Browsing by Author "Serro, A. P."
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- 3D-Printing of zirconia dental prosthesesPublication . Rodrigues, I.; Olhero, S.; Guedes, M.; Serro, A. P.; Figueiredo-Pina, C. G.
- Drug release from liposome coated hydrogels for soft contact lenses: the blinking and temperature effectPublication . Paradiso, P.; Colaço, R.; Mata, J. L. G.; Krastev, R.; Saramago, B.; Serro, A. P.In this article, liposome-based coatings aiming to control drug release from therapeutic soft contact lenses (SCLs) materials are analyzed. A PHEMA based hydrogel material loaded with levofloxacin is used as model system for this research. The coatings are formed by polyelectrolyte layers containing liposomes of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and DMPC + cholesterol (DMPC + CHOL). The effect of friction and temperature on the drug release is investigated. The aim of the friction tests is to simulate the blinking of the eyelid in order to verify if the SCLs materials coated with liposomes are able to keep their properties, in particular the drug release ability. It was observed that under the study conditions, friction did not affect significantly the drug release from the liposome coated PHEMA material. In contrast, increasing the temperature of release leads to an increase of the drug diffusion rate through the hydrogel. This phenomenon is recorded both in the control and in the coated samples.
- 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.
- Effect of bleaching teeth with hydrogen peroxide on the morphology, hydrophilicity, and mechanical and tribological properties of the enamelPublication . Rodrigues, F. T.; Serro, A. P.; Polido, M.; Ramalho, A.; Figueiredo-Pina, C. G.The tooth whitening process is intended to restore the original color of teeth. It consists of the application of oxidizing agents, including hydrogen peroxide. Although these products considerably improve the color of teeth, their effects on other properties of enamel are not fully understood. This work aimed to study the effects of hydrogen peroxide concentration on hydrophilicity, roughness, morphology, and mechanical and tribological properties of human tooth enamel. Human teeth were subjected to bleaching sessions with 6%, 15%, and 35% hydrogen peroxide to achieve a similar level of whitening. The enamel roughness and morphology were characterized by atomic force microscopy and scanning electron microscopy. Vickers microindentation hardness data were obtained. The hydrophilicity was determined using the captive bubble method. Reciprocating, ball-on-flat friction, and wear tests were conducted in artificial saliva using zirconia as the ball and polished enamel as the flat specimens. Although all three test solutions improved tooth color, they also changed the properties of the enamel. Morphological and roughness changes were observed, and there was a decrease in hardness and wear resistance. The wettability was nearly unaffected. It was found that the 15% hydrogen peroxide solution damaged the enamel the least. It was concluded that there is an ideal concentration of hydrogen peroxide for whitening treatments.
- Effect of H2O2 solution’s pH on the human enamel micro and nanowearPublication . Branco, A. C; Rodrigues, I.; Paradiso, P.; Polido, M.; Colaço, R.; Figueiredo-Pina, C. G.; Serro, A. P."The effect of 30% H2O2 solutions with different pH (2, 4 and 6) on the wear of human dental enamel was studied. Additionally, the whitening efficiency and changes in hardness and morphology were evaluated. The enamel tribological response was accessed through two different approaches: ball-on-plate and atomic force microscopy (AFM), the later following a tribological model based on a single asperity contact. The results showed differences in the specific wear rate and wear mechanisms between the two used approaches. Regardless of the tribological approach used, the wear resistance of enamel was lower for pH = 2. It was observed that pH = 6 leads to a safe and efficient whitening treatment."
- Effect of pH of H2O2 solutions on the morphology and wear resistance of human dental enamel: an AFM studyPublication . Branco, A. C.; Polido, M.; Colaço, R.; Figueiredo-Pina, C. G.; Serro, A. P.
- Effect of sterilization on drugs and lenses for ophthalmic applicationsPublication . Topete, Ana; Oliveira, Andreia; Galante, Raquel; Bozukova, Dimitriya; Saramago, Benilde; Serro, A. P.
- Effect of tetracaine on DMPC and DMPC + cholesterol biomembrane models: Liposomes and monolayersPublication . Serro, A. P.; Galante, R.; Kozica, A.; Paradiso, P.; Gonçalves da Silva, A.M.P.S.; Luzyanina, K. V.; Fernandes, A. C.; Saramago, B."Different types of lipid bilayers/monolayers have been used to simulate the cellular membranes in the investigation of the interactions between drugs and cells. However, to our knowledge, very few studies focused on the influence of the chosen membrane model upon the obtained results. The main objective of this work is to understand how do the nature and immobilization state of the biomembrane models influence the effect of the local anaesthetic tetracaine (TTC) upon the lipid membranes. The interaction of TTC with different biomembrane models of dimyristoylphosphatidylcholine (DMPC) with and without cholesterol (CHOL) was investigated through several techniques. A quartz crystal microbalance with dissipation (QCM-D) was used to study the effect on immobilized liposomes, while phosphorus nuclear magnetic resonance (31P-NMR) and differential scanning calorimetry (DSC) were applied to liposomes in suspension. The effect of TTC on Langmuir monolayers of lipids was also investigated through surface pressure-area measurements at the air-water interface. The general conclusion was that TTC has a fluidizing effect on the lipid membranes and, above certain concentrations, induced membrane swelling or even solubilization. However, different models led to variable responses to the TTC action. The intensity of the disordering effect caused by TTC increased in the following order: supported liposomes < liposomes in solution < Langmuir monolayers. This means that extrapolation of the results obtain in in vitro studies of the lipid/anaesthetic interactions to in vivo conditions should be done carefully."
- Effect of the saliva biomolecules on the interface zirconia/Ti6Al4V triboactivityPublication . Teixeira, H.; Serro, A. P.; Figueiredo-Pina, C. G.
- Hydrogels based on poly(vinyl alcohol) for cartilage substitutionPublication . Oliveira, A. S.; Colaço, R.; Serro, A. P.
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