Comparison between different fracture toughness techniques in zirconia dental ceramics.

Vickers indentation (IF) and single-edge-V-notched beam (SEVNB), to measure the fracture toughness (KIC ) of zirconia-based dental ceramics and mathematical models were proposed to establish a correlation between both. Zirconia (ZrO2 ) stabilized with 3 mol. % of Y2 O3 (3Y-TZP) and 5 mol% of Y2 O3 (5Y-PSZ) were compacted (n = 42) and sintered for 2 h at different temperatures (1475°C, 1500°C, 1550°C, or 1600°C). After sintering, they were characterized by relative density using the ASTM C373-88 standard, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The average grain size was measured according to the ASTM E1382-97 standard. The fracture toughness (KIC ) was determined using two methods: Vickers indentation fracture toughness (KIC-IF ): method based on mathematical modeling that considers the parameters used for the Vickers hardness test and Fracture toughness by the single-edge-V-notch-beam (KIC-SEVNB ): method proposed by ISO 23146:08. The main phases of the 3Y-TZP and 5Y-PSZ ceramics were ZrO2 -tetragonal and ZrO2 -cubic, respectively. The 3Y-TZP specimens showed equiaxed grains with average grain sizes ranging from 0.55 to 0.79 µm. The grain sizes of 5Y-PSZ of specimens sintered at 1475°C and 1600°C were 0.62 and 2.32 µm, respectively. For all ceramics the crack size ratio was c/a < 2.5, suggesting a Palmqvist-type crack system. The fracture toughness measured by the Vickers indentation method (KIC-IF ) and by the SEVNB method (KIC-SEVNB ) was the same when the experimental data were fit to a mathematical model.

Efficacy and Safety of a Plant-Based Virus-Like Particle Vaccine for COVID-19 Adjuvanted with AS03

BackgroundSeveral COVID-19 vaccines are currently being deployed but supply constraints, concerns over durability of immune responses, solidifying vaccine hesitancy/resistance and vaccine efficacy in the face of emerging variants mean that new vaccines continue to be needed to fight the ongoing pandemic. The vaccine described here is an enveloped, coronavirus-like particle produced in plants (CoVLP) that displays the prefusion-stabilized spike (S) glycoprotein of SARS-CoV-2 (ancestral Wuhan strain) and is adjuvanted with AS03 (CoVLP+AS03). MethodsThis Phase 3 randomized, observer-blind, placebo-controlled trial was conducted at 85 centers in Argentina, Brazil, Canada, Mexico, the UK, and the USA. Adults [≥]18 years of age including those at high risk for COVID-19 complications were randomly assigned 1:1 to receive two intramuscular injections of CoVLP (3.75 g) adjuvanted with AS03 or placebo, 21 days apart. The primary efficacy endpoint was prevention of symptomatic ([≥] 1 symptom), PCR-confirmed SARS-CoV-2 infection with onset at least 7 days after the second injection and was triggered by the identification of [≥]160 virologically-confirmed cases. Tolerability and safety of CoVLP+AS03 were also determined. ResultsA total of 24,141 volunteers were randomly assigned 1:1 to receive vaccine or placebo (N= 12,074 and 12,067, respectively: median age 29, range 18 to 86 years). Overall, 83% received both doses. 14.8% were SARS-CoV-2 seropositive at baseline. Symptomatic SARS-CoV-2 infection was confirmed in 165 study participants in the intention to treat (ITT) set and 157 in the per-protocol population (PP) set. Of the 157 in the PP set, 118 COVID-19 cases were in the placebo group and 39 COVID-19 cases were in the CoVLP+AS03 group for an overall vaccine efficacy (VE) of 71.0% (95% confidence interval (CI) 58.6, 80.0). Moderate-to-severe COVID-19 occurred in 8 and 32 participants in the CoVLP+AS03 and placebo groups, respectively: VE 78.1% (95% CI: 53.9, 90.5) in the PP set overall and 84.5% (95% CI: 62.0, 94.7) in those seronegative at recruitment. To date, 100% of the sequenced strains (122/165 cases: 73.39%) were variants, dominated by Delta (45.9%) and Gamma (43.4%) strains. Vaccine efficacy by variant was 75.3% (95% CI 52.8, 87.9) against Delta and 88.6% (95% CI 74.6, 95.6) against Gamma. Cross-protection was also observed against Alpha, Lambda and Mu variants; although fewer cases were identified, all were in the placebo group. At diagnosis, viral loads in the CoVLP+AS03 breakthrough cases were >100-fold lower than in the placebo cases. Reactogenicity data for solicited adverse events (AEs) was analysed for a subset (N=4,136 in vaccine arm and N=3,683 for placebo) of participants. Reactogenicity was mostly mild to moderate, and transient, and occurred more frequently in the CoVLP+AS03 group. The safety analysis set used for unsolicited AE assessment comprised 24,076 participants who received at least one study injection: 12,036 received CoVLP+AS03 and 12,040 received placebo. All serious adverse events were assessed as unrelated, except two events reported in the same subject in the placebo group. No significant imbalance or safety concern was noted in medically attended AEs (MAAEs), adverse event of special interest (AESIs), AEs leading to withdrawal, deaths, or adverse events potentially associated with currently authorized vaccines. ConclusionsThe CoVLP+AS03 vaccine candidate conferred an efficacy of 71.0% in preventing symptomatic SARS-CoV-2 infection caused by a spectrum of variants. Vaccine efficacy of 78.1% was observed against moderate and severe disease, while variant-specific efficacy ranged from 75.3% to 100%. Markedly lower viral loads in the CoVLP+AS03 group at the time of diagnosis suggests a significant virologic impact of vaccination even in the breakthrough cases. CoVLP+AS03 vaccine candidate was well tolerated, and no safety concerns were identified during the study. If approved by regulators, this more traditional protein+adjuvant vaccine produced using the novel plant-based platform may be able to make an important contribution to the global struggle against the increasingly complex family of SARS-CoV-2 viruses (Funded by Medicago with grants from the governments of Quebec and Canada; NCT04636697).

Mechanical properties of ceramic composites based on ZrO2 co-stabilized by Y2O3-CeO2 reinforced with Al2O3 platelets for dental implants.

OBJECTIVES: The objective of this work was the development and characterization of a ceramic composite based on (Ce,Y)-TZP/Al2O3 aiming an application on dental implants, comparing it with conventional monolithic 3Y-TZP ceramics, currently used for the same type of application. METHODS: Ceramic samples, 3Y-TZP (n = 40) and (Ce,Y)-TZP/Al2O3 (n = 40), were sintered at 1500 °C - 2h and characterized by relative density, X-Ray diffraction (XRD) and microstructure. Then, the samples of both materials were divided into two groups: 1) samples with original (as sintered) surfaces; 2) samples with conditioned, polished, surfaces. All samples were submitted to hydrothermal degradation tests, on an autoclave (134 °C - 2 bar), for 10 h in artificial saliva. The degraded samples were characterized by XRD and the polished group were also characterized by their elastic moduli, Vickers hardness and fracture toughness (Vickers indentation method). Both groups were also submitted to a flexural strength test, 3B-P testing, for which the data were interpreted using Weibull statistics. RESULTS: All sintered specimens presented nearly full densification. After the hydrothermal degradation tests, 3Y-TZP samples presented 16.4% of monoclinic (m)-ZrO2 phase while the composite samples withheld 100% of tetragonal (t)-ZrO2 phase. Both materials presented equiaxial ZrO2 grains with an average size of 0.48 ± 0.17 µm and 0.75 ± 0.22 µm, respectively, for the monolithic and composite ceramics. In the composites, is observed the presence of well distributed Al2O3 grains on the ZrO2 matrix, in two distinct morphologies: equiaxial grains and platelets. The composites (Ce,Y)-TZP/Al2O3 presented average values of elastic moduli, Vickers hardness and fracture toughness of 228.3 ± 6.5 GPa, 1427 ± 46 HV e 11.3 ± 0.4 MPa m1/2, respectively. An inversely proportional relationship is observed between the roughness and the bending strength, since the 3Y-TZP samples presented a average strength of 860.7 ± 81 MPa (as-sintered) and 965.4 ± 93 MPa (polished) while the (Ce,Y)-TZP/Al2O3 composites presented average strength of 810.6 ± 147 MPa (as-sintered) and 952.6 ± 88 MPa (polished). CONCLUSIONS: The composites (Ce,Y)-TZP/Al2O3 showed high resistance to degradation in saliva and adequate properties for use as dental implants. Values of flexural strength (>950 MPa) and Weibull modulus (m > 10) were similar to the conventional 3Y-TZP ceramics. Moreover, its hardness, elastic modulus and fracture toughness were higher than those obtained for 3Y-TZP. The expressive values of KIC obtained for (Ce,Y)-TZP/Al2O3 composites are results of association of different toughening mechanisms acting simultaneously in the material.

Effect of hydrothermal aging on the properties of zirconia with different levels of translucency.

OBJECTIVES: The aim of this study was to evaluate the effect of hydrothermal aging on the mechanical properties and translucency of dental zirconia with different levels of translucency. METHODS: Three different types of dental yttria-stabilized zirconia were used: 3Y-TZP (ZrO2 - 3 mol.% Y2O3) of medium opacity (designated Z3OP), 3Y-TZP of medium translucency (Z3MT), and 5Y-PSZ (ZrO2 - 5 mol.% Y2O3) of high translucency (Z5HT). A total of 120 specimens were sintered (n = 40 specimens/group). The control group (sintered→polished→heat-treated) and the aged group (sintered→polished→heat-treated→hydrothermally degraded at 134 °C, 2 bar, 5h) were characterized by relative density, quantitative phase analysis by X-ray diffraction using the Rietveld method, microstructural analysis by scanning electron microscopy, surface roughness and translucency. All groups were submitted to a biaxial flexural strength test. Data analysis using Kruskal-Wallis, Nemenyi (p-value = 0.05), and Weibull statistics were used. RESULTS: All sintered specimens presented full densification. After aging, an increase of the m-ZrO2 phase content was observed for the Z3OP group. On the other hand, Z3MT and Z5HT did not show any m-ZrO2 phase, indicating resistance to the hydrothermal degradation. Smaller grains were observed in the Z3MT group in relation to Z3OP group and the Z5HT group presented a bimodal grain distribution, where the largest grains were associated to cubic ZrO2. Z3OP exhibited a slight increase in roughness as a function of degradation, while the roughness remained statistically stable in the other groups. Translucency was little influenced by degradation, but considerably affected by increasing thickness. The Z5HT samples were the group with the highest translucency among the control groups. Z3OP exhibited the highest flexural strength, while being the most susceptible to hydrothermal degradation. The lowest values were presented by Z5HT in all groups, due to the high concentration of c-ZrO2 grains. CONCLUSION: Hydrothermal aging is less critical to the flexural strength of zirconia-based materials than the materials' composition and microstructure. Z5HT zirconia showed the highest translucency, however the measured difference is not visually perceptible. Z5HT was considered the most resistant to hydrothermal degradation.

Estudo comparativo da helmintofauna de bovinos caprinos de criação extensiva no semiárido nordestino: uma análise das relações com a saúde pública e a conservação da biodiversidade / Comparative study of the helminth parasites of cattle goats extensive farming in semi-arid northeast: an analysis of relations with public health and biodiversity conservation

No semiárido nordestino, a criação de bovinos e caprinos sempre se caracterizou pelo uso extensivo da Caatinga e o livre acesso dos animais ao perídomicilio e às unidades de conservação (UCs), o que possibilita o fluxo de parasitos entre animais silvestres, domésticos e populações humanas. A paisagem do semiárido vem se transformando rapidamente, impactada por grandes empreendimentos, principalmente o Projeto de Integração do Rio São Francisco (PISF) com as bacias hidrográficas do Nordeste Setentrional. Com o objetivo de compreender o impacto destas transformações ambientais sobre as criações extensivas, a biodiversidade e a saúde, buscou-se o estudo da diversidade de helmintos nesta região. Para isso foram comparados as frequências e abundância de ovos e larvas em amostras de fezes e índices de diversidade de helmintos gastrintestinais, encontradas nas fezes de bovinos e caprinos criados no entorno das UCs e nas áreas do PISF. Foram analisadas 142 amostras de fezes de bovinos e 74 amostras de caprinos, coletadas oportunisticamente no solo. As coletas foram georrefenciadas com auxílio de GPS. As amostras foram acondicionadas em recipientes plásticos, identificadas e levadas ao Laboratório de Ecologia da Escola Nacional de Saúde Pública /Fundação Oswaldo Cruz onde foram analisadas. Para o encontro dos ovos foi utilizada a técnica de Lutz (1919) e para a cultura de larvas utilizou-se a técnica de Roberts & O’Sullivan (1950). Os resultados obtidos foram analisados, com auxílio do software PC-ORD®, quanto à suficiência amostral, à abundância de ovos e larvas de helmintos nas amostras (Boxplots), à frequência de ovos e larvas em amostras positivas, aos índices de diversidade de Shannon e Simpson em relação aos períodos de seca, chuva e intermediário e categorias de antropização da paisagem. Foram encontrados ovos e larvas de nove helmintos em fezes de bovinos e onze em fezes de caprinos. Larvas de, Haemonchus sp., Trichostrongylus sp., Cooperia sp e Oesophagostomum sp. foram encontrados em bovinos e caprinos, em ordem decrescente de frequência e abundancia. Além destas nos bovinos, larvas de Strongyloides sp. e Bunostomum sp.. Ovos de Trichostrongylidae foram encontrados em amostras de fezes de bovinos e caprinos e em caprinos ovos de Ancylostomatidae, Trichuris sp., Strongyloides sp. e do cestódeo Moniezia sp. A diversidade de helmintos foi maior em caprinos (...) Nas fezes de caprinos, os ovos de Trichostrongylidae e Trichuris sp. apresentaram as maiores frequências em áreas próximas a pequenos povoados. Ovos e larvas foram mais abundantes no período de chuva, embora tenham permanecido com pouca alterações em bovinos mesmo na seca e em caprinos o número de amostras negativas tem sido relevantes. O gênero Trichostrongylus sp. , de importância para a saúde pública por ocasionar a tricostrongilíase humana está associado às áreas com Caatinga alterada com a presença de casas, para os bovinos, foi encontrado frequência de 86,66 por cento em área de Caatinga preservada. A baixa frequência de helmintos nas áreas do PISF, indicaram que a remoção da vegetação e do solo, nestas áreas tornaram o ambiente desfavorável para o desenvolvimento dos helmintos e seus hospedeiros. Planos de monitoramento de verminoses, nas áreas de entorno de UCs devem ser elaborados, de modo a garantir a saúde da fauna silvestre e das populações humanas, e melhorar a qualidade e produtividade dos rebanhos de pequenas populações...