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Environmental Science & Technology Oct 2023Microplastics (MP) including tire wear particles (TWP) are ubiquitous. However, their mass loads, transport, and vertical behavior in water bodies and overlying air are...
Microplastics (MP) including tire wear particles (TWP) are ubiquitous. However, their mass loads, transport, and vertical behavior in water bodies and overlying air are never studied simultaneously before. Particularly, the sea surface microlayer (SML), a ubiquitous, predominantly organic, and gelatinous film (<1 mm), is interesting since it may favor MP enrichment. In this study, a remote-controlled research catamaran simultaneously sampled air, SML, and underlying water (ULW) in Swedish fjords of variable anthropogenic impacts (urban, industrial, and rural) to fill these knowledge gaps in the marine-atmospheric MP cycle. Polymer clusters and TWP were identified and quantified with pyrolysis-gas chromatography-mass spectrometry. Air samples contained clusters of polyethylene terephthalate, polycarbonate, and polystyrene (max 50 ng MP m). In water samples (max. 10.8 μg MP L), mainly TWP and clusters of poly(methyl methacrylate) and polyethylene terephthalate occurred. Here, TWP prevailed in the SML, while the poly(methyl methacrylate) cluster dominated the ULW. However, no general MP enrichment was observed in the SML. Elevated anthropogenic influences in urban and industrial compared to the rural fjord areas were reflected by enhanced MP levels in these areas. Vertical MP movement behavior and distribution were not only linked to polymer characteristics but also to polymer sources and environmental conditions.
Topics: Microplastics; Water; Plastics; Seawater; Polyethylene Terephthalates; Polymethyl Methacrylate; Water Pollutants, Chemical; Environmental Monitoring
PubMed: 37853526
DOI: 10.1021/acs.est.3c05002 -
Clinical and Experimental Dental... Apr 2024This study aimed to compare the color change of computer-aided design (CAD)/computer-aided manufacturing (CAM) polymethyl methacrylate (PMMA) denture teeth and...
OBJECTIVE
This study aimed to compare the color change of computer-aided design (CAD)/computer-aided manufacturing (CAM) polymethyl methacrylate (PMMA) denture teeth and conventional acrylic teeth after immersion in three staining beverages (coffee, red tea, and cola) for a day, 7 days, and 30 days.
MATERIALS AND METHODS
Group 1: Conventional acrylic teeth (n = 32). Group 2: Milled CAD/CAM teeth out of PMMA disc (n = 32). The specimens of each material were further divided into four subgroups: (1) Control group, distilled water (n = 16). (2) Red tea solution (n = 16). (3) Coffee solution (n = 16). (4) Cola (n = 16). The color change ( ) was assessed using a spectrophotometer at four time points: at the baseline (t ), on the 1st day (t ), on the 7th day (t ), and the 30th day (t ) of immersion. Kolmogorov-Smirnov test was applied, followed by performing independent samples t test, one-way analysis of variance and post-hoc Tukey tests to compare the color change values at different time points.
RESULTS
The mean score of NBS values of the coffee solution indicates perceivable color change at the end of the 30th day in the conventional acrylic teeth group. It was 0.843 ± 0.395 at t , then increased to 1.017 ± 0.477 at t and to 2.259 ± 1.059 at t . There is a statistically significant difference (p < 0.05) in color change values between both tooth types at the end of the 30th day of immersion in red tea solution and a statistically significant difference at the end of the 7th day (p < 0.05) and the 30th day (p < 0.05) of immersion in coffee solution.
CONCLUSIONS
CAD/CAM PMMA teeth are more color stable than conventional acrylic teeth after 30 days of immersion in coffee and red tea solution.
Topics: Coffee; Polymethyl Methacrylate; Beverages; Computer-Aided Design; Staining and Labeling; Dentures; Tea
PubMed: 38433287
DOI: 10.1002/cre2.869 -
Clinical and Experimental Dental... Oct 2023The aim of this in vitro study was to compare the effect of printing layer thickness on the marginal and internal fit of interim crowns.
OBJECTIVE
The aim of this in vitro study was to compare the effect of printing layer thickness on the marginal and internal fit of interim crowns.
MATERIAL AND METHODS
A maxillary first molar model was prepared for ceramic restoration. Thirty-six crowns were printed with three different layer thicknesses using a digital light processing-based three-dimensional printer (25, 50, and 100 µm [LT 25, LT 50, and LT 100]). The marginal and internal gaps of the crowns were measured with replica technique. An analysis of variance was conducted to determine if there were significant differences between the groups (ɑ = .05).
RESULTS
The marginal gap of LT 100 group was significantly higher than that LT 25 (p = .002) and LT 50 groups (p ≤ .001). The LT 25 group has significantly larger axial gaps than LT 50 group (p = .013); however, there were no statistically significant differences between other groups. The LT 50 group showed the smallest axio-occlusal gap. The mean occlusal gap differed significantly by printing layer thickness (p ≤ .001), with the largest gap occurring for LT 100.
CONCLUSIONS
Provisional crowns printed with 50 µm layer thickness provided the best marginal and internal fit.
CLINICAL SIGNIFICANCE
It is recommended that provisional crowns be printed with a 50 µm layer thickness to ensure optimal marginal and internal fit.
Topics: Polymethyl Methacrylate; Computer-Aided Design; Dental Prosthesis Design; Dental Marginal Adaptation; Crowns; Printing, Three-Dimensional
PubMed: 37386767
DOI: 10.1002/cre2.758 -
The Journal of Prosthetic Dentistry Jun 2024Additive (AM) and subtractive (SM) manufacturing have become popular for fabricating occlusal devices with materials of different chemical compositions. However,...
Effect of material and antagonist type on the wear of occlusal devices with different compositions fabricated by using conventional, additive, and subtractive manufacturing.
STATEMENT OF PROBLEM
Additive (AM) and subtractive (SM) manufacturing have become popular for fabricating occlusal devices with materials of different chemical compositions. However, knowledge on the effect of material and antagonist type on the wear characteristics of occlusal devices fabricated by using different methods is limited.
PURPOSE
The purpose of this in vitro study was to evaluate the effect of material and antagonist type on the wear of occlusal devices fabricated by using conventional manufacturing, AM, and SM.
MATERIAL AND METHODS
Two-hundred and forty Ø10×2-mm disk-shaped specimens were fabricated by using heat-polymerized polymethylmethacrylate (control, CM), AM clear device resin fabricated in 3 different orientations (horizontal [AMH], diagonal [AMD], and vertical [AMV]), SM polymethylmethacrylate (SMP), and SM ceramic-reinforced polyetheretherketone (SMB) (n=40). Specimens were then divided into 4 groups based on the antagonists: steatite ceramic (SC); multilayered zirconia (ZR); lithium disilicate (EX); and zirconia-reinforced lithium silicate (ZLS) used for thermomechanical aging (n=10). After aging, the volume loss (mm) and maximum wear depth (μm) were digitally evaluated. Data were analyzed with 2-way analysis of variance and Tukey honestly significant difference tests (α=.05).
RESULTS
The interaction between the device material and the antagonist affected volume loss and maximum depth of wear (P<.001). AMH had volume loss and depth of wear that was either similar to or higher than those of other materials (P≤.044). When SC was used, CM had higher volume loss and depth of wear than AMV, and, when EX was used, AMD had higher volume loss and depth of wear than SMP (P≤.013). SC and ZR led to higher volume loss of CM and AMH than EX and led to the highest depth of wear for these materials, while ZR also led to the highest volume loss and depth of wear of AMD and AMV (P≤.019). EX led to the lowest volume loss and depth of wear of AMV and SMP and to the lowest depth of wear of AMH (P≤.021). Regardless of the antagonist, SMB had the lowest volume loss and depth of wear (P≤.005).
CONCLUSIONS
AMH mostly had higher volume loss and depth of wear, while SMB had the lowest volume loss, and its depth of wear was not affected by the tested antagonists. ZR mostly led to higher volume loss and maximum depth of wear, while EX mostly led to lower volume loss and maximum depth of wear of the tested occlusal device materials.
Topics: Materials Testing; Dental Materials; Polymethyl Methacrylate; Zirconium; Ceramics; Humans; In Vitro Techniques; Occlusal Splints; Dental Restoration Wear; Dental Prosthesis Design; Benzophenones; Dental Porcelain; Polymers; Surface Properties; Polyethylene Glycols; Ketones
PubMed: 38594086
DOI: 10.1016/j.prosdent.2024.03.026 -
Orthopaedic Surgery Nov 2023To develop a novel semi-cannulated lateral mass screw (SC-LMS) for cervical posterior fixations and compare the fixation stability and safety of SC-LMS with regular...
A Novel Semi-Cannulated Screw Enhanced Bone Cement Augmentation and Pullout Strength in Posterior Cervical Lateral Mass Screw Fixations: An In Vitro Biomechanical and Morphological Study.
OBJECTIVE
To develop a novel semi-cannulated lateral mass screw (SC-LMS) for cervical posterior fixations and compare the fixation stability and safety of SC-LMS with regular solid lateral mass screw (S-LMS) in bone cement augmentation and pullout strength using fresh cadaveric cervical vertebrae.
METHODS
The conventional multiaxial screw for cervical lateral mass fixation was modified to a cannulated screw with two lateral holes, used for bone cement injection in situ. Eight fresh human cervical vertebrae (C3, C4, and C5) were collected and used. μCT scan was performed to evaluate the bone quality of the lateral masses, including bone mineral density (BMD), trabecular thickness (Tb.Th), and trabecular separation (Tb.Sp). SCLMS or S-LMS were randomly inserted into the paired cervical vertebrae and pulled out as a screw loosening model. These screws were reinserted in with bone cement augmentation, scanned by μCT to obtain the bone cement distribution along the screws, and pulled out to test the screw purchase strength.
RESULTS
Fmax values exhibited strong positive correlations with the local BMD (𝑟 = 0.8640, p < 0.0001) and Tb.Th (𝑟 = 0.6795, p = 0.0038), whereas a negative correlation with Tb.Sp (𝑟 = -0.5567, p = 0.0251). A significant difference was observed between the Fmax before and after PMMA injection on the SC-LMS side (p = 0.019). The SC-LMS exhibited lower risk of cement leakage than S-LMS after PMMA injection, and a positive correlation was observed between 𝐹max and the distribution volumes on the SC-LMS side.
CONCLUSION
The novel SC-LMS provides more robust fixation stability and is safer than the S-LMS for PMMA augmentation, which may be related to the cement-screw-cement-bone complex formation.
Topics: Humans; Bone Cements; Polymethyl Methacrylate; Bone Screws; Bone Density; Cervical Vertebrae; Biomechanical Phenomena
PubMed: 37712328
DOI: 10.1111/os.13859 -
Journal of Orthopaedic Surgery and... Sep 2023Polymethylmethacrylate (PMMA) bone cement promotes the development of local thrombi. Our study found that a novel material, ES-PMMA bone cement, can reduce local...
OBJECTIVE
Polymethylmethacrylate (PMMA) bone cement promotes the development of local thrombi. Our study found that a novel material, ES-PMMA bone cement, can reduce local thrombosis. We used a simple and reproducible animal model to confirm the reduction in local thrombosis and explored the associated molecular mechanism.
METHODS
New Zealand rabbits, which were used to model thrombosis using extracorporeal carotid artery shunts, were divided into the following two groups, with 3 rabbits in each group: the PMMA bone cement group and the ES-PMMA bone cement group. Four hours after modelling, experimental samples, including thrombotic and vascular tissues, were collected. Thrombotic samples from the PMMA group and ES-PMMA group were subjected to lncRNA sequencing, and a lncRNA microarray was used to screen the differentially expressed lncRNAs. The expression of thrombomodulin in endothelial cells was quantified in vascular tissue samples. Differences in the lncRNA expression profiles between the thrombotic samples of the PMMA group and ES-PMMA group were assessed by base-to-base alignment in the intergenic regions of genomes. The lncRNA-miRNA-mRNA competitive endogenous RNA (ceRNA) network was established in light of ceRNA theory. Thrombosis was observed in the PMMA group and ES-PMMA group.
RESULTS
The thrombotic weight was 0.00706 ± 0.00136 g/cm in the PMMA group and 0.00551 ± 0.00115 g/cm in the ES-PMMA group. Quantitative real-time polymerase chain reaction (RT-q-CR) and Western blotting revealed that the expression of CD40, which can regulate thrombosis in vascular endothelial cells, was significantly lower in the ES-PMMA group than in the PMMA group. High-throughput sequencing was used to identify 111 lncRNAs with lower expression in the ES-PMMA group than in the PMMA group. Through bioinformatics investigation, lncRNA MSTRG22719.16/ocu-miR-326-5p/CD40 binding sites were selected. Fluorescent in situ RNA hybridization (FISH) was performed to verify the lower expression of lncRNA MSTRG.22719.16 in vascular tissues from the ES-PMMA group. A dual-luciferase reporter gene assay was applied to verify that ocu-miR-326-5p binds the CD40 3'-UTR and targets lncRNA MSTRG.22719.16.
CONCLUSION
Compared with PMMA bone cement, ES-PMMA bone cement can reduce thrombosis through the lncRNA MSTRG.22719.16/ocu-miR-326-5p/CD40 axis.
Topics: Animals; Rabbits; Bone Cements; Polymethyl Methacrylate; RNA, Long Noncoding; Endothelial Cells; Viscosity
PubMed: 37736740
DOI: 10.1186/s13018-023-04109-5 -
Journal of Dentistry May 2024This study aimed to investigate the effect of post-washing duration and crown thickness on the bond strength between additively manufactured crown materials and dental...
OBJECTIVES
This study aimed to investigate the effect of post-washing duration and crown thickness on the bond strength between additively manufactured crown materials and dental cement in vitro.
METHODS
Rectangular-shaped specimens of two thicknesses (1.5 and 2.0 mm) were additively manufactured from permanent VarseoSmile Crown (VC) and long-term temporary NextDent (ND) materials. The specimens were post-washed (n = 160) in ethanol for 5 min, 10 min, 1 h, and 8 h then cemented with dual-cure resin cement. Twenty PMMA (TC) were milled as a control. A chevron-notch test was performed to measure the maximum load until failure (N). Interfacial bond strength (J/m) was calculated and statistically analysed. The mode of failure was analysed by scanning electron microscopy (SEM).
RESULTS
There was a significant difference in the bond strength between all groups (p < 0.01). VC at 1.5mm thickness post-washed for 10 min showed the highest mean bond strength (1.77 ±0.96 J/m) while VC at 2.0mm thickness post-washed for 8 h showed the lowest (0.22 ±0.10 J/m). Exposure to ethanol for 8 h resulted in lower bond strength. Within the type of material, there were no differences in bond strength between the thicknesses when post-washed for the same duration.
CONCLUSIONS
Prolonged post-washing of AM crown materials can significantly decrease the bond strength to resin cement. There were no differences between the permanent and long-term temporary AM materials. When post-washed for 5 min, AM materials observed comparable or higher bond strength values compared to PMMA.
CLINICAL SIGNIFICANCE
The output of this research serves as a guide for dental practitioners, emphasising the importance of adhering to correct post-washing procedures for optimal bond strength of additively manufactured crown materials.
Topics: Ethanol; Dental Bonding; Crowns; Materials Testing; Microscopy, Electron, Scanning; Resin Cements; Time Factors; Humans; Dental Stress Analysis; Surface Properties; Polymethyl Methacrylate; Dental Materials; Stress, Mechanical; Cementation
PubMed: 38316198
DOI: 10.1016/j.jdent.2024.104873 -
Journal of Orthopaedic Surgery and... Aug 2023Non-leaching antibacterial bone cement can generate long-term antibacterial activity, it cannot treat serious infections that have occurred like antibiotic-loaded bone...
BACKGROUND
Non-leaching antibacterial bone cement can generate long-term antibacterial activity, it cannot treat serious infections that have occurred like antibiotic-loaded bone cement. Currently, the antibacterial activity and biocompatibility of non-leaching cement when loaded with antibiotics have yet to be determined.
METHODS
Non-leaching antibacterial nitrofuran bone cement (NFBC) specimens were prepared with low-dose and high-dose antibiotics. The antibacterial activity and biocompatibility of NFBC loaded with vancomycin, gentamicin, and tigecycline were compared. The agar diffusion method was employed to observe the inhibition zone of the samples against two bacterial strains from day one to day seven. The CCK-8 assay and acute liver and kidney toxicity test were conducted to assess the effects of the samples on mouse embryo osteoblast precursor cells and C57 mice, respectively.
RESULTS
Gentamicin-loaded cement exhibited the most potent antibacterial activity, effectively inhibiting both bacterial strains at a low dose. Tigecycline-loaded cement demonstrated superior biocompatibility, showing no acute liver and kidney toxicity in mice and minimal cytotoxicity to osteoblasts.
CONCLUSIONS
NFBC loaded with gentamicin, vancomycin, and tigecycline not only maintains sustained antibacterial activity but also exhibits excellent biocompatibility.
Topics: Animals; Mice; Vancomycin; Gentamicins; Tigecycline; Bone Cements; Anti-Bacterial Agents; Nitrofurans; Polymethyl Methacrylate
PubMed: 37542269
DOI: 10.1186/s13018-023-04055-2 -
Journal of Pharmaceutical Sciences Dec 2023Flow imaging microscopy (FIM) is widely used to characterize biopharmaceutical subvisible particles (SVPs). The segmentation threshold, which defines the boundary...
Flow imaging microscopy (FIM) is widely used to characterize biopharmaceutical subvisible particles (SVPs). The segmentation threshold, which defines the boundary between the particle and the background based on pixel intensity, should be properly set for accurate SVP quantification. However, segmentation thresholds are often subjectively and empirically set, potentially leading to variations in measurements across instruments and operators. In the present study, we developed an objective method to optimize the FIM segmentation threshold using poly(methyl methacrylate) (PMMA) beads with a refractive index similar to that of biomolecules. Among several candidate particles that were evaluated, 2.5-µm PMMA beads were the most reliable in size and number, suggesting that the PMMA bead size analyzed by FIM could objectively be used to determine the segmentation threshold for SVP measurements. The PMMA bead concentrations measured by FIM were highly consistent with the indicative concentrations, whereas the PMMA bead size analyzed by FIM decreased with increasing segmentation threshold. The optimal segmentation threshold where the analyzed size was closest to the indicative size differed between an instrument with a black-and-white camera and that with a color camera. Inter-instrument differences in SVP concentrations in acid-stressed recombinant adeno-associated virus (AAV) and protein aggregates were successfully minimized by setting an optimized segmentation threshold specific to the instrument. These results reveal that PMMA beads can aid in determining a more appropriate segmentation threshold to evaluate biopharmaceutical SVPs using FIM.
Topics: Biological Products; Microscopy; Polymethyl Methacrylate; Refractometry; Particle Size
PubMed: 37813302
DOI: 10.1016/j.xphs.2023.10.007 -
European Journal of Pharmaceutics and... Jun 2024Lipid-polymer nanoparticles offer a promising strategy for improving gene nanomedicines by combining the benefits of biocompatibility and stability associated with the...
Lipid-polymer nanoparticles offer a promising strategy for improving gene nanomedicines by combining the benefits of biocompatibility and stability associated with the individual systems. However, research to date has focused on poly-lactic-co-glycolic acid (PLGA) and resulted in inefficient transfection. In this study, biocompatible Eudragit constructs E100 and RS100 were formulated as lipid-polymer nanoparticles loaded with pDNA expressing red fluorescent protein (RFP) as a model therapeutic. Using a facile nanoprecipitation technique, a core-shell structure stabilised by lipid-polyethylene glycol (PEG) surfactant was produced and displayed resistance to ultracentrifugation. Both cationic polymers E100 (pH-sensitive dissolution at 5) and RS100 (pH-insensitive dissolution) produced 150-200 nm sized particles with a small positive surface charge (+3-5 mV) and high pDNA encapsulation efficiencies (EE) of 75-90%. The dissolution properties of the Eudragit polymers significantly impacted the biological performance in human embryonic kidney cells (HEK293T). Nanoparticles composed of polymer RS100 resulted in consistently high cell viability (80-100%), whereas polymer E100 demonstrated dose-dependent behaviour (20-90% cell viability). The low dissolution of polymer RS100 over the full pH range and the resulting nanoparticles failed to induce RFP expression in HEK293T cells. In contrast, polymer E100-constructed nanoparticles resulted in reproducible and gradually increasing RFP expression of 26-42% at 48-72 h. Intraperitoneal (IP) injection of the polymer E100-based nanoparticles in C57BL/6 mice resulted in targeted RFP expression in mouse testes with favourable biocompatibility one-week post-administration. These findings predicate Eudragit based lipid-polymer nanoparticles as a novel and effective carrier for nucleic acids, which could facilitate pre-clinical evaluation and translation of gene nanomedicines.
Topics: Humans; Animals; Nanoparticles; Hydrogen-Ion Concentration; Plasmids; Transfection; HEK293 Cells; Mice; DNA; Lipids; Polymers; Solubility; Particle Size; Polyethylene Glycols; Red Fluorescent Protein; Polymethacrylic Acids; Male; Acrylates
PubMed: 38643953
DOI: 10.1016/j.ejpb.2024.114299