Browsing by Author "Figueiredo-Pina, C. G."
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- 3D-Printing of zirconia dental prosthesesPublication . Rodrigues, I.; Olhero, S.; Guedes, M.; Serro, A. P.; Figueiredo-Pina, C. G.
- 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 the saliva biomolecules on the interface zirconia/Ti6Al4V triboactivityPublication . Teixeira, H.; Serro, A. P.; Figueiredo-Pina, C. G.
- Suitability of 3D printed pieces of nanocrystalline zirconia for dental applicationsPublication . Branco, A. C.; Silva, R.; Santos, T.; Jorge, H.; Rodrigues, A. R.; Fernandes, R.; Bandarra, S.; Barahona, I.; Matos, A. P. A.; Lorenz, K.; Polido, M.; Colaço, R.; Serro, A. P.; Figueiredo-Pina, C. G.Objectives: The main goal of this work is to evaluate the suitability of nanostructured zirconia pieces obtained by robocasting additive manufacturing (AM), for dental applications. Methods: The density, crystalline structure, morphology/porosity, surface roughness, hardness, toughness, wettability and biocompatibility of the produced samples were compared with those of samples obtained by conventional subtractive manufacturing (SM) of a similar commercial zirconia material. Chewing simulation studies were carried out against dental human cusps in artificial saliva. The wear of the material was quantified and the wear mechanisms investigated, as well as the influence of glaze coating. Results: AM samples, that revealed to be biocompatible, are slightly less dense and more porous than SM samples, showing lower hardness, toughness and wettability than SM samples. After chewing tests, no wear was found both on AM and SM samples. However, the dental wear was significantly lower when AM samples were used as counterbody. Concerning the glazed samples, both coated surfaces and dental cusps suffered wear, being the cusps’ wear higher than that found for unglazed samples. More, cusps tested against AM coated samples suffered less wear comparatively to those opposed to SM coated samples. Significance. Overall, the results presented in this paper show that AM processed nanostructured zirconia can be used in dental restorations, with important advantages from the point of view of processing and tribological performance. Moreover, the option for glaze finishing should be carefully considered both in SM and AM processed specimens.
- Tribological behavior of unveneered and veneered lithium disilicate dental materialPublication . Figueiredo-Pina, C. G.; Patas, N.; Canhoto, J.; Cláudio, R.; Olhero, S.M.; Serro, A.P.; Ferro, A.C.; Guedes, M.The friction and wear behaviour of a lithium disilicate dental ceramic against natural dental enamel is studied, including the effect of the presence of a fluorapatite veneering upon the tribological properties of the material. The tribological behaviour was assessed using reciprocating pin-on-plate test configuration, at pH 3 and pH 7. The surface energy of the plates was determined, as well as the zeta potential of fluorapatite, lithium disilicate and enamel particles in artificial saliva. It was found that the friction and wear behaviour of the tested enamel/plate material tribocouples is less severe in unveneered plates. Initial surface roughness of the plate does not affect wear results. However the topography of the resulting wear track affects the corresponding wear loss: a smoother final wear track is associated with lower wear. The surface topography of the wear track, and thus the tribological performance of the tested materials, is very sensitive to the pH of the sliding solution. This is because the dissolution trend, wettability and surface charge of the used materials are pH dependent. Overall friction and wear are higher under basic pH conditions, especially when plates are veneered. A wear model is proposed that correlates the effect of the described parameters with the observed tribological behaviour at pH 7. Attained results show that fluorapatite coating of lithium disilicate dental crowns affects tooth/crown wear behaviour, resulting in increased wear of both the artificial crown and the opposing natural teeth. Coating should therefore be avoided in occlusal crown surfaces.
- Tribological performance of the pair human teeth vs 3D printed zirconia : an in vitro chewing simulation studyPublication . Branco, A. C.; Silva, R.; Jorge, H.; Santos, T.; Lorenz, K.; Polido, M.; Colaço, R.; Serro, A. P.; Figueiredo-Pina, C. G.This study aims to evaluate the tribological performance of the pair human teeth/robocasted zirconia, with a special focus on the enamel wear mechanisms. Zirconia pieces produced by robocasting (RC) and unidirectional compression (UC) were compared in terms of crystalline structure, density, porosity, hardness and toughness. Chewing simulation tests were performed against human dental cusps. The cusps wear was quantified and the wear mechanisms identified. Although most of the properties of UC and RC samples are similar, differences were observed for surface roughness and porosity. Although the samples did not suffer wear, the antagonist cusps worn in a similar way. In conclusion, robocasting seems a promising technique to produce customized zirconia dental pieces, namely in what concerns the overall tribological behaviour.