Developing an optimised method for accurate wear testing of dental materials using the 'Rub&Roll' device.

Dental materials are challenged by wear processes in the oral environment and should be evaluated in laboratory tests prior to clinical use. Many laboratory wear-testing devices are high-cost investments and not available for cross-centre comparisons. The 'Rub&Roll' wear machine enables controlled application of force, chemical and mechanical loading, but the initial design was not able to test against rigid antagonist materials. The current study aimed to probe the sensitivity of a new 'Rub&Roll' set-up by evaluating the effect of force and test solution parameters (deionized water; water + abrasive medium; acid + abrasive medium) on the wear behaviour of direct and indirect dental resin-based composites (RBCs) compared with human molars against 3D-printed rod antagonists. Molars exhibited greater height loss than RBCs in all test groups, with the largest differences recorded with acidic solutions. Direct RBCs showed significantly greater wear than indirect RBCs in the groups containing abrasive media. The acidic + abrasive medium did not result in increased wear of RBC materials. The developed method using the 'Rub&Roll' wear machine in the current investigation has provided a sensitive wear test method to allow initial screening of resin-based composite materials compared with extracted human molars under the influence of different mechanical and erosive challenges.

Early monitoring of inlay wear after total knee arthroplasty on plain radiographs using model-based wear measurement.

Wear of the ultra-high molecular-weight polyethylene (UHMWPE) component in total knee arthroplasty contributes to implant failure. It is often detected late, when patients experience pain or instability. Early monitoring could enable timely intervention, preventing implant failure and joint degeneration. This study investigates the accuracy and precision (repeatability) of model-based wear measurement (MBWM), a novel technique that can estimate inlay thickness and wear radiographically. Six inlays were milled from non-crosslinked UHMWPE and imaged via X-ray in anteroposterior view at flexion angles 0°, 30°, and 60° on a phantom knee model. MBWM measurements were compared with reference values from a coordinate measurement machine. Three inlays were subjected to accelerated wear generation and similarly evaluated. MBWM estimated inlay thickness with medial and lateral accuracies of 0.13 ± 0.09 and 0.14 ± 0.09 mm, respectively, and linear wear with an accuracy of 0.07 ± 0.06 mm. Thickness measurements revealed significant lateral differences at 0° and 30° (0.22 ± 0.08 mm vs. 0.06 ± 0.06 mm, respectively; t-test, p = 0.0002). Precision was high, with average medial and lateral differences of - 0.01 ± 0.04 mm between double experiments. MBWM using plain radiographs presents a practical and promising approach for the clinical detection of implant wear.

Aligners: review of their chemical components, recycling, mechanical properties and therapeutic needs - Part 1 / Aligneurs : mise en perspective de la composition chimique, du recyclage, des propriétés mécaniques et des besoins thérapeutiques ­ Partie 1.

Introduction: The aligner is a thermoformed plastic device composed of various chemical components: polyurethane, polyethylene terephthalate glycol, polypropylene… All these plastics must be sufficiently resistant to abrasion and translucent for aesthetic purposes, but their solubility to salivary enzymes, insertion-disinsertion fatigue and recyclability vary according to material. From an orthodontic point of view, they must facilitate tooth movement. However, their behavior differs from that of orthodontic archwires: their Young's modulus, resilience and unloading curve are distinct, resulting in mechanical properties that fall significantly below the orthodontic requirements of multi-bracket systems. Objective: The aim of this article was to review the chemical composition, recycling and mechanical properties of aligners, and to put them into perspective with therapeutic indications. Materials and Methods: Literature data were approximated to orthodontic needs. Results: Neither plastic nor direct printing can match the mechanical properties of our archwires or the procedures of a reliable vestibular multi-attachment appliance. Discussion: Aligners remain an interesting tool in targeted indications.

Introduction: L'aligneur est un dispositif en plastique thermoformé dont la composition chimique est diverse : polyuréthane, polyéthylène téréphtalate glycol, polypropylène… Tous ces plastiques doivent être suffisamment résistants à l'abrasion et translucides pour être esthétiques mais ils présentent une solubilité aux enzymes salivaires, une fatigue liée à l'insertion-désinsertion et une recyclabilité qui sont variables selon le matériau. D'un point de vue orthodontique, ils doivent permettre de déplacer les dents. Mais leur comportement ne ressemble pas à celui des arcs orthodontiques : leur module de Young, leur résilience et leur courbe de décharge en sont éloignés et confèrent des propriétés mécaniques très inférieures aux exigences orthodontiques des appareils multi-attaches. Objectif: L'objectif de l'article était de faire le point sur la composition chimique, le recyclage, les propriétés mécaniques des aligneurs et de les mettre en perspective avec les indications thérapeutiques. Matériel et méthode: Les données de la littérature sont approchées des besoins orthodontiques. Résultats: Ni le plastique, ni l'impression directe ne sont en capacité de rivaliser avec les propriétés mécaniques de nos arcs ou avec les procédures d'un appareil multi-attache vestibulaire fiables. Discussion: Les aligneurs restent un outil intéressant dans des indications ciblées.

[Study on fatigue resistance of mechanical nickel-titanium files by phase-locked infrared flaw detection method].

PURPOSE: The fatigue resistance of mechanical nickel-titanium files was tested by phase-locked infrared flaw detection method, in order to timely detect instrument wear, providing reference for clinical safe use and timely abandonment of nickel-titanium files. METHODS: Twenty sets of mechanical nickel-titanium files were selected from Reciproc-Blue(RB), MTWO and S3 respectively, and resin simulated root canals with 60° and 90° bending were prepared, which were divided into 6 subgroups. The fatigue value after use, the number of uses before breaking and the length of fracture of file 25# of each group of files were recorded and compared with SPSS 26.0 software package. RESULTS: With the increase of the times of use, the fatigue value of the three kinds of files increased gradually. Among the two types of curved root canals, the number of uses before fracture in RB group was significantly increased compared with that in MTWO group and S3 group (P＜0.05). The number of uses of the three kinds of files in the 90° curved root canal were significantly less than in the corresponding groups in the 60° curved root canal(P＜0.05). There was no significant difference in the length of fracture among the three kinds of files(P＞0.05). CONCLUSIONS: Phase-locked infrared flaw detection method can be used for non-destructive testing and quantitative analysis of the fatigue degree of nickel-titanium files.

Forecasting the rheological state properties of self-compacting concrete mixes using the response surface methodology technique for sustainable structural concreting.

It is structurally pertinent to understudy the important roles the self-compacting concrete (SCC) yield stress and plastic viscosity play in maintaining the rheological state of the concrete to flow. It is also important to understand that different concrete mixes with varying proportions of fine to coarse aggregate ratio and their nominal sizes produce different and corresponding flow- and fill-abilities, which are functions of the yield stress/plastic viscosity state conditions of the studied concrete. These factors have necessitated the development of regression models, which propose optimal rheological state behavior of SCC to ensure a more sustainable concreting. In this research paper on forecasting the rheological state properties of self-compacting concrete (SCC) mixes by using the response surface methodology (RSM) technique, the influence of nominal sizes of the coarse aggregate has been studied in the concrete mixes, which produced experimental mix entries. A total of eighty-four (84) concrete mixes were collected, sorted and split into training and validation sets to model the plastic viscosity and the yield stress of the SCC. In the field applications, the influence of the sampling sizes on the rheological properties of the concrete cannot be overstretched due to the importance of flow consistency in SCC in order to achieve effective workability. The RSM is a symbolic regression analysis which has proven to exercise the capacity to propose highly performable engineering relationships. At the end of the model exercise, it was found that the RSM proposed a closed-form parametric relationship between the outputs (plastic viscosity and yield stress) and the studied independent variables (the concrete components). This expression can be applied in the design and production of SCC with performance accuracies of above 95% and 90%, respectively. Also, the RSM produced graphical prediction of the plastic viscosity and yield stress at the optimized state conditions with respect to the measured variables, which could be useful in monitoring the performance of the concrete in practice and its overtime assessment. Generally, the production of SCC for field applications are justified by the components in this study and experimental entries beyond which the parametric relations and their accuracies are to be reverified.

Comparative evaluation on surface nanohardness, surface microhardness, surface roughness, and wettability of plant-based organic nanoparticle reinforced polyetheretherketone as an implant material - An in vitro study.

AIM: Synthetic inorganic materials are commonly used as reinforcing agents in polyetheretherketone (PEEK) composite, whereas natural organic plant-based reinforcing agents are negligible. Surface hardness, roughness, and wettability are indicative factors of osseointegration behavior to be used as an implant material. This study evaluated micro surface hardness (MSH), nano surface hardness (NSH), surface roughness (SR), and contact angle (CA) of PEEK-Azadirachta indica reinforced at 10 wt%, 20 wt%, and 30 wt%. SETTINGS AND DESIGN: This was an in vitro study. MATERIALS AND METHODS: Neem (A. indica) leaf nanoparticles were prepared and reinforced with PEEK powder at 10%, 20%, and 30% weight ratios by injection molding. Sixty specimens underwent the microhardness and CA testing using a digital microhardness tester, and CA goniometer, respectively, and later nanoindentation test to analyze the nanohardness and SR. STATISTICAL ANALYSIS USED: A one-way ANOVA test with a 95% confidence interval for MSH and NSH, SR, and CA was performed on the samples. A post hoc Bonferroni test was conducted (α = 0.05) to compare the groups. RESULTS: There was a significant increase in nanohardness (P = 0.000) with zero difference in microhardness (P = 0.514). The addition of 10 wt%, 20 wt%, and 30 wt% nanoparticles increased the SR value of the pure PEEK from 273.19 nm to 284.10 (3.99%), 296.91 (8.68%), and 287.54 (5.24%), respectively. In the analysis of the CA, CA 20% shows the lowest angle (63.69) with the highest for control specimens (82.39). There is an increase in the PEEK composite SR with a decrease in CA. CONCLUSIONS: The addition of plant-derived nanoparticles into the PEEK matrix has a significant impact on the hardness and hydrophobicity enhancing cell growth and osteoblastic differentiation during osseointegration of dental implants.

Tensile strength analysis of additively manufactured CM 247LC alloy specimen by employing machine learning classifiers.

Using a cutting-edge net-shape manufacturing technique called Additive Layer Manufacturing (ALM), highly complex components that are not achievable with conventional wrought and cast methods can be produced. As a result, the aerospace sector is paying closer attention to using this technology to fabricate superalloys based on nickel to develop the holistic gas turbine. Because of this, there is an increasing need for the mechanical characterisation of such material. Conventional mechanical testing is hampered by the limited availability of material that has been processed, especially given the large number of process factors that need to be assessed. Thus, the present study focuses on manufacturing CM247LC Ni-based superalloy with exceptional mechanical characteristics by laser powder bed fusion (L-PBF). This study evaluates the effect of input process variables such as laser power, scan speed, hatch distance and volumetric energy density on the mechanical performance of the LPBF CM247LC superalloy. The maximum value of as-built tensile strength obtained in the study is 997.81 MPa. Plotting Pearson's heatmap and the Feature importance (F-test) was used in the data analysis to examine the impact of input parameters on tensile strength. The accuracy of the tensile strength data classification by machine learning algorithms, such as k-nearest neighbours, Naïve Baiyes, Support vector machine, XGBoost, AdaBoost, Decision tree, Random forest, and logistic regression algorithms, was 92.5%, 83.75%, 83%, 85%, 87.5%, 90%, 91.25%, and 77.5%, respectively.

Effect of bioceramic intracanal medication on the dentinal bond strength of bioceramic cements: an ex-vivo study.

Background: The present study evaluated the effect of a bioceramic intracanal medicament (Bio-C Temp) on the push-out bond strength of bioceramic cements. Methods: Forty-eight human single-canaled premolars were prepared and randomly divided into three groups: Group (A) received no intracanal medicament; Group (B) calcium hydroxide (CH); and Group (C) Bio-C Temp. After medicament removal, the roots were sectioned transversely. The slices in each group were separated into two subgroups (n = 16): in Subgroup (1), mineral trioxide aggregate (MTA) was placed, and in Subgroup (2) Bio-C Repair. Push-out bond strength was determined using a universal testing machine, applying a constant compressive force on the cement until bond failure. The failure mode was also evaluated. Data were analyzed using the Chi-square test and two-way ANOVA followed by Tukey's post hoc tests. The level of significance was set at 5%. Results: The pushout bond strength of Bio-C Repair was significantly higher than that of MTA irrespective of intracanal medication (p = 0.005). The placement of Bio-C Temp was associated with significantly lower bond strength (p = 0.002, p = 0.001). Conclusion: Bio-C Repair showed better bond strength compared to MTA, irrespective of intracanal medication. Bio-C Temp intracanal medicament, however, decreased the bond strength of both these cements.

Impact of screw tip design on screw anchorage: mechanical testing and numerical simulation.

BACKGROUND: Screw loosening is a commonly reported issue following spinal screw fixation and can lead to various complications. The initial cause of screw loosening is biomechanical deterioration. Previous studies have demonstrated that modifications in screw design can impact the local biomechanical environment, specifically the stress distribution on bone-screw interfaces. There are several different designs of screw tips available for clinically used pedicle screws; however, it remains unclear whether these variations affect the local stress distribution and subsequent screw anchorage ability. METHODS: This study conducted comprehensive biomechanical research using polyurethane foam mechanical tests and corresponding numerical simulations to investigate this topic. Models of pedicle screw-fixed osteoporotic polyurethane foam were created with two different clinically used screw tip designs (flat and steep) featuring varying tip lengths, taper angles, and diameters, as well as identical flank overlap areas and thread designs. The anchorage ability of the different models was assessed through toggle and pull-out test. Additionally, numerical mechanical models were utilized to compute the stress distributions at the screw and bone-screw interfaces in the different models. RESULTS: Mechanical tests revealed superior anchorage ability in models utilizing flat-tipped screws. Furthermore, numerical modeling indicated improved anchorage ability and reduced stress concentration tendency in these models. CONCLUSION: Changes in screw tip design can significantly impact the biomechanical anchoring capability of screws. Specifically, flatter tip pedicle screws may mitigate the risk of screw loosening by alleviating stress concentration on bone-screw interfaces.

Improving assay feasibility and biocompatibility of 3D cyclic olefin copolymer microwells by superhydrophilic modification via ultrasonic spray deposition of polyvinyl alcohol.

Sample partitioning is a crucial step towards digitization of biological assays on polymer microfluidic platforms. However, effective liquid filling into microwells and long-term hydrophilicity remain a challenge in polymeric microfluidic devices, impeding the applicability in diagnostic and cell culture studies. To overcome this, a method to produce permanent superhydrophilic 3-dimensional microwells using cyclic olefin copolymer (COC) microfluidic chips is presented. The COC substrate is oxidized using UV treatment followed by ultrasonic spray coating of polyvinyl alcohol solution, offering uniform and long-term coating of high-aspect ratio microfeatures. The coated COC surfaces are UV-cured before bonding with a hydrophobic pressure-sensitive adhesive to drive selective filling into the wells. The surface hydrophilicity achieved using this method remains unchanged (water contact angle of 9°) for up to 6 months and the modified surface is characterized for physical (contact angle & surface energy, morphology, integrity of microfeatures and roughness), chemical composition (FTIR, Raman spectroscopy) and coating stability (pH, temperature, time). To establish the feasibility of the modified surface in biological applications, PVA-coated COC microfluidic chips are tested for DNA sensing (digital LAMP detection of CMV), and biocompatibility through protein adsorption and cell culture studies (cell adhesion, viability, and metabolic activity). Kidney and breast cells remained viable for the duration of testing (7 days) on this modified surface, and the coating did not affect the protein content, morphology or quality of the cultured cells. The ultrasonic spray coated system, coating with 0.25 % PVA for 15 cycles with 0.12 A current after UV oxidation, increased the surface energy of the COC (naturally hydrophobic) from 22.04 to 112.89 mJ/m2 and improved the filling efficiency from 40 % (native untreated COC) to 94 % in the microwells without interfering with the biocompatibility of the surface, proving to be an efficient, high-throughput and scalable method of microfluidic surface treatment for diagnostic and cell growth applications.

Tailorable acrylate-endcapped urethane-based polymers for precision in digital light processing: Versatile solutions for biomedical applications.

Bioengineering seeks to replicate biological tissues exploiting scaffolds often based on polymeric biomaterials. Digital light processing (DLP) has emerged as a potent technique to fabricate tissue engineering (TE) scaffolds. However, the scarcity of suitable biomaterials with desired physico-chemical properties along with processing capabilities limits DLP's potential. Herein, we introduce acrylate-endcapped urethane-based polymers (AUPs) for precise physico-chemical tuning while ensuring optimal computer-aided design/computer-aided manufacturing (CAD/CAM) mimicry. Varying the polymer backbone (i.e. poly(ethylene glycol) (PEG) versus poly(propylene glycol) (PPG)) and photo-crosslinkable endcap (i.e. di-acrylate versus hexa-acrylate), we synthesized a series of photo-crosslinkable materials labeled as UPEG2, UPEG6, UPPG2 and UPPG6. Comprehensive material characterization including physico-chemical and biological evaluations, was followed by a DLP processing parametric study for each material. The impact of the number of acrylate groups per polymer (2 to 6) on the physico-chemical properties was pronounced, as reflected by a reduced swelling, lower water contact angles, accelerated crosslinking kinetics, and increased Young's moduli upon increasing the acrylate content. Furthermore, the different polymer backbones also exerted a substantial effect on the properties, including the absence of crystallinity, remarkably reduced swelling behaviors, a slight reduction in Young's modulus, and slower crosslinking kinetics for UPPG vs UPEG. The mechanical characteristics of DLP-printed samples showcased the ability to tailor the materials' stiffness (ranging from 0.4 to 5.3 MPa) by varying endcap chemistry and/or backbone. The in vitro cell assays confirmed biocompatibility of the material as such and the DLP-printed discs. Furthermore, the structural integrity of 3D scaffolds was preserved both in dry and swollen state. By adjusting the backbone chemistry or acrylate content, the post-swelling dimensions could be customized towards the targeted application. This study showcases the potential of these materials offering tailorable properties to serve many biomedical applications such as cartilage TE.

Verifying the cytotoxicity of a biodegradable zinc alloy with nanodiamond sensors.

Metals are widely utilized as implant materials for bone fixtures as well as stents. Biodegradable versions of these implants are highly desirable since patients do not have to undergo a second surgery for the materials to be removed. Attractive options for such materials are zinc silver alloys since they also offer the benefit of being antibacterial. However, it is important to investigate the effect of the degradation products of such alloys on the surrounding cells, taking into account silver cytotoxicity. Here we investigated zinc alloyed with 1 % of silver (Zn1Ag) and how differently concentrated extracts (1 %-100 %) of this material impact human umbilical vein endothelial cells (HUVECs). More specifically, we focused on free radical generation and oxidative stress as well as the impact on cell viability. To determine free radical production we used diamond-based quantum sensing as well as conventional fluorescent assays. The viability was assessed by observing cell morphology and the metabolic activity via the MTT assay. We found that 1 % and 10 % extracts are well tolerated by the cells. However, at higher extract concentrations we observed severe impact on cell viability and oxidative stress. We were also able to show that quantum sensing was able to detect significant free radical generation even at the lowest tested concentrations.

Rheological Analysis and Evaluation of Measurement Techniques for Curing Poly(Methyl Methacrylate) Bone Cement in Vertebroplasty.

Vertebroplasty is a minimally invasive surgical procedure used to treat vertebral fractures, which conventionally involves injecting poly(methyl methacrylate) (PMMA) bone cement into the fractured vertebra. A common risk associated with vertebroplasty is cement leaking out of the vertebra during the injection, which may occur due to a lack of understanding of the complex flow behavior. Therefore, experiments to quantify the cement's flow properties are necessary for understanding and proper handling of the bone cement. In this study, we aimed to characterize the behavior of PMMA bone cement in its curing stages to obtain parameters that govern the flow behavior during injection. We used rotational and oscillatory rheometry for our measurements, as well as a custom-made injector setup that replicated a typical vertebroplasty setting. Our results showed that the complex viscoelastic behavior of bone cement is significantly affected by deformations and temperature. We found that the results from rotational tests, often used for characterizing the bone cement, are susceptible to measurement artifacts caused by wall slip and "ridge"-like formations in the test sample. We also found the Cox-Merz rule to be conditionally valid, which affects the use of oscillatory tests to obtain the shear-thinning characteristics of bone cement. Our findings identify important differences in the measured flow behavior of PMMA bone cement when assessed by different rheological methods, an understanding that is crucial for its risk-free usage in downstream medical applications.

The Impact of Repeated Steam Sterilization Cycles on the Efficacy of Chairside Adjustment Kits for Polishing Monolithic Multi-Layered Zirconia Dental Restoration Material.

BACKGROUND Before insertion, chairside adjustment kits are heat sterilized for positioning and polishing dental restorations. This study aimed to evaluate the effects of 2 steam sterilization cycles on the efficacy of polishing highly translucent monolithic zirconia (HTMLZ) dental restoration material. MATERIAL AND METHODS 100 HTMLZ disc-shaped specimens were adjusted (grinding, finishing, polishing) with EVE Diacera kit. Two steam sterilization techniques [standard (Gp S), immediate/flash (Gp (F)] of CAK were further subgrouped based on number of sterilization cycles [cycle 1 (control), cycle 5, 10, 15, and 20 (experimental)] (n=10 each). Each subgroup accordingly was evaluated for average surface roughness (Ra) and root mean square roughness (Rq) using a profilometer. Mean and standard deviation of 5 subgroups were statistically analyzed using one-way ANOVA/post hoc Tukey's test. Scanning electron microscopy complemented Ra, Rq measurements. Statistical differences of P≤0.05 were considered significant. RESULTS HTMLZ specimens in both groups showed increased (Ra/Rq) values after repeated sterilization of EVE Diacera kit, with Gp F showing lesser increase than Gp S (20 cycles). Gp F at 10 cycles and Gp S at 15 cycles showed clinically unacceptable roughness threshold (0.25 µm). Differences between subgroups for Ra and Rq values were significant (P≤0.05) with less differences within groups observed in early cycles (1, 10). Results validate the manufacturer's recommendations of using flash sterilization/10 cycles for EVE Diacera kit. CONCLUSIONS Repeated sterilization reduces efficacy of chairside adjustment kit to produce smooth surfaces on HTMLZ. This study recommends flash sterilization to a maximum of 10 times to get the clinically acceptable results of Ra and Rq.

Designing an experimental method for assessing biocompatibility of circuit coatings using biomarkers for platelet activation during cardiopulmonary bypass.

INTRODUCTION: Cardiopulmonary bypass is an essential component of cardiothoracic surgeries. However, significant complications such as systemic inflammatory response syndrome (SIRS) resulting from cardiopulmonary bypass (CPB) are a common occurrence due to contact between circulating blood and foreign surfaces that leads to platelet activation. It is suggested that different available CPB circuit coatings can potentially reduce platelet activation. However, there have been no published evidence-based reports confirming these claims. In addition, there is no well-established protocol for studying platelet activation biomarkers during CPB in vitro in a laboratory setting. METHODS: CPB was simulated in the laboratory using bovine blood in two different types of coated CPB circuits: Trillium® Biosurface by Medtronic, and XcoatingTM Surface by Terumo. Fresh bovine blood samples were collected and circulated through the CPB circuit following the standard protocol used in the operation rooms. Blood samples were then collected at 5 min, 30 min, and 55 min during the circulation. Blood plasmas were separated and subjected to enzyme-linked immunosorbent assay to measure most established platelet activation markers P-selectin, Platelet Factor 4 (PF4), Glycoprotein IIb/IIIa (GPIIb/IIIa), and ß-thromboglobulin (ß-TG) at different time points. RESULTS: The biomarker values at 30 min and 55 min were compared to the base values at 5 min for each type of CPB circuit. The results of the means from all measured biomarkers showed data measurements that indicated no significant variability within each coating. All collected data points fell within ±2 SD of the means, which was considered acceptable variations across technical replicates.  Conclusion: In this study, we were able to establish an in vitro protocol in the laboratory setting that is precise and reliable with minimum intra-variability. This established protocol will allow for future studies in which different coated CPB circuits can be compared for their effectiveness in blocking platelet activation during the CPB.

Effect of Dentin Contamination with Hemostatic Agents and Cleaning Techniques on Bonding with Self-Adhesive Resin Cement.

BACKGROUND Dentin contamination with hemostatic agents before bonding indirect restorations negatively affects the bond strength. However, the consensus on which materials could be used to clean contamination of hemostatic agents has not been explored. The aim of this study was to assess the effect of Katana Cleaner applied on the surface of dentin contaminated with hemostatic agents on the shear bond strength (SBS) of self-adhesive resin cement by comparing it with three other surface cleaners. MATERIAL AND METHODS Ninety dentin specimens were divided into a no contamination group (control) (n=10), 4 groups contaminated with 25% aluminum chloride (Viscostat Clear) (n=40), and 4 groups contaminated with 20% ferric sulfate (Viscostat) (n=40). Subsequently, 4 different cleaners were used for each contamination group (water rinse, phosphoric acid, chlorhexidine, and Katana Cleaner). Then, self-adhesive resin cement was directly bonded to the treated surfaces. All specimens were subjected to 5000 thermal cycles of artificial aging. The shear bond strength was measured using a universal testing machine. RESULTS Two-way analysis of variance showed that the contaminant type as the main factor was statistically non-significant (p=0.655), cleaner type as the main factor was highly significant (p<0.001), and interaction between the contaminant and cleaner was non-significant (p=0.51). The cleaner type was the main factor influencing the bond strength. Phosphoric acid and chlorhexidine showed better performance than Katana Cleaner. CONCLUSIONS Cleaning dentin surface contamination with phosphoric acid and chlorhexidine had better performance than with Katana Cleaner.

Predicting concrete strength early age using a combination of machine learning and electromechanical impedance with nano-enhanced sensors.

To ensure the structural integrity of concrete and prevent unanticipated fracturing, real-time monitoring of early-age concrete's strength development is essential, mainly through advanced techniques such as nano-enhanced sensors. The piezoelectric-based electro-mechanical impedance (EMI) method with nano-enhanced sensors is emerging as a practical solution for such monitoring requirements. This study presents a strength estimation method based on Non-Destructive Testing (NDT) Techniques and Long Short-Term Memory (LSTM) and artificial neural networks (ANNs) as hybrid (NDT-LSTMs-ANN), including several types of concrete strength-related agents. Input data includes water-to-cement rate, temperature, curing time, and maturity based on interior temperature, allowing experimentally monitoring the development of concrete strength from the early steps of hydration and casting to the last stages of hardening 28 days after the casting. The study investigated the impact of various factors on concrete strength development, utilizing a cutting-edge approach that combines traditional models with nano-enhanced piezoelectric sensors and NDT-LSTMs-ANN enhanced with nanotechnology. The results demonstrate that the hybrid provides highly accurate concrete strength estimation for construction safety and efficiency. Adopting the piezoelectric-based EMI technique with these advanced sensors offers a viable and effective monitoring solution, presenting a significant leap forward for the construction industry's structural health monitoring practices.

Assessment of glove stretch and storage temperature on fentanyl permeation: Implications for standard test methods and PPE recommendations.

The National Institute for Occupational Safety and Health recommends the use of nitrile gloves with a minimum thickness of 5.0 ± 2.0 mil [0.127 ± 0.051 millimeters] in situations where it is suspected or known that fentanyl or other illicit drugs are present. However, there is limited data available on fentanyl permeation through gloves. Current test methods used to measure fentanyl permeation do not consider the effect of glove fit and flexion. Furthermore, first responders need to have PPE readily available in the field, and storage conditions may affect the protective performance of the gloves. The objective of this study was to evaluate the effects of glove stretch and storage temperatures on glove durability and barrier performance against fentanyl. Nine nitrile glove models previously shown to be resistant to fentanyl permeation were selected for this investigation. These nine models were stretched 25% in one linear direction, to consider glove fit and flexion, and tested against fentanyl hydrochloride permeation. Additionally, four of the nine glove models were stored at 48 °C, 22 °C, and -20 °C, and evaluated for tensile strength, ultimate elongation, and puncture resistance after up to 16 wk of storage and fentanyl permeation after up to 8 wk of storage. At least one sample for six of the nine tested models had maximum permeation over the test method fail threshold when stretched. The tested storage temperatures showed no effect on glove tensile strength, ultimate elongation, and puncture resistance. The findings of this study can be used to inform PPE recommendations, with consideration to storage practices and proper sizing for first responders with potential exposure to fentanyl and other illicit drugs. The results of this study can be used to assess the need for new standard test methods to evaluate the barrier performance of gloves and shelf-life determination with consideration to glove fit.

Mechanical Testing of Sliding on Pivot-Locking Clamp (SOP-LC) Fracture Repair System in Four-Point Bending and Torsion.

OBJECTIVES: The first objective of this study was to compare the mechanical performance of a straight and contoured rod for the sliding on pivot-locking clamp (SOP-LC) system. The second objective was to compare single-cycle bending and torsion of the SOP-LC rod-bone constructs to a bone gap model between two clamp configurations. STUDY DESIGN: First experiment, 5 mm diameter rods from the 3.5 mm SOP-LC system, 4 straight and 4 bent rods were mechanically compared in four-point bending. The second experiment, 8 constructs with clamps on a single side of the rod and 8 constructs with clamps on alternating sides were compared in four-point bending and torsion. A torque limiting screwdriver at 2.5N was used for all constructs. RESULTS: There were not significant differences between the noncontoured versus contoured rods. Constructs with clamps on a single side had a significantly higher yield load, yield displacement and bending strength, but the constructs with alternating clamps had a significantly higher initial torsional stiffness. There were no other significant differences. Mild clamp slippage and mild screw bending were noted in all the torsion tested constructs graphically with multiple stiffness slopes and visually on the post-tested constructs. CONCLUSION: Torque applied to initial screw placement may play a role in reducing clamp slippage. Although bending yield load, bending yield displacement, bending strength and torsional stiffness were improved by different clamp placement, clinically this will depend on fracture type. Further studies are needed for clinical significance.

Interface stress transfer model and modulus parameter equivalence method for composite materials embedded with tensile pre-strain shape memory alloy fibers.

The constitutive model and modulus parameter equivalence of shape memory alloy composites (SMAC) serve as the foundation for the structural dynamic modeling of composite materials, which has a direct impact on the dynamic characteristics and modeling accuracy of SMAC. This article proposes a homogenization method for SMA composites considering interfacial phases, models the interface stress transfer of three-phase cylinders physically, and derives the axial and shear stresses of SMA fiber phase, interfacial phase, and matrix phase mathematically. The homogenization method and stress expression were then used to determine the macroscopic effective modulus of SMAC as well as the stress characteristics of the fiber phase and interface phase of SMA. The findings demonstrate the significance of volume fraction and tensile pre-strain in stress transfer between the fiber phase and interface phase at high temperatures. The maximum axial stress in the fiber phase is 705.05 MPa when the SMA is fully austenitic and the pre-strain increases to 5%. At 10% volume fraction of SMA, the fiber phase's maximum axial stress can reach 1000 MPa. Ultimately, an experimental verification of the theoretical calculation method's accuracy for the effective modulus of SMAC lays the groundwork for the dynamic modeling of SMAC structures.