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1.
Sci Rep ; 13(1): 1397, 2023 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-36697465

RESUMO

Fibre-reinforced biocomposites usage has gained prominence over the past decade. Although higher fracture toughness was observed when fibres were added to biocomposites, material degradation could occur due to filler and fibre content intolerance in the biocomposite matrix. Optimisation of resin-fibre-filler ratios helps in increasing the tribological performance of high load-bearing applications. However, the tribological performance is less understood due to limited in-vitro studies on the effect of fibre microstructures. A comprehensive investigation of the reciprocating and rotary wear behaviour of different compositions was carried out by varying fibre (0%, 5%, 10% and 15%) to particulate filler (40%, 45%, 50%, and 55%) weight fractions. The investigation aimed to identify the optimal composition of fibre-reinforced biocomposites based on the in-vitro ball-on-disc reciprocating and rotary wear tests in the presence of modified Fusayama solution. The cross-sectional areas of wear tracks were analysed using laser microscopy and scanning electron microscopy techniques to assess the surface morphology and subsurface damage of the wear tracks on biocomposites and the antagonist. The numerical results were statistically analysed using two-way ANOVA followed by a posthoc Tukey's test (p = 0.05). The results showed a combination of adhesive, abrasive and fatigue wear for all the tested Groups. The friction coefficient had a longer transient period for the 5 wt% and 10 wt% Groups. Based on the surface roughness, coefficient of friction, SEMs, specific wear rate, and ease of manufacturing, the threshold limit for fibre loading was found to be 10 wt%. The rotary test had a considerably lower specific wear rate compared to the reciprocating test. Fibre weight fraction was found to be the influencing factor of the abrasive wear behaviour compared to fibre length for the tested Groups.


Assuntos
Vidro , Teste de Materiais , Fricção , Vidro/química , Suporte de Carga
2.
Sensors (Basel) ; 23(2)2023 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-36679488

RESUMO

Increased absorption of optical materials arising from exposure to ionizing radiation must be accounted for to accurately analyze laser-induced breakdown spectroscopy (LIBS) data retrieved from high-radiation environments. We evaluate this effect on two examples that mimic the diagnostics placed within novel nuclear reactor designs. The analysis is performed on LIBS data measured with 1% Xe gas in an ambient He environment and 1% Eu in a molten LiCl-KCl matrix, along with the measured optical absorption from the gamma- and neutron-irradiated low-OH fused silica and sapphire glasses. Significant changes in the number of laser shots required to reach a 3σ detection level are observed for the Eu data, increasing by two orders of magnitude after exposure to a 1.7 × 1017 n/cm2 neutron fluence. For all cases examined, the spectral dependence of absorption results in the introduction of systematic errors. Moreover, if lines from different spectral regions are used to create Boltzmann plots, this attenuation leads to statistically significant changes in the temperatures calculated from the Xe II lines and Eu II lines, lowering them from 8000 ± 610 K to 6900 ± 810 K and from 15,800 ± 400 K to 7200 ± 800 K, respectively, for exposure to the 1.7 × 1017 n/cm2 fluence. The temperature range required for a 95% confidence interval for the calculated temperature is also broadened. In the case of measuring the Xe spectrum, these effects may be mitigated using only the longer-wavelength spectral region, where radiation attenuation is relatively small, or through analysis using the iterative Saha-Boltzmann method.


Assuntos
Óxido de Alumínio , Análise de Dados , Masculino , Humanos , Vidro , Radiação Ionizante , Análise Espectral
3.
Int J Mol Sci ; 24(2)2023 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-36674421

RESUMO

Silanized glass fibers are popular reinforcements of acrylic denture base materials. To increase the number of surface hydroxyl groups and to improve interfacial adhesion between the matrix and reinforcements, acid or base treatments of glass fibers are commonly performed before the silanization. However, limited data are available on the effect of these treatments on the mechanical properties of acrylic matrix composite materials used for denture base applications. In this work, before the silanization of a woven glass fiber fabric (GF) with 3-(trimethoxysilyl) propyl methacrylate, activation pretreatments using HCl and NH4OH aqueous solutions have been performed. To characterize the glass surface, FTIR spectroscopy was used. Specimens of cured acrylic denture base resin and composites were divided into five groups: (1) cured acrylic denture base resin-control group; (2) composite with non-silanized GF; (3) composite with silanized GF; (4) composite with NH4OH activated and silanized GF; (5) composite with HCl activated and silanized GF. The flexural and impact properties of specimens were evaluated by means of three-point-bending tests and Charpy impact testing, respectively. The residual reactivity of the samples was analyzed using differential scanning calorimetry. The results of mechanical testing showed that acid and base pretreatments of the glass fabric had a positive effect on the flexural modulus of prepared composites but a negative effect on their impact strength. Possible interfacial adhesion mechanisms and the diffusion control of isothermal cure reactions due to vitrification have been discussed.


Assuntos
Bases de Dentadura , Polimetil Metacrilato , Polimetil Metacrilato/química , Teste de Materiais , Análise de Variância , Vidro/química , Resinas Acrílicas/química , Propriedades de Superfície , Estresse Mecânico
4.
Int J Mol Sci ; 24(2)2023 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-36674660

RESUMO

In this research, we investigated the structural and biological properties of phosphate glasses (PGs) after the addition of V2O5. A xV2O5∙(100 - x)[CaF2∙3P2O5∙CaO] glass system with 0 ≤ x ≤ 16 mol% was synthesized via a conventional melt-quenching technique. Several analysis techniques (dissolution tests, pH, SEM-EDS, FT-IR, and EPR) were used to obtain new experimental data regarding the structural behavior of the system. In vitro tests were conducted to assess the antitumor character of V2O5-doped glass (x = 16 mol%) compared to the matrix (x = 0 mol%) and control (CTRL-) using several tumoral cell lines (A375, A2780, and Caco-2). The characterization of PGs showed an overall dissolution rate of over 90% for all vitreous samples (M and V1-V7) and the high reactivity of this system. EPR revealed a well-resolved hyperfine structure (hfs) typical of vanadyl ions in a C4v symmetry. FT-IR spectra showed the presence of all structural units expected for P2O5, as well as very clear depolymerization of the vitreous network induced by V2O5. The MTT assay indicated that the viability of tumor cells treated with V7-glass extract was reduced to 50% when the highest concentration was used (10 µg/mL) compared to the matrix treatment (which showed no cytotoxic effect at any concentration). Moreover, the matrix treatment (without V2O5) provided an optimal environment for tumor cell attachment and proliferation. In conclusion, the two types of treatment investigated herein were proven to be very different from a statistical point of view (p < 0.01), and the in vitro studies clearly underline the cytotoxic potential of vanadium ions from phosphate glass (V7) as an antitumor agent.


Assuntos
Neoplasias Ovarianas , Vanádio , Feminino , Humanos , Vanádio/farmacologia , Espectroscopia de Infravermelho com Transformada de Fourier , Linhagem Celular Tumoral , Células CACO-2 , Vanadatos , Fosfatos , Vidro/química , Íons
5.
Int J Mol Sci ; 24(2)2023 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-36674818

RESUMO

In this study, zinc (Zn)- and copper (Cu)-doped 13-93B3 borate mesoporous bioactive glasses (MBGs) were successfully synthesized using nitrate precursors in the presence of Pluronic P123. We benefited from computational approaches for predicting and confirming the experimental findings. The changes in the dynamic surface tension (SFT) of simulated body fluid (SBF) were investigated using the Du Noüy ring method to shed light on the mineralization process of hydroxyapatite (HAp) on the glass surface. The obtained MBGs were in a glassy state before incubation in SBF. The formation of an apatite-like layer on the SBF-incubated borate glasses was investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The incorporation of Zn and Cu into the basic composition of 13-93B3 glass led to changes in the glass transition temperature (Tg) (773 to 556 °C), particle size (373 to 64 nm), zeta potential (-12 to -26 mV), and specific surface area (SBET) (54 to 123 m2/g). Based on the K-means algorithm and chi-square automatic interaction detection (CHAID) tree, we found that the SFT of SBF is an important factor for the prediction and confirmation of the HAp mineralization process on the glasses. Furthermore, we proposed a simple calculation, based on SFT variation, to quantify the bioactivity of MBGs. The doped and dopant-free borate MBGs could enhance the proliferation of mouse fibroblast L929 cells at a concentration of 0.5 mg/mL. These glasses also induced very low hemolysis (<5%), confirming good compatibility with red blood cells. The results of the antibacterial test revealed that all the samples could significantly decrease the viability of Pseudomonas aeruginosa. In summary, we showed that Cu-/Zn-doped borate MBGs can be fabricated using a cost-effective method and also show promise for wound healing/skin tissue engineering applications, as especially supported by the cell test with fibroblasts, good compatibility with blood, and antibacterial properties.


Assuntos
Cobre , Zinco , Animais , Camundongos , Cobre/farmacologia , Zinco/farmacologia , Boratos/farmacologia , Vidro , Antibacterianos/farmacologia , Durapatita/farmacologia , Cicatrização
6.
Inhal Toxicol ; 35(1-2): 40-47, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36648029

RESUMO

OBJECTIVE: We developed predictive formulae for the in vitro dissolution rate constant kdis of acid-soluble synthetic vitreous fibers (SVF), paralleling our earlier work with glass wools, which are typically more soluble at neutral pH. Developing simple models for predicting the kdis of a fiber can allow prediction of in vivo behavior, aid fiber developers, and potentially reduce in vivo testing. METHODS: The kdis of several acid-soluble SVF were determined using high simulant fluid flow/fiber surface area (F/A) conditions via a single-fiber measurement system. Four fluids were employed, varying in base composition and citrate levels. Equations predicting the kdis were derived from fiber chemistry and dissolution measurements for two of the fluids. RESULTS: Testing of several fibers showed a ∼10× increase in the kdis when citrate was included in the simulant solution. Data from tests with Stefaniak's citrate-free Phagoloysosmal Simulant Fluid (PSF) yielded kdis values aligned with expectations from in vivo results, unlike results from citrate-containing modified Gamble's solution. Predictive equations relating fiber chemistry to kdis showed reasonable agreement between the measured and predicted values. CONCLUSIONS: Citrate inclusion in the solution under high F/A conditions significantly increased the measured kdis. This resulted in more biorelevant data being obtained using the PSF fluid with the high F/A method used. The developed predictive equations, sufficient for fiber development work, require refinement before a recommending their use in place of in vivo biopersistence testing. Significant fit improvements are possible through additional measurements under these experimental conditions.


Assuntos
Fibras Minerais , Silicatos , Solubilidade , Minerais/química , Vidro/química , Ácido Cítrico
7.
Proc Natl Acad Sci U S A ; 120(2): e2213182120, 2023 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-36608290

RESUMO

The X-ray-induced, nonthermal fluidization of the prototypical SiO2 glass is investigated by X-ray photon correlation spectroscopy in the small-angle scattering range. This process is initiated by the absorption of X-rays and leads to overall atomic displacements which reach at least few nanometers at temperatures well below the glass transition. At absorbed doses of ∼5 GGy typical of many modern X-ray-based experiments, the atomic displacements display a hyperdiffusive behavior and are distributed according to a heavy-tailed, Lévy stable distribution. This is attributed to the stochastic generation of X-ray-induced point defects which give rise to a dynamically fluctuating potential landscape, thus providing a microscopic picture of the fluidization process.


Assuntos
Vidro , Dióxido de Silício , Dióxido de Silício/química , Raios X , Vidro/química
9.
Biotechnol Lett ; 45(2): 225-233, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36504269

RESUMO

Glass, a near infinitely recyclable material, can be upcycled to create new products such as foamed glass ceramics, which are essentially a synthetic pumice-like material. This material has been demonstrated to sustain preserved biofilms which have application in various fields based on the deployability of the product and the preserved microbes. Foamed glass ceramics have increased surface area compared to typical soda-lime glass cullet. This material has been explored for variety of applications including the growth, storage and transport of biofilms and microbial colonies which can be preserved and deployed later. Here, we demonstrate the ability for microbial cultures including BioTiger™, Escherichia coli K-12, Bacillus thuringiensis, and two environmental eukaryotic cells to colonize the upcycled glass products, undergo preservation, and regrow after 84 days of storage. The growth of preserved samples is correlated to the time spent incubating prior to preservation. These results demonstrate the applicability of this novel glass-biofilm combination in which various preserved microorganisms are able to be rapidly grown after storage on an upcycled glass product.


Assuntos
Escherichia coli K12 , Biofilmes , Vidro , Cerâmica , Escherichia coli
10.
J Chem Inf Model ; 63(1): 87-100, 2023 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-36512692

RESUMO

Glass fragments found in crime scenes may constitute important forensic evidence when properly analyzed, for example, to determine their origin. This analysis could be greatly helped by having a large and diverse database of glass fragments and by using it for constructing reliable machine learning (ML)-based glass classification models. Ideally, the samples that make up this database should be analyzed by a single accurate and standardized analytical technique. However, due to differences in equipment across laboratories, this is not feasible. With this in mind, in this work, we investigated if and how measurement performed at different laboratories on the same set of glass fragments could be combined in the context of ML. First, we demonstrated that elemental analysis methods such as particle-induced X-ray emission (PIXE), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), scanning electron microscopy with energy-dispersive X-ray spectrometry (SEM-EDS), particle-induced Gamma-ray emission (PIGE), instrumental neutron activation analysis (INAA), and prompt Gamma-ray neutron activation analysis (PGAA) could each produce lab-specific ML-based classification models. Next, we determined rules for the successful combinations of data from different laboratories and techniques and demonstrated that when followed, they give rise to improved models, and conversely, poor combinations will lead to poor-performing models. Thus, the combination of PIXE and LA-ICP-MS improves the performances by ∼10-15%, while combining PGAA with other techniques provides poorer performances in comparison with the lab-specific models. Finally, we demonstrated that the poor performances of the SEM-EDS technique, still in use by law enforcement agencies, could be greatly improved by replacing SEM-EDS measurements for Fe and Ca by PIXE measurements for these elements. These findings suggest a process whereby forensic laboratories using different elemental analysis techniques could upload their data into a unified database and get reliable classification based on lab-agnostic models. This in turn brings us closer to a more exhaustive extraction of information from glass fragment evidence and furthermore may form the basis for international-wide collaboration between law enforcement agencies.


Assuntos
Vidro
11.
J Mech Behav Biomed Mater ; 138: 105607, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36549251

RESUMO

The characteristics of dental ceramics have been extensively studied over the years to provide highly qualified materials for use in prosthetic restorations. The ability to adhere to dental substrates, outstanding aesthetics (translucency, color, and substrate masking ability) and improved mechanical properties provide these materials with optical features and high strength to withstand masticatory stimuli. Different classifications are adopted, and it is generally considered that glass-ceramics have better optical characteristics due to the high glass content, and polycrystalline ceramics have superior strength favored by their densified and organized crystals, hampering crack growth. This knowledge was largely built-up during years of scientific research through different testing methodologies, but mainly employing static loads. It is important to not only take into account the intensity of loads that these materials will be exposed to, but also the effect of the intermittence of cyclic load application leading to mechanical fatigue and the influence of factors related to the crack origin and their propagation under this condition. Furthermore, the bonding surface of ceramic restorations requires surface treatments that improve the bond strength to luting agents; however, these treatments require caution because of their potential to produce defects and affect the structural behavior. Moreover, ceramic restorations often require internal adjustments for proper seating or external adjustments for fitting the occlusal contact with the antagonist. In this sense, finishing/polishing protocols may alter the defect population, as luting agents may also interact by filling in the superficial defects on the restoration intaglio surface. Thus, the balance among all these factors will define the performance of a restorative setup, as well as the posterior exposure to the humid environment and the masticatory stimuli (cyclical loading), which may favor developing slow and subcritical growth of cracks in ceramic materials and the degradation of the bond interface. Therefore, it is essential that the concepts which explain the fatigue mechanism are understood, as well as the crack propagation and failure patterns of restorative ceramic materials.


Assuntos
Cerâmica , Vidro , Teste de Materiais , Cerâmica/química , Cimentos Dentários , Odontologia , Porcelana Dentária , Propriedades de Superfície , Desenho Assistido por Computador , Análise do Estresse Dentário , Falha de Restauração Dentária
12.
J Mater Chem B ; 11(3): 519-545, 2023 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-36541433

RESUMO

Bioactive glass-based organic/inorganic hybrids are a family of materials holding great promise in the biomedical field. Developed from bioactive glasses following recent advances in sol-gel and polymer chemistry, they can overcome many limitations of traditional composites typically used in bone repair and orthopedics. Thanks to their unique molecular structure, hybrids are often characterized by synergistic properties that go beyond a mere combination of their two components; it is possible to synthesize materials with a wide variety of mechanical and biological properties. The polymeric component, in particular, can be tailored to prepare tough, load-bearing materials, or rubber-like elastomers. It can also be a key factor in the determination of a wide range of interesting biological properties. In addition, polymers can also be used within hybrids as carriers for therapeutic ions (although this is normally the role of silica). This review offers a brief look into the history of hybrids, from the discovery of bioactive glasses to the latest developments, with a particular emphasis on polymer design and chemistry. First the benefits and limitations of hybrids will be discussed and compared with those of alternative approaches (for instance, nanocomposites). Then, key advances in the field will be presented focusing on the polymeric component: its chemistry, its physicochemical and biological advantages, its drawbacks, and selected applications. Comprehensive tables summarizing all the polymers used to date to fabricate sol-gel hybrids for biomedical applications are also provided, to offer a handbook of all the available candidates for hybrid synthesis. In addition to the current trends, open challenges and possible avenues of future development are proposed.


Assuntos
Vidro , Polímeros , Vidro/química , Dióxido de Silício/química , Elastômeros
13.
Luminescence ; 38(1): 71-82, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36511851

RESUMO

Eu3+ -doped-bismuth-based phosphate glasses with chemical equation (60 - x)P2 O5 -20Bi2 O3 -10Na2 CO3 -10SrF2 -xEu2 O3 (PBNSEu), (where x = 0, 0.1, 0.5, 1.0, 1.5 and 2 mol%) were fabricated using the melt-quenching method. Obtain X-ray diffraction (XRD), energy-dispersive X-ray (EDAX), and Fourier transform infrared (FTIR) spectra were used to characterize the structure of the prepared PBNSEu glass. The J-O (Judd-Ofelt) intensity parameters (Ω2 , Ω4 ) were estimated using photoluminescence emission spectra. When excited with a xenon lamp at λexc  = 394 nm, the most intense red-emission transition occurred at ~612 nm (5 D0 →7 F2 ). J-O intensity parameters were used to calculate radiative properties, whereas the radiative branching ratio (ßR ), radiative transition probability (AR ), radiative lifetime (τR ), and total radiative transition rate (Aτ ) were calculated for the transitions 5 D0 →7 FJ (where J = 0-4) and were obtained in the emission spectra for europium ion-doped in the current glass. Using the CIE1931 chromaticity coordinates axes, the colours of various concentrations of Eu3+ ion-doped PBNS glass were evaluated using the emission spectra. Temperature-dependent luminescence spectra were recorded for the optimized PBNSEu20 glass to calculate the activation energy. These results strongly suggested red components in w-LEDs and visible display laser applications.


Assuntos
Bismuto , Luz , Bismuto/química , Vidro/química , Fosfatos/química , Lasers
14.
Mayo Clin Proc ; 97(12): 2389-2390, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36464469

RESUMO

Recognizing the contribution art has had in the Mayo Clinic environment since the original Mayo Clinic Building was finished in 1914, Mayo Clinic Proceedings features some of the numerous works of art displayed throughout the buildings and grounds on Mayo Clinic campuses as interpreted by the author.


Assuntos
Instituições de Assistência Ambulatorial , Vidro , Humanos , Análise por Conglomerados
15.
Eur Rev Med Pharmacol Sci ; 26(23): 8832-8840, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-36524502

RESUMO

OBJECTIVE: The current study aimed to inspect the fracture resistance of fiber post to canal dentin using a different technique of cementation. MATERIALS AND METHODS: 60 sound single-rooted central incisors with comparable size and length were stored in normal saline. Each tooth was immersed in 5% sodium hypochlorite (NaOCl). The specimens were randomly divided into 6 groups of 10 specimens each. All included specimens received root canal treatment (RCT). Post-space preparation was done using Gates Glidden drills. Post space was standardized with 10 mm length, keeping 3 to 5 mm as an apical seal. Based on the cementation technique samples were divided into six study groups. Group A: One step-Monoblock; Group B: One step- Monoblock-NA-FP; Group C: One step-Monoblock-RX-MC; Group D: Two-step- RX-MC; Group E: Two-step- RX-FZ; Group F: Two-step- RX-FZ-Custom post. Following cementation, all teeth will be prepared to receive a monolithic zirconia crown with a finish line of 1 mm above the CEJ. Each specimen was mounted in auto-polymerizing clear acrylic resin using a preformed tube. All samples were subjected to pushing forces to measure the fracture strength of the specimen using a universal testing machine. To compare the means among different experimental groups Post Hoc Tukey multiple comparison tests and analysis of variance (ANOVA) were adopted. RESULTS: The highest fracture resistance was observed in group A. Whereas, the lowest fracture resistance was observed in group D samples. Fracture strength in group A samples showed significantly higher fracture resistance values compared to all other groups (p < 0.05). Fracture resistance values in group F specimens were significantly higher than specimens in groups B, C, D, and E respectively (p < 0.05). CONCLUSIONS: Monoblock technique using single cementation and core material (Multicore Flow) when polymerized simultaneously exhibited the highest fracture resistance of glass fiber post compared to other cementation techniques.


Assuntos
Cimentação , Técnica para Retentor Intrarradicular , Cimentação/métodos , Resinas Compostas , Vidro , Incisivo , Tratamento do Canal Radicular , Teste de Materiais
16.
PeerJ ; 10: e14604, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36570015

RESUMO

Collisions with windows on buildings are a major source of bird mortality. The current understanding of daytime collisions is limited by a lack of empirical data on how collisions occur in the real world because most data are collected by recording evidence of mortality rather than pre-collision behaviour. Based on published literature suggesting a causal relationship between bird collision risk and the appearance of reflections on glass, the fact that reflections vary in appearance depending on viewing angle, and general principles of object collision kinematics, we hypothesized that the risk and lethality of window collisions may be related to the angle and velocity of birds' flight. We deployed a home security camera system to passively record interactions between common North American bird species and residential windows in a backyard setting over spring, summer and fall seasons over 2 years. We captured 38 events including 29 collisions and nine near-misses in which birds approached the glass but avoided impact. Only two of the collisions resulted in immediate fatality, while 23 birds flew away immediately following impact. Birds approached the glass at variable flight speeds and from a wide range of angles, suggesting that the dynamic appearance of reflections on glass at different times of day may play a causal role in collision risk. Birds that approached the window at higher velocity were more likely to be immediately killed or stunned. Most collisions were not detected by the building occupants and, given that most birds flew away immediately, carcass surveys would only document a small fraction of window collisions. We discuss the implications of characterizing pre-collision behaviour for designing effective collision prevention methods.


Assuntos
Aves , Vidro , Animais , Fatores de Risco , Estações do Ano
17.
J Indian Prosthodont Soc ; 22(1): 38-47, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36510946

RESUMO

Settings and Design: Department of Prosthodontics, KMSDCH, SVDU, Randomised Controlled study. Materials and Methods: Thirty-six teeth that satisfied selection criteria were randomly allocated and treated in the two intervention groups - metal fiber post with composite core and dentin post with composite core. Patient characteristics with respect to gender, tooth guidance, type of tooth, and mobility amount of tooth structure left were recorded. The primary outcome of tooth loss and the secondary outcomes of recurrent caries detected at the crown margin, de-cementation of crown, and fracture of the core, post, and root were recorded at baseline, 3, 6, and 12 month follow up. Statistical Analysis Used: Chi Square test. Results: Thirty-six teeth in 17 patients (10 males and 7 females) were treated using metal fiber post (18 teeth) and dentin post (18 teeth). No loss of tooth was seen at the end of 3, 6, and 12 months. The secondary outcomes also showed no recurrent caries at margin and no fracture of core, post, and root in both the groups at the end of 3, 6, and 12 months. One case of de-cementation was observed in both the groups at the 12-month period. Periodontal and periapical conditions showed no clinical and radiographic signs at any of the follow-up periods in both the groups. Conclusion: This twelve month randomized controlled clinical study concluded a similar success rate for endodontically treated teeth restored with crowns on both metal fiber post with composite core and dentin post with composite core.


Assuntos
Técnica para Retentor Intrarradicular , Fraturas dos Dentes , Dente não Vital , Masculino , Feminino , Humanos , Dente não Vital/terapia , Fraturas dos Dentes/terapia , Resinas Compostas/química , Falha de Restauração Dentária , Planejamento de Prótese Dentária , Vidro/química , Dentina
18.
J Chem Phys ; 157(24): 244504, 2022 Dec 28.
Artigo em Inglês | MEDLINE | ID: mdl-36586975

RESUMO

We investigate the structural relaxation of a soft-sphere liquid quenched isochorically (ϕ = 0.7) and instantaneously to different temperatures Tf above and below the glass transition. For this, we combine extensive Brownian dynamics simulations and theoretical calculations based on the non-equilibrium self-consistent generalized Langevin equation (NE-SCGLE) theory. The response of the liquid to a quench generally consists of a sub-linear increase of the α-relaxation time with system's age. Approaching the ideal glass-transition temperature from above (Tf > Ta), sub-aging appears as a transient process describing a broad equilibration crossover for quenches to nearly arrested states. This allows us to empirically determine an equilibration timescale teq(Tf) that becomes increasingly longer as Tf approaches Ta. For quenches inside the glass (Tf ≤ Ta), the growth rate of the structural relaxation time becomes progressively larger as Tf decreases and, unlike the equilibration scenario, τα remains evolving within the whole observation time-window. These features are consistently found in theory and simulations with remarkable semi-quantitative agreement and coincide with those revealed in a previous and complementary study [P. Mendoza-Méndez et al., Phys. Rev. 96, 022608 (2017)] that considered a sequence of quenches with fixed final temperature Tf = 0 but increasing ϕ toward the hard-sphere dynamical arrest volume fraction ϕHS a=0.582. The NE-SCGLE analysis, however, unveils various fundamental aspects of the glass transition, involving the abrupt passage from the ordinary equilibration scenario to the persistent aging effects that are characteristic of glass-forming liquids. The theory also explains that, within the time window of any experimental observation, this can only be observed as a continuous crossover.


Assuntos
Vidro , Simulação de Dinâmica Molecular , Temperatura , Temperatura de Transição , Vidro/química
20.
PLoS One ; 17(12): e0279647, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36580482

RESUMO

The current work presents the development of hybrid glass fiber reinforced polyester resin (GFRPs) composite. The composite integrates functionalized carbon nanotubes (f-MWCNTs) with glass fiber (GF) using polyester resin as a media. Hand lay-up method was adopted to prepare GFRPs samples in the form of rectangular sheets. Morphological characteristics of the GFRPs were investigated through scanning electron microscopy (SEM), to analyze the f-MWCNTs distribution and agglomeration of the developed composite's surface due to varying concentrations from 0.0 to 0.5 wt.%. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were performed to confirm the presence of f-MWCNTs in the developed GFRPs. Sample with 0.4 wt. % f-MWCNTs showed the highest tensile strength and impact energy of 79 MPa, indicating a 31.66% improvement and 1.6 Nm with 77% improvement, respectively as compared to the control sample (0.wt.% f-MWCNT). The same sample also showed the thermal stability till 390 °C as measured through thermogravimetric analysis (TGA). Deposition of extra 10 layers initially increased the composite strength from 40 MPa to 128 MPa, however further increase in layers to 15 resulted decrease in strength to 100 MPa due to the poor interaction between the polyester resin and GF. The addition of f-MWCNTs in the composite effectively strengthens the interfacial bonding, which significantly improved the tensile and impact strength of the composite, making it tougher and thermally stable. However, further increase in the concentration of f-MWCNTs degraded the mechanical properties of developed composite such as compressive strength because of agglomeration of these nanoparticles and void formation in the composite.


Assuntos
Nanotubos de Carbono , Nanotubos de Carbono/química , Poliésteres , Materiais Dentários , Vidro
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