Browsing by Author "Silva, D."
Now showing 1 - 7 of 7
Results Per Page
Sort Options
- Effect of albumin, urea, lysozyme and mucin on the triboactivity of Ti6Al4V/zirconia pair used in dental implantsPublication . Teixeira, H.; Branco, A. C.; Rodrigues, I.; Silva, D.; Cardoso, S.; Colaço, R.; Serro, A. P.; Figueiredo-Pina, CélioThe titanium implant/zirconia abutment interface can suffer failure upon mechanical and biological issues, ul- timately leading to the loss of the artificial tooth. The study of the effect of the organic compounds present in saliva on the tribological behavior of these systems is of utmost importance to understand the failure mechanisms and better mimic the in vivo conditions. The aim of the present work is to evaluate the effect of the addition of albumin, urea, lysozyme and mucin to artificial saliva, on the triboactivity of Ti6Al4V/zirconia pair commonly used in dental implants and then, compare the results with those obtained with human saliva. The solutions’ viscosity was measured and the adsorption of the different biomolecules to both Ti6Al4V and zirconia was accessed. Tribological tests were performed using Ti6Al4V balls sliding on zirconia plates inside of a corrosion cell. Friction and wear coefficients were determined, and the open circuit potential (OCP) was monitored during the tests. Also, the wear mechanisms were identified. The presence of mucin in the artificial lubricant led to the lowest wear coefficients. The main wear mechanism was abrasion, independently of the used lubricant. Adhesive wear was observed for the systems without mucin. Tribocorrosion activity and wear coefficient were lower in the presence of mucin. None of the studied artificial lubricants mimicked the effect of human saliva (HS) on the tribological behavior of the studied pair since this lubricant led to the lowest friction coefficient and highest corrosion activity.
- Handicap as a measure of perceived health status in Parkinson’s diseasePublication . Silva, D.; Coelho, M.; Soares, T.; Vale, T.; Guedes, L.; Maciel, R.; Antunes, A. P.; Camargos, S.; Valadas, A.; Godinho, Catarina; Maia, D.; Lobo, P. P.; Maia, R.; Teodoro, T.; Rieder, C.; Velon, A.; Rosas, M. J.; Calado, A.; Caniça, V.; Cardoso, F.; Ferreira, J.
- Measuring perceived-health status in Parkinson’s Disease – the role of London Handicap ScalePublication . Silva, D.; Coelho, M.; Soares, T.; Vale, T.; Guedes, L.; Maciel, R.; Antunes, A.; Camargos, S.; Valadas, A.; Godinho, Catarina; Maia, D.; Lobo, P.; Maia, R.; Teodoro, T.; Rieder, C.; Velon, A.; Rosas, M.; Calado, A.; Caniça, V.; Cardoso, F.; Ferreira, J.
- Os peixes na rota de Magalhães : proposta de nomenclatura portuguesaPublication . Carneiro, Miguel; Martins, Rogélia; Silva, D.; Quaresma, I.; Batista, IrineuFernão de Magalhães navegou por mares e oceanos e parte dessas áreas geográficas percorridas estão agora incluídas em 47 zonas económicas exclusivas sob jurisdição dos atuais “países” que as administram. Nestas regiões ocorrem cerca de 9500 espécies de peixes. Para além destas, incluem-se outras espécies não diretamente relacionadas com as rotas de Fernão de Magalhães, mas que importa acrescentar, pela sua importância histórica (antigos enclaves, praças fortes e territórios que estiveram sob administração portuguesa) e económica para Portugal, por serem importadas para o mercado nacional, ou por ocorrerem num dos atuais países de língua oficial portuguesa (Angola) não visitado por Fernão de Magalhães. O objetivo principal deste trabalho é estabelecer um único nome vulgar português (europeu) para cada uma das 16767 espécies listadas, propondo-o como denominação “oficial” portuguesa. Os nomes propostos encontram-se assinalados a negrito.
- Polyvinyl alcohol/chitosan wound dressings loaded with antisepticsPublication . Massarelli, E.; Silva, D.; Pimenta, A. F. R.; Fernandes, A.I.; Mata, J. L. G.; Armês, H.; Salema-Oom, Madalena; Saramago, B.; Serro, A.P.Wound care remains a challenge in healthcare. This work aimed to develop a new polyvinyl alcohol (PVA)/chitosan (Ch) based wound dressing able to ensure protection, hydration and a controlled release of antiseptics, as alternative to actual treatments. Two distinct formulations (1:1 and 3:1, w/w) were prepared, sterilized by autoclaving and characterized concerning surface morphology, degradation over the time, mechanical properties and hydrophilicity. Both dressings revealed adequate properties for the intended purpose. The dressings were loaded with chlorhexidine (CHX) and polyhexanide (PHMB) and the drug release profiles were determined using Franz diffusion cells. The release of PHMB was more sustained than CHX, lasting for 2 days. As the amounts of drugs released by PVA/Ch 1:1 were greater, the biological tests were done only with this formulation. The drug loaded dressings revealed antibacterial activity against S. aureus and S. epidermidis, but only the ones loaded with PHMB showed adequate properties in terms of cytotoxicity and irritability. The application of this elastic dressing in the treatment of wounds in a dog led to faster recovery than conventional treatment, suggesting that the material can be a promising alternative in wound care.
- Reabilitação multidisciplinar de dentes endodonciados – Caso clínicoPublication . Antão, M.; Amorim, T.; Silva, D.; Mendes, José João; Azul, A. C.
- The effect of albumin and cholesterol on the biotribological behavior of hydrogels for contact lensesPublication . Silva, D.; Fernandes, A. C.; Nunes, T. G.; Colaço, R.; Serro, A. P.The irritation/discomfort associated with the use of contact lenses (CLs) is often related to the eyelid-lens friction. Although the use of such devices is widespread, the information about the influence of the lacrimal fluid biomolecules on the tribological behavior of the CLs hydrogels is scarce. In this work, we investigated the effect of the presence of albumin and cholesterol in the lubricant medium, on the frictional response of two model hydrogels for CLs: a hydroxyethylmethacrylate based hydrogel, HEMA/PVP, and a silicone based one, TRIS/NVP/HEMA. Tribological experiments were done in a nanotribometer, in water and in the presence of solutions of those biomolecules. It was observed a significant increase of the friction coefficient (μ) for HEMA/PVP when the lubricant contains cholesterol, and for TRIS/NVP/HEMA when it contains albumin. Solid-state NMR and DSC analysis revealed that HEMA/PVP hydrated in cholesterol solution has a lower amount of free and loosely bound water than the hydrogel hydrated in water. Therefore, a smaller amount of water shall be released into the contact region during the friction tests with cholesterol solution, leading to a thinner film in the contact zone, and consequently to a higher μ. Concerning TRIS/NVP/HEMA, QCM-D studies showed that this hydrogel adsorbs less albumin than HEMA/PVP and that the formed film is more rigid, which can explain the increase of μ. The obtained results contribute to understand the influence of lacrimal fluid composition on the tribological behavior of CLs materials, being relevant for the selection and optimization of these devices.