Testing Machine Research Articles

Effect of different ceramic materials and dentin sealing on occlusal veneers bond strength and fracture resistance.

The effect of immediate dentin sealing (IDS) or delayed dentin sealing (DDS) on bond strength of different ceramic occlusal veneer restorations, was not examined yet, but the digital quantification of surface area of preparations helped in the calculation of the actual bond strength of these restorations, besides that, dentin sealing could influence the fracture resistance values of different ceramic occlusal veneer restorations. This study aimed to examine the effect of different dentin sealing strategies and different restorative materials on the debonding forces, bond strength and fracture resistance of occlusal veneer restorations. Human mandibular molars (N = 64/test) were prepared for occlusal veneer restorations fabricated from Lithium disilicate ceramic (LS) (control group), Zirconia-reinforced lithium Silicate ceramic (ZLS), High translucent zirconia ceramic (HZ), and Resin nano ceramic (LU) (n = 16). Each material was subdivided according to IDS or DDS application, (n = 8). Bond strength testing and fracture resistance values were measured using universal testing machine. Two-way ANOVA was performed to investigate the effects of the two variables, dentin sealing and material selection, and their interaction (α = 0.05), followed by One-way ANOVA and post hoc or Student t-test for further determination of significance. For debonding forces and bond strength testing there were significant differences regarding different materials and dentin sealing strategies, while for fracture resistance, the material selection had a significant effect on it with no significant effects of dentin sealing strategies. The interaction between materials and dentin sealing showed no significant differences concerning all tests. For debonding forces and bond strength there was a higher result related to IDS application than DDS (p < 0.001*), and there was a significant effect of material selection on them (LS > ZLS > HZ > LU), (p = 0.001*). Regarding the fracture resistance there was significant increase of all studied materials than LU (p = 0.002*). Immediate dentin sealing increased the required debonding forces of occlusal veneers made of different materials and their bond strength without significant effect on their fracture resistance, however this improvement was found to be material dependant. All the used materials can withstand lateral and occlusal forces higher than the values recommended for restoring posterior teeth.

The influence of thermal tempering on the fracture resistance, surface microstructure, elemental surface composition, and phase analysis of four heat-pressed lithia-based glass ceramic crowns

Abstract Background This in-vitro study aimed to evaluate the impact of thermal tempering and ceramic type on the fracture resistance, surface microstructure, elemental surface composition and phase analysis of four heat-pressed glass ceramics. Methods A total of 84 glass-ceramic crowns were pressed and randomly allocated into four equal groups (n = 21) according to the ceramic type: Group (E): IPS e.max Press, Group (L): GC initial LiSi Press, Group (C): Celtra Press and Group (A): VITA Ambria. The crowns of each group were equally allocated into three subgroups (n = 7) regarding the subsequent thermal tempering temperature. Subgroup (T0): No tempering. Subgroup (T1): Tempering at 9% below pressing temperature. Subgroup (T2): Tempering at 5% below pressing temperature. Samples were tested for fracture resistance using a universal testing machine. A scanning electron microscope, X-ray diffraction, and Energy Dispersive x-ray analysis were utilized to disclose the microstructural features. Results When there is no tempering, IPS e.max press showed a significant elevated fracture resistance (P-value = 0.002). There was an insignificant difference between other ceramics. While with tempering (T2) as well as (T1), Lisi press (L) showed a significant elevated fracture resistance. There was an insignificant difference between other ceramics (P-value = 0.004). Conclusions Incorporation of zirconia oxide into the lithium disilicate glass matrix did not show improvement in the fracture resistance. Thermal tempering procedure had significant effect on fracture resistance. Thermal tempering technique had no influence the elemental surface composition and phase analysis yet T2 samples showed changes in crystal size and orientation.

Microstructure, XRD characteristics and tribological behavior of SiC–graphite reinforced Cu-matrix hybrid composites

Abstract This study’s main goal is to investigate how the properties of pure copper are impacted by the addition of silicon carbide–graphite reinforcement. Here in this research a powder metallurgy procedure is used to make copper matrix composites with different amounts of silicon carbide–graphite reinforcement (2 %, 5 %, 8 %, and 10 %) by weight. The microstructure, phases present, wear analysis, and X-ray diffraction analysis were all thoroughly examined, while scanning electron microscopy was used for imaging the microstructure of materials. The absence of any intermediate phases between the reinforcing materials and the copper matrix, according to X-ray diffraction data, suggests a strong interfacial interaction between them. A microstructural analysis of the copper matrix indicated a consistent dispersion of silicon carbide–graphite. The amount of reinforcement employed was found to have an impact on the wear characteristics of these copper matrix composites. Notably, the softness of graphite caused the hardness to drop when it was added. The 5 % reinforcement composite material outperformed the other evaluated composite materials in terms of wear rate, which was calculated in term of specific wear rate by using a pin-on-disc testing machine. This implies that this specific composite could be useful for tribological applications.

Machine learning-based pH quantification from test strip images using multiple color spaces

Abstract Recent advances in colorimetric analysis have focused on improving measurement accuracy through the integration of smartphone cameras and machine learning. Particular focus has been placed on enhancing predictive accuracy by combining variables from multiple color spaces. In this study, we developed a model incorporating multiple color spaces using images of universal pH test strips. For model selection, we focused on localized errors and used the mean absolute error for each pH value as an evaluation metric. As a result, by emphasizing localized errors, we were able to build a model with better generalization performance than the model selected on the basis of overall error. We implemented this model in a real-time pH measurement demo web application.

On the Rheological Behavior of Pine (Pinus sylvestris L.) Shavings and the Briquettes Obtained from Them

The aim of this paper is to carry out a rheological study of the pressing of pine wood sawdust, after which obtaining briquettes from the same wood material with a hydraulic installation and analyzing their properties. In order to know the rheological behavior during pressing, the fractions resulting from sorting the sawdust with 4 × 4, 3 × 3, 2 × 2, and 1 × 1 mm2 sieves were used, respectively, six fractions (the fraction larger than 4 × 4 mm2 and the smaller one of 1 × 1 mm2 are added) and a specific pressing device, placed on a universal testing machine. The results obtained in the rheological study showed that the obtained density does not increase proportionally with the pressure, the best results (density of 1030 kg/m3) being obtained at a pressure of 180 MPa. Within the briquettes, higher densities were obtained for the sawdust fraction smaller than 1 × 1 mm2, but the breaking strength was higher for the fraction larger than 4 × 4 mm2. As a general conclusion, it was found that pine sawdust is easily compressible, and the briquettes obtained from it have good properties for use in combustion.

Biobased Acrylate Composites with Enhanced Strength for Additive Manufacturing

Abstract With the expanding use of polymers in additive manufacturing, sustainable resins for use in vat photopolymerization are required to reduce their environmental impact. One promising approach to achieve this is to incorporate biobased fillers that replace the acrylates in photopolymer resins as ‘green’ alternatives. In this study, photopolymer composites consisting of a methacrylate resin with varying calcium carbonate powder content between 0 and 50 wt.% were investigated. A digital light processing technique was used to fabricate tensile test specimens for mechanical testing. Good printability, dimensional accuracy, and good interlayer adhesion were observed for composite resin formulations that incorporated calcium carbonate up to 50 wt.%. Green parts were subsequently washed and exposed to ultraviolet radiation at various post-cure temperatures between 20 and 80 °C. Specimens were tested on an Instron universal testing machine to evaluate stress–strain characteristics, which included Young’s modulus, ultimate tensile strength, yield strength at 0.2% offset, resilience, toughness, and percent elongation at break. Elevated calcium carbonate content and higher post-cure temperatures demonstrated higher Young’s modulus values, reaching 4297 MPa for 50 wt.% calcium carbonate at a post-cured temperature of 80 °C, indicating increased stiffness and resistance to elastic deformation under load for the compositions with increased biobased filler content. The ultimate tensile strength of the composite resin formulations was higher when exposed to elevated curing temperatures and remained between 22 and 32 MPa for all concentrations of calcium carbonate. The biobased composites evaluated in this study demonstrated that the modification of acrylate resins with biobased filler powders such as calcium carbonate is a feasible approach to sustainably enhance the mechanical properties of polymeric materials for additive manufacturing.

How Universal Adhesive Systems With Nanoencapsulated Flavonoids Improve Long-Term Bonding to Caries-Affected Dentin.

To determine the presence of nano-encapsulated flavonoids and their effect in universal adhesives on resin-dentin bond-strength (μTBS) and nanoleakage (NL) on artificial caries-affected dentin (CAD) after 24-h and 6 months of water storage (WS). Artificial CAD was created on the occlusal dentin surfaces of 60 human third molars by a microbiological assay. Nanoencapsulated quercetin (Q) and naringin (N) were incorporated into Prime&Bond Universal (PBU; Dentsply-Sirona) and Single Bond Universal (SBU, 3M ESPE). The adhesive systems with and without (control) flavonoids were applied to the CAD surface, and a 4-mm resin composite block (TPH Spectrum, Dentsply Sirona) was built up and light-cured. Specimens were sectioned into resin-dentin beams (0.8 mm2). The hybrid layer (HL) was subjected to micro-Raman analysis to detect N and Q. The specimens were tested in tension in a universal testing machine at 0.5 mm/min. μTBS and NL tests were performed after 24-h and WS. μTBS and NL data were analyzed using a nonparametric three-way ANOVA test followed by Bonferroni's test (α = 5%). Q and N were detected within the HL. N and Q nanocapsules increased μTBS and reduced NL values after WS. At 24 h, the PBU group showed higher NL values than the SBU group, and the values decreased after WS. Incorporating nanoencapsulated flavonoids may improve the longevity of universal bonding systems applied to CAD. Adhesive restorations incorporating nanoencapsulated quercetin or naringin might be a promising alternative for achieving long-term bonding stability.

Poly(vinyl alcohol) Nanocomposites Reinforced with CuO Nanoparticles Extracted by Ocimum sanctum: Evaluation of Wound-Healing Applications

This study focused on the synthesis of plant-mediated copper-oxide nanoparticles (OsCuONPs) via the sol–gel technique and the fabrication of OsCuONP-infused PVA composite films (POsCuONPs) utilizing the solvent casting method for wound-healing applications. The prepared OsCuONPs and nanocomposite films were characterized using UV–visible spectra, FTIR, SEM, XRD, TGA, water contact-angle (WCA) measurements, and a Universal testing machine (UTM) for mechanical property measurements. The UV and FTIR tests showed that OsCuONPs were formed and were present in the PVA composite film. Moreover, the mechanical study confirmed that there is an increase in the tensile strength (TS) and Young’s modulus (Ym) with 21.75 MPa to 32.50 MPa for TS and 24.80 MPa to 1128.36 MPa for Ym, and a decrease in the % elongation at break (Eb) (394.32 to 75.6). The TGA and WCA study results demonstrated that PVA films containing OsCuONPs are more stable when subjected to high temperatures and demonstrate a decreased hydrophilicity (60.89° to 89.62°). The cytotoxicity and hemolysis tests showed that the CuONPs-3 containing composite films (PVA/OsCuONPs with a wt. ratio of 1.94/0.06) are safe to use, have a good level of cell viability, and do not break down blood. This is true even at high concentrations. The study also discovered that cells moved considerably in 12 and 24 h (13.12 to 19.26 for OsCuONPs and 312.53 to 20.60 for POsCuONPs), suggesting that 60% of the gaps were filled. Therefore, the fabricated POsCuONP nanocomposites may serve as a promising option for applications in wound healing.

Performance of Asphalt Concrete Mixtures Containing Nickel Slag

Recent advancements in material technology have led to an increased interest in using alternative materials in the asphalt mixtures. One such material is Nickel Slag (SN), a byproduct of nickel ore smelting. With the growing volume of slag produced during nickel smelting, research has focused on using SN as a component in pavement materials to reduce the steel waste accumulation. The primary objective of this study is to explore the optimal use of SN as a coarse aggregate in asphalt concrete mixtures, aiming to achieve the maximum asphalt content. The study also evaluates the impact of SN on the stability, volumetric characteristics of the asphalt mixtures, and Ultrasonic Pulse Velocity (UPV) wave patterns. The research involved Marshall testing using a Universal Testing Machine (UTM) and UPV testing. The results indicated that SN mixtures reached maximum stability at 5.8% asphalt content and demonstrated higher stability values than conventional mixtures. As a coarse aggregate replacement, SN enhances the resistance to permanent deformation due to its hardness, interlocking properties, and the silica content that improves adhesion to the asphalt. Incorporating SN into asphalt mixtures improves mix stability, reduces industrial waste, conserves natural resources, and enhances road infrastructure quality. This method supports the principles of sustainable development.

A Study on the Optimization of FDM Parameters for the Manufacturing of Compression Specimens from recycled ASA in the Context of the Transition to the Circular Economy

The present study investigates the optimization of the FDM parameters, that is, the height of the deposited layer in one pass (Lh) and the filling percentage (Id), for the manufacture of compression specimens from recycled ASA (rASA) in the context of transitioning to the circular economy. The Anycubic 4Max Pro 2.0 3D printer was utilized, where compression specimens were additively manufactured from rASA 45 using the following variable parameters: Lh = 0.10 mm, 0.15 mm, and 0.20 mm, and Id = 50%, 75%, and 100%. All compression specimens were tested on the Barrus White 20 kN universal testing machine. It was found that the Compressive strength (Cs) is influenced by the two considered variable parameters of the Fused Deposition Modeling (FDM), Lh and Id, but the overwhelmingly influencing parameter is Id. According to the results of the FDM parameter optimization for the manufacture of compression specimens from rASA, Lh = 0.10 mm and Id = 100%.

Trypanosoma cruzi Transmission Through Blood Samples and Derivatives: Main Routes, Control Strategies, and Recent Advancements in Blood Banks

Neglected Tropical Diseases are a group of 25 conditions caused by diverse agents. They mostly affect people with poorer health outcomes, particularly preventable diseases. The social determinants of health influence the development and progression of these poverty diseases, with inadequate sanitation presenting chronicity, high morbidity, and economic impacts. Chagas disease, a prominent Neglected Tropical Disease caused by the intracellular pathogen Trypanosoma cruzi, is endemic in Latin America but is increasing as a global concern due to population migration. It is transmitted through insect vectors, congenitally, orally via contaminated food and beverage, via transfusions and organ donation, and due to laboratory accidents, among other minor relevant routes. As a silent illness, with many infected individuals remaining asymptomatic, it contributes to underdiagnosis, and delayed treatment that involves nitro derivatives is often discontinued due to side effects. Chagas disease spreads in non-endemic areas like the United States of America and Europe. Blood screening practices vary, with endemic regions implementing universal testing, while non-endemic areas rely on selective methods. Recent innovations, such as riboflavin–ultraviolet light treatment and arylimidamide compounds, represent promising alternatives to reduce transfusion transmission. This review presents an analysis of Trypanosoma cruzi transmission through blood and derivatives, addressing the main routes, globally implemented control strategies, and recent advancements in blood bank safety.

A comparative evaluation of the resistance to vertical root fracture after removal of separated instruments using three instrument retrieval systems: An in vitro study

Abstract Introduction: Separated instruments have been retrieved from root canals using different systems of instruments. However, it has been a common observation that usage of available retrieval systems may weaken the roots of teeth making them prone to fracture and subsequent failure of the treatment as a whole. Hence, the following study was conducted to evaluate and compare the resistance to vertical root fracture after retrieval of separated instruments from the root canal using Ultrasonic U Files, Ultrasonic Tip (Acteon Endo Success ET25 Retreatment Tip), or the Endo Rescue System under magnification of the dental operating microscope. Materials and Methods: Forty-two moderately curved mesiobuccal roots of extracted decoronated mandibular first molar teeth were hemisectioned to standardize them to a length of 15 mm each. Following biomechanical preparation, 4-mm length ProTaper gold rotary finishing files F2 were intentionally separated in the middle third of the mesiobuccal root canal and verified radiographically. The samples were then randomly divided into three groups, and retrieval of the separated instrument was performed using the Ultrasonic U files, Ultrasonic ET25 Retreatment tip, or Endo Rescue System, respectively. After retrieval of the separated instruments, the samples were subjected to testing for vertical root fracture resistance using a universal testing machine with an accuracy of ± 1%. The data collected from all the samples were then subjected to statistical analysis. Result: Ultrasonic U files (Group A) showed the highest vertical root fracture resistance, with a statistically significant difference from the samples treated with ET 25 Ultrasonic retreatment tips(Group B). No significant differences were observed between Group A and C or Group B and Endo Rescue System (Group C) (P &gt; 0.05). Summary and Conclusion: It was observed that Ultrasonic U files offer the least reduction in the vertical root fracture resistance after removal of separated instruments followed by the Endo Rescue system and then the ultrasonic ET25 retreatment tips. While no single instrument retrieval system is universally suitable for all situations due to various factors such as root anatomy, instrument type, location, size, pulpal status, and operator skill, clinicians should determine the treatment protocol by carefully considering the tooth’s future prognosis.

Fracture resistance, failure mode and restorability of CAD CAM Zirconia endocrowns with different pulpal extension depths bonded to maxillary molars: an in-vitro study

BackgroundPulpal extension depth (PED) is critical for endocrowns restored teeth stability and longevity. There is a conflicting result regarding the minimum PED needed for the success of endocrowns. The aim of the current study was to compare Fracture resistance, failure mode, and restorability of CAD-CAM zirconia endocrowns with different pulpal extension depths bonded to maxillary molars.Materials and methodsForty maxillary 1st molars were selected, decoronated, and randomly divided into 4 main groups (n = 10) according to the PED measured from the pulpal floor to the occlusal end of the wall height into; group D2, PED was 2 mm, group D3, PED was 3 mm, group D4, PED was 4 mm, group D5 PED was 5 mm. Teeth were prepared and secured in resin dies with pseudo periodontal ligament. Specimens from all groups were individually scanned using an intra oral digital scanner. Monolithic zirconia endocrowns were constructed and bonded to their corresponding. Following thermal cycling, each specimen was axially loaded in a universal testing machine at a 0.5 mm/min crosshead speed. Failure modes were inspected, and restorability of specimens was recorded. Data was collected, tabulated, and statistically analyzed.ResultsDescriptive statistics displayed higher mean value of the D2 group (3657 1673.8 N) followed by the D3 group (3009.3 853.5 N), then the D4 group (2087.3 413.9 N) and finally the D5 group (1972.7 ±330.4 N). At a 95% confidence level, one-way analysis of variance (ANOVA) revealed significant differences between tested groups. (P = 0.014). Regarding failure mode, D2 recorded 100% restorable failures, followed by D3 (90%) and D4 (60%), while the least was D5 (50%).ConclusionsEndocrowns with 2 mm PED recorded the highest fracture resistance and the highest restorable failure modes. Endocrowns with 5 mm PED recorded the lowest fracture resistance and the lowest restorable failure modes. Tall walls should be shortened during the preparation of endocrowns in maxillary molars.

Caries affected Dentin biomodification using Bromelain, Riboflavin photosensitizer via UVA, and Chitosan Nanoparticles on shear bond strength and microleakage scores: A SEM evaluation.

Assessment of the impact of different dentin bio-modifiers i.e., Bromelain, Riboflavin photosensitizer (RFP/Ultraviolet-A), and Chitosan nanoparticles (CHNPs) on the shear bond strength (SBS) and microleakage of composite bonded to acid etched carious affected dentin (CAD). Sixty-four human molars in which carious lesions extend till the middle third of the dentin were included. The infected dentin was removed and CAD was exposed. All specimens were categorized into four groups based on the application of dentin bio-modifier (n = 16) Group 1 (No dentin modifier), Group 2 (Bromelain), Group 3 (RFP/UVA), and Group 4 (CHNPs). Dental adhesive application and composite buildup were performed. A dye penetration test was used to assess marginal leakage. Resin CAD interface assessment was performed using SEM. For SBS and failure pattern analysis, a universal testing machine and stereomicroscope were used respectively. One-way ANOVA followed by Bonferroni's posthoc test was employed to analyze the differences among various groups (p≤0.05) RESULTS: The lowest microleakage (13.27 ± 0.10) and highest SBS (11.64 ± 0.16 MPa) were observed in Group 2 (Bromelain). However, the maximum values of marginal leakage (37.21 ± 0.21) and minimum SBS (7.34 ± 0.07 MPa) were detected in Group 1 samples. The length of resin tags in the Group 2 specimens (Bromelain) was found to be the highest (102.11 ± 5.12 μm). However, Group 1 (No modifier) exhibited the lowest resin tag length (50.45 ± 2.37 μm). Caries-affected dentin modified with Bromelain resulted in satisfactory SBS with minimal microleakage scores. Chitosan nanoparticles and RFP/Ultraviolet-A also presented better outcomes in terms of microleakage and SBS than the control.

Comparative evaluation of the effect of nitrofurantoin and triple antibiotic paste on the push-out bond strength of epoxy resin sealer: An in vitro study

Abstract Context: Following chemomechanical preparation, the application of intracanal medicaments is recommended to further decrease the microbial count. To combat endodontic infections, the application of antibiotics as intracanal medicaments has been an option for years in endodontics. Aim: The aim of this study was to compare and evaluate the effect of antibiotic pastes on the push-out bond strength (POBS) of resin-based root canal sealer. Materials and Methods: Forty-eight extracted single-rooted teeth were used after decoronation to a standardized root length of 15 mm. Canals were enlarged up to size F3 using Protaper rotary instruments. Samples were randomly divided into three groups according to the intracanal medicament used. Group A: Nitrofurantoin (NIT) Paste, Group B: Triple antibiotic paste (TAP), and Group C: Control group (without intracanal dressing). After removal of the medicament (endoactivator), obturation was done with AH Plus sealer. Push-out bond strength was calculated using universal testing machine. Statistical Analysis: Data were analyzed using one-way ANOVA followed by post hoc Tukey and Kruskal–Wallis test (with a significance level of P &lt; 0.05). Results: Compared to the control group, the POBS significantly increased after using intracanal medicaments with P &lt; 0.05 (The results showed that the mean bond strength of TAP was highest, closely followed by NIT and least with the control group). Conclusion: Under the limitations of this study, it can be concluded that the use of TAP and NIT increases the POBS of the Epoxy Resin Sealer.

Technological dental sealants: in vitro evaluation of material properties and antibiofilm potential

BackgroundDue to the launch of new self-etching and self-adhesive sealing materials combined with the release of bioactive ions in the dental market, this in vitro study aimed to compare physical values of surface roughness (RS), vickers microhardness (VM), compositional energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), microbiological tests (inhibition halo-HI and surface microbial adhesion-MAS) and mechanical microshear bond strength (MBS).MethodsThe following groups were analyzed: Beautisealant® self-etching sealant (Shofu)(G1), FluroShield® conventional sealant (Dentsply)(G2- Control Group), Flow Constic® self-adhesive/self-etching resin (DMG)(G3) and Beautifil Flow Plus F03® conventional resin (Shofu)(G4). For the physical and compositional tests, specimens were molded and submitted to finishing/polishing in a metallographic polisher. RS and VM were measured through 5 readings. For the HI test, specimens were exposed to S. mutans for 24 h in brain–heart infusion (BHI) agar under microaerophilic conditions, with the diameter of the HI (mm) measured by digital caliper. For the MAS test, a bacterial biofilm of S. mutans was induced for five days in BHI broth + 5% sucrose and measurement of CFU/ml (log10 from serial dilutions). For the MBS test, specimens were made in bovine enamel with the addition of the experimental group FluroShield® (Dentsply) + Single Bond Universal® adhesive (3 M)(G5) and measured in a universal testing machine. Data were submitted to ANOVA and Tukey's post hoc tests (p < 0.05) using the SPSS software.ResultsDifferent compositions proven in the EDS test were not determinants of the promotion of different RS: G1 = 0,19 (± 0,07), G2 = 0,15 (± 0,053), G3 = 0,13 (± 0,046), G4 = 0,14 (± 0,056); HI: G1 = 17,7 (± 1,36), G2 = 18,7 (± 3,47), G3 = 18,9 (± 4,87), G4 = 17,9 (± 3,61) and MAS: G1 = 5,22 (± 0,12), G2 = 5,15 (± 0,15), G3 = 5,12 (± 0,20), G4 = 5,06 (± 0,24). However, statistically influenced the values of VM: G1 = 16,71 (± 1,93), G2 = 16,28 (± 4,91), G3 = 26,11 (± 3,46), G4 = 37.9 (± 4.87), promoted lesser bacterial adhesion (G4 = 5.06 ± 0.24), and demonstrated fluoride ion only in the G4. Higher MBS was found in the conventional materials G5 = 8.38 (± 2.05) and G2 = 6.28 (± 1.35).ConclusionsBioactive materials and self-adhesive/self-etching for sealing pits and fissures did not demonstrate superior mechanical and antimicrobial properties performance compared to conventional techniques.

Impact of simulated gastric acid on the physical and mechanical properties of vacuum-formed retainers: an in vitro study

BackgroundA decrease in oral pH levels may have detrimental effects on vacuum-formed retainers since an acidic oral environment could impact the mechanical and physical properties of these retainers. The present In vitro study aimed to evaluate the effect of simulated gastric acid at pH 4 and 1.2 on the surface microhardness, flexural strength, and color change of three different types of orthodontic retainer materials.MethodsA total of 144 vacuum-formed commercially available retainer materials: copolyesters, polypropylene, and PET-G (n = 48/group) were evaluated. Each specimen was immersed in distilled water, and then the specimens were divided into two subgroups: those with a pH of 4 and those with a pH of 1.2. The microhardness test was performed using Innovatest, the flexural strength was evaluated by a universal testing machine, and the color change was analyzed using a spectrophotometer. The data were analyzed using One-Way ANOVA and independent sample t test at a significance value of P ≤ 0.05.ResultsOur findings indicated a significant decrease in flexural strength in all the experimental groups after immersion in pH 1.2 and 4 solutions (P < 0.001), with PET-G being the most affected material, followed by copolyester and polypropylene. Only copolyester demonstrated a significant decrease in surface microhardness following immersion in a pH 4 solution (P = 0.025). All materials exhibited the greatest degree of color alteration CP (P = 0.006), PP (P = 0.001), and PET-G (P = 0.009) respectively.ConclusionThe study concluded that copolyester adversely affects flexural strength, surface microhardness, and color when subjected to immersion in simulated gastric acid. Therefore, care is recommended for patients diagnosed with gastroesophageal reflux disease.

Computational and Experimental Investigation &amp; Analysis on the Effect of Milled Basalt Fibre Fillers on Static Flexural Properties of the Natural Fibre Composites for Aerospace and Automobile Industrial Applications

Academic and industry researchers are focused on developing a material that satisfies various parameters such as durability, manufacturability, low cost, lightweight, adaptability, high strength, bio-degradability, etc. to meet the current day trends across aerospace and automotive industries. In engineering and technology, fiber-reinforced matrix composites and their applications are extensive. The addition of fillers (both natural and synthetic) along with matrix and fibers is considered to be a better option to increase the efficiency and performance of the composite materials. Recently, researchers have focussed on adding fillers along with matrix and its hybridization to lift the composite properties and applications. This research paper describes the computational and experimental investigation &amp; analysis on the effect of milled basalt fibre fillers on static flexural properties of the natural fibre composites for aerospace and automobile applications. As a first step, an optimized milled filler percentage is examined by incorporating the basalt milled filler into the epoxy laminates from 0.5% to 3% weight percentages concerning epoxy laminates. Finally, the 1% filler incorporated epoxy laminates showed better results than the base samples. Then, the 1% milled basalt filler material was incorporated into basalt fiber and areca fiber with epoxy resin and hardener to make the composite laminates for static testing. The static testing was carried out with the help of a Universal Testing Machine (UTM) i.e. the three-point bending test. The filler-incorporated basalt and areca nut epoxy composite laminates show higher flexural properties than the base samples with 0% filler material. The project work was also carried out with the help of ANSYS software with proper filler material and epoxy composite laminates for static testing. The flexural properties of the filler-incorporated composite laminates show higher properties than the base samples. Results reveal that the flexural properties of the composite laminates from experimental testing and software analysis are of less error percentage difference. Key Words: Composite materials &amp; structures, Matrix, Fibres, Fillers, Mechanical properties, Static testing, Flexural properties and ANSYS

Germline pathogenic variants in a cohort of individuals with biliary tract cancer.

559 Background: Biliary tract cancers (BTC) are rare but have been implicated in hereditary cancer conditions such as Lynch syndrome (LS) and BRCA1 and BRCA2. Data from paired somatic and germline genetic testing on BTC have shown that ~5% may be related to germline pathogenic variants in BRCA1 and BRCA2. Identification of these germline pathogenic variants (PV) often provide patients with an opportunity for personalized treatment including platinum-based chemotherapies, PARP inhibitors and/or immunotherapy. Germline testing also provides crucial data to relatives regarding cancer risk and access to increased cancer surveillance and risk-reducing surgeries. Current guidelines recommend germline genetic testing when the likelihood of identifying a PV is &gt;5%. The contribution of germline PV in BTC has not been described in a diverse patient population. Methods: In this prospective clinic-based study, individuals with BTC were referred by their oncologist for genetic counselling and testing. The majority of individuals were enrolled based on participation in the Legresley Biliary Registry, which recruits all individuals with BTC. Blood was sent for germline multi-gene panel testing. Results: Germline genetic testing was performed for 139 individuals. Average age of diagnosis was 57.8 years (range 28-84). The majority of individuals were diagnosed with intrahepatic cholangiocarcinoma (CCA) (54.7%), followed by extrahepatic CCA (20.9%) and gallbladder cancer (10.1%). The majority of individuals were male (56.1%). The population was ethnically diverse with 55% European, 24% Asian, 9% Middle Eastern/North African and 6% African. A minority of individuals had a previous cancer (18%) and 24.5% met current provincial eligibility criteria. Germline testing was complete on 136 individuals. 25/136 (14.7%) PV were identified in 20 individuals. 8/136 (5.9%) of the cohort carried PV in genes known to increase the risk for BTC ( BRCA1, BRCA2 and LS genes), 9/136 (6.6%) carried PV in other genes with clinically actionability (e.g. PALB2, ATM ), and 8/136 (5.9%) carried heterozygous PV in genes for recessive diseases. Variants of uncertain significance were identified in 42/136 (30.9%) and negative results were identified in 74/136 (54.4%). Personal and/or family history was not suggestive of the associated cancer condition in 9/16 (56%) of the PV cohort. Tumor profiling by whole genome sequencing on some individuals with PV found corresponding somatic mutational signatures, consistent with variant pathogenicity. Conclusions: Detection rates for PV in a diverse BTC cohort was up to 14.7%, including 5.9% among genes known to increase the risk for BTC. The majority of PV were found in individuals lacking personal and/or family history suggestive of the associated hereditary cancer condition. These results suggest that guidelines should be updated to recommend universal germline genetic testing for individuals with BTC.

Magneto-mechanical effects in a flexible magnetic system studied through combined MOKE magnetometry and mechanical testing.

We explore the magnetic properties of a thin Co film deposited on Kapton® substrates using the magneto-optical Kerr effect in a longitudinal configuration. We developed a magnetometer integrated with a tensile testing machine to investigate magnetization reversal phenomena under applied strain. The tensile machine, custom-designed to fit the experimental constraints, applies uniaxial stress to the samples, facilitating the study of magnetoelastic effects. Calibration using digital image correlation ensures accurate strain measurements. Our findings demonstrate that the application of strain significantly influences the magnetization curves, highlighting the emergence of anisotropies and changes in coercive and saturation fields.