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Bio-Implants Derived from Biocompatible and Biodegradable Biopolymeric Materials
Published in P. Mereena Luke, K. R. Dhanya, Didier Rouxel, Nandakumar Kalarikkal, Sabu Thomas, Advanced Studies in Experimental and Clinical Medicine, 2021
PLA is fully biodegradable under the composting condition in a large-scale operation with temperatures of 60°C and above (Pranamuda and Tokiwa, 1999). PBS can degrade by hydrolysis mechanism and termed as hydro-biodegradable. The polymer molecular weights reduction takes place by hydrolysis at the ester linkages, further degradation may occur by the actions of microorganisms [38]. Polyethylene (PE) can biodegrade by two mechanisms which are hydro-biodegradation and oxo-biodegradation [36].
What Are Polymeric Carriers?
Published in Mesut Karahan, Synthetic Peptide Vaccine Models, 2021
Gülderen Karakuş, Dolunay Şakar Daşdan
A large number of monomers connected to each other by covalent bonds of molecules are composed of many repeating subunits to form polymer molecule. A polymer is a macromolecule composed of many monomer units or segments. The conversion of ethylene into polyethylene, the most common plastic in the world found in items ranging from shopping bags to storage containers; polymerization is shown in (Figure 6.1).
Packaging and Shelf-Life Evaluation of Shoots
Published in Nirmala Chongtham, Madho Singh Bisht, Bamboo Shoot, 2020
Nirmala Chongtham, Madho Singh Bisht
Formed by polymerization of ethylene, polyethylene is one of the most extensively used and inexpensive food packaging material because of its significant mechanical properties like tensile and tear strength, elasticity, weightlessness, stability, barrier to gases, moisture and chemicals, recyclability and reusability. High density polyethylene (HDPE) and low density polyethylene (LDPE) are the two categories of polyethylene. Because of its stiffness, HDPE is used for making liquid containers, margarine tubs, bags for retail, grocery and scrap and so on, whereas squeezable food bottles, bendy lids, bread and frozen food bags are made up of LDPE due to its flexible and transparent nature.
Interaction between microorganisms and dental material surfaces: general concepts and research progress
Published in Journal of Oral Microbiology, 2023
Yan Tu, Huaying Ren, Yiwen He, Jiaqi Ying, Yadong Chen
The surface charge can also influence the structure of biofilms for an extended period. Terada et al. used the radiation-induced graft polymerization of monomers to modify polyethylene sheets. They introduced diethylamine and sodium sulfite as corresponding functional groups in the experimental research process, opened the epoxy group of GMA under the action of a certain electrostatic force, and then analyzed these modified surfaces to determine their impact on the initial adhesion of E. coli. Statistical analysis of the experimental data showed that the main factor affecting the robustness of the E. coli biofilm was the surface charge property of the substrate, and the correlation with other factors was not obvious. Their research showed that the bottom layer surface based on RIGP had a strong regulatory role in the formation process of this film [46]. Other environmental factors in the complex system may complicate the surface charge impact on biofilms. For example, the formation of salivary pellicles induced a negative charge on the surface, mediating the adhesion of Ca2+ and promoting the adhesion of Fusobacterium nucleatum to the titanium surface [47]. Moreover, the performance of dental materials will significantly impact the density, configuration, and strength-related factors of the formed biofilm [16]. Therefore, further research is needed to clarify how surface charges affect the properties of the biofilm and determine whether surface charges can be customized to promote the integration of host cells and reject or kill bacterial pathogens that cause oral diseases.
Thirteen-year results of cementless total hip arthroplasty with zirconia heads on highly cross-linked polyethylene
Published in Modern Rheumatology, 2021
Yohei Naito, Masahiro Hasegawa, Shine Tone, Hiroki Wakabayashi, Akihiro Sudo
The cementless cup consisted of a titanium alloy metal shell (QPOC; Kyocera, Osaka, Japan) and a highly cross-linked polyethylene shell (Excellink; Kyocera). The surface of the metal shell was porous-coated with pure titanium, and a coating of apatite-wollastonite (AW) glass-ceramic was applied to the porous area. The metal shell was fixed with titanium screws to ensure primary fixation. The highly cross-linked polyethylene shell was gamma-irradiated to 50 kGy, heat annealed, and sterilized with 25 kGy of gamma radiation in nitrogen. The stem was a HS-6 collarless stem made of titanium alloy and was proximally porous-coated with an AW glass-ceramic. Zirconia balls of 26-mm diameter were used for the femoral head. Yttria-stabilized zirconia heads were used, and since 2002, the zirconia heads contained 0.25 wt% alumina (89 THAs).
Crosslinked Polyethylene Demonstrates Substantially Improved Performance at Minimum 10-Year Follow-up Compared to Conventional Polyethylene
Published in Journal of Investigative Surgery, 2021
Recognition of these complications prompted the orthopedic community to investigate different polyethylene formulations and processing techniques. While promising laboratory performance data often preceded the introduction of new materials, clinical performance proved to be marginally improved, at best, and sometimes worse than historically available materials. As investigators began to examine how particular factors influenced wear, the terminal sterilization method was found to be among the most important [1]. Although there is considerable variation among individual patients, CPE liners sterilized with gamma radiation dosages ranging from 2.5 to 4.0 Mrad have demonstrated mean wear rates in the neighborhood of 0.1 mm per year (mm/yr) [1,2]. In contrast, CPE liners terminally sterilized with non-crosslinking chemical surface treatments, such as ethylene oxide or gas plasma, usually have mean rates on the order of 0.2 mm/yr [1,3]. Since terminal sterilization using gamma radiation had demonstrated reduced wear compared to non-crosslinked polyethylene owing to radiation-induced crosslinking despite the presence of residual free radicals that could oxidize prior to implantation or in vivo, there was reason to be optimistic that higher crosslinking dosages coupled with additional processing to reduce or eliminate free radicals might further reduce wear rates. However, laboratory testing indicated that wear reductions tended to decrease with increasing crosslinking dosages and crosslinking was also accompanied by reductions in material properties including ultimate tensile strength and fracture toughness [4,5].