Objective: Nanotechnology has progressed significantly and particles as small as 3 nm are being employed in resin-based restorative materials to improve clinical performance. The goal of this review is to report the progress of nanotechnology in Restorative Dentistry by reviewing the advantages, limitations, and applications of resin-based restorative materials with nanoparticles.Materials and Methods: A literature review was conducted using PubMed/ Medline, Scopus and Embase databases. In vitro, in vivo and in situ research studies published in English between 1999 and 2020, and which focused on the analysis of resin-based restorative materials containing nanoparticles were included.Results: A total of 140 studies were included in this review. Studies reported the effect of incorporating different types of nanoparticles on adhesive systems or resin composites. Mechanical, physical, and anti-bacterial properties were described. The clinical performance of resin-based restorative materials with nanoparticles was also reported. Conclusions:The high surface area of nanoparticles exponentially increases the bioactivity of materials using bioactive nanofillers. However, the tendency of nanoparticles to agglomerate, the chemical instability of the developed materials and the decline of rheological properties when high ratios of nanoparticles are employed are some of the obstacles to overcome in the near future. Clinical significance: In spite of the recent advancements of nanotechnology in resin-based restorative materials, some challenges need to be overcome before new nano-based restorative materials are considered permanent solutions to clinical problems. K E Y W O R D S dental adhesives, nanohybrid, nanoparticles, resin composite | INTRODUCTIONNanotechnology, also known as molecular technology or molecular engineering, consists of the steps involved in processing, separating, consolidating, and deforming materials by one atom or molecule 1 to generate structures in the size range of 0.1-100 nanometers. 2 The inorganic fillers employed in dental materials may be categorized according to their size range, varying from macrofillers to nanofillers, and their size is controlled either by a top-down or a bottom-up manufacturing approach. Figure 1 summarizes the historical

The aim of this study was to evaluate the effect of chewing simulation on wear of artificial enamel abraded against zirconia-based crowns. Fifteen crown preparations were scanned for the manufacturing of crowns using computer-aided-design/computer-aided-machining technique (CAD/CAM), according to the following (n = 5): Polished (PM) and glazed (GM) monolithic zirconia (1.5 mm uniform thickness), and Bilayer (BL -0.8 mm zirconia coping, 0.7 mm porcelain veneer) crowns. The samples were cemented and chewing simulation (2.5 million cycles/0-80N/artificial saliva/37˚C) was performed with steatite indenters (6 mm diameter) as antagonists. Assuming the uniformity of the unaged samples, antagonists were scanned using a surface profilometer and the material loss volume was calculated. Roughness of the crowns' occlusal surface was also analyzed using the profilometer. Scanning electron microscopy was used to characterize the abraded surface. One-way ANOVA and Tukey test (p = 0.05) were employed for analysis of wear results. A significant difference was observed among the groups (p < 0.001). Artificial enamel abraded against porcelain (BL) had significantly higher material loss (0.217 mm 3 ± 0.015) than those abraded against monolithic zirconia, polished (PM -0.167 mm 3 ± 0.02) and glazed (0.101 mm 3 ± 0.03), which were similar to each other. Veneering porcelain results in more pronounced wear of the artificial enamel than monolithic zirconia. However, mastication against monolithic Y-TZP also imposes wear to the opposing teeth.

O objetivo deste trabalho é investigar o comportamento de corrosão de ímãs Nd-Fe-B produzidos por metalurgia do pó e avaliar a proteção conferida por dois diferentes tratamentos de superfície: uma camada de conversão de fosfato e um silano não-funcional. Os ensaios eletroquímicos foram realizados em solução tampão de fosfato (PBS) com pH neutro, em que a concentração iônica coincide com a do corpo humano. A corrosão foi monitorada por meio de espectroscopia de impedância eletroquímica (EIS), curvas de polarização anódica, e as análises de MEV-EDS foram utilizadas para observar a superfície e controlar a deposição do revestimento. A resposta de EIS evidenciou um comportamento de eletrodo poroso para os ímãs Nd-Fe-B de acordo com a teoria de Levie. Os resultados também indicaram um bom desempenho da camada de fosfato, enquanto o silano não funcional não melhorou a resistência à corrosão dos ímãs. O bom desempenho anti-corrosão da camada de fosfato foi explicada com base na formação de uma camada de fosfato insolúvel tanto na superfície do eletrodo quanto nas paredes dos poros. A precipitação de fosfato de Nd insolúvel sobre a fase rica em Nd também contribui para a proteção contra a corrosão oferecida por este revestimento.The aim of this work is to investigate the corrosion behavior of powder metallurgy produced Nd-Fe-B magnets and to evaluate the corrosion protection afforded by two different surface treatments: a phosphate conversion and a non-functional silane (BTSE) layer. The electrochemical tests were performed in a phosphate buffered solution (PBS) at neutral pH, which ionic concentration coincides with that of the human body. The corrosion behavior was monitored by means of electrochemical impedance spectroscopy (EIS) and anodic potentiodynamic polarization curves, and SEM-EDS analyses were used to monitor coating deposition. EIS response has evidenced a porous electrode behavior for the Nd-Fe-B magnets according to the de Levie theory. The results also indicated a good performance of the phosphate layer, whereas the BTSE layer did not improve the corrosion resistance of the magnets. The good anticorrosion performance of the phosphate layer was explained on the basis of the formation of an insoluble phosphate layer both on the electrode surface (identified by interference colors) and on the pore walls. Precipitation of insoluble Nd phosphate on the Nd-rich phase also contributes to the superior corrosion protection afforded by this coating.

OBJECTIVE: The etiology of LNC's is complex and not fully understood and seem to influence and interact in their formation diverse factors as stress concentration, the presence of acids of various origins and various tribological mechanisms. The purpose of this in vitro study was to evaluate whether there are differences in the influence of tensile stress, compression stress and brushing on the lesion's depth, hardness and roughness of bovine enamel subjected to acid challenge. The work consisted of assessing damage to bovine enamel subjected to an erosive acid challenge (and abrasive) with simultaneous mechanical loading. METHODS: The work consisted of assessing the mineral loss in enamel subjected to an erosive acid challenge and biomechanical loading. We evaluated 48 sticks containing enamel and dentin, with dimensions (2.7 x 2.7 x 16 mm). These sticks were planned with sandpapers with granulation 600 and 800 and after subsequently polished with sandpaper granulation 1000, 1200, 2400 and 4000. A transverse notch of 1,5 mm diameter was made on dentin leaving a ''neck'' of 1,7mm of enamel and dentin. The entire surface of the specimen, except for a window of 4 mm on the buccal enamel (the region of highest stress concentration), received a protection against the acid challenge. The specimens were fixed at one end and divided into two groups (n = 24): subjected to a continuous bending load (650 gf) applied to the other end (where 12 of them were fixed with the notch facing up-compression-and 12 with the notch down-tensile) and another group of specimens unloaded (n = 24). With this division, all specimens suffered the first acid challenge (2 hours in 400 ml of buffered citric acid solution, adjusted to pH 3.75 at 37 ° C) and, then, were measured (lesion depth and surface roughness with profilometer, and also micro hardness). Then each group was subdivided into two with the same number (n = 6 for loaded ones and n=12 for unloaded ones): A group received brushing with toothpaste and other just with water, then they were protected again and exposed to the second acid challenge (with load or without load). After remeasurement (lesion depth and roughness with profilometer, and micro hardness) and re-protection, the specimens were subjected to the third acid challenge and again measured. An extra set of 24 sticks was used for the

O objetivo deste trabalho é investigar o comportamento de corrosão de ímãs Nd-Fe-B produzidos por metalurgia do pó e avaliar a proteção conferida por dois diferentes tratamentos de superfície: uma camada de conversão de fosfato e um silano não-funcional. Os ensaios eletroquímicos foram realizados em solução tampão de fosfato (PBS) com pH neutro, em que a concentração iônica coincide com a do corpo humano. A corrosão foi monitorada por meio de espectroscopia de impedância eletroquímica (EIS), curvas de polarização anódica, e as análises de MEV-EDS foram utilizadas para observar a superfície e controlar a deposição do revestimento. A resposta de EIS evidenciou um comportamento de eletrodo poroso para os ímãs Nd-Fe-B de acordo com a teoria de Levie. Os resultados também indicaram um bom desempenho da camada de fosfato, enquanto o silano não funcional não melhorou a resistência à corrosão dos ímãs. O bom desempenho anti-corrosão da camada de fosfato foi explicada com base na formação de uma camada de fosfato insolúvel tanto na superfície do eletrodo quanto nas paredes dos poros. A precipitação de fosfato de Nd insolúvel sobre a fase rica em Nd também contribui para a proteção contra a corrosão oferecida por este revestimento. The aim of this work is to investigate the corrosion behavior of powder metallurgy produced Nd-Fe-B magnets and to evaluate the corrosion protection afforded by two different surface treatments: a phosphate conversion and a non-functional silane (BTSE) layer. The electrochemical tests were performed in a phosphate buffered solution (PBS) at neutral pH, which ionic concentration coincides with that of the human body. The corrosion behavior was monitored by means of electrochemical impedance spectroscopy (EIS) and anodic potentiodynamic polarization curves, and SEM-EDS analyses were used to monitor coating deposition. EIS response has evidenced a porous electrode behavior for the Nd-Fe-B magnets according to the de Levie theory. The results also indicated a good performance of the phosphate layer, whereas the BTSE layer did not improve the corrosion resistance of the magnets. The good anticorrosion performance of the phosphate layer was explained on the basis of the formation of an insoluble phosphate layer both on the electrode surface (identified by interference colors) and on the pore walls. Precipitation of insoluble Nd phosphate on the Nd-rich phase also contributes to the superior corrosion protection afforded by this coating.