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1.
J Indian Soc Pedod Prev Dent ; 38(3): 253-258, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33004723

RESUMO

Background: In cases where there is an extensive loss of crown structure, these treatments require intracanal posts placement for retention as occlusal forces make the tooth structure weak and prone to fracture. Thus, restoration of primary anterior teeth, followed by post placement and cementation with pediatric zirconia crowns helps withstand masticatory forces to a greater extent. Aim: This in vitro study evaluates the compressive strength of two different post systems in the primary anterior teeth, restored with pediatric zirconia crowns. Materials and Methods: The present study was an in vitro, experimental, comparative study, with a study sample selected using a convenience sampling method. Forty-five primary anterior teeth were obturated and restored with enhanced omega-shaped loop and reinforced glass-fiber posts were cemented with pediatric zirconia crowns. The compressive strength and the type of fracture were evaluated for each group. Results: This study demonstrated that the glass-fiber posts had a higher compressive strength, although omega-shaped posts showed a higher presence of favorable fracture. Conclusion: Retentive omega-shaped loops and reinforced glass-fiber posts were both capable of withstanding high fracture loads. The addition of cemented pediatric zirconia crown on decayed primary anterior teeth restored with post systems helped withstand the load to a greater extent.


Assuntos
Técnica para Retentor Intrarradicular , Fraturas dos Dentes , Criança , Força Compressiva , Coroas , Humanos , Zircônio
2.
Braz Dent J ; 31(4): 445-452, 2020 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-32901723

RESUMO

The aim of this study was to assess the effect of different commercial liquid phases (Ketac, Riva, and Fuji IX) and the use of spherical pre-reacted glass (SPG) fillers on cement maturation, fluoride release, compressive (CS) and biaxial flexural strength (BFS) of experimental glass ionomer cements (GICs). The experimental GICs (Ketac_M, Riva_M, FujiIX_M) were prepared by mixing SPG fillers with commercial liquid phases using the powder to liquid mass ratio of 2.5:1. FTIR-ATR was used to assess the maturation of GICs. Diffusion coefficient of fluoride (DF) and cumulative fluoride release (CF) in deionized water was determined using the fluoride ion specific electrode (n=3). CS and BFS at 24 h were also tested (n=6). Commercial GICs were used as comparisons. Riva and Riva_M exhibited rapid polyacrylate salt formation. The highest DF and CF were observed with Riva_M (1.65x10-9 cm2/s) and Riva (77 ppm) respectively. Using SPG fillers enhanced DF of GICs on average from ~2.5x10-9 cm2/s to ~3.0x10-9 cm2/s but reduced CF of the materials on average from ~51 ppm to ~42 ppm. The CS and BFS of Ketac_M (144 and 22 MPa) and Fuji IX_M (123 and 30 MPa) were comparable to commercial materials. Using SPG with Riva significantly reduced CS and BFS from 123 MPa to 55 MPa and 42 MPa to 28 MPa respectively. The use of SPG fillers enhanced DF but reduced CF of GICs. Using SPG with Ketac or Fuji IX liquids provided comparable strength to the commercial materials.


Assuntos
Cimentos Dentários , Cimentos de Ionômeros de Vidro , Força Compressiva , Teste de Materiais , Resistência à Tração
3.
Nat Commun ; 11(1): 4502, 2020 09 09.
Artigo em Inglês | MEDLINE | ID: mdl-32908136

RESUMO

Biological tissues, such as muscle, can increase their mechanical strength after swelling due to the existence of many biological membrane barriers that can regulate the transmembrane transport of water molecules and ions. Oppositely, typical synthetic materials show a swelling-weakening behavior, which always suffers from a sharp decline in mechanical strength after swelling, because of the dilution of the network. Here, we describe a swelling-strengthening phenomenon of polymer materials achieved by a bioinspired strategy. Liposomal membrane nanobarriers are covalently embedded in a crosslinked network to regulate transmembrane transport. After swelling, the stretched network deforms the liposomes and subsequently initiates the transmembrane diffusion of the encapsulated molecules that can trigger the formation of a new network from the preloaded precursor. Thanks to the tough nature of the double-network structure, the swelling-strengthening phenomenon is achieved to polymer hydrogels successfully. Swelling-triggered self-strengthening enables the development of various dynamic materials.


Assuntos
Materiais Biomiméticos/química , Hidrogéis/química , Lipossomos/química , Nanoestruturas/química , Força Compressiva , Reagentes para Ligações Cruzadas/química , Lipossomos/ultraestrutura , Teste de Materiais , Microscopia Eletrônica de Transmissão , Nanoestruturas/ultraestrutura , Resistência à Tração
4.
J Environ Manage ; 271: 111013, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32778296

RESUMO

The copper production process causes waste and by-products called waste copper slag (WCS). A considerable amount of WCS is produced globally. This research aims to utilise WCS as an alternative to natural coarse aggregate in self-compacting concrete (SCC). To achieve this goal, WCS was utilised in different percentages (0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%) as a natural coarse aggregate replacement in SCC production. Following this, the fresh, mechanical, and durability characteristics of SCCs incorporating WCS as a partial replacement of coarse aggregates were investigated in-depth. Incorporating 100% WCS as coarse aggregates in SCCs showed 27%, 29%, and 26% growth in compressive, split, and flexural strengths in 28 days, respectively. The reduction of free drying shrinkage of the mixture containing 100% WCS compared to the control mixture was approximately 36%, and the water absorption of all the specimens was less than 6%. Further, the increase in weight for the mixture containing 100% WCS as coarse aggregates was less than 15% compared to the control mixture. A cost analysis of the SCCs showed that incorporating WCS for all coarse aggregates reduced production costs by 19%. Investigating the economic index of concrete containing WCS as a coarse aggregate showed that utilising the WCS in green SCC was feasible.


Assuntos
Materiais de Construção , Cobre , Força Compressiva , Conservação dos Recursos Naturais , Água
5.
Phys Rev Lett ; 125(6): 068101, 2020 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-32845697

RESUMO

Shape, dynamics, and viscoelastic properties of eukaryotic cells are primarily governed by a thin, reversibly cross-linked actomyosin cortex located directly beneath the plasma membrane. We obtain time-dependent rheological responses of fibroblasts and MDCK II cells from deformation-relaxation curves using an atomic force microscope to access the dependence of cortex fluidity on prestress. We introduce a viscoelastic model that treats the cell as a composite shell and assumes that relaxation of the cortex follows a power law giving access to cortical prestress, area-compressibility modulus, and the power law exponent (fluidity). Cortex fluidity is modulated by interfering with myosin activity. We find that the power law exponent of the cell cortex decreases with increasing intrinsic prestress and area-compressibility modulus, in accordance with previous finding for isolated actin networks subject to external stress. Extrapolation to zero tension returns the theoretically predicted power law exponent for transiently cross-linked polymer networks. In contrast to the widely used Hertzian mechanics, our model provides viscoelastic parameters independent of indenter geometry and compression velocity.


Assuntos
Actinas/química , Fibroblastos/química , Fibroblastos/citologia , Modelos Biológicos , Actinas/fisiologia , Animais , Fenômenos Biomecânicos , Linhagem Celular , Membrana Celular/química , Membrana Celular/fisiologia , Força Compressiva , Cães , Elasticidade , Microscopia de Força Atômica , Miosinas/química , Miosinas/fisiologia , Reologia/métodos , Viscosidade
6.
Niger J Clin Pract ; 23(8): 1068-1072, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32788483

RESUMO

Aims: The aim of this study was to compare the influence of operators on the microhardness and compressive strength of mineral trioxide aggregate (MTA). Materials and Methods: Forty dental specialists were asked to prepare a series of MTA samples. The tested material was ProRoot MTA (DentsplyMaillefer, Switzerland). Each participant prepared one sample to a consistency they considered acceptable for use in practice (improvised group) and another one according to the manufacturer's recommended water-to-powder (WP) ratio (pre-weighed group). The samples were incubated at 37°C and 95% humidity for 4 days. Parameters evaluated in this study were microhardness and compressive strength. Results: Operators mixed MTA samples with varying WP ratios. However, there was no significant difference between the microhardness and compressive strength values of MTA samples between the improvised, the pre-weighed and the control groups. MTA was mixed in a thicker consistency than the manufacturers recommended ratio (0.33) by 62.5% of the operators. Conclusion: According to the results of this study, even though the WP ratios that were utilized in the clinical setting vary, microhardness and compressive strength values of MTA was not significantly affected.


Assuntos
Compostos de Alumínio/química , Compostos de Cálcio/química , Força Compressiva , Teste de Materiais/métodos , Óxidos/química , Materiais Restauradores do Canal Radicular , Silicatos/química , Estudos de Casos e Controles , Combinação de Medicamentos , Dureza , Humanos , Água
7.
J Environ Manage ; 275: 111253, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32858268

RESUMO

In this work, the study of the biomass application of a microphyte plant Slavinia auriculata Aublet in red ceramic was carried out. The waste comes from the phytoremediation process, used in sewage treatment plants. Characterization tests were carried out by chemical, mineralogical, dilatometry, thermal and mass spectrometry techniques, where it was possible to prove that biomass is compatible in its composition for application in ceramic materials and also has great potential to act as a source of energy. The production of specimens was carried out using an industrial clay mass and incorporating 0-10% of biomass in samples produced by pressing and burned at temperatures between 750 and 1050 °C. Properties of plasticity, firing shrinkage, apparent drying and firing density, water absorption, compressive strength and tensile strength in flexion were evaluated, where the feasibility of using up to 2.5% biomass in ceramics firing in 1050 °C s was proven. Although the results of water absorption at the firing temperature of 1050 °C have increased from 18.3% to 19.4% with the use of 2.5% of the residue, the results of tensile strength in flexion have reduced from 4.80 to 3.75 MPa and the results of compressive strength have reduced from 27.6 to 22 MPa, the values obtained meet international recommendations and are in accordance with the recommendations of the bibliography. Finally, an economic analysis of the application of biomass in ceramic materials was carried out, where it was observed that it was possible to save up to 5.04% with the use of the biomass under study, providing an annual savings of $ 2668.8 for the ceramic industry.


Assuntos
Cerâmica , Argila , Biomassa , Força Compressiva , Temperatura
8.
Nat Protoc ; 15(8): 2321-2340, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32681151

RESUMO

We recently developed an in vivo compression device that simulates the solid mechanical forces exerted by a growing tumor on the surrounding brain tissue and delineates the physical versus biological effects of a tumor. This device, to our knowledge the first of its kind, can recapitulate the compressive forces on the cerebellar cortex from primary (e.g., glioblastoma) and metastatic (e.g., breast cancer) tumors, as well as on the cerebellum from tumors such as medulloblastoma and ependymoma. We adapted standard transparent cranial windows normally used for intravital imaging studies in mice to include a turnable screw for controlled compression (acute or chronic) and decompression of the cerebral cortex. The device enables longitudinal imaging of the compressed brain tissue over several weeks or months as the screw is progressively extended against the brain tissue to recapitulate tumor growth-induced solid stress. The cranial window can be simply installed on the mouse skull according to previously established methods, and the screw mechanism can be readily manufactured in-house. The total time for construction and implantation of the in vivo compressive cranial window is <1 h (per mouse). This technique can also be used to study a variety of other diseases or disorders that present with abnormal solid masses in the brain, including cysts and benign growths.


Assuntos
Encéfalo/diagnóstico por imagem , Neuroimagem , Estresse Mecânico , Animais , Neoplasias Encefálicas/diagnóstico por imagem , Força Compressiva , Feminino , Masculino , Camundongos
9.
PLoS One ; 15(7): e0235822, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32658896

RESUMO

Studies concerning the mechanical properties of the human periodontal ligament under dynamic compression are rare. This study aimed to determine the viscoelastic properties of the human periodontal ligament under dynamic compressive loading. Ten human incisor specimens containing 5 maxillary central incisors and 5 maxillary lateral incisors were used in a dynamic mechanical analysis. Frequency sweep tests were performed under the selected frequencies between 0.05 Hz and 5 Hz with a compression amplitude that was 2% of the PDL's initial width. The compressive strain varied over a range of 4%-8% of the PDL's initial width. The storage modulus, ranging from 28.61 MPa to 250.21 MPa, increased with the increase in frequency. The loss modulus (from 6.00 MPa to 49.28 MPa) also increased with frequency from 0.05 Hz- 0.5 Hz but remained constant when the frequency was higher than 0.5 Hz. The tanδ showed a negative logarithmic correlation with frequency. The dynamic moduli and the loss tangent of the central incisor were higher than those of the lateral incisor. This study concluded that the human PDL exhibits viscoelastic behavior under compressive loadings within the range of the used frequency, 0.05 Hz- 5 Hz. The tooth position and testing frequency may have effects on the viscoelastic properties of PDL.


Assuntos
Incisivo/fisiologia , Ligamento Periodontal/fisiologia , Adulto , Fenômenos Biomecânicos , Força Compressiva , Elasticidade , Humanos , Masculino , Pessoa de Meia-Idade , Estresse Mecânico , Viscosidade
10.
Braz Oral Res ; 34: e053, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32578763

RESUMO

The objective was to evaluate the compressive strength (CS), diametral tensile strength (DTS), flexural strength (FS), and Knoop microhardness (KH) of different conventional restorative glass-ionomer cements (GICs) and to correlate these mechanical properties (MP) with the stabilization time (ST) of their chemical bonds. Eighteen GICs were tested: Bioglass [B], Chemfil Rock [CR], Equia Forte [EF], Gold Label 2 [GL2], Gold Label 9 [GL9], Glass Ionomer Cement II [GI], Ionglass [IG], Ion Z[ IZ], Ionomaster [IM], Ionofil Plus [IP], Ionostar Plus [IS], Ketac Molar Easymix [KM], Magic Glass [MG], Maxxion R [Ma], Riva Self Cure [R], Vidrion R [V], Vitro Fil [VF] and Vitro Molar [VM]. The mechanical strength tests were performed in a universal testing machine. KH readings were done with a diamond indenter. STs were examined by Fourier Transform Infrared spectroscopy (FTIR). Data were analyzed with ANOVA and Tukey test (p<0.05). The Spearman rank test was used to evaluate the dependence between the MPs and ST results. The highest MP values were EF, GL2, GL9, GI and KM and the lowest for MG, MA, B, VF and IM. The longest ST was for GL2 and the shortest was for B. ST correlated positively with MP. GICs with longer chemical bonds ST are generally stronger and the ST value obtained from FTIR was useful in predicting the strength of GICs tested.


Assuntos
Cimentos de Ionômeros de Vidro/química , Autocura de Resinas Dentárias/métodos , Análise de Variância , Força Compressiva , Resistência à Flexão , Testes de Dureza , Teste de Materiais , Valores de Referência , Reprodutibilidade dos Testes , Espectroscopia de Infravermelho com Transformada de Fourier , Resistência à Tração , Fatores de Tempo
11.
J Environ Manage ; 267: 110638, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32421671

RESUMO

To solve the problems of low early strength and severe plastic cracking caused by high volume fly ash used in cement-based materials. Triethanolamine (TEA), calcium hydroxide (Ca(OH)2), and sodium silicate (Na2SiO3) or sodium sulfate (Na2SO4) were selected to conduct a ternary doping test. The compressive strength of samples was measured to determine the best ratio, content, and time effect of the activator, and its action mechanism was studied by various micro test. The quantitative calculation model of main hydration products was established in the fly ash-cement system. Based on the simulation of molecular dynamics, the structure of NASH gel was studied under alkali activation. The results show that the optimal mixing mass ratio of TEA:Ca(OH)2:Na2SiO3 is 2:75:25 and the optimal dosage is 1.02% of the cementitious material. There are a large number of needle-like ettringite, petaloid hydrated calcium aluminate and clusters of hydrated calcium silicate gel in the system, whereas the amount of plate-like CH decreased significantly at hydration for 14 days. The Si/Al is three and aluminium coordination is predominantly tetrahedral, and the order of bonds stability and atoms mobility are Si-O > Al-O > Na-O and Na > O > Al> in the NASH gel, respectively. Under the Na+ and alkali environment, the Si(OH)4 and Al(OH)4- formed polycondensation reaction to reform polymers Si-O-Si and Al-O-Si, forming a large amount of NASH gel.


Assuntos
Cinza de Carvão , Materiais de Construção , Álcalis , Alumínio , Força Compressiva
12.
Niger J Clin Pract ; 23(5): 720-728, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32367882

RESUMO

Objective: To evaluate the effects of surface coating and 1-year water aging on flexural strength, compressive strength (CS) and surface roughness of fluoride-releasing restorative materials. Materials and Methods: The specimens were prepared from seven materials: GCP Glass Fill (GCP), Amalgomer CR (AHL), Zirconomer (Shofu), Fuji IX GP Capsule (GC), Beautifil II (Shofu), Estelite Σ Quick (Tokuyama), and reliaFIL LC (AHL). The specimens were randomly divided into two groups for each test: surface coated with G-Coat Plus (GC) and uncoated. Each group was subdivided into two groups stored in distilled water at 37°C for 24 h and 1 year before testing (n = 10). The flexural and CS were evaluated according to ISO standards on a universal testing machine. The surface roughness was assessed with AFM. After flexural strength test, a cross-section of the coated specimens was evaluated with SEM. Data were analyzed with one-way analysis of variance, Duncan and independent t-tests (P = 0.05). Results: After 24 h, a significant increase was observed on the flexural and CS of Amalgomer CR, Zirconomer, and Fuji IX GP by coating (P < 0.05). After 1 year, the coating increased the flexural strength of Amalgomer CR and Zirconomer, and CS of GCP Glass Fill (P < 0.05). The coating decreased the surface roughness of GCP Glass Fill, Amalgomer CR, and Zirconomer after 1 year (P < 0.05). The water aging decreased the mechanical properties of glass ionomer-based materials and increased their surface roughness (P < 0.05). Conclusion: The mechanical properties and surface roughness of glass ionomer-based materials were affected by coating and water aging.


Assuntos
Materiais Dentários/química , Fluoretos/química , Força Compressiva , Resistência à Flexão , Teste de Materiais , Propriedades de Superfície , Fatores de Tempo , Água
13.
J Appl Oral Sci ; 28: e20190544, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32348440

RESUMO

Objective To evaluate the influence of three levels of dental structure loss on stress distribution and bite load in root canal-treated young molar teeth that were filled with bulk-fill resin composite, using finite element analysis (FEA) to predict clinical failure. Methodology Three first mandibular molars with extensive caries lesions were selected in teenager patients. The habitual occlusion bite force was measured using gnathodynamometer before and after endodontic/restoration procedures. The recorded bite forces were used as input for patient-specific FEA models, generated from cone-beam computed tomographic (CT) scans of the teeth before and after treatment. Loads were simulated using the contact loading of the antagonist molars selected based on the CT scans and clinical evaluation. Pre and post treatment bite forces (N) in the 3 patients were 30.1/136.6, 34.3/133.4, and 47.9/124.1. Results Bite force increased 260% (from 36.7±11.6 to 131.9±17.8 N) after endodontic and direct restoration. Before endodontic intervention, the stress concentration was located in coronal tooth structure; after rehabilitation, the stresses were located in root dentin, regardless of the level of tooth structure loss. The bite force used on molar teeth after pulp removal during endodontic treatment resulted in high stress concentrations in weakened tooth areas and at the furcation. Conclusion Extensive caries negatively affected the bite force. After pulp removal and endodontic treatment, stress and strain concentrations were higher in the weakened dental structure. Root canal treatment associated with direct resin composite restorative procedure could restore the stress-strain conditions in permanent young molar teeth.


Assuntos
Força de Mordida , Resinas Compostas/química , Resinas Compostas/uso terapêutico , Restauração Dentária Permanente/métodos , Dente Molar , Dente não Vital/terapia , Criança , Força Compressiva , Tomografia Computadorizada de Feixe Cônico , Análise do Estresse Dentário , Módulo de Elasticidade , Análise de Elementos Finitos , Humanos , Modelagem Computacional Específica para o Paciente , Valores de Referência , Reprodutibilidade dos Testes , Resistência à Tração , Dente não Vital/diagnóstico por imagem , Resultado do Tratamento
14.
PLoS One ; 15(4): e0231421, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32310981

RESUMO

Polymers are commonly used in medical device manufacturing, e.g. for drug delivery systems, bone substitutes and stent coatings. Especially hydrogels exhibit very promising properties in this field. Hence, the development of new hydrogel systems for customized application is of great interest, especially regarding the swelling behavior and mechanical properties as well as the biocompatibility. The aim of this work was the preparation and investigation of various polyelectrolyte and poly-ionic liquid based hydrogels accessible by radical polymerization. The obtained polymers were covalently crosslinked with N,N'-methylenebisacrylamide (MBAA) or different lengths of poly(ethyleneglycol)diacrylate (PEGDA). The effect of different crosslinker-to-monomer ratios has been examined. In addition to the compression curves and the maximum degree of swelling, the biocompatibility with L929 mouse fibroblasts of these materials was determined in direct cell seeding experiments and the outcome for the different hydrogels was compared.


Assuntos
Materiais Biocompatíveis/química , Hidrogéis/química , Líquidos Iônicos/química , Acrilamidas/química , Animais , Materiais Biocompatíveis/farmacologia , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Força Compressiva , Hidrogéis/farmacologia , Camundongos , Polietilenoglicóis/química
15.
Chemosphere ; 253: 126754, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32302914

RESUMO

This study sought to analyze the effect of curing temperature on mechanical strength and microstructure of a copper tailing-based geopolymer via scanning electron microscopy (SEM), HCl extraction, nuclear magnetic resonance (NMR), and X-ray diffraction (XRD). The distribution of gel formed in geopolymers tended to be uniform with increasing curing temperature from 25 to 80 °C. Moreover, the percentage of Si sites in C-S-H and N-A-S-H gels increased from 62.08% to 78.94% and more tetrahedral [AlO4] was incorporated into the tetrahedron [SiO4] backbone, leading to an increase of compressive strength from 10.2 to 39.6 MPa. When the curing temperature was increased to 120 °C, the percentage of Si sites in C-S-H and N-A-S-H gel decreased to 69.52%, and the compressive strength decreased to 27.5 MPa. Moderately elevated curing temperature promoted the dissolution of aluminosilicate while curing temperatures above 80 °C hindered it. Excessive curing temperature led to a decrease in the geopolymer alkaline medium.


Assuntos
Silicatos de Alumínio/química , Materiais de Construção/análise , Cobre/química , Resíduos Industriais/análise , Gerenciamento de Resíduos/métodos , Força Compressiva , Microscopia Eletrônica de Varredura , Mineração , Propriedades de Superfície , Temperatura , Difração de Raios X
16.
Arch Osteoporos ; 15(1): 62, 2020 04 25.
Artigo em Inglês | MEDLINE | ID: mdl-32333189

RESUMO

The higher the dietary fat intake is in men, the worse their bone strength. By contrast, in women, both low and high fat intakes have negative impacts on bone strength. Dietary fat intake may be a modifiable factor affecting bone health, but this needs to be reconfirmed in further studies. PURPOSE: Despite the general belief that higher fat intake may be harmful for bone health, its impact on bone strength has not been thoroughly studied. METHODS: We conducted a population-based cross-sectional study derived from the Korea National Health and Nutrition Examination Surveys, including 2590 participants. Composite indices of femoral neck strength, such as the compression strength index (CSI), bending strength index (BSI), and impact strength index (ISI), were generated by combining bone mineral density, weight, and height with the femoral axis length and width. Nutritional status was assessed using a 24-h dietary recall questionnaire. RESULTS: Dietary fat intake (%: energy from fat intake/total energy intake × 100) was inversely related to CSI and ISI in men, but not in women. Men in the highest three fat intake quintiles had lower CSI, BSI, and/or ISI than those in the lowest quintile (P = 0.003-0.041). In women, compared with participants in the third fat intake quintile, those in the other four quintiles had lower CSI, BSI, and/or ISI (P = 0.004-0.049). When participants were allocated to three groups according to the dietary reference intake of fat in Koreans [low (< 15%), moderate (15-30%), or high (≥ 30%)], men with a moderate or high fat intake had significantly lower ISIs than those with a low fat intake (P = 0.045 and 0.040, respectively). By contrast, compared with women consuming a moderate amount of fat, those with a high intake had lower CSI, BSI, and ISI (P = 0.024-0.048). CONCLUSION: Higher fat intake in men may contribute to deteriorations in bone strength. However, this finding and the observed sex differences need to be reconfirmed using established methods for assessment of dietary intake other than the 24-h dietary recall method employed in this study.


Assuntos
Absorciometria de Fóton/estatística & dados numéricos , Dieta/efeitos adversos , Gorduras na Dieta/análise , Osteoporose/epidemiologia , Fatores Sexuais , Adulto , Densidade Óssea , Força Compressiva , Estudos Transversais , Inquéritos sobre Dietas , Feminino , Colo do Fêmur/diagnóstico por imagem , Colo do Fêmur/fisiopatologia , Humanos , Masculino , Pessoa de Meia-Idade , Inquéritos Nutricionais , Estado Nutricional , Osteoporose/etiologia , República da Coreia/epidemiologia
17.
J Bone Miner Metab ; 38(5): 620-630, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32296985

RESUMO

INTRODUCTION: Existing osteoporosis models in sheep exhibit some disadvantages, e.g., challenging surgical procedures, serious ethical concerns, failure of reliable induction of substantial bone loss, or lack of comparability to the human condition. This study aimed to compare bone morphological and mechanical properties of old and young sheep, and to evaluate the suitability of the old sheep as a model for senile osteopenia. MATERIALS AND METHODS: The lumbar vertebral body L3 of female merino sheep with two age ranges, i.e., old animals (6-10 years; n = 41) and young animals (2-4 years; n = 40), was analyzed concerning its morphological and mechanical properties by bone densitometry, quantitative histomorphometry, and biomechanical testing of the corticalis and/or central spongious region. RESULTS: In comparison with young sheep, old animals showed only marginally diminished bone mineral density of the vertebral bodies, but significantly decreased structural (bone volume, - 15.1%; ventral cortical thickness, - 11.8%; lateral cortical thickness, - 12.2%) and bone formation parameters (osteoid volume, osteoid surface, osteoid thickness, osteoblast surface, all - 100.0%), as well as significantly increased bone erosion (eroded surface, osteoclast surface). This resulted in numerically decreased biomechanical properties (compressive strength; - 6.4%). CONCLUSION: Old sheep may represent a suitable model of senile osteopenia with markedly diminished bone structure and formation, and substantially augmented bone erosion. The underlying physiological aging concept reduces challenging surgical procedures and ethical concerns and, due to complex alteration of different facets of bone turnover, may be well representative of the human condition.


Assuntos
Doenças Ósseas Metabólicas/patologia , Modelos Animais de Doenças , Ovinos/fisiologia , Animais , Fenômenos Biomecânicos , Densidade Óssea , Doenças Ósseas Metabólicas/fisiopatologia , Osso Esponjoso/patologia , Osso Esponjoso/fisiopatologia , Força Compressiva , Módulo de Elasticidade , Feminino , Vértebras Lombares/patologia , Vértebras Lombares/fisiopatologia , Osteogênese
18.
Dent Mater ; 36(6): e169-e183, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32307121

RESUMO

OBJECTIVE: The aim of this study was to synthesize poly(acrylic acid-co-itaconic acid) (PAA-co-PIA) ionomer through a novel precipitation photopolymerization technique. The ionomer was characterized and the effect of its structural parameters, such as molecular weight and copolymer composition were investigated on the mechanical properties of glass-ionomer prepared using the ionomer. METHODS: Design of experiment (DOE) was used to examine the effect of monomer ratio and the amount of chain transfer agent on the molecular weight and final conversion of the ionomers synthesized through the precipitation photopolymerization. The copolymer compositions were identified using FTIR and 1H-NMR spectroscopy. The molecular weights of the copolymers were evaluated by GPC. A series of PAA-co-PIA copolymers were then synthesized via the photopolymerization technique in three monomer ratios and two molecular weight ranges (high and low) to study the properties of the glass ionomers thereof. Experimental dental glass-ionomer cements were prepared by mixing the synthesized polymers with glass powder and their compressive properties were determined according to ISO 9917-1:2007 after storing for 0, 1, 7 and 28 days in distilled water. The scanning electron microscopy (SEM) was used to study the fracture surface morphology of the cements. RESULTS: The PAA-co-PIA polymers were synthesized by the photopolymerization method in a short time and high purity. The DOE showed that by decreasing the acrylic acid/itaconic acid ratio and increasing the amount of transfer agent, the molecular weight and final conversion decreased significantly. By increasing the itaconic acid content in the copolymer composition and increasing the molecular weight in a constant copolymer composition, the compressive strength and modulus were increased. Microstructures revealed that cements made of the higher molecular weight poly acids showed lower cracks and voids. SIGNIFICANCE: The precipitation photopolymerization technique provides a promising and facile method in the synthesis of ionomers which are used in dental cements and other application.


Assuntos
Cimentos de Ionômeros de Vidro , Succinatos , Força Compressiva , Teste de Materiais
19.
Chemosphere ; 251: 126367, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32143080

RESUMO

The present work studies consolidation of phosphate mine tailings through alkaline activation process with the addition of slag for adjusting the gel structure. As increasing slag contents in the raw materials, more (Na,K)2O-CaO-Al2O3-SiO2-H2O (C-A-S-H) and (Na,K)2O-Al2O3-SiO2-H2O (N-A-S-H) gels were formed in the mine tailings-based mortars. Compressive strength of the mortars increased as increasing the slag contents from 0 to 40%, and then it kept a plateau. Evolution in microstructure of these mortars were characterized through scanning electron microscopy (SEM), X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) measurements. The study provides fundamentals for the co-disposal of phosphate mine tailings with blast furnace slag through alkaline activation process.


Assuntos
Fosfatos/química , Álcalis/química , Força Compressiva , Microscopia Eletrônica de Varredura , Mineração , Dióxido de Silício , Difração de Raios X
20.
Chemosphere ; 250: 126269, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32126330

RESUMO

MSWI(Municipal solid waste incineration) fly ash as hazardous wastes usually is treated properly with OPC(ordinary Portland cement) based binders prior to being disposed in security landfill, but some toxic elements present poor stability in its highly alkaline environment. This study developed a novel solidification/stabilization technology based on MgO-SiO2-H2O (M-S-H) cementious material with compatibility with contaminants for MSWI fly ash encapsulation. Compressive strength and leaching toxicity tests were undertaken to evaluate the immobilization effect of MSWI fly ash treated with M-S-H matrix. And TAM, XRD, DTA/TGA and SEM techniques were employed to explore hydration process and microstructure morphology of M-S-H solidified body. Results demonstrated that M-S-H cement matrix played a positive impact on the immobilization of heavy metals, and the immobilization rate of Cd, Pb and Zn was 97.5%, 99.8% and 98.7%, which was far more than that fixed in Portland cement. The incorporation of MSWI fly ash inhibited the hydration process of M-S-H matrix on the whole, which was mainly due to its poor pozzolanic activity. Moreover, there were some new hydration phases including CdSiO3, Ca3PbSiO6 and Zn(OH)2 generated and some MSWI fly ash embedded in the core-shell structure of M-S-H matrix in depth. These results suggested that heavy metals of MSWI fly ash were mainly fixed in M-S-H solidified bodies by physical encapsulation, isomorphous replacement and chemical precipitation. Overall, this study demonstrated that M-S-H matrix is a promising candidate that can serve as low-carbon and high-efficient materials for hazardous MSWI fly ash.


Assuntos
Incineração , Carbono/química , Força Compressiva , Materiais de Construção , Resíduos Perigosos , Óxido de Magnésio/química , Metais Pesados/análise , Material Particulado/química , Eliminação de Resíduos/métodos , Dióxido de Silício/química , Resíduos Sólidos/análise
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