High-Verdet Constant and Low-Optical Loss Tb3+ Doped Magnetite Nanoparticles.

Magneto-optical (MO) polymer nanocomposites have emerged as alternatives to conventional MO crystals, particularly in nanophotonics applications, thanks to their better processing flexibility and superior Verdet constants. However, a higher Verdet constant commonly comes with excessive optical loss due to increased absorption and scattering, resulting in a constant or reduced figure-of-merit (FOM) defined as the Verdet constant over optical loss. By doping magnetite (Fe3O4) nanoparticles with Tb3+ ions, we report a new strategy to enhance the Verdet constant without increasing the optical loss. The Fe3O4:Tb3+ nanocomposite is one of a kind that simultaneously achieves a state-of-the-art Verdet constant of 5.6 × 105 °/T·m and a state-of-the-art FOM of 31°/T in the near-infrared region.

Mass Spectrometry-Based Proteomics of Poly(methylmethacrylate)-Embedded Bone.

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is a widely employed technique in proteomics research for studying the proteome biology of various clinical samples. Hard tissues, such as bone and teeth, are routinely preserved using synthetic poly(methyl methacrylate) (PMMA) embedding resins that enable histological, immunohistochemical, and morphological examination. However, the suitability of PMMA-embedded hard tissues for large-scale proteomic analysis remained unexplored. This study is the first to report on the feasibility of PMMA-embedded bone samples for LC-MS/MS analysis. Conventional workflows yielded merely limited coverage of the bone proteome. Using advanced strategies of prefractionation by high-pH reversed-phase liquid chromatography in combination with isobaric tandem mass tag labeling resulted in proteome coverage exceeding 1000 protein identifications. The quantitative comparison with cryopreserved samples revealed that each sample preparation workflow had a distinct impact on the proteomic profile. However, workflow replicates exhibited a high reproducibility for PMMA-embedded samples. Our findings further demonstrate that decalcification prior to protein extraction, along with the analysis of solubilization fractions, is not preferred for PMMA-embedded bone. The biological applicability of the proposed workflow was demonstrated using samples of human PMMA-embedded alveolar bone and the iliac crest, which revealed anatomical site-specific proteomic profiles. Overall, these results establish a crucial foundation for large-scale proteomics studies contributing to our knowledge of bone biology.

Nanoscale Mechanical Manipulation of Ultrathin SiN Membranes Enabling Infrared Near-Field Microscopy of Liquid-Immersed samples.

Scattering scanning near-field optical microscopy (s-SNOM) is a powerful technique for mid-infrared spectroscopy at nanometer length scales. By investigating objects in aqueous environments through ultrathin membranes, s-SNOM has recently been extended toward label-free nanoscopy of the dynamics of living cells and nanoparticles, assessing both the optical and the mechanical interactions between the tip, the membrane and the liquid suspension underneath. Here, the study reports that the tapping AFM tip induces a reversible nanometric deformation of the membrane manifested as either an indentation or protrusion. This mechanism depends on the driving force of the tapping cantilever, which is exploited to minimize topographical deformations of the membrane to improve optical measurements. Furthermore, it is shown that the tapping phase delay between driving signal and tip oscillation is a highly sensitive observable to study the mechanics of adhering objects, exhibiting highest contrast at low tapping amplitudes where the membrane remains nearly flat. Mechanical responses are correlated with simultaneously recorded spectroscopy data to reveal the thickness of nanometric water layers between membrane and adhering objects. Besides a general applicability of depth profiling, the technique holds great promise for studying mechano-active biopolymers and living cells, biomaterials that exhibit complex behaviors when under a mechanical load.

Optimization of e-beam lithography parameters for nanofabrication of sub-50 nm gold nanowires and nanogaps based on a bilayer lift-off process.

Electron beam lithography (EBL) stands out as a powerful direct-write tool offering nanometer-scale patterning capability and is especially useful in low-volume R&D prototyping when coupled with pattern transfer approaches like etching or lift-off. Among pattern transfer approaches, lift-off is preferred particularly in research settings, as it is cost-effective and safe and does not require tailored wet/dry etch chemistries, fume hoods, and/or complex dry etch tools; all-in-all offering convenient, 'undercut-free' pattern transfer rendering it useful, especially for metallic layers and unique alloys with unknown etchant compatibility or low etch selectivity. Despite the widespread use of the lift-off technique and optical/EBL for micron to even sub-micron scales, existing reports in the literature on nanofabrication of metallic structures with critical dimension in the 10-20 nm regime with lift-off-based EBL patterning are either scattered, incomplete, or vary significantly in terms of experimental conditions, which calls for systematic process optimization. To address this issue, beyond what can be found in a typical photoresist datasheet, this paper reports a comprehensive study to calibrate EBL patterning of sub-50 nm metallic nanostructures including gold nanowires and nanogaps based on a lift-off process using bilayer polymethyl-methacrylate as the resist stack. The governing parameters in EBL, including exposure dose, soft-bake temperature, development time, developer solution, substrate type, and proximity effect are experimentally studied through more than 200 EBL runs, and optimal process conditions are determined by field emission scanning electron microscope imaging of the fabricated nanostructures reaching as small as 11 nm feature size.

Flexible, photoluminescent 0D Cs4PbX6 (X = Br, Br/I)-PMMA composite films for white LED via water-induced recrystallization.

3D CsPbX3 inorganic perovskite materials have attracted much attention in optoelectronic devices because of their strong absorbance, high photoluminescent quantum yield, tunable band gap, and narrow emission bandwidth. However, their practical usefulness is limited due to their poor stability in ambient conditions. Here, we created photoluminescent 0D Cs4PbX6 (X = Br, Br/I) suspensions in toluene by adding a small amount of water. The photoluminescent 0D Cs4PbX6 perovskite was mixed with polymethylmethacrylate (PMMA) forming 0D Cs4PbX6/PMMA composite films with higher PL, stability, transparency, and transmittance than that of the 3D CsPbX3/PMMA composite films prepared separately. Moreover, the PL intensity maintains 90% of the initial value after 30 days in water, showing excellent water stability. The flexible white-light LED device prepared by the composite films illustrated good luminescence performance with color rendering index 74.77, chromaticity coordinates (0.32, 0.33), and color temperature 6997 K.

Assessment of cranial reconstruction utilizing various implant materials: finite element study.

The human head can sometimes experience impact loads that result in skull fractures or other injuries, leading to the need for a craniectomy. Cranioplasty is a procedure that involves replacing the removed portion with either autologous bone or alloplastic material. While titanium has traditionally been the preferred material for cranial implants due to its excellent properties and biocompatibility, its limitations have prompted the search for alternative materials. This research aimed to explore alternative materials to titanium for cranial implants in order to address the limitations of titanium implants and improve the performance of the cranioplasty process. A 3D model of a defective skull was reconstructed with a cranial implant, and the implant was simulated using various stiff and soft materials (such as alumina, zirconia, hydroxyapatite, zirconia-reinforced PMMA, and PMMA) as alternatives to titanium under 2000N impact forces. Alumina and zirconia implants were found to reduce stresses and strains on the skull and brain compared to titanium implants. However, PMMA implants showed potential for causing skull damage under current loading conditions. Additionally, PMMA and hydroxyapatite implants were prone to fracture. Despite these findings, none of the implants exceeded the limits for tensile and compressive stresses and strains on the brain. Zirconia-reinforced PMMA implants were also shown to reduce stresses and strains on the skull and brain compared to PMMA implants. Alumina and zirconia show promise as alternatives to titanium for the production of cranial implants. The use of alternative implant materials to titanium has the potential to enhance the success of cranial reconstruction by overcoming the limitations associated with titanium implants.

Diesters of monoimide of perylene-3,4,9,10-tetracarboxylic acid - Synthesis, characterization, and application for dyeing polyester fibre, polystyrene, and poly (methyl methacrylate) films.

Three dyes-diesters of monoimides of perylene-3,4,9,10-tetracarboxylic acid were synthesized in three-stage process: esterification, hydrolysis, and monoimidation as potential fluorescent light-stable colorants for high visibility safety wear. The structure of these compounds was confirmed by 1H nuclear magnetic resonance spectroscopy and mass spectrometry, and their spectroscopic and physicochemical properties were determined. Colorants were applied to dyeing polyester fibre and polystyrene and poly (methyl methacrylate) films. The light, wash, and rubbing fastness of the dyeings were determined, and chromaticity coordinates were measured and discussed.

Full configurational and conformational analysis of artemisinin by one-bond carbon-carbon residual dipolar couplings at natural abundance.

Configurational and conformational analysis of the biologically relevant natural product artemisinin was conducted using carbon-carbon residual dipolar couplings (1DCC RDCs) at natural abundance. These RDCs were measured through the 2D-INADEQUATE NMR experiment using a sample aligned in a compressed poly (methyl methacrylate) (PMMA) gel swollen in CDCl3. Singular value decomposition (SVD) fitting analysis of all carbon-carbon bonds, 1DCC RDCs, in relation to the full configuration/conformational space (32 diastereoisomers) of artemisinin, unambiguously identified the correct configuration of artemisinin.

Comparison of Locking Plate Alone and Locking Plate Combined with 3D Printed Polymethylmethacrylate Augmentation in Treating Proximal Humerus Fractures in the Elderly.

BACKGROUND: Locking plates are widely used in open reduction internal fixation (ORIF) for proximal humeral fracture (PHF). However, the optimal surgical treatment of unstable, displaced PHF in elderly patients remains controversial. This study aimed to compare the radiological and clinical outcomes of surgical treatment of PHF in the elderly with locking plate (LP) alone and locking plate combined with 3D printed polymethylmethacrylate (PMMA) prosthesis augmentation (LP-PA). METHODS: From May 2015 to April 2021, a total of 97 patients aged ≥ 60 years with acute unstable PHF who underwent osteosynthesis with either LP (46 patients) or LP-PA (51 patients) were retrospectively analyzed. For the LP-PA group, a customized proximal humeral prosthesis made of PMMA cement was intra-operatively fabricated by a three-dimensional (3D) printed prototype mold for the humeral medial support. Radiological outcomes were analyzed by measuring the value of neck-shaft angle (NSA) and humeral head height (HHH). The clinical outcomes were evaluated using Constant-Murley Score (CMS), Disabilities of the Arm Shoulder and Hand (DASH) score, American Shoulder and Elbow Surgeons (ASES) score, and the shoulder range of motion (ROM). Pain was measured using a visual analogue scale (VAS). RESULTS: At the one-year follow-up, all fractures healed radiologically and clinically. The mean changes of NSA and HHH over the follow-up period were markedly smaller in the LP-PA group (3.8 ± 0.9° and 1.7 ± 0.3 mm) than those in the LP group (9.7 ± 2.1° and 3.2 ± 0.6 mm, both P < 0.0001). The LP-PA group also presented lower DASH score (17.1 ± 3.6), higher ASES score (89.5 ± 11.2) and better ROM in forward elevation (142 ± 26°) and external rotation (59 ± 11°) compared to the LP group (28.9 ± 4.8 for DASH score, P < 0.0001; 82.3 ± 9.0 for ASES score, P < 0.001; 129 ± 21° for forward elevation, P = 0.008; and 52 ± 9° for external rotation, P = 0.001). There was no significant difference in overall complication rate between the two groups, although the complication rate of screw perforation was higher in the LP-PA group (P = 0.172). CONCLUSIONS: For PHF in elderly patients, the combination of LP fixation and PMMA prosthesis augmentation effectively improved humeral head support and reduction maintenance, providing satisfactory outcomes both radiologically and clinically. This technique also reduced the incidence of screw perforation associated with plate fixation alone, making it a reasonable option to ensure satisfactory clinical outcomes.

Biofilm Formation is Durably Prevented on Pre-Fabricated Antibiotic Cement Spacers Compared to Cobalt Chrome and Polyethylene.

BACKGROUND: A two-stage revision remains the standard for managing chronic periprosthetic joint infection (PJI). Despite multiple spacer options, whether a particular one better resists biofilm formation remains unclear. Prefabricated polymethylmethacrylate (PMMA) articulating spacers containing antibiotics and a proprietary pore structure were developed to increase antibiotic elution characterized by a rapid burst phase for the initial 1 to 2 days and an extended slow-release phase for > 28 days. This in vitro study determined whether biofilm formation is prevented during the initial rapid burst phase and/or the slow-release phase. METHODS: S. aureus-Xen36 was incubated in 1.5 ml of Luria-Bertani broth with PMMA discs with the proprietary pore structure either with or without gentamycin and vancomycin, or with 'Hoffman style' positive-control discs (ultra-high molecular weight polyethylene (UHMWPE) or cobalt-chrome). Non-adherent bacteria were removed by three Phosphate Buffered Saline rinses every 20 to 24 hours. Planktonic bacterial growth in the culture broth and biofilm formation on the discs were measured by Colony Forming Unit (CFU) counting and resazurin reduction assays. Experiments were repeated > 4 times. RESULTS: No detectable planktonic bacterial growth or biofilm formation occurred in cultures containing PMMA with antibiotics (≤ 15 CFUs/disc), whereas biofilms formed on PMMA without antibiotics, UHMWPE, and cobalt-chrome (1x107 to 4x108 CFUs/disc, P < 0.0001). Biofilm formation was confirmed by a 100-fold decrease in sensitivity to vancomycin. To determine whether the antibiotic slow-release phase is sufficient to block biofilm formation, PMMA discs with antibiotics were pre-eluted for 14 days with multiple saline changes prior to bacterial inoculation. After antibiotic elution, still no detectable biofilms formed on PMMA discs with antibiotics (≤ 15 CFUs/disc, P <0.0001). CONCLUSION: Antibiotic release during both the initial and slow-release phases prevented biofilm formation on PMMA with the proprietary pore structure. This may translate into improved infection eradication rates clinically.

Fast Fabrication Nanopores on a PMMA Membrane by a Local High Electric Field Controlled Breakdown.

The sensitivity and accuracy of nanopore sensors are severely hindered by the high noise associated with solid-state nanopores. To mitigate this issue, the deposition of organic polymer materials onto silicon nitride (SiNx) membranes has been effective in obtaining low-noise measurements. Nonetheless, the fabrication of nanopores sub-10 nm on thin polymer membranes remains a significant challenge. This work proposes a method for fabricating nanopores on polymethyl methacrylate (PMMA) membrane by the local high electrical field controlled breakdown, exploring the impact of voltage and current on the breakdown of PMMA membranes and discussing the mechanism underlying the breakdown voltage and current during the formation of nanopores. By improving the electric field application method, transient high electric fields that are one-seven times higher than the breakdown electric field can be utilized to fabricate nanopores. A comparative analysis was performed on the current noise levels of nanopores in PMMA-SiNx composite membranes and SiNx nanopores with a 5 nm diameter. The results demonstrated that the fast fabrication of nanopores on PMMA-SiNx membranes exhibited reduced current noise compared to SiNx nanopores. This finding provides evidence supporting the feasibility of utilizing this technology for efficiently fabricating low-noise nanopores on polymer composite membranes.

Reduction in the Sensor Effect on Acoustic Emission Data to Create a Generalizable Library by Data Merging.

The aim of this paper is to discuss the effect of the sensor on the acoustic emission (AE) signature and to develop a methodology to reduce the sensor effect. Pencil leads are broken on PMMA plates at different source-sensor distances, and the resulting waves are detected with different sensors. Several transducers, commonly used for acoustic emission measurements, are compared with regard to their ability to reproduce the characteristic shapes of plate waves. Their consequences for AE descriptors are discussed. Their different responses show why similar test specimens and test conditions can yield disparate results. This sensor effect will furthermore make the classification of different AE sources more difficult. In this context, a specific procedure is proposed to reduce the sensor effect and to propose an efficient selection of descriptors for data merging. Principal Component Analysis has demonstrated that using the Z-score normalized descriptor data in conjunction with the Krustal-Wallis test and identifying the outliers can help reduce the sensor effect. This procedure leads to the selection of a common descriptor set with the same distribution for all sensors. These descriptors can be merged to create a library. This result opens up new outlooks for the generalization of acoustic emission signature libraries. This aspect is a key point for the development of a database for machine learning.

Novel biocompatible denture material incorporating type I collagen with improved functional properties for oral health.

The use of collagen is the recent development in various medical fields. Huge quantities of hide and skin trimmings are generated during the leather processing are wasted or underutilized. Trimmings contain collagen which can be beneficially extracted and utilized for high value products. Poly methyl methacrylate based denture materials exhibit serious concerns such as high porosity, presence of residual monomer, shrinkage, distortion and high rate of deterioration of the materials. This study aims to incorporate extracted Type I collagen with polymer to obtain denture base and investigate its chemical and mechanical properties. The present research methodology also reduces the quantity of monomer and acrylic resin usage. The collagen was extracted from animal skin and hide trimmings which are otherwise disposed as wastes. This study investigated the effect of visco-elastic characteristics of resulted specimens and their transition temperature, mechanical properties, decomposition temperature and leachability. The collagen-based specimens have better tensile strength with high decomposition temperature compared to control specimens. Scanning Electron Microscopy analysis revealed that the experimental specimens was cohesive and homogeneous which explained the higher tensile and decomposition values. The study suggests that collagen cross-linked acrylic denture base exhibit better mechanical and thermal resistance properties when compared to control specimens. The study indicates that biomaterials are emerging as smart products of value in human health.

Development of Bioactive Hybrid Poly(lactic acid)/Poly(methyl methacrylate) (PLA/PMMA) Electrospun Fibers Functionalized with Bioglass Nanoparticles for Bone Tissue Engineering Applications.

Hybrid scaffolds that are based on PLA and PLA/PMMA with 75/25, 50/50, and 25/75 weight ratios and functionalized with 10 wt.% of bioglass nanoparticles (n-BG) were developed using an electrospinning technique with a chloroform/dimethylformamide mixture in a 9:1 ratio for bone tissue engineering applications. Neat PLA and PLA/PMMA hybrid scaffolds were developed successfully through a (CF/DMF) solvent system, obtaining a random fiber deposition that generated a porous structure with pore interconnectivity. However, with the solvent system used, it was not possible to generate fibers in the case of the neat PMMA sample. With the increase in the amount of PMMA in PLA/PMMA ratios, the fiber diameter of hybrid scaffolds decreases, and the defects (beads) in the fiber structure increase; these beads are associated with a nanoparticle agglomeration, that could be related to a low interaction between n-BG and the polymer matrix. The Young's modulus of PLA/PMMA/n-BG decreases by 34 and 80%, indicating more flexible behavior compared to neat PLA. The PLA/PMMA/n-BG scaffolds showed a bioactive property related to the presence of hydroxyapatite crystals in the fiber surface after 28 days of immersion in a Simulated Body Fluids solution (SBF). In addition, the hydrolytic degradation process of PLA/PMMA/n-BG, analyzed after 35 days of immersion in a phosphate-buffered saline solution (PBS), was less than that of the pure PLA. The in vitro analysis using an HBOF-1.19 cell line indicated that the PLA/PMMA/n-BG scaffold showed good cell viability and was able to promote cell proliferation after 7 days. On the other hand, the in vivo biocompatibility evaluated via a subdermal model in BALC male mice corroborated the good behavior of the scaffolds in avoiding the generation of a cytotoxic effect and being able to enhance the healing process, suggesting that the materials are suitable for potential applications in tissue engineering.

Enhancing the sustainable immobilization of laccase by amino-functionalized PMMA-reinforced graphene nanomaterial.

Human health and the environment are negatively affected by endocrine-disrupting chemicals (EDCs), such as bisphenol A. Therefore, developing appropriate remediation methods is essential for efficiently removing phenolic compounds from aqueous solutions. Enzymatic biodegradation is a potential biotechnological approach for responsibly addressing water pollution. With its high catalytic efficiency and few by-products, laccase is an eco-friendly biocatalyst with significant promise for biodegradation. Herein, two novel supporting materials (NH2-PMMA and NH2-PMMA-Gr) were fabricated via the functionalization of poly(methylmethacrylate) (PMMA) polymer using ethylenediamine and reinforced with graphene followed by glutaraldehyde activation. NH2-PMMA and NH2-PMMA-Gr were utilized for laccase immobilization with an immobilization yield (IY%) of 78.3% and 82.5% and an activity yield (AY%) of 81.2% and 85.9%, respectively. Scanning electron microscope (SEM) and Fourier-transform infrared (FTIR) were used to study the characteristics of fabricated material supports. NH2-PMMA-Gr@laccase exhibited an optimal pH profile from 4.5 to 5.0, while NH2-PMMA@laccase exhibited optimum pH at 5.0 compared to a value of 4.0 for free form. A wider temperature ranges of 40-50 °C was noted for both immobilized laccases compared to a value of 40 °C for the free form. Additionally, it was reported that immobilized laccase outperformed free laccase in terms of substrate affinity and storage stability. NH2-PMMA@laccase and NH2-PMMA-Gr@laccase improved stability by up to 3.9 and 4.6-fold when stored for 30 days at 4 °C and preserved up to 80.5% and 86.7% of relative activity after ten cycles of reuse. Finally, the degradation of BPA was achieved using NH2-PMMA@laccase and NH2-PMMA-Gr@laccase. After five cycles, NH2-PMMA@laccase and NH2-PMMA-Gr@laccase showed that the residual degradation of BPA was 77% and 84.5% using 50 µm of BPA. This study introduces a novel, high-performance material for organic pollution remediation in wastewater that would inspire further progress.

Mechanofluorochromic Properties of 1,4-Diphenylanthracene Derivatives with Hypsochromic Shift.

Several types of 1,4-diphenylanthracene derivatives 1-4 were prepared, and their photophysical properties were observed in the solid and solution states. Interestingly, the CN-group-substituted 1,4-diphenylanthracene derivative 2 was found to exhibit a higher fluorescence quantum yield (ϕf = 0.71) in the solid state than in the solution state, probably due to the formation of an intermolecular Ar-CN⋯H-Ar hydrogen bond and antiparallel type locked packing structure in the solid state. Furthermore, for some derivatives, an increase in the fluorescence quantum yield was observed in the PMMA film (1 wt%) over both the solid state and the solution state. More interestingly, some of the 1,4-diphenylanthracene derivatives exhibited unusual mechanofluorochromic properties with a "hypsochromic shift" in luminous color depending on the substituents of the phenyl group, and with the derivatives having CF3, OMe, CN, and two F substituents (1d-1f, 2-4) showing a significant luminous color change with a "hypsochromic shift" after grinding. However, no change in the luminous color was observed for the derivatives having H, Me, and one F substituent (1a-1c), and especially for some of the CN-substituted derivatives, a reversible luminous color change with a "hypsochromic shift" was observed, probably due to the formation of an antiparallel type packing structure. These "hypsochromic" anthracene derivatives could probably be utilized as new mechanofluorochromic materials.

A comparative evaluation of physical properties of CAD/CAM complete denture resins- an in vitro study.

BACKGROUND: In dentistry, there is a growing preference for computer-aided design and computer-aided manufacturing (CAD/CAM) systems over traditional laboratory procedures. However, there is not much literature comparing various CAD/CAM materials. Thus, this study aimed to assess and compare the color stability and hardness of gingival and tooth colored milled and 3D-printed acrylic resins. MATERIALS AND METHODS: Four types of CAD/CAM materials were prepared: 3D-printed pink shade (PP), milled polymenthymethacrylate (PMMA) pink shade (MP), 3D-printed tooth shade (PT) and milled PMMA tooth shade (MT) (n = 6). For hardness, disc shaped samples of 15 mm × 2 mm and for color stability, bar shaped samples of 65mmx10mmx2.5 mm were prepared and polished. Vickers hardness test was performed in a microhardness tester. Color stability test was done by immersing in coffee solution and coca cola for 7 days. Day 0 and day 7 measurements were recorded using a digital spectrophotometer and the change in color was calculated. For statistical analysis, one-way ANOVA and Tukey's post hoc tests were done. RESULTS: For color stability, milled PMMA was superior to 3D-printed resin samples. Milled pink and tooth shade samples had similar color stability, whereas 3D-printed tooth shade samples were more color stable as compared to pink shade 3D-printed samples. For hardness, milled tooth shade PMMA was the most superior one, followed by 3D-printed tooth shade, whereas pink shade milled PMMA and 3D-printed resin samples had similar hardness values and were inferior to the tooth shade CAD/CAM materials. CONCLUSION: Color stability of milled PMMA is superior to that of 3D-printed resins. Hardness of tooth shade milled and 3D-printed resins is more than that of pink shade milled and 3D-printed resins.

Modification of polymethylmethacrylate bone cement with halloysite clay nanotubes.

BACKGROUND: Polymethylmethacrylate (PMMA) bone cement is used in orthopedics and dentistry to get primary fixation to bone but doesn't provide a mechanically and biologically stable bone interface. Therefore, there was a great demand to improve the properties of the PMMA bone cement to reduce its clinical usage limitations and enhance its success rate. Recent studies demonstrated that the addition of halloysite nanotubes (HNTs) to a polymeric-based material can improve its mechanical and thermal characteristics. OBJECTIVES: The purpose of the study is to assess the compressive strength, flexural strength, maximum temperature, and setting time of traditional PMMA bone cements that have been manually blended with 7 wt% HNT fillers. METHODS: PMMA powder and monomer liquid were combined to create the control group, the reinforced group was made by mixing the PMMA powder with 7 wt% HNT fillers before liquid mixing. Chemical characterization of the HNT fillers was employed by X-ray fluorescence (XRF). The morphological examination of the cements was done using a scanning electron microscope (SEM). Analytical measurements were made for the compressive strength, flexural strength, maximum temperature, and setting time. Utilizing independent sample t-tests, the data was statistically assessed to compare mean values (p < 0.05). RESULTS: The findings demonstrated that the novel reinforced PMMA-based bone cement with 7 wt% HNT fillers showed higher mean compressive strength values (93 MPa) and higher flexural strength (72 MPa). and lower maximum temperature values (34.8 °C) than the conventional PMMA bone cement control group, which was (76 MPa), (51 MPa), and (40 °C), respectively (P < 0.05). While there was no significant difference in the setting time between the control and the modified groups. CONCLUSION: The novel PMMA-based bone cement with the addition of 7 wt% HNTs can effectively be used in orthopedic and dental applications, as they have the potential to enhance the compressive and flexural strength and reduce the maximum temperatures.

Evaluation of flexural strength, impact strength, and surface microhardness of self-cured acrylic resin reinforced with silver-doped carbon nanotubes.

BACKGROUND: Poly-methyl methacrylate (PMMA) is a type of polymer mostly used to make denture bases. Self-cured acrylic resin (PMMA) can be used to repair a fractured acrylic denture base; however, even after repair, this area remains vulnerable. Carbon nanotubes (CNTs) could be used as a filler for polymer reinforcement. Furthermore, silver nanoparticles are efficient agents for the prevention of dental biofilm and improving their mechanical properties. The doping of CNTs with silver nanoparticles may lead to a synergistic interaction that is predicted to enhance the mechanical characteristics of the fillers. OBJECTIVES: The aim of the study was to assess the influnce of manual incorporation of 0.5% weight percent (%wt.) of silver doped carbon nanotubes (Ag-doped CNTs) into commercial self-cured PMMA on its flexural strength, impact strength, and surface microhardness. METHODS: In this investigation, a total of 60 specimens comprised of acrylic resin were employed. They are divided into two main groups: (a) the control group, which was made by using liquid monomer and commercial self-cured PMMA powder; and (b) the modified group, prepared by hand mixing the purchased silver-doped CNTs powder (0.5% wt.) to self-cured PMMA powder (99.5%wt.), and then the blended powder was incorporated into the liquid monomer. Flexural strength, flexural modulus, impact strength, and surface microhardness were evaluated. Independent sample t-tests were used to statistically analyze the data and compare the mean values of flexural strength, flexural modulus, impact strength, and surface microhardness (p-value ≤ 0.05). RESULTS: The flexural strength of the modified groups with Ag-doped CNTs (132.4 MPa) was significantly greater than that of the unmodified (control) groups (63.2 MPa). Moreover, the flexural modulus of the modified groups with Ag-doped CNTs (3.067 GPa) was significantly greater than that of the control groups (1.47 GPa). Furthermore, the impact strength of the modified groups with Ag-doped CNTs (11.2 kJ/mm2) was significantly greater than that of the control groups (2.3 kJ/mm2). Furthermore, the microhardness of the modified groups with Ag-doped CNTs (29.7 VHN) was significantly greater than that of the control groups (16.4 VHN), (p-value = 0.0001). CONCLUSION: The incorporation of 0.5% wt. silver doped CNTs fillers to the self-cured acrylic resin enhanced its flexural strength, flexural modulus, impact strength, and surface microhardness.

Flexural properties and fatigue limit of 3D-printed and milled resin-based materials.

PURPOSE: The purpose of this study was to evaluate the flexural strength (FS), flexural modulus (FM), and fatigue limit (FL) of 3D-printed resin-based polymers and composites and compare them to 3D-printed composites. MATERIALS AND METHODS: A bar-shaped specimen (25 × 2 × 2 mm) was CAD designed according to ISO 4049:2019, and 60 duplicates of the 3D model were nested at a 45-degree angle with the printing platform and 3D-printed with three materials: denture teeth resin (Denture Teeth, Formlabs), temporary crown and bridge resin (Temporary CB, Formlabs), and composite (Flexcera Smile Ultra+, Desktop Health). The 3D model was also imported into a dental CAM software, duplicated 60 times, nested, and milled from a 3D-milled composite puck (Ivotion Denture Teeth, Ivoclar). All specimens were post-processed following the manufacturer's recommendation. The specimens were then subjected to a three-point bending test until failure using a Universal Testing Machine at a crosshead speed of 0.75 mm/min, and FS and FM were calculated. The remaining thirty specimens were tested for Fatigue Limit using the staircase approach starting at 50% FS maximum up to 1.2 M cycles at 10 Hz. The data were analyzed using one-way ANOVA and the Weibull distribution (α = 0.05). RESULTS: The results showed that Ivotion and Flexcera had higher FS (110.3 ± 7.1 MPa and 107.6 ± 6.4 MPa, respectively) and FM (3.3 ± 0.1 GPa and 3.0 ± 0.2 GPa, respectively) compared to the 3D-printed Denture Teeth (FS = 66.4 ± 18.5 MPa and FM = 1.8 ± 0.1 GPa) and Temporary CB (FS = 79.6 ± 12.1 MPa and FM = 2.7 ± 0.4 GPa). Weibull analysis showed that the Ivotion and Flexcera had a more uniform and narrower spatial distribution of defects (m: 27.98 and 29.19) than the printed materials, which had m values of 8.17 and 4.11 for Temporary CB and Denture Teeth, respectively. Although no differences were found in the static properties (FS and FM) between Ivotion and Flexcera, Ivotion presented a higher endurance limit than Flexcera (51.43 vs. 40.95 MPa). The Temporary CB presented 21.08 MPa and Denture Teeth presented 17.80 MPa of endurance limit. CONCLUSIONS: 3D-milled (Ivotion Denture Teeth) and 3D-printed (Flexcera Smile Ultra+) composites outperformed 3D-printed resins (Formlabs Denture Teeth and Temporary Crown & Bridge) in terms of flexural properties and fatigue resistance. 3D-milled (Ivotion) and 3D-printed (Flexcera) composites exhibited similar flexural properties, but 3D-milled composites showed a 25% higher fatigue endurance limit, suggesting improved clinical longevity.