimodal radiopaque magnetic particles were also prepared by coating p(MAOETIB-GMA) particles via nucleation of γ-Fe2O3 nanoparticles on the surface [42]. These particles were used as a bimodal contrast medium for CT and MRI during embolization processes.
Biomaterial, Host, and Microbial Interactions
Published in Mary Anne S. Melo, Designing Bioactive Polymeric Materials for Restorative Dentistry, 2020
The predominant base monomer used for the polymeric matrix is 2,2-bis[4(2-hydroxy-3-methacryloxypropoxy)-phenyl] propane, also known as bisphenol A glycidyl methacrylate (BisGMA) (Bowen 1956). BisGMA is a high-molecular-weight monomer that has low chain mobility due to the hydrophobic aromatic rings in its backbone (Delaviz et al. 2014). The high viscosity of BisGMA, due to the pi-pi interactions between the aromatic rings and the hydrogen bonding within the molecule, prevents a high amount of filler from being added and reduces the degree of conversion in the polymer. To overcome this, diluent monomers, such as triethylene glycol dimethacrylate (TEGDMA), urethane dimethacrylate (UDMA), and ethoxylated bisphenol A based dimethacrylate (Bis-EMA) (Figure 5.1), are mixed with BisGMA to increase the efficiency of polymerization, decrease the overall viscosity, and enhance resin mobility, thereby improving the handling and manipulation of the material (Delaviz et al. 2014; Ferracane 2011; Santerre et al. 2001; Smith 1985).
The cytotoxic and oxidative effects of restorative materials in cultured human gingival fibroblasts
Published in Drug and Chemical Toxicology, 2021
Neslihan Celik, Damla Binnetoglu, Nurcan Ozakar Ilday, Ahmet Hacimuftuoglu, Nilgun Seven
The remaining monomer, filling particles, and other components may be released from restorative materials. Triethylene glycol dimethacrylate (TEGDMA), bisphenol A-glycidyl methacrylate (BisGMA), urethane dimethacrylate (UDMA), 2-hydroxyethyl methacrylate (HEMA), and methyl methacrylate (MMA) have been reported to be released from the resin matrix due to inadequate polymerization (Lee et al.2006). Mercury released from the amalgam fillings has been reported to cause increased levels of mercury in body fluids such as blood, plasma, and saliva, and also to accumulate in various tissues. In addition, transition metals, such as mercury, have been implicated in the oxidative destruction of biological macromolecules. Toxicity caused by these metals has therefore been considered to be at least in partly due to the generation of the oxidative tissue damage (Stohs and Bagchi 1995, Mutter et al.2004).
Poly(glycerol methacrylate)-based degradable nanoparticles for delivery of small interfering RNA
Published in Pharmaceutical Development and Technology, 2018
Noha G. Morsi, Shimaa M. Ali, Sherouk S. Elsonbaty, Ahmed A. Afifi, Mostafa A. Hamad, Hui Gao, Mahmoud Elsabahy
Aminated linear trimethylethylenediamine poly(glycerol methacrylate) polymer was synthesized and characterized as reported previously (Gao et al. 2010). Glycidyl methacrylate was polymerized in THF using methyl 2-bromo-2-methylpropionate as initiator to yield linear PGMA (L-PGMA) (Mn = 8000, polydispersity = 1.19, as determined by gel permeation chromatography using THF as eluent). The L-PGMA was then modified with N, N, N′-trimethylethylenediamine (T), by ring-opening reaction of the epoxide groups to obtain ALT-PGMA. Briefly, ALT-PGMA was dissolved in acetonitrile, followed by addition of excess amine (amine/epoxy group 3:1 molar ratio) to ensure the completion of the reaction. The mixture was refluxed at 90 °C overnight under argon. The solution was cooled down, and the products were dialyzed (Spectra/Por RC, cutoff 15,000) against water (water soluble LT) for 48 h. Polymer was then freeze-dried to obtain the pure products (yields ca. 90–95%).
Reduced administration frequency for the treatment of fungal keratitis: a sustained natamycin release from a micellar solution
Published in Expert Opinion on Drug Delivery, 2020
Yiyuan Guo, Fatemeh Karimi, Qiang Fu, Greg. G. Qiao, Hong Zhang
In the present study, we report a straightforward method to initiate drug release where the environment itself is used to initiate intrinsic changes to the chemical structure of the micelles. As a result, these changes can enhance the drug release into the outer environment without entire particle degradation. In order to achieve this, we developed a micellar delivery system by synthesizing a biocompatible poly(ethylene glycol)-block-poly(glycidyl methacrylate) (PEG-b-PGMA). Of particular note, the hydrolysis of hydrophobic segments usually occurred at a non-neutral pH in previous study. The glycidyl methacrylate units have been explored for post-polymerization modifications through ring opening reactions of the epoxy group by a nucleophilic agent at neutral pH [22,23]. Taking this advantage, the incorporation of PGMA into micellar carrier can intrinsically alter overall structural hydrophilicity at neutral pH, inducing drug release in a sustained manner for topical administration on eye. For the first time, we reported the preparation of the micelles via self-assembly of the block copolymers where partial of the epoxy groups (approximately 15 units) were used for cross-linking to covalently stabilize the micelles and the remaining epoxy groups (approximately units) can undergo sustained hydrolysis at neutral pH to enhance self-initiated drug release over prolonged time periods. Additionally, PEGylated shell of the micelles can enhance the contact time with the mucus layer of the tear film, act as mucoadhesion promoters and enhance the corneal penetration of the drug-loaded micelles [24,25]. This system was used as a new delivery platform for the sustained and controlled long-term release of hydrophobic natamycin in vitro and in vivo to treat fungal keratitis.