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Journal of Dental Sciences Oct 2023The strength of aligners themselves has a high decay rate and is susceptible to accelerated degradation in the environment. The purpose of this study was to compare...
BACKGROUND/PURPOSE
The strength of aligners themselves has a high decay rate and is susceptible to accelerated degradation in the environment. The purpose of this study was to compare three types of invisible aligner films after being immersed in coffee, tea, cola, and red wine for seven days and to evaluate the changes in their strengths.
MATERIALS AND METHODS
Three types of invisible aligner plates with a thickness of 0.75 mm, i.e., Duran T (polyethylene terephthalate glycol, PETG), Biolon (polyethylene terephthalate, PET), and Zendura FLX (polyurethane, PU), were soaked in artificial saliva and four drinks (coffee, tea, cola, red wine) for 1, 4, and 7 days. The strength test was performed by using the three-point bending test method. The residual strength ratio for the same type of invisible correction film at the same time was separately recorded. The independent -test was used to indicate significant differences at < 0.05.
RESULTS
The Biolon invisible correction film soaked in cola, red wine and artificial saliva showed significant differences on the 1st and 4th days ( < 0.05). The Duran T invisible correction film soaked in coffee and artificial saliva showed significant differences on the first day ( < 0.05). The Zendura FLX invisible correction film had a waterproof layer on the surface, and there was no significant difference between soaking in any drink and soaking in saliva ( > 0.05).
CONCLUSION
Invisible correction films with different ingredients soaked in solutions show a strength decay phenomenon, except for those with TPU ingredients.
PubMed: 37799905
DOI: 10.1016/j.jds.2023.06.017 -
Pharmaceuticals (Basel, Switzerland) Oct 2023Meloxicam (MX) is a nonsteroidal anti-inflammatory drug (NSAID) used mainly to reduce pain, inflammation, and fever. In the present study, thermosensitive polyurethane...
Meloxicam (MX) is a nonsteroidal anti-inflammatory drug (NSAID) used mainly to reduce pain, inflammation, and fever. In the present study, thermosensitive polyurethane (PU)-based hydrogels with various excipients (PEG, PVP, HPC, and essential oil) were prepared and loaded with MX. Rheological investigations were carried out on the PU-based formulations in various shear regimes, and their viscoelastic characteristics were determined. The average size of the PU micelles was 35.8 nm at 37 °C and slightly increased at 37 nm in the presence of MX. The zeta potential values of the hydrogels were between -10 mV and -11.5 mV. At pH = 6 and temperature of 37 °C, the formulated PU-based hydrogels loaded with MX could deliver significant amounts of the active substance, between 60% and 80% over 24-48 h and more than 90% within 2 weeks. It was found that anomalous transport phenomena dominated MX's release mechanism from the PU-based networks. The results are encouraging for further studies aiming to design alternative carriers to commercial dosage forms of nonsteroidal anti-inflammatory drugs.
PubMed: 38004376
DOI: 10.3390/ph16111510 -
Materials (Basel, Switzerland) Mar 2024Invisible orthodontic aligners are having a great impact on tooth movement in an aesthetic and effective way. Different techniques, models, and clinical aspects have...
Invisible orthodontic aligners are having a great impact on tooth movement in an aesthetic and effective way. Different techniques, models, and clinical aspects have been studied for their proper use. However, the aim of this research has been to determine the effect of the shaping process on mechanical properties and their bacterial behavior. For this study, 40 original polyurethane plates and 40 identical models, obtained by hot forming the original plates, were used. The static tensile mechanical properties were studied with a Zwick testing machine using testing speeds of 5 mm/min at a temperature of 37 °C. The original plate and the aligner have been studied with a creep test by subjecting the samples to a constant tension of 30 N, and determining the elongation using a long-distance, high-resolution microscope at different time periods between 1 and 720 h. Studies of water absorption has been realized with artificial saliva for 5 h. Bacterial cultures of and strains were grown on the original plates and on new and used models, to determine the proliferation of each bacterium through metabolic activity, colony-forming units, and LIVE/DEAD assays. The mechanical results showed an increase in the strength of the inserts with respect to the models obtained from 3.44 to 3.95 MPa in the elastic limit and a lower deformation capacity. It has been proven that the transition zone in the creep curves lasts longer in the original plate, producing the rapid increase in deformation at a shorter time (400 h) in the aligner. Therefore, the shaping process reduces the time of dental correction exerted by the aligner. The results of the bacterial culture assays show an increase in the number of bacterial colonies when the aligners have been used and when the polyurethane is conformed due to the internal energy of the model, with respect to the original polyurethane. It has been observed that between the original plate and the aligner there are no statistically significant differences in water absorption and therefore the forming process does not affect water absorption. A slight increase in water absorption can be observed, but after five hours of exposure, the increase is very small.
PubMed: 38541514
DOI: 10.3390/ma17061360 -
Polymers Sep 2023The depletion of natural resources and increasing environmental apprehension regarding the reduction of harmful isocyanates employed in manufacturing polyurethanes (PUs)... (Review)
Review
The depletion of natural resources and increasing environmental apprehension regarding the reduction of harmful isocyanates employed in manufacturing polyurethanes (PUs) have generated significant attention from both industrial and academic sectors. This attention is focused on advancing bio-based non-isocyanate polyurethane (NIPU) resins as viable and sustainable substitutes, possessing satisfactory properties. This review presents a comprehensive analysis of the progress made in developing bio-based NIPU polymers for wood adhesive applications. The main aim of this paper is to conduct a comprehensive analysis of the latest advancements in the production of high-performance bio-based NIPU resins derived from lignin and tannin for wood composites. A comprehensive evaluation was conducted on scholarly publications retrieved from the Scopus database, encompassing the period from January 2010 to April 2023. In NIPU adhesive manufacturing, the exploration of substitute materials for isocyanates is imperative, due to their inherent toxicity, high cost, and limited availability. The process of demethylation and carbonation of lignin and tannin has the potential to produce polyphenolic compounds that possess hydroxyl and carbonyl functional groups. Bio-based NIPUs can be synthesized through the reaction involving diamine molecules. Previous studies have provided evidence indicating that NIPUs derived from lignin and tannin exhibit enhanced mechanical properties, decreased curing temperatures and shortened pressing durations, and are devoid of isocyanates. The characterization of NIPU adhesives based on lignin and tannin was conducted using various analytical techniques, including Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), matrix-assisted laser desorption/ionization with time-of-flight (MALDI-TOF) mass spectrometry, and gel permeation chromatography (GPC). The adhesive performance of tannin-based NIPU resins was shown to be superior to that of lignin-based NIPUs. This paper elucidates the potential of lignin and tannin as alternate sources for polyols in the manufacturing of NIPUs, specifically for their application as wood adhesives.
PubMed: 37835913
DOI: 10.3390/polym15193864 -
ACS Omega Feb 2024Synthesizing polymeric materials that are both sustainable and practical has become a priority. Polyurethanes (PUs) are becoming more popular because of their countless...
Synthesizing polymeric materials that are both sustainable and practical has become a priority. Polyurethanes (PUs) are becoming more popular because of their countless applications and exclusive properties in many sectors. While considering the current issue of environmental problems and the excessive use of petroleum products, nonisocyanate PU (NIPU) are favored due to their sustainability and low toxicity compared to conventional PU. In this work, flexible NIPU films were made using a green and facile method. For that, soybean oil (SBO) was used as the starting material and converted into epoxide SBO, followed by its chemical conversion into carbonated SBO (CSBO) using carbon dioxide gas. Following that, the CSBO reacted with three different aliphatic amines, namely, 1,2-ethylenediamine, 1,4-butylenediamine, and 1,6-hexamethylenediamine, in a solventless and catalyst-free system. The films were cast and cured at 85 °C for different curing times. The effects of the aliphatic diamines and curing times on the NIPU films were evaluated. The individual materials were confirmed with Fourier transform infrared, H nuclear magnetic resonance, and gel permeation chromatography. To analyze the thermal and mechanical properties, thermogravimetric analysis, dynamic mechanical analysis, and differential scanning calorimetry were performed. Furthermore, mechanical tests such as hardness and tensile strength were also performed along with the degree of swelling, gel content, and contact angle by using several solvents. This study elucidated the structure-property relationship based on the effect of curing time and aliphatic chain size of diamines in the properties of a NIPU film. The satisfactory thermal and mechanical properties, accompanied by a green and facile approach, displayed the potential scalability of the NIPU films.
PubMed: 38343913
DOI: 10.1021/acsomega.3c09185 -
Biomedical Optics Express Sep 2023We propose a new, user-friendly and accessible approach for fabricating thin phantoms with controllable absorption properties in magnitude, spectral shape, and spatial...
We propose a new, user-friendly and accessible approach for fabricating thin phantoms with controllable absorption properties in magnitude, spectral shape, and spatial distribution. We utilize a standard office laser color printer to print on polyurethane thin films (40 - 60 m), commonly available as medical film dressings and ultrasound probe covers. We demonstrate that the optical attenuation and absorption of the printed films correlate linearly with the printer input settings (opacity), which facilitates a systematic phantom design. The optical and acoustic properties of these polyurethane films are similar to biological tissue. We argue that these thin phantoms are applicable to a wide range of biomedical applications. Here, we introduce two potential applications: (1) homogeneous epidermal melanin phantoms and (2) spatially resolved absorbers for photoacoustic imaging. We characterize the thin phantoms in terms of optical properties, thickness, microscopic structure, and reproducibility of the printing process.
PubMed: 37791261
DOI: 10.1364/BOE.491695 -
Toxicology and Industrial Health Aug 2023This paper provides an overview of airborne methylene diphenyl diisocyanate (MDI) concentrations in workplaces across North America and Europe. A total of 7649 samples... (Review)
Review
This paper provides an overview of airborne methylene diphenyl diisocyanate (MDI) concentrations in workplaces across North America and Europe. A total of 7649 samples were collected between 1998 and 2020 by producers of MDI during product stewardship activities at customer sites, primarily using validated OSHA or ISO sampling and analysis techniques. As would be expected from the low vapor pressure of MDI, 80% of the concentrations were less than 0.01 mg/m (1 ppb) and 93% were less than 0.05 mg/m (5 ppb). Respiratory protection is an integral part of Industrial Hygiene practices; therefore, its use was studied and summarized. While covering a variety of MDI applications, a large number of samples was obtained from composite wood manufacturing facilities, offering specific insight into potential exposures associated with different process sections and job types in this industry sector. Given the potential presence in industrial processes of MDI-containing dust or aerosols, future work should place increased emphasis on also investigating dermal exposure. The data reported in this paper provide valuable information for product stewardship and industrial hygiene purposes throughout the MDI-processing industry.
Topics: Industry; Isocyanates; Occupational Exposure; Occupational Health
PubMed: 37269111
DOI: 10.1177/07482337231176604 -
Polymers Sep 2023Three-dimensional (3D) printing is a versatile manufacturing method widely used in various industries due to its design flexibility, rapid production, and mechanical...
Three-dimensional (3D) printing is a versatile manufacturing method widely used in various industries due to its design flexibility, rapid production, and mechanical strength. Polyurethane (PU) is a biopolymer frequently employed in 3D printing applications, but its susceptibility to UV degradation limits its durability. To address this issue, various additives, including graphene, have been explored to enhance PU properties. Graphene, a two-dimensional carbon material, possesses remarkable mechanical and electrical properties, but challenges arise in its dispersion within the polymer matrix. Surface modification techniques, like polydopamine (PDA) coating, have been introduced to improve graphene's compatibility with polymers. This study presents a method of 3D printing PU scaffolds coated with PDA and graphene for enhanced UV stability. The scaffolds were characterized through X-ray diffraction, Fourier-transform infrared spectroscopy, mechanical testing, scanning electron microscopy, and UV durability tests. Results showed successful PDA coating, graphene deposition, and improved mechanical properties. The PDA-graphene-modified scaffolds exhibited greater UV resistance over time, attributed to synergistic effects between PDA and graphene. These findings highlight the potential of combining PDA and graphene to enhance the stability and mechanical performance of 3D-printed PU scaffolds.
PubMed: 37765597
DOI: 10.3390/polym15183744 -
Medicina (Kaunas, Lithuania) Mar 2024: Nucleotide delivery has emerged as a noteworthy research trend in recent years because of its potential utility in addressing a range of genetic defects resulting in...
: Nucleotide delivery has emerged as a noteworthy research trend in recent years because of its potential utility in addressing a range of genetic defects resulting in the presence of incorrect nucleotides. The primary goals of this research were to create and to characterize polyurethane microstructures, with the aim of utilizing them for nucleotide transport. : Two samples were prepared using an aliphatic diisocyanate in reaction with a mixture of polyethylene glycol and polycaprolactone diol, where 2'-deoxycytidinic acid was used as the active agent and glycerol 1,2-diacetate was used as an enhancer of the aqueous solubility. The solubility, pH, size distribution, and surface charge of the samples were measured, and encapsulation efficacy and release, cell proliferation, and irritation tests on mouse skin were conducted. : The results showed almost neutral acidic-basic structures with a high heterogeneity, and a medium tendency to form clusters with non-cytotoxic and non-irritative potentials. : Future research could explore the efficacy of this carrier in delivering other nucleotides, as well as investigating the long-term effects and safety of these microstructures in vivo.
Topics: Animals; Mice; Drug Carriers; Polyurethanes; Polyethylene Glycols; Solubility; Nucleotides
PubMed: 38541217
DOI: 10.3390/medicina60030491 -
Preparation and Properties of UV-Curable Waterborne Polyurethane Acrylate/MXene Nanocomposite Films.Nanomaterials (Basel, Switzerland) Nov 2023In this study, waterborne polyurethane acrylate (WPUA)/MXene nanocomposite films with varying MXene loadings were fabricated using UV-curing technology, where MXene...
In this study, waterborne polyurethane acrylate (WPUA)/MXene nanocomposite films with varying MXene loadings were fabricated using UV-curing technology, where MXene (TiCT) was employed as a nanofiller. The microstructure and chemical structure of the WPUA/MXene nanocomposite films were examined by XRD and FTIR, respectively. The water contact angle testing demonstrated that the incorporation of MXene into the nanocomposite films led to an increase in their hydrophilic properties. The tensile strength, the elongation at break, and Young's modulus of the WPUA/MXene nanocomposite coatings exhibited an initial increase followed by a decrease with increasing MXene loadings. Compared to the pure WPUA film, the tensile strength and elongation at break of nanocomposites with 0.077 wt% MXene loading reached their maximum values, which increased by 39.9% and 38.5%, respectively. Furthermore, the glass transition temperature and the thermal stability were both enhanced by MXene to some extent. This study introduces a novel method for utilizing MXene in UV-curable waterborne coatings.
PubMed: 38063718
DOI: 10.3390/nano13233022