Effect of calcination on minimally processed recycled zirconia powder derived from milling waste.

OBJECTIVE: To assess the influence of calcination process on the properties of minimally processed recycled 3Y-TZP, and to compare it with its commercial counterpart. METHODS: Non-milled 3Y-TZP waste was collected, fragmented and ball-milled to a granulometric < 5 µm. Half of the recycled powder was calcined at 900 °C. Recycled 3Y-TZP disks were uniaxially pressed and sintered to create two recycled groups: 1) Calcined and 2) Non-calcined to be compared with a commercial CAD/CAM milled 3Y-TZP. The microstructure of experimental groups was assessed through density (n = 6), scanning electron microscopy (n = 3) and energy-dispersive X-ray spectroscopy (n = 3); and the crystalline content was evaluated through X-ray diffraction (XRD) (n = 3). Optical and mechanical properties were investigated through reflectance tests (n = 10), and Vickers hardness, fracture toughness (n = 5), and biaxial flexural strength tests (n = 16), respectively. Fractographic analysis was performed to identify fracture origin and crack propagation. Statistical analyses were performed through ANOVA followed by Tukey´s test, and by Weibull statistics. RESULTS: Particle size distribution of recycled powder revealed an average diameter of ∼1.60 µm. The relative density of all experimental groups was > 98.15 % and XRD analysis exhibited a predominance of tetragonal-phase in both recycled groups, which were similar to the crystallographic pattern of the control group. Cross-section micrographs presented flaws on the non-calcined group, and a more homogeneous microstructure for the calcined and commercial groups. Commercial samples showed lower contrast-ratio and higher translucency-parameter than the recycled groups, where non-calcined presented higher translucency-parameter and lower contrast-ratio than its calcined counterpart. The commercial group presented higher fracture toughness and characteristic strength than the recycled groups. Moreover, the calcined group exhibited higher hardness, characteristic strength, and probability of survival at higher loads than the non-calcined group. Fractographic analysis depicted the presence of microstructural flaws in the non-calcined group, which may have acted as stress-raisers and led to failures at lower flexural strengths values. SIGNIFICANCE: The calcination process improved the microstructure, optical, and mechanical properties of the recycled 3Y-TZP.

Aging resistance of an experimental zirconia-toughened alumina composite for large span dental prostheses: Optical and mechanical characterization.

PURPOSE: To synthesize a zirconia-toughened alumina (ZTA) composite with 85% alumina matrix reinforced by 15% zirconia and to characterize its optical and mechanical properties before and after artificial aging, to be compared with a conventional dental zirconia (3Y-TZP). MATERIAL AND METHODS: After syntheses, ZTA and 3Y-TZP powders were uniaxially and isostatically pressed. Green-body samples were sintered and polished to obtain 80 disc-shaped specimens per group (12 × 1 mm, ISO 6872:2015). The crystalline content and microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Optical properties were determined by the calculation of contrast ratio (CR) and translucency parameter (TP) using reflectance data. Mechanical properties were assessed by Vickers hardness, fracture toughness and biaxial flexural strength test (BFS). All analyses were conducted before and after artificial aging (20h, 134 °C, 0.22 MPa). Optical parameters and microhardness differences were evaluated through repeated-measures analysis of variance (p < 0.05). BFS data were analyzed using Weibull statistics (95% CI). RESULTS: The synthesis of the experimental ZTA composite was successful, with 98% of theoretical density, as shown in the SEM images. XRD patterns revealed typical zirconia and alumina crystalline phases. ZTA optical properties parameters showed no effect of aging, with a high CR and low TP values denoting a high masking-ability. 3Y-TZP presented lower masking-ability and aging significantly affected its optical properties. ZTA Vickers hardness, fracture toughness and Weibull parameters, including characteristic stress and Weibull modulus were not influenced by aging, while 3Y-TZP presented a significant decrease in characteristic stress and increase in fracture toughness after aging. The ZTA probability of survival for missions of 300 and 500 MPa was estimated at ~99% validating its use for 3-unit posterior fixed dental prostheses (FDP), and no different from conventional 3Y-TZP. At high-stress mission (800 MPa) a significant decrease in probability of survival was observed for aged 3Y-TZP (84%) and for immediate and aged ZTA (73 and 82% respectively). CONCLUSION: The ZTA composite presented a dense microstructure, with preservation of the crystalline content, optical and mechanical properties after artificial aging, which encourages future research to validate its potential use for large span FDP.

Multitemporal analysis of estimated soil loss for the river Mourão watershed, Paraná - Brazil.

The multitemporal behavior of soil loss by surface water erosion in the hydrographic basin of the river Mourão in the center-western region of the Paraná state, Brazil, is analyzed. Forecast was based on the application of the Universal Soil Loss Equation (USLE) with the data integration and estimates within an Geography Information System (GIS) environment. Results had shown high mean annual rain erosivity (10,000 MJ.mm.ha(-1).h(-1).year(-1)), with great concentration in January and December. As a rule, soils have average erodibilities, exception of Dystroferric Red Latisol (low class) and Dystrophic Red Argisol (high class). Although the topographic factor was high (>20), rates lower than 1 were predominant. Main land uses comprise temporal crops and pasture throughout the years. The watershed showed a natural potential for low surface erosion. When related to usage types, yearly soil loss was also low (<50 ton.ha(-1).year(-1)), with more critical scores that reach rates higher than 150 ton.ha(-1).year(-1). Soil loss over the years did not provide great distinctions in distribution standards, although it becames rather intensified in some sectors, especially in the center-eastern and southwestern sections of the watershed.

Multitemporal analysis of estimated soil loss for the river Mourão watershed, Paraná – Brazil / Análise multitemporal da perda de solo estimada para a bacia hidrográfica do rio Mourão, Paraná – Brasil

The multitemporal behavior of soil loss by surface water erosion in the hydrographic basin of the river Mourão in the center-western region of the Paraná state, Brazil, is analyzed. Forecast was based on the application of the Universal Soil Loss Equation (USLE) with the data integration and estimates within an Geography Information System (GIS) environment. Results had shown high mean annual rain erosivity (10,000 MJ.mm.ha–1.h–1.year–1), with great concentration in January and December. As a rule, soils have average erodibilities, exception of Dystroferric Red Latisol (low class) and Dystrophic Red Argisol (high class). Although the topographic factor was high (>20), rates lower than 1 were predominant. Main land uses comprise temporal crops and pasture throughout the years. The watershed showed a natural potential for low surface erosion. When related to usage types, yearly soil loss was also low (<50 ton.ha–1.year–1), with more critical scores that reach rates higher than 150 ton.ha–1.year–1. Soil loss over the years did not provide great distinctions in distribution standards, although it becames rather intensified in some sectors, especially in the center-eastern and southwestern sections of the watershed.

Resumo Este estudo visa analisar o comportamento multitemporal da perda de solo por erosão hídrica laminar na bacia hidrográfica do rio Mourão, localizada na região centro-ocidental do Estado do Paraná – Brasil. A predição foi baseada na aplicação da Equação Universal de Perdas de Solo (USLE), com integração dos dados e estimativas realizados em ambiente SIG (Sistema de Informações Geográficas). Os resultados mostram elevada erosividade da chuva média anual (10.000 MJ.mm.ha–1.h–1.ano–1). Os solos apresentam, em geral, média erodibilidade, com exceções do Latossolo Vermelho Distroférrico (classe baixa) e o Argissolo Vermelho Distrófico (classe alta). O fator topográfico atingiu índices elevados (>20), no entanto, predominaram os valores inferiores a 1. Os tipos de usos principais são as lavouras temporárias e pastagem, para todos os anos. A bacia apresentou Potencial Natural a Erosão laminar predominante baixo, quando relacionado aos tipos de usos resultou numa perda de solo anual estimada também baixa (<50 ton.ha–1.ano–1), com pontos mais críticos que atingem valores superiores a 150 ton.ha–1.ano–1. A perda de solo entre os anos não apresentou grandes distinções nos padrões de distribuição, apenas intensificou-se em alguns setores, como nas porções centro-leste e sudoeste da bacia.

Multitemporal analysis of estimated soil loss for the river Mourão watershed, Paraná Brazil

The multitemporal behavior of soil loss by surface water erosion in the hydrographic basin of the river Mourão in the center-western region of the Paraná state, Brazil, is analyzed. Forecast was based on the application of the Universal Soil Loss Equation (USLE) with the data integration and estimates within an Geography Information System (GIS) environment. Results had shown high mean annual rain erosivity (10,000 MJ.mm.ha1.h1.year1), with great concentration in January and December. As a rule, soils have average erodibilities, exception of Dystroferric Red Latisol (low class) and Dystrophic Red Argisol (high class). Although the topographic factor was high (>20), rates lower than 1 were predominant. Main land uses comprise temporal crops and pasture throughout the years. The watershed showed a natural potential for low surface erosion. When related to usage types, yearly soil loss was also low ( 50 ton.ha1.year1), with more critical scores that reach rates higher than 150 ton.ha1.year1. Soil loss over the years did not provide great distinctions in distribution standards, although it becames rather intensified in some sectors, especially in the center-eastern and southwestern sections of the watershed.

Resumo Este estudo visa analisar o comportamento multitemporal da perda de solo por erosão hídrica laminar na bacia hidrográfica do rio Mourão, localizada na região centro-ocidental do Estado do Paraná Brasil. A predição foi baseada na aplicação da Equação Universal de Perdas de Solo (USLE), com integração dos dados e estimativas realizados em ambiente SIG (Sistema de Informações Geográficas). Os resultados mostram elevada erosividade da chuva média anual (10.000 MJ.mm.ha1.h1.ano1). Os solos apresentam, em geral, média erodibilidade, com exceções do Latossolo Vermelho Distroférrico (classe baixa) e o Argissolo Vermelho Distrófico (classe alta). O fator topográfico atingiu índices elevados (>20), no entanto, predominaram os valores inferiores a 1. Os tipos de usos principais são as lavouras temporárias e pastagem, para todos os anos. A bacia apresentou Potencial Natural a Erosão laminar predominante baixo, quando relacionado aos tipos de usos resultou numa perda de solo anual estimada também baixa ( 50 ton.ha1.ano1), com pontos mais críticos que atingem valores superiores a 150 ton.ha1.ano1. A perda de solo entre os anos não apresentou grandes distinções nos padrões de distribuição, apenas intensificou-se em alguns setores, como nas porções centro-leste e sudoeste da bacia.

A multidimensional approach to the generation of helmets' design criteria: a preliminar study.

The design and development process of helmets incorporates systematically design criteria related to safety to accomplish European and local standards for the commercialization. However, there are few studies focused on user's comfort and adaptation. Present study tackles a multidimensional approach to gain better understanding of the interaction between helmet and user to generate design criteria for the internal helmet surface. Morphological characteristics of the target population, pressure distribution over head and subjective perception of fitting and discomfort are the factors considered to establish the criteria that assure a proper fit. Ten men corresponding to helmet size M and usual drivers of motorbike wore two helmet models in three sizes (S, M and L). The head shape of participants was acquired using the head scanner of I-Ware laboratory and an instrumented pad was used to measure pressure in five head regions. After wearing the helmet, users filled in a perception questionnaire about fitting, comfort and usability considering the five regions. Users' fitting perception provided the relation between pressure levels and the comfort felt in the five regions. This study constitutes a first approach to a new methodology to generate criteria to improve the design of helmets under a multidimensional approach.

The flexible endaural tympanoplasty: pathology-guided, pathogenesis-oriented surgery for the middle ear.

The flexible approach to tympanoplasty has been found to be adaptable to various forms of pathologic conditions found in the temporal bone, including inflammation and infection, congenital stenosis, benign and malignant tumors, and traumatic injuries. This approach finds its best indication among all pathologic conditions in the temporal bone, in the surgical treatment of otitis media, and its sequelae. A procedure conceived to treat this dynamic process must be adaptable to new circumstances and new findings and be ready to manage unexpected situations. The flexible tympanoplasty is a step-wise approach designed to explore the contents of the middle ear methodically and in the process disclose, confirm, and often treat disease.