Evaluation of immediate bone-cell viability and of drill wear after implant osteotomies: Immunohistochemistry and scanning electron microscopy analysis

Purpose: This study sought to evaluate the effect of repeated implant drilling on the immediate bone-cell viability, and to evaluate drill wear by scanning electron microscopy.Materials and Methods: The tibiae of 10 rabbits were used, divided into 5 groups (G): G1 corresponded to new drills, and G2, G3, G4, and G5 corresponded to drills used 10, 20, 30, and 40 times, respectively. The animals received 10 sequential osteotomies in each tibia. The animals were euthanized immediately after the osteotomies by perfusion with 4% formaldehyde. Samples then underwent immunohistochemistry processing for ordinal qualitative analysis of osteoprotegerin (OPG), the RANK ligant (RANKL; a tumor-related necrosis factor receptor family), and osteocalcin protein immunolabels, as detected by the immunoperoxidase method and revealed with 3,3-diaminobenzidine. Drill wear and plastic deformation were analyzed by scanning electron microscopy (SEM).Results: The proteins were expressed in osteocytes of the superior bone cortical during the 40 drillings. However, in G4 and G5, a discrete increase in the expression of RANKL was observed, when compared with OPG; this increase was statistically significant in G5 (P = .016). The SEM analysis revealed major plastic deformation and drill wear in G4 and G5.Conclusion: Based on the present methodology, it may be concluded that cell viability is preserved if a less traumatic surgical protocol is used. However, the repeated use of drills alters the protein balance as of the thirtieth perforation. (C) 2008 American Association of Oral and Maxillofacial Surgeons.

Influencia da Carga no Comportamento quanto ao Desgaste de um Aco ABNT-1020 Bifasico Revenido a 450°C

The wear rate of the dual-phase steel ABNT-1020 tempered at 450°C sliding against cemented steel ABNT-1020 in function of load value is investigated in wide load range. The alteration in behavior of this function at intermediate load level, like in the case of low hardness steel sliding against high hardness steel, is observed. The analysis by scanning electronic microscope before and after this alteration showed a change of wear mechanism from plastic displacement to embrittlement.

Avaliação da deformação, perda de massa e rugosidade das fresas, após osteotomia para implantes osseointegrados, com diferentes tipos de metais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação de um modelo matemático para a determinação do coeficiente de atrito no processo de conformação por dobramento

Pós-graduação em Engenharia Mecânica - FEG

Estudo do alívio das tensões residuais, em peça estampada, pela técnica de vibrações mecânicas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A influência da deformação plástica sobre a estabilidade mecânica da Austenita retida em aços 300M

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo do envelhecimento após deformação em um aço complex phase

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Investigação da retração plástica e da fissuração da argamassa do concreto auto-adensável

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Desenvolvimento de um programa paramétrico para simulação do processo de estampagem utilizando elementos finitos

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Avaliação das propriedades mecânicas e elétricas da liga 6201 não refinada, modificada com os teores de cobre (0,05 e 0,3)% para transporte de energia elétrica

No presente trabalho, foram feitos experimentos com a liga de Al – 0,6%Mg - 0,8%Si não refinada, com variações no teor de cobre (0,05% e 0,3%), que objetivaram avaliar dois aspectos do comportamento da liga. O primeiro aspecto diz respeito a afinidade entre esta e o molde, no qual busca se observar o efeito das variáveis térmicas de solidificação sobre a estrutura do fundido e sua correlação com propriedades mecânicas e elétricas, o segundo aspecto está relacionado com o comportamento intrínseco da variação da composição química quando submetida a baixas velocidades e taxas de resfriamento. Para a avaliação das variáveis térmicas de solidificação (velocidades das isotermas liquidus, taxas de resfriamento) utilizouse um dispositivo de solidificação unidirecional horizontal. Os lingotes produzidos a partir da solidificação da liga passaram pelos processos mecânicos de usinagem, laminação e trefilação, examinados em diferentes posições e diâmetros, através do ensaio de tração e condutividade elétrica. Foram analisadas as fraturas em função das microcavidades e diferentes concentrações de teores de cobre constatando-se que em relação ao material deformado a frio, o LRT tem uma tendência de crescimento para a liga de maior concentração de cobre. Os valores avaliados também possibilitaram concluir que a condutividade elétrica cresce quanto maior for o diâmetro das microcavidades e menor o teor de cobre. Com o objetivo de se avaliar somente o comportamento intrínseco da variação da composição química da liga, foi utilizado um segundo dispositivo de solidificação, molde em “U”, pintado internamente com solução de caulim que atribui ao molde baixas velocidades de resfriamento. Os resultados mostram que para os dois teores de cobre há uma tendência de crescimento do LRT com o aumento da redução sofrida pelas amostras, sendo o LRT maior para a liga com maior teor de cobre. Atribuímos este comportamento ao maior teor de soluto que por sua vez apresentou melhor resposta a deformação plástica, encruando mais o material. Entretanto, a caracterização elétrica ocorre de modo inverso, a exemplo do constatado na solidificação unidirecional, onde o menor teor de cobre foi mais eficiente.

Avaliação do comportamento reológico na retração plástica e na fissuração de argamassas de concreto auto-adensável

This paper investigated the influence of the amount of superplasticizer and mineral adding - silica fume and basaltic filer - in plastic shrinkage and cracking of self-compacting concrete (SCC) mortars. Initially analysis was performed of the rheological behavior of cement paste and mortars phases of the compositions of SCC. Then the deformations of mortars were measured by the effect of shrinkage and evaluation of cracking. On plastic shrinkage and cracking, the composition with silica fume showed superior results, independent of wind and superplasticizer content, relative to the composition with addition of basalt filler. However, the composition with silica fume showed superior results only in the tests with imposed ventilation at vertical plastic deformation. The rheological behavior affected directly the plastic shrinkage and cracking at early ages, fact confirmed by the analysis of capillary pressures of mortars tested.

Estudo da deformação heterogênea no ensaio do anel de atrito

The plastic deformation is widely used in the metallurgical market due to its positive factors such as low prices and high speed production. Forming process products are obtained in high quality, both surface quality and mechanical properties. Friction is an importante factor in metal forming. Friction study in metal forming can be accomplished indirectly, such as the ring test of friction. Two samples of different materials being mild steel and copper alloy were used. The results showed the influence of friction in the flow behavior of the deformation of the second phase, as evidenced by standard metallography. It is observed that in the outer regions of the ring, plastic deformation occured in the radial direction. In the central region of the disc deformation occured in the direction of compression and the inner region of the ring flux lines showed a significant deformation in the radial direction towards the center of the ring

Análise da reversão do fundo de latas de alumínio para bebidas - Buckle

This work approaches the main methods of plastic deformation of metals, with a focus on the deep drawing process. The mechanical properties were evaluated with the tension tests. It is presented the aluminum alloys designation, followed by applying heat treatments and the designation of tempers. The manufacture of aluminum beverage cans is described step by step, in general terms. The main objective is to analyze how different cans background geometries have great influence on the dome reversal. To be able to achieve the goal it was necessary to use cans of different manufacturers, which were used in buckle tests to obtain the reversal pressures, tensile tests and geometric analysis. Finally empirical equations were obtained correlating these variables, and it was observed that the conformation of reforming change significantly it's behavior

Estudo do efeito Bauschinger em tubos de aço API 5l x70 aplicados no transporte de petróleo e gás

Despite the growing concern in seeking more sustainable energy sources, oil demand is likely to grow in coming years. To keep up with this growth, the oil industry has increasingly invested in innovation and efficiency. Knowing that, new technologies have been developed to explore deeper waters, without giving up the best practices in worldwide operational safety. The use of rigid pipelines in deepwater offshore facilities is increasing quickly and because of this, the ways of storing and launching pipe have been studied and perfected. In this paper the Bauschinger effect on API 5L X70 steel was analyzed proving that there was a reduction in yield strength when an effort was applied in a previous direction, then an effort was then applied in the opposite direction. To observe this phenomenon, the tensile test was conducted to determine the mechanical properties of the base metal, such as yield stress, tensile strength, elasticity and maximum tensile, so then compare it with the results obtained in the Bauschinger Effect Test. The analysis results showed that the steel had high resistance, with good plastic deformation capacity without failing, well-defined yield point, showing itself appropriate for the operation of oil and gas pipes

Estudo do efeito Bauschinger em tubos de aço API 5l x70 aplicados no transporte de petróleo e gás

Despite the growing concern in seeking more sustainable energy sources, oil demand is likely to grow in coming years. To keep up with this growth, the oil industry has increasingly invested in innovation and efficiency. Knowing that, new technologies have been developed to explore deeper waters, without giving up the best practices in worldwide operational safety. The use of rigid pipelines in deepwater offshore facilities is increasing quickly and because of this, the ways of storing and launching pipe have been studied and perfected. In this paper the Bauschinger effect on API 5L X70 steel was analyzed proving that there was a reduction in yield strength when an effort was applied in a previous direction, then an effort was then applied in the opposite direction. To observe this phenomenon, the tensile test was conducted to determine the mechanical properties of the base metal, such as yield stress, tensile strength, elasticity and maximum tensile, so then compare it with the results obtained in the Bauschinger Effect Test. The analysis results showed that the steel had high resistance, with good plastic deformation capacity without failing, well-defined yield point, showing itself appropriate for the operation of oil and gas pipes