Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 5.126
Filtrar
1.
Int J Nanomedicine ; 16: 147-159, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33456309

RESUMEN

Background: There is still a big challenge to achieve a balance between mechanical characteristics and biological properties in biphasic calcium phosphate (BCP) ceramics. Purpose: The present study focused on the in-situ whisker growth on BCP ceramics via different hydrothermal treatments and investigated the influences of these whiskers on the mechanical property and biological performance of the ceramics. Methods: Five kinds of BCP ceramics with in-situ whisker growth, ie, BCP-C, BCP-HNO3, BCP-Citric, BCP-NaOH, BCP-CaCl2 and BCP-Na3PO4 were fabricated by different hydrothermal treatments. The phase compositions, morphologies, crystal structures and mechanical strengths of the obtained BCP ceramics were firstly characterized. Then, the in vitro cell adhesion, proliferation and alkaline  phosphatase (ALP) activity of bone marrow stromal cells (BMSCs) on the BCP ceramics were evaluated. Lastly, the effects of in-situ whisker growth on the bone-like apatite formation abilities of BCP ceramics were also investigated by immersing them in simulated body fluid (SBF). Results: The results demonstrated that the hydrothermal conditions, especially the hydrothermal media, were crucial to determine the phase composition and morphology of the in-situ whisker. Especially among the five media used (HNO3, Citric, NaOH, CaCl2 and Na3PO4), the Na3PO4 treatment resulted in the shortest whisker with a unique hollow structure, and kept the original biphasic composition. All five kinds of whiskers increased the mechanical strength of BCP ceramics to some extent, and showed the good ability of bone-like apatite formation. The in vitro cell study demonstrated that the in-situ whisker growth had no adverse but even positive effect on the adhesion, proliferation and ALP activity of BMSCs. Conclusion: Due to the growth of in-situ whiskers, the mechanical property and biological performance of the obtained BCP ceramics could increase simultaneously. Therefore, in-situ whiskers growth offers a promising strategy for the expanded application of BCP ceramics to meet the requirements of regenerative medicine.


Asunto(s)
Fosfatos de Calcio/química , Cerámica/química , Temperatura , Agua/química , Fosfatasa Alcalina/metabolismo , Animales , Apatitas/metabolismo , Adhesión Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Ensayo de Materiales , Células Madre Mesenquimatosas/citología , Células Madre Mesenquimatosas/efectos de los fármacos , Células Madre Mesenquimatosas/ultraestructura , Ratones , Osteogénesis/efectos de los fármacos , Espectroscopía Infrarroja por Transformada de Fourier , Difracción de Rayos X
2.
Sensors (Basel) ; 21(2)2021 Jan 12.
Artículo en Inglés | MEDLINE | ID: mdl-33445501

RESUMEN

This research paper is concentrated on the design of biologically compatible lead-free piezoelectric composites which may eventually replace traditional lead zirconium titanate (PZT) in micromechanical fluidics, the predominantly used ferroelectric material today. Thus, a lead-free barium-calcium zirconate titanate (BCZT) composite was synthesized, its crystalline structure and size, surface morphology, chemical, and piezoelectric properties were analyzed, together with the investigations done in variation of composite thin film thickness and its effect on the element properties. Four elements with different thicknesses of BCZT layers were fabricated and investigated in order to design a functional acoustophoresis micromechanical fluidic element, based on bulk acoustic generation for particle control technologies. Main methods used in this research were as follows: FTIR and XRD for evaluation of chemical and phase composition; SEM-for surface morphology; wettability measurements were used for surface free energy evaluation; a laser triangular sensing system-for evaluation of piezoelectric properties. XRD results allowed calculating the average crystallite size, which was 65.68 Å3 confirming the formation of BCZT nanoparticles. SEM micrographs results showed that BCZT thin films have some porosities on the surface with grain size ranging from 0.2 to 7.2 µm. Measurements of wettability showed that thin film surfaces are partially wetting and hydrophilic, with high degree of wettability and strong solid/liquid interactions for liquids. The critical surface tension was calculated in the range from 20.05 to 27.20 mN/m. Finally, investigations of piezoelectric properties showed significant results of lead-free piezoelectric composite, i.e., under 5 N force impulse thin films generated from 76 mV up to 782 mV voltages. Moreover, an experimental analysis showed that a designed lead-free BCZT element creates bulk acoustic waves and allows manipulating bio particles in this fluidic system.


Asunto(s)
Acústica/instrumentación , Materiales Biocompatibles/química , Cerámica/química , Circonio/química , Bario/química , Electroforesis/métodos , Diseño de Equipo , Glicerol/química , Plomo , Microscopía Electrónica de Rastreo , Aceite de Oliva/química , Espectrometría por Rayos X , Espectroscopía Infrarroja por Transformada de Fourier , Difracción de Rayos X
3.
Nat Commun ; 11(1): 5678, 2020 11 10.
Artículo en Inglés | MEDLINE | ID: mdl-33173053

RESUMEN

While many organisms synthesize robust skeletal composites consisting of spatially discrete organic and mineral (ceramic) phases, the intrinsic mechanical properties of the mineral phases are poorly understood. Using the shell of the marine bivalve Atrina rigida as a model system, and through a combination of multiscale structural and mechanical characterization in conjunction with theoretical and computational modeling, we uncover the underlying mechanical roles of a ubiquitous structural motif in biogenic calcite, their nanoscopic intracrystalline defects. These nanoscopic defects not only suppress the soft yielding of pure calcite through the classical precipitation strengthening mechanism, but also enhance energy dissipation through controlled nano- and micro-fracture, where the defects' size, geometry, orientation, and distribution facilitate and guide crack initialization and propagation. These nano- and micro-scale cracks are further confined by larger scale intercrystalline organic interfaces, enabling further improved damage tolerance.


Asunto(s)
Biomineralización , Bivalvos/metabolismo , Carbonato de Calcio/metabolismo , Cerámica/química , Animales , Simulación por Computador , Modelos Biológicos
4.
Int J Nanomedicine ; 15: 6705-6720, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32982228

RESUMEN

Over the last decades, joint arthroplasty has become a successful treatment for joint disease. Nowadays, with a growing demand and increasingly younger and active patients accepting these approaches, orthopedic surgeons are seeking implants with improved mechanical behavior and longer life span. However, aseptic loosening as a result of wear debris from implants is considered to be the main cause of long-term implant failure. Previous studies have neatly illustrated the role of micrometric wear particles in the pathological mechanisms underlying aseptic loosening. Recent osteoimmunologic insights into aseptic loosening highlight the important and heretofore underrepresented contribution of nanometric orthopedic wear particles. The present review updates the characteristics of metallic and ceramic nanoparticles generated after prosthesis implantation and summarizes the current understanding of their hazardous effects on peri-prosthetic cells.


Asunto(s)
Artroplastia de Reemplazo de Cadera/instrumentación , Nanopartículas/efectos adversos , Nanopartículas/química , Prótesis e Implantes/efectos adversos , Animales , Artroplastia de Reemplazo de Cadera/efectos adversos , Interfase Hueso-Implante , Cerámica/química , Humanos , Nanopartículas del Metal/efectos adversos , Nanopartículas del Metal/química , Osteoblastos/patología , Osteoclastos/patología
5.
Acta Odontol Latinoam ; 33(2): 98, 2020 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-32920611

RESUMEN

The aim of the current study was to compare the effect of two lithium disilicate ceramic processing techniques (pressing and CAD/CAM) on the degree of conversion of resin cement when it is photoactivated and the microshear bond strength of resin cement to ceramics. Two ceramic discs were manufactured: one by the Press technique and another by CAD/CAM technique. Five Variolink Veneer resin cement samples were photoactivated through each ceramic disc and subjected to attenuated total reflectance Fourier transform infrared spectroscopy to evaluate their degree of conversion. To evaluate microshear bond strength, 20 ceramic bars were prepared: 10 using the Press technique and 10 using the CAD/CAM technique. The bars were air abraded with 50-µm Al2O3 particles, treated with 10% hydrofluoric acid for 20 s and subjected to RelyX Ceramic Primer application. Adper Scotchbond Multi-Purpose Adhesive was applied to the bars and cured for 10 s. Two 1-mm-height plastic tubes were placed on each bar and filled with Variolink Veneer resin cement. Each cylinder was cured for 20 s. Then the plastic tubes were removed and the microshear bond strength of each cylinder was tested. Data for degree of conversion (%) and microshear bond strength (MPa) were subjected to Student's t-test (α = 0.05). Both degree of conversion of resin cement photoactivated through ceramic and microshear bond strength of resin cement to ceramic were statistically higher in the group in which ceramic was prepared by CAD/CAM technique (44.74% and 22.18 MPa) than in the group in which the ceramic was prepared by the Press technique (25.71% and 19.83 MPa). The lithium disilicate ceramic processing techniques affected the degree of conversion of resin cement when it is photoactivated through the ceramics and the microshear bond strength of resin cement to ceramics.


Asunto(s)
Cerámica/química , Recubrimiento Dental Adhesivo , Porcelana Dental/química , Cementos de Resina/química , Humanos , Ensayo de Materiales , Propiedades de Superficie
6.
Proc Natl Acad Sci U S A ; 117(38): 23450-23459, 2020 09 22.
Artículo en Inglés | MEDLINE | ID: mdl-32913055

RESUMEN

Cuttlefish, a unique group of marine mollusks, produces an internal biomineralized shell, known as cuttlebone, which is an ultra-lightweight cellular structure (porosity, ∼93 vol%) used as the animal's hard buoyancy tank. Although cuttlebone is primarily composed of a brittle mineral, aragonite, the structure is highly damage tolerant and can withstand water pressure of about 20 atmospheres (atm) for the species Sepia officinalis Currently, our knowledge on the structural origins for cuttlebone's remarkable mechanical performance is limited. Combining quantitative three-dimensional (3D) structural characterization, four-dimensional (4D) mechanical analysis, digital image correlation, and parametric simulations, here we reveal that the characteristic chambered "wall-septa" microstructure of cuttlebone, drastically distinct from other natural or engineering cellular solids, allows for simultaneous high specific stiffness (8.4 MN⋅m/kg) and energy absorption (4.4 kJ/kg) upon loading. We demonstrate that the vertical walls in the chambered cuttlebone microstructure have evolved an optimal waviness gradient, which leads to compression-dominant deformation and asymmetric wall fracture, accomplishing both high stiffness and high energy absorption. Moreover, the distribution of walls is found to reduce stress concentrations within the horizontal septa, facilitating a larger chamber crushing stress and a more significant densification. The design strategies revealed here can provide important lessons for the development of low-density, stiff, and damage-tolerant cellular ceramics.


Asunto(s)
Materiales Biomiméticos/química , Huesos/química , Sepia/química , Animales , Fenómenos Biomecánicos , Cerámica/química , Diseño de Equipo , Dureza , Porosidad
7.
Nat Commun ; 11(1): 3840, 2020 07 31.
Artículo en Inglés | MEDLINE | ID: mdl-32737293

RESUMEN

Currently, human magnetic resonance (MR) examinations are becoming highly specialized with a pre-defined and often relatively small target in the body. Conventionally, clinical MR equipment is designed to be universal that compromises its efficiency for small targets. Here, we present a concept for targeted clinical magnetic resonance imaging (MRI), which can be directly integrated into the existing clinical MR systems, and demonstrate its feasibility for breast imaging. The concept comprises spatial redistribution and passive focusing of the radiofrequency magnetic flux with the aid of an artificial resonator to maximize the efficiency of a conventional MR system for the area of interest. The approach offers the prospect of a targeted MRI and brings novel opportunities for high quality specialized MR examinations within any existing MR system.


Asunto(s)
Neoplasias de la Mama/diagnóstico por imagen , Cerámica/efectos de la radiación , Espectroscopía Dieléctrica/métodos , Imagen por Resonancia Magnética/métodos , Espectroscopía de Resonancia Magnética/métodos , Adulto , Cerámica/química , Espectroscopía Dieléctrica/instrumentación , Radiación Electromagnética , Diseño de Equipo , Femenino , Voluntarios Sanos , Humanos , Imagen por Resonancia Magnética/instrumentación , Fantasmas de Imagen , Relación Señal-Ruido
8.
J Chromatogr A ; 1629: 461465, 2020 Oct 11.
Artículo en Inglés | MEDLINE | ID: mdl-32827903

RESUMEN

Modeling the chromatographic separations of proteins at manufacturing scale is important since downstream processing costs are often dominant. At such scales, the columns are highly overloaded heightening the challenge of predicting performance. In this work, the separation of a monoclonal antibody monomer-dimer mixture is conducted by gradient elution chromatography with ceramic hydroxyapatite (CHT) columns Type I and Type II under overloaded conditions. Phosphate gradients are shown to be preferable over sodium chloride gradients since the latter result in undesirable pH transitions generated within the column itself. Using sodium phosphate gradients separation is obtained with both CHT types, achieving approximately 90% recovery at 99% monomer purity starting with a mixture containing 30% dimer at total protein loads up to 30 mg/mL. Because of its higher binding capacity, even higher loadings can be obtained with CHT Type I without monomer breakthrough. A hybrid model is developed to describe the separation. The model, based on an empirical description of two-component, competitive isotherms at low sodium phosphate concentration coupled with the stoichiometric displacement model at higher sodium phosphate concentrations, is in good agreement with the experiments using the linear driving force (LDF) approximation to describe adsorption/desorption kinetics. The same LDF rate coefficient predicts the separation at loadings between 0.8 and 30 mg/mL. The model developed in this work can be used as a general tool to optimize operating conditions, understand what factors limit performance, and compare different operating modes.


Asunto(s)
Anticuerpos Monoclonales/aislamiento & purificación , Cerámica/química , Durapatita/química , Multimerización de Proteína , Adsorción , Anticuerpos Monoclonales/química , Simulación por Computador , Iones , Cinética , Modelos Químicos , Polímeros/química , Unión Proteica , Sodio/química , Temperatura
9.
PLoS One ; 15(8): e0237608, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32817620

RESUMEN

The application of biomolecular techniques to archaeological materials from the Balkans is providing valuable new information on the prehistory of the region. This is especially relevant for the study of the neolithisation process in SE Europe, which gradually affected the rest of the continent. Here, to answer questions regarding diet and subsistence practices in early farming societies in the central Balkans, we combine organic residue analyses of archaeological pottery, taxonomic and isotopic study of domestic animal remains and biomolecular analyses of human dental calculus. The results from the analyses of the lipid residues from pottery suggest that milk was processed in ceramic vessels. Dairy products were shown to be part of the subsistence strategies of the earliest Neolithic communities in the region but were of varying importance in different areas of the Balkan. Conversely, milk proteins were not detected within the dental calculus. The molecular and isotopic identification of meat, dairy, plants and beeswax in the pottery lipids also provided insights into the diversity of diet in these early Neolithic communities, mainly based on terrestrial resources. We also present the first compound-specific radiocarbon dates for the region, obtained directly from absorbed organic residues extracted from pottery, identified as dairy lipids.


Asunto(s)
Agricultura/métodos , Cerámica/química , Industria Lechera/métodos , Dieta , Lípidos/análisis , Proteínas de la Leche/análisis , Leche/química , Animales , Arqueología , Peninsula Balcánica , Agricultores , Humanos , Ceras
10.
Proc Natl Acad Sci U S A ; 117(33): 19780-19791, 2020 08 18.
Artículo en Inglés | MEDLINE | ID: mdl-32719145

RESUMEN

The international scope of the Mediterranean wine trade in Late Antiquity raises important questions concerning sustainability in an ancient international economy and offers a valuable historical precedent to modern globalization. Such questions involve the role of intercontinental commerce in maintaining sustainable production within important supply regions and the vulnerability of peripheral regions believed to have been especially sensitive to environmental and political disturbances. We provide archaeobotanical evidence from trash mounds at three sites in the central Negev Desert, Israel, unraveling the rise and fall of viticulture over the second to eighth centuries of the common era (CE). Using quantitative ceramic data obtained in the same archaeological contexts, we further investigate connections between Negev viticulture and circum-Mediterranean trade. Our findings demonstrate interrelated growth in viticulture and involvement in Mediterranean trade reaching what appears to be a commercial scale in the fourth to mid-sixth centuries. Following a mid-sixth century peak, decline of this system is evident in the mid- to late sixth century, nearly a century before the Islamic conquest. These findings closely correspond with other archaeological evidence for social, economic, and urban growth in the fourth century and decline centered on the mid-sixth century. Contracting markets were a likely proximate cause for the decline; possible triggers include climate change, plague, and wider sociopolitical developments. In long-term historical perspective, the unprecedented commercial florescence of the Late Antique Negev appears to have been unsustainable, reverting to an age-old pattern of smaller-scale settlement and survival-subsistence strategies within a time frame of about two centuries.


Asunto(s)
Arqueología/economía , Cerámica/química , Arqueología/historia , Cerámica/economía , Cerámica/historia , Cambio Climático/historia , Comercio , Cultura , Historia Antigua , Humanos , Israel
11.
J Vis Exp ; (160)2020 06 18.
Artículo en Inglés | MEDLINE | ID: mdl-32628166

RESUMEN

The externally-heated diamond anvil cell (EHDAC) can be used to generate simultaneously high-pressure and high-temperature conditions found in Earth's and planetary interiors. Here we describe the design and fabrication of the EHDAC assemblies and accessories, including ring resistive heaters, thermal and electrical insulating layers, thermocouple placement, as well as the experimental protocol for preparing the EHDAC using these parts. The EHDAC can be routinely used to generate megabar pressures and up to 900 K temperatures in open air, and potentially higher temperatures up to ~1200 K with a protective atmosphere (i.e., Ar mixed with 1% H2). Compared with a laser-heating method for reaching temperatures typically >1100 K, external heating can be easily implemented and provide a more stable temperature at ≤900 K and less temperature gradients to the sample. We showcased the application of the EHDAC for synthesis of single crystal ice-VII and studied its single-crystal elastic properties using synchrotron-based X-ray diffraction and Brillouin scattering at simultaneously high-pressure high-temperature conditions.


Asunto(s)
Diamante/química , Elasticidad , Hielo/análisis , Presión , Temperatura , Cerámica/química , Cristalización , Análisis Espectral , Sincrotrones , Difracción de Rayos X
12.
Niger J Clin Pract ; 23(6): 792-797, 2020 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-32525113

RESUMEN

Background: There is no information about the shear bond strengths (SBS) of zirconia ceramic to primary tooth dentin. Aim: To investigate the effect of different surface treatments and cements on the shear bond strength (SBS) of zirconia ceramic to primary tooth dentin. Materials and Methods: Prepared zirconia bars were distributed into four groups according to surface treatment procedure: control, sandblasting, CoJet and hot etching. The zirconia specimens in each group were further divided into subgroups according to cement (n = 13): self-adhesive resin (Rely-X Unicem), resin-modified glass ionomer (Ketac-Cem Plus), and universal bioactive (BioCem). Zirconia specimens were bonded to the primary tooth dentin surface by cement. SBS was measured, and the data were subjected to two-way ANOVA and Tukey's tests. Results: Statistical differences were observed in the surface treatment procedures for Rely-X Unicem (P < 0.05), but no statistically significant differences were found in the sandblasting, CoJet and hot-etching groups for Ketac-Cem Plus (P > 0.05). For BioCem, the SBS value for the hot etching group was significantly lower than those for the CoJet and sandblasting groups (P < 0.05). The SBS values for the Rely-X Unicem subgroups (sandblasting, CoJet and hot etching) were significantly higher than those for the other cements (P < 0.05). Conclusion: The bond strength of zirconia ceramic to primary tooth dentin is affected by surface treatments and cements.


Asunto(s)
Cerámica/química , Recubrimiento Dental Adhesivo , Dentina , Cementos de Resina/química , Resistencia al Corte , Diente Primario , Circonio/química , Resinas Acrílicas , Adhesivos , Cementos de Ionómero Vitreo , Humanos , Ensayo de Materiales , Dióxido de Silicio , Propiedades de Superficie
13.
Proc Natl Acad Sci U S A ; 117(26): 14688-14693, 2020 06 30.
Artículo en Inglés | MEDLINE | ID: mdl-32541039

RESUMEN

Traces of lipids, absorbed and preserved for millennia within the inorganic matrix of ceramic vessels, act as molecular fossils and provide manifold information about past people's subsistence, diet, and rituals. It is widely assumed that lipids become preserved after adsorption into nano- to micrometer-sized pores, but to this day the distribution of these lipids in the ceramics was virtually unknown, which severely limits our understanding about the process of lipid preservation. Here we use secondary ion mass spectrometry (SIMS) imaging for direct in situ analysis of lipids absorbed in 700- to 2,000-y-old archaeological pottery. After sectioning from larger sherds, wall cross-sections of smaller fragments were used for SIMS analysis. Lipids were found in relatively large zones of 5- to 400-µm diameter, which does not support the notion of absorption only into individual nanometer-scale pores but indicates that more macroscopic structures in the ceramics are involved in lipid preservation as well. Furthermore, lipids were found concentrated on calcium carbonate inclusions in the ceramics, which suggests that precipitation of fatty acids as calcium salts is an important aspect of lipid preservation in archaeological samples. This has important implications for analytical methods based on extraction of lipids from archaeological ceramics and needs to be considered to maximize the yield and available information from each unique sample.


Asunto(s)
Arqueología/métodos , Cerámica/química , Arcilla/química , Lípidos , Espectrometría de Masa de Ion Secundario/métodos , Cerámica/historia , Culinaria/historia , Historia Antigua , Humanos , Lípidos/análisis , Lípidos/química , Imagen Molecular , Reino Unido
14.
Int J Food Microbiol ; 332: 108764, 2020 Nov 02.
Artículo en Inglés | MEDLINE | ID: mdl-32585372

RESUMEN

Here we present a research of bacterial adhesion to two most often used materials in modern kitchens, namely food grade ceramics and Teflon. To test the bacterial adhesion on kitchen worktops Escherichia coli, Pseudomonas aeruginosa and Campylobacter jejuni were used as the most common foodborne contaminants. Contact angle, roughness and streaming potential measurements were used for surface characterization. Crystal violet staining and scanning electron microscopy were applied for bacterial adhesion analysis. We showed that the adhesion of tested bacteria strains was lower on the Teflon surface compared to the ceramics. The hydrophobicity of the surface substantially contributed to the bacterial adhesion rate. On the other hand, the surface roughness and charge did not play a crucial role in the adhesion process.


Asunto(s)
Adhesión Bacteriana/fisiología , Cerámica , Artículos Domésticos , Politetrafluoroetileno , Bacterias/aislamiento & purificación , Cerámica/química , Contaminación de Equipos , Fómites/microbiología , Enfermedades Transmitidas por los Alimentos/microbiología , Interacciones Hidrofóbicas e Hidrofílicas , Politetrafluoroetileno/química , Propiedades de Superficie
15.
Niger J Clin Pract ; 23(5): 660-667, 2020 May.
Artículo en Inglés | MEDLINE | ID: mdl-32367873

RESUMEN

Aims: The aim of this study is to investigate the color changes of three different traditional composites, one ceramic and two resin-based composites CAD/CAM blocks in different solutions. Methods: The materials used in the study were CAD/CAM block containing lithium disilicate glass ceramic (Ivoclar), Vita Enamic containing resin (VITA), Lava Ultimate Block containing resin (3M ESPE), G-aenial anterior composite (GC,), Filtek™ Ultimate Universal composite (3M ESPE) and Clearfil Majesty Esthetic composite (Kuaray). As colouring solutions, red wine (Buzbaǧ), black tea (Lipton), coffee (Nescafe) and distilled water (EAU distillee) were used. For the preparation of the traditional composite samples to be used in the study, 7 × 7 mm square-shaped plexiglass moulds, 1.2 mm in thickness, were used. The CAD/CAM blocks with ceramic and resin content were cut at the same thickness using a Struers sensitive cutting device. The samples were then randomly separated into grups of 10 and of the 240 samples, groups were separated into 6 different materials and 4 different solutions. The colour measurements of the 240 samples were taken at baseline, 30 days and 120 days with a Lovibond spectrophotometer (Tintometer). Results: A statistically significant difference was determined between the materials in respect of the ΔE values in the 30-day solution groups (P < 0.05). No statistically significant difference was determined in the ΔE values of the different materials in the 30-day and 120-day distilled water groups (P > 0.05). A statistically significant difference was determined between the materials in respect of the ΔE values in the 120-day solution groups (P < 0.05). Conclusion: In respect of discolouration, ceramic blocks are more successful. Resin-based blocks and traditional aesthetic composites showed more discolouration. The dietary habits of the patient should be taken into consideration in the selection of the restorative material.


Asunto(s)
Cerámica/química , Materiales Dentales/química , Ensayo de Materiales/métodos , Color , Resinas Compuestas/química , Diseño Asistido por Computadora
16.
Braz Oral Res ; 34: e035, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32321053

RESUMEN

Although fiber-reinforced composites are commonly used in dental practice, whether fiber-reinforced crowns and fixed partial dentures can be used as definitive prostheses remains to be determined. This study used scanning electron microscopy to evaluate the load-bearing capacity of non-reinforced and fiber-reinforced composite (FRC) molar crowns prepared by computer-aided design/computer-aided manufacturing (CAD/CAM). The crowns were fabricated from three empirical FRC blocks, one empirical composite block, and one commercial ceramic block. The FRC resin was prepared by mixing BaO silicate particles, E-glass fiber, and dimethacrylate resin. Specimens were divided into five groups (n = 10), differing in the amounts of filler, resin, and fiber. Crowns were statically loaded until fracture. One-way analysis of variance and Tukey's post hoc multiple comparison tests were used for statistical analyses. The groups showed significant differences in load-bearing capacity; empirical bidirectional FRC resin blocks had the highest capacity, while commercial ceramic blocks had the lowest capacity. Molar crowns formed from FRC resin blocks had higher load-bearing capacity compared to non-reinforced composite resin and ceramic blocks. These results show that fiber reinforcement increased the load-bearing capacity of molar crowns.


Asunto(s)
Resinas Compuestas/química , Diseño Asistido por Computadora , Coronas , Soporte de Peso , Análisis de Varianza , Cerámica/química , Diseño de Prótesis Dental , Humanos , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Diente Molar , Valores de Referencia , Reproducibilidad de los Resultados , Propiedades de Superficie
17.
Nature ; 580(7804): 506-510, 2020 04.
Artículo en Inglés | MEDLINE | ID: mdl-32322061

RESUMEN

Pottery is one of the most commonly recovered artefacts from archaeological sites. Despite more than a century of relative dating based on typology and seriation1, accurate dating of pottery using the radiocarbon dating method has proven extremely challenging owing to the limited survival of organic temper and unreliability of visible residues2-4. Here we report a method to directly date archaeological pottery based on accelerator mass spectrometry analysis of 14C in absorbed food residues using palmitic (C16:0) and stearic (C18:0) fatty acids purified by preparative gas chromatography5-8. We present accurate compound-specific radiocarbon determinations of lipids extracted from pottery vessels, which were rigorously evaluated by comparison with dendrochronological dates9,10 and inclusion in site and regional chronologies that contained previously determined radiocarbon dates on other materials11-15. Notably, the compound-specific dates from each of the C16:0 and C18:0 fatty acids in pottery vessels provide an internal quality control of the results6 and are entirely compatible with dates for other commonly dated materials. Accurate radiocarbon dating of pottery vessels can reveal: (1) the period of use of pottery; (2) the antiquity of organic residues, including when specific foodstuffs were exploited; (3) the chronology of sites in the absence of traditionally datable materials; and (4) direct verification of pottery typochronologies. Here we used the method to date the exploitation of dairy and carcass products in Neolithic vessels from Britain, Anatolia, central and western Europe, and Saharan Africa.


Asunto(s)
Arqueología/métodos , Cerámica/química , Cerámica/historia , Datación Radiométrica/métodos , Datación Radiométrica/normas , África del Norte , Arqueología/normas , Teorema de Bayes , Radioisótopos de Carbono , Europa (Continente) , Ácidos Grasos/química , Ácidos Grasos/aislamiento & purificación , Alimentos/historia , Historia Antigua , Lípidos/química , Lípidos/aislamiento & purificación , Espectrometría de Masas
18.
Niger J Clin Pract ; 23(4): 456-463, 2020 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-32246650

RESUMEN

Aims: The purpose of this study was to observe the stresses of all-on-four implant designs in an edentulous mandible in the implant, surrounding bone, and monolithic ceramics. Materials and Methods: In mandibular all-on-four implant models, anterior implants were placed vertically, and posterior implants were differently inclined. On the full-arch fixed prosthetic restoration monolithic zirconia framework, monolithic lithium disilicate was prepared as the superstructure. Model 1M (1M-15.5); posterior implants angled at 15° to the occlusion plane and a cantilever length of 5 mm, Model 2M; (2M-15.9), Model 3M; (3M-30.5), and Model 4M; (4M-30.9) were prepared. A total of 300 N bilateral force was applied at an angle of 30° and oblique to the occlusion plane. Stress values on dental implants, abutments, the surrounding bone, and prosthetic restorations were calculated. Results: The highest stress concentration was observed in the 2nd connector region between the canine and the 1st premolar tooth in the monolithic zirconia frameworks (457.21 MPa). Stress concentration in the cortical bone was 60.93 MPa in posterior implants. Stress was higher in posterior angled implants than straight implants. Stress at posterior angulation increased by 21 MPa in implants angled at 15°. Conclusion: In bilateral loading, the force applied to anterior implants does not have a significant effect on the bone structure. Stress concentration increases in posterior angled implants and surrounding bone. Moreover, stress concentration increases as the length of the cantilever, the weakest part in all-on-four implants, increases. As posterior implant angulation increases, stress concentration level and localization are affected.


Asunto(s)
Cerámica/química , Implantes Dentales , Prótesis Dental de Soporte Implantado/métodos , Imagenología Tridimensional/métodos , Titanio/química , Circonio/química , Diente Premolar , Arco Dental/fisiología , Modelos Dentales , Diseño de Prótesis Dental , Análisis del Estrés Dental , Análisis de Elementos Finitos , Humanos , Mandíbula/fisiología , Estrés Mecánico
19.
Niger J Clin Pract ; 23(4): 523-533, 2020 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-32246660

RESUMEN

Objectives: The purpose of this study was to evaluate the effect of the tooth color, ceramic color, and ceramic thickness on the final color parameters of a feldspathic computer-aided design (CAD)/computer-aided manufacturing (CAM) ceramic material. Materials and Methods: Resin specimens (12 × 14 × 4 mm) were prepared from six shades, namely, 0M1S, 1M1S, 2M3S, 3M2S, 4M3S, and 5M3S, to simulate tooth color. Ceramic slices with thicknesses of 0.3, 0.5, 0.7, and 1 mm were sectioned from Vitablocs Mark II (12 × 14 × 18 mm) in 10 shades-OM1C, 1M1C, 1M2C, 2M1C, 2M2C, 2M3C, 3M1C, 3M2C, 3M3C, and 4M2C. An intraoral spectrophotometer was used and three axes of Commission Internationale de l'Eclairage (CIE) LAB color space (CIE L* a* b*) and chroma (C) and hue (H) values were obtained. Results: The a* and b* values showed a decrease with increasing thickness. Generally, C decreased with the increasing ceramic thickness. The effect of ceramic thickness on H changed depending on the block and substructure color. The change of ceramic thickness resulted in changes in the lightness parameter (L*) of the ceramics. Generally, with an increase in the thickness, the L* value increased. The univariate analysis of variance (ANOVA) indicated a significant interaction between ceramic thickness and substructure color (P <. 005) and ceramic thickness and ceramic color (P <. 005). Conclusion: The final color parameters of a feldspathic CAD/CAM block were significantly affected by the changes in the ceramic thickness and substructure color.


Asunto(s)
Cerámica/química , Diseño Asistido por Computadora , Materiales Dentales/química , Color
20.
Niger J Clin Pract ; 23(3): 355-361, 2020 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-32134035

RESUMEN

Objectives: This study evaluated the effect of Er, Cr: YSGG laser irradiation at different powers on repair bond strength (RBS) between ceramic restoration and composite resin (CR). Materials and Methods: Sixty ceramic samples were prepared and thermocycled for 2,500 cycles between 5°C and 55°C. Samples randomly divided into six groups (n = 10) according to the different surface treatment: control group (no surface treatment), 9.6% hydrofluoric acid etching, 37% phosphoric acid etching, and irradiations with Er, Cr: YSGG lasers (1 to 3W). The Cimara System was applied to all samples surface according to the manufacturer's instructions. CR resin was built-up on each ceramic surface using a tygon tube. The RBS test was performed at a crosshead speed of 1 mm/min, and one sample of each group was also observed under SEM and EDS was used to measure the elemental profiles of each specimen. Data was analyzed with one-way ANOVA and Tukey HSD test. Results: The lowest RBS was recorded in Group OF, and the highest RBS was recorded in Group HF, followed by Group 3W. There was no statistical difference between Group Control, 1W and 2W. Furthermore, differences in RBSs between Group 3W and the other groups except Group 2W were significant (P < 0.05). In EDS analysis, there are evident differences between surface treated samples and controls. Conclusions: 3W laser irradiation may be an alternative method to acid etching for enhancing the RBS of CR to ceramic.


Asunto(s)
Cerámica/química , Resinas Compuestas/química , Láseres de Estado Sólido , Ensayo de Materiales , Propiedades de Superficie
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA
...