Paired evaluation of calvarial reconstruction with prototyped titanium implants with and without ceramic coating

To investigate the osseointegration properties of prototyped implants with tridimensionally interconnected pores made of the Ti6Al4V alloy and the influence of a thin calcium phosphate coating. Bilateral critical size calvarial defects were created in thirty Wistar rats and filled with coated and uncoated implants in a randomized fashion. The animals were kept for 15, 45 and 90 days. Implant mechanical integration was evaluated with a push-out test. Bone-implant interface was analyzed using scanning electron microscopy. The maximum force to produce initial displacement of the implants increased during the study period, reaching values around 100N for both types of implants. Intimate contact between bone and implant was present, with progressive bone growth into the pores. No significant differences were seen between coated and uncoated implants. Adequate osseointegration can be achieved in calvarial reconstructions using prototyped Ti6Al4V Implants with the described characteristics of surface and porosity.To investigate the osseointegration properties of prototyped implants with tridimensionally interconnected pores made of the Ti6Al4V alloy and the influence of a thin calcium phosphate coating.METHODS:Bilateral critical size calvarial defects were created in thirty Wistar rats and filled with coated and uncoated implants in a randomized fashion. The animals were kept for 15, 45 and 90 days. Implant mechanical integration was evaluated with a push-out test. Bone-implant interface was analyzed using scanning electron microscopy.RESULTS:The maximum force to produce initial displacement of the implants increased during the study period, reaching values around 100N for both types of implants. Intimate contact between bone and implant was present, with progressive bone growth into the pores. No significant differences were seen between coated and uncoated implants. CONCLUSION:Adequate osseointegration can be achieved in calvarial reconstructions using prototyped Ti6Al4V Implants with the described characteristics of surface and porosity29957958

Wear resistance of plasma electrolytic oxidation coatings on Ti-6Al-4V ELI alloy processed by additive manufacturing

The additive manufacturing (AM) technique can produce Ti-6Al-4V ELI (extra low interstitial) alloy for personalized biomedical devices. However, the Ti-6Al-4V ELI alloy presents poor tribological behavior. Regarding this, coatings are a feasible approach to improve the wear resistance of this alloy. In the literature, the tribological behavior of TiO2 coatings incorporated with Ca and P formed by one-step plasma electrolytic oxidation (PEO) on Ti-6Al-4V ELI alloy processed by AM has not been investigated. Thus, in the present work, it was studied the influence of Ti-6Al-4V ELI alloy processed by AM on the wear resistance and morphologic of the coating obtained by PEO (plasma electrolytic oxidation). In this way, three different voltages (200, 250, and 300 V) were employed for the PEO process and the voltage effect on the properties of the coatings. The coatings were characterized by contact profilometry, scanning electron microscopy, energy-dispersive spectroscopy, the sessile drop method, grazing-incidence X-ray diffraction, and wear tests, on a ball-on-plate tribometer. The increase in applied voltage promoted an increase in roughness, pore area, and a decrease in the pore population of the coatings. In addition, the coatings, mainly composed of anatase and rutile, showed good adhesion to the metallic substrate, and the presence of bioactive elements Ca and P were detected. The thickness of the coatings obtained by PEO increases drastically for voltages higher than 250 V (from 4.50 ± 0.33 to 23.83 ± 1.5 µm). However, coatings obtained with lower voltages presented thin and dense layers, which promoted a superior wear resistance (increase in wear rate from 1.99 × 10−6 to 2.60 × 10−5 mm3/s). Finally, compared to the uncoated substrate, the PEO coatings increased the wear resistance of the titanium alloy obtained by AM, also showing a superior wear resistance compared to the commercial Ti-6Al-4V alloy previously evaluated, being such a positive and promising behavior for application in the area of metallic implants

Cura localizada de resina termosensivel utilizando o laser de CO2 como fonte seletiva de calor

Orientadores: Maria Clara Filippini Ierardi, Marco Antonio Fiori ScarparoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia MecanicaResumo: Este trabalho apresenta uma técnica inovadora de pesquisa, conhecida como estereolitografia térmica em três dimensões, que permite fabricar protótipos em resinas termosensíveis, com aplicação da radiação inffavermelha (10,6 um)do laser de CO2. Usualmente esta técnica de fabricação de protótipos é realizada com o laser operando na região espectral do ultravioleta (352 nm).O processo da cura localizada ocorre com o feixe laser de CO2 focalizado na superficie da amostra de um material composto de resina epoxi, dietileno triamina e sílica em pó, em proporções adequadas. Neste trabalho, foram criados os modelos fisico e químico para controlar o volume curado em função dos parâmetros operacionais do laser e das características térmicas e ópticas da amostra. As análises experimentais determinaram a faixa de temperatura em que a cura se inicia, e o comportamento da profundidade de absorção óptica em função da variação de sílica na composição. Um modelo matemático foi aplicado, resolvendo-se a equação da condução de calor dependente do tempo na coordenadas cilíndricas, que permite prever o comportamento da cura em função das condições de irradiação. Os resultados comprovaram que pode-se confinar a cura localizada muito próxima da dimensão do feixe laser, apresentando concordância com os resultados experimentais preliminares onde peças tridimensionais foram construídas por sobreposição de camadas com espessuras individuaisda ordem de 0,1 a 0,2 mmAbstract: We present a new three dirnensions stereolithography technique with applications to the produce of prototypes in thermosetting resins. In contrast conventional stereolithography which utilize ultraviolet illurnination (typically ernanating a HeCd laser - 0,352 um) to cure a photosensitive polymer, we achieve a localized cure in thermosensitive epoxy using a scanned CO2 laser (10,6 um). The sample consists of the epoxy resin mixed with optimum concetration of diethilene triamine and silica powder with laser power adjusted to produce setting only at the focus of the scanned bearn. We present models of the physical and chemical to described and to control of parameter involved of localized curing. Special consideration is given to the laser parameters, scanning speed as well as the sample parameters involved in the curing process. In particular a series experiments were performed to determine the optimum silica concetration for efficient curing as a function of temperature. Tn order to model the flow of the heat in laser-induced curing we used mathematical approach to solve the time dependent heat equation in cylindrical coordenator. Results show the numerical simulation that in the time required for curing, we can successfully confine curing laterally to within the roughly the diameter of the laser bearn and vertically to within the absorption depth and show a good agrement with experimental data obtain by the previous workMestradoMateriais e Processos de FabricaçãoMestre em Engenharia Mecânic

From biodegradable to long-term polyurethanes: In vitro fibroblasts adhesion and degradation study of electrospun polyurethane membranes

Among the synthetic polymers, polyurethanes are one of the most important polymers applied in Tissue Engineering (TE). Their segmented block structure enables the control of different properties, such as, biocompatibility, blood compatibility, mechanical properties and also biodegradability. In this work, polyurethane membranes were obtained using the electrospinning apparatus. Fibroblasts cells were seeded on the membrane and the morphology, structure and cell adhesion and proliferation were studied using Scanning Electron Microscopy (SEM). Finally, the degradation behavior of the membranes was investigated by in vitro degradation studies. SEM results showed that the membrane presents high porosity, high surface area:volume ratio, it was observed a random fiber network. In vitro evaluation of fibroblasts cells showed that fibroblasts adhered and spread over the membrane surface and in vitro degradation study showed that the developed membrane can be considered a non-degradable polyurethane. This study supports further investigations of electrospun membranes as long-term devices for TE applications6721319CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPsem informação2008/57860-

Finite element analysis of temporomandibular Joint: detachment of the lateral pterygoid muscle

In biomedical engineering field, Temporomandibular joint (TMJ) is considered as a bi-component joint composed by fossa and condyle. It is considered the most active human joint and it performs daily activities such as speaking and chewing. Due to cyclic loading, TMJ disorders impair TMJ function so that it is necessary to replace the natural joint with an alloplastic prosthesis TMJ orthopedic prosthesis are made of metal alloys and ultra high molecular weight polymers. According to the literature, TMJ replacement surgery is commonly performed worldwide achieving good outcomes. However clinical outcomes point out that TMJ prosthesis present reduced joint kinematics with a limited translational mobility compared to natural joint. In case of unilateral TMJ replacement, this result generates a unilateral hipomobility and a contralateral overload. According to previous studies, this is caused by lateral pterygoid muscle detachment during condylectomy of replacement surgery. To investigate this phenomenon, this study use computational simulation with Ansys software. Finite element analysis is performed with the aim of evaluating effect of unilateral and bilateral pterygoid muscle detachment on mechanical behaviour of a natural human mandible subjected to molar and incisal bite

The influence of additive manufacturing on the micromilling machinability of Ti6Al4V: A comparison of SLM and commercial workpieces

International audienc

Empirical models for end-use properties prediction of LDPE: application in the flexible plastic packaging industry

The objective of this work is to develop empirical models to predict end use properties of low density polyethylene (LDPE) resins as functions of two intrinsic properties easily measured in the polymers industry. The most important properties for application in the flexible plastic packaging industry were evaluated experimentally for seven commercial polymer grades. Statistical correlation analysis was performed for all variables and used as the basis for proper choice of inputs to each model output. Intrinsic properties selected for resin characterization are fluidity index (FI), which is essentially an indirect measurement of viscosity and weight average molecular weight (MW), and density. In general, models developed are able to reproduce and predict experimental data within experimental accuracy and show that a significant number of end use properties improve as the MW and density increase. Optical properties are mainly determined by the polymer morphology