Navegando por Autor "Silva, Filipe Samuel"

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Effect of laser surface texturing on primary stability and surface properties of zirconia implants
(Elsevier, 2017-12-01) Nascimento, Rubens Maribondo do; Moura, Filipe Samuel; Pereira, Rafael Santiago Floriani; Buciumeanu, Mihaela; Carvalho, Oscar; Bartolomeu, Flávio; Silva, Filipe Samuel
The aim of this study was to investigate the influence of different laser surface texturing parameters on static and dynamic coefficient of friction values of Yttria-tetragonal zirconia polycrystals (3Y-TZP) against bone to assess the primary stability of implants. The ability of the textures to promote osseointegration, as measured by wettability, and eventual changes in roughness, due to possible aging during sterilization, were also assessed. 3Y-TZP disks were divided into four groups: as sintered sample, sandblasting and etching treatment, laser irradiation using two output power of 0.9 and 1.8 W. The friction tests were carried out by using a pin-on-plate configuration, being the pins the 3Y-TZP disks and the plates the bone. The surfaces were inspected by SEM/ EDS and by surface roughness profilometer. Wettability characteristics were also evaluated by drop contact angle, and aging was assessed, after laser treatments, by XRD analysis. Results demonstrate that with laser surface texturing of zirconia it is possible to combine better wettability, better aging performance, and better primary stability, as compared to traditional - Sand blasting and Etching treatments. Thus, it is shown that the laser irradiation technique is a promising alternative to conventional sandblasting and etching procedures
Effects of laser fluence and liquid media on preparation of small Ag nanoparticles by laser ablation in liquid
(Elsevier, 2017-12-01) Nascimento, Rubens Maribondo do; Moura, Caroline Gomes; Pereira, Rafael Santiago Floriani; Andritschky, Martin; Lopes, Augusto Luís Barros; Grilo, João Paulo de Freitas; Silva, Filipe Samuel
This study aims to assess a method for preparation of small and highly stable Ag nanoparticles by nanosecond laser ablation in liquid. Effect of liquid medium and laser fluence on the size, morphology and structure of produced nanoparticles has been studied experimentally. Pulses of a Nd:YAG laser of 1064 nm wavelength at 35 ns pulse width at different fluences were employed to irradiate the silver target in different environments (water, ethanol and acetone). The UV-Visible absorption spectra of nanoparticles exhibit surface plasmon resonance absorption peak in the UV region. STEM and TEM micrographs were used to evaluate the size and shape of nanoparticles. The stability of silver colloids in terms of oxidation at different liquid media was analyzed by SAED patterns. The results showed that characteristics of Ag nanoparticles and their production rate were strongly influenced by varying laser fluence and liquid medium. Particles from 2 to 80 nm of diameter were produced using different conditions and no oxidation was found in ethanol and acetone media. This work puts in evidence a promising approach to produce small nanoparticles by using high laser fluence energy
Finite element analysis of the residual thermal stresses on functionally gradated dental restorations
(Elsevier, 2015) Henriques, Bruno; Miranda, G.; Gasik, Michael; Souza, Júlio César Matias de; Nascimento, Rubens Maribondo do; Silva, Filipe Samuel
The aim of this work was to study, using thefinite element method (FEM), the distributionof thermal residual stresses arising in metal–ceramic dental restorations after cooling fromthe processing temperature. Three different interface configurations were studied: withconventional sharp transition; one with a 50% metal–50% ceramic interlayer; and one witha compositionally functionally gradated material (FGM) interlayer. The FE analysis wasperformed based on experimental data obtained from Dynamic Mechanical Analysis (DMA)and Dilatometry (DIL) studies of the monolithic materials and metal/ceramic composites.Results have shown significant benefits of using the 50% metal–50% ceramic interlayerand the FGM interlayer over the conventional sharp transition interface configuration inreduction of the thermal residual stress and improvement of stress profiles. Maximumstresses magnitudes were reduced by 10% for the crowns with 50% metal–50% ceramicinterlayer and by 20% with FGM interlayer. The reduction in stress magnitude andsmoothness of the stress distribution profile due to the gradated architectures mightexplain the improved behavior of these novel dental restorative systems relative to theconventional one, demonstrated by in-vitro studies already reported in literature.
Laser printing of micro-electronic communication systems for smart implants applications
(Elsevier, 2020-08) Nascimento, Rubens Maribondo do; Moura, Caroline Gomes; Magalhães, Vitor H.; Pereira, Rafael Santiago Floriani; Carvalho, Oscar; Cerqueira, Maria de Fátima; Gonçalves, Luis Miguel V.; Silva, Filipe Samuel
Endow the implant with intrinsic communication system between sensors and actuators or between implant and patient is a key factor for its long-term success. The capacity of early diagnosis of failures and the ability to remedy them are necessary to minimize expensive complications and reducing revision procedures. Ti6Al4V is the most used titanium alloy for implant’s fabrication. In this sense, this work presents a promising approach to print communication systems by using laser technology, aiming integrate the smart components on titanium implants. Laser has been employed as a versatile tool to modify the surface in different ways, such as texturing, oxidizing and sintering. Silver wires have been printed on Ti6Al4V surface in order to conduct electrical current. To minimize current loss for the substrate, titanium oxide layer has been produced by different methods (laser and anodization). Laser sintering (LS) has been also compared to a conventional method (Hot-pressing- HP) to consolidate the silver powder into the cavities. In comparison to the conventional techniques, laser demonstrated to be a competitive approach to oxidizing the surface and also for consolidating the micro-wires on Ti6Al4V surface. Consequently, the micro-wires printed by laser approach presented satisfactory results in terms of electrical resistance, actuating as the conductor path for electrical current, with values of 0.0131 Ω, which is similar to the resistance of the wire printed in an insulator substrate
Laser surface texturing of Ti-6Al-4V by nanosecond laser: surface characterization, Ti-oxide layer analysis and its electrical insulation performance
(Elsevier, 2019-11) Nascimento, Rubens Maribondo do; Moura, Caroline Gomes; Carvalho, Oscar; Gonçalves, Luis Miguel V.; Cerqueira, Maria de Fátima; Silva, Filipe Samuel
The development of smart biomedical implants with intrinsic communication system between sensors and actuators, or between implant and patient, remains a challenge for scientific community. Titanium and its alloys, especially Ti6Al4V, are the most used materials in the implant's fabrication. The present work is concerned with implant internal communication printing process and presents a detailed study o titanium alloy (Ti6Al4V) surface texturing and their characterization (morphological and chemical) produced by a Nd: YAG laser, aiming to create localized electrical insulation zones, necessary to accommodate electrical communication systems. The characterization of the textured surface was carried out by scanning electron microscopy and the heat affected zone was analyzed by X-ray diffraction. The results showed the formation of α-Ti, Ti6O and Ti2O phases on the textured surface. Through simulations in TINA software, the outer oxide layer formed during laser texturing had efficiency above 90% as insulator when an electrical current was applied
Mechanical and chemical analyses across dental porcelain fused to CP titanium or Ti6Al4V
(Elsevier, 2014) Souza, Júlio César Matias de; Henriques, Bruno; Ariza, Edith; Martinelli, Antonio Eduardo; Nascimento, Rubens Maribondo do; Silva, Filipe Samuel; Rocha, Luís A.; Celis, Jean-Pierre
The aim of this study was to evaluate the evolution of mechanical properties and chemical variation across veneering dental porcelain fused to different titanium-based substrates. Test samples were synthesized by fusing dental feldspar-based porcelain onto commercially pure titanium grade II or Ti6Al4V alloy. Samples were cross-sectioned at angles of 10 and 90° to the interface plane. Afterwards, nanoindentation tests and Scanning Electron Microscopy (SEM) imaging coupled to an Energy Dispersive Spectroscopy (EDS) system were carried out across interfaces extending from the metal towards the porcelain area. Elemental diffusion profiles across the porcelain-to-metal interfaces were also obtained by EDS analysis. The mismatch in mechanical properties found in porcelain-to-Ti6Al4V interfaces was lower than that of porcelain-to-CP titanium. Cracking was noticed at low-thickness veneering dental porcelain regions after the nanoindentation tests of samples cross-sectioned at low angles to the interface plane. A wide reaction zone between titanium and porcelain as well as higher incidence of defects was noticed at the porcelain-to-CP titanium interfaces. This study confirmed Ti6Al4V as an improved alternative to CP-titanium as it showed to establish a better interface with the veneering dental porcelain considering the slight chemical interaction and the lower mechanical properties mismatch. The elastic modulus of porcelain-to-Ti6Al4V samples showed to be less sensitive to porcelain thickness variations.
Mechanical strength and wear of dental glass-ionomer and resin composites affected by porosity and chemical composition
(Springer Link, 2015-08-13) Rodrigues, Daniela S.; Buciumeanu, Mihaela; Martinelli, Antonio Eduardo; Nascimento, Rubens Maribondo do; Henriques, Bruno; Silva, Filipe Samuel; Souza, Júlio César Matias de
The main aim of this study was to evaluate the influence of porosity, microstructure, and chemical composition on the wear and compressive strength of dental glass-ionomer or resin composite. Cylindrical samples (6 9 4 mm) were prepared from a nano-hybrid resin composite (GrandioSO/RC, VOCO), a resin-modified glass ionomer (VitremerTM/VI, 3 M-ESPE) and a conventional glass ionomer (IonofilMolar/CO, VOCO). Porosity and topography of the materials were evaluated by optical and scanning electron microscopy (SEM). Roughness was evaluated by Ra and Rt parameters at 0.1 mm/s under cutoff of 0.8 mm. Then, compressive tests were performed at 1 mm/min. Wear tests were carried out at 20 N, 2.5 mm of displacement, at 1 Hz for 90 min in artificial saliva solution. The results were statistically analyzed with a one-way ANOVA and Tukey’s test (p\0.05). Resin composite revealed a significantly lower porosity (1.21 ± 0.20 %) than glass-ionomer restoratives (5.69–7.54 %) as well as lower values of Ra and Rt roughness (p\0.05). Also, resin composite showed significantly higher values of mechanical strength (334 ± 15.9 MPa) compared to conventional (78.78 ± 13.30 MPa) or modified glass ionomer (169.50 ± 20.98 MPa) (p\0.05). For maximal depth of wear, resin composite also showed significantly lower values than glass ionomer (p\0.05). Homogeneous wear morphology was noticed by SEM analyses on glass ionomers in opposition to resin composite. Glass ionomers showed a poor mechanical behavior associated to a high porosity and wear rate when compared to resin composite.
On the mechanical properties and microstructure of zirconia-reinforced feldspar-based porcelain
(Elsevier, 2016-09) Nascimento, Rubens Maribondo do; Santos, Rafaela Luiz Pereira; Silva, Filipe Samuel; Motta, Fabiana Villela da; Henriques, Bruno; Souza, Júlio César Matias de
The aim of this study was to produce and to evaluate the mechanical properties of a dental feldspar-based porcelain reinforced by zirconia particles. The specimens were prepared by incorporating different volume fractions (10, 20, 30, 40 or 50%) of zirconia particles (3Y-TZP) in a porcelain matrix. The mixtures were hot pressed in vacuum at 970°C for 2 min. Flexural strength of the composites was measured using a three-point-bending test. Hardness, Young’s modulus and fracture toughness were also measured for all the composites. The microstructure and fracture surfaces were characterized by Field Emission Guns Scanning Electron Microscopy (FEG-SEM). Chemical analyses were performed by Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD). The highest flexural strength (218 ± 24 MPa) and fracture toughness (2.1 ± 0.1 MPa m 1/2) values were recorded for composites containing 30% zirconia particles. That corresponded to improvement in mechanical properties of about 2 times relative to those registered for feldspar-based porcelain. It was not noticed any significant difference in hardness values. The Young’s moduli also increased with the addition of zirconia particles. The addition of zirconia particles to porcelain improved significantly the mechanical properties of the base material. Zirconia-reinforced porcelain can constitute a promising alternative to conventional feldspar-based porcelains to produce prosthetic restorations, mainly for posterior teeth where high strength and toughness are demanded
Shear bond strength of veneering porcelain to zirconia: Effect of surface treatment by CNC-milling and composite layer deposition on zirconia
(Elsevier, 2016-07) Nascimento, Rubens Maribondo do; Santos, Rafaela Luiz Pereira; Silva, Filipe Samuel; Souza, Júlio César Matias de; Motta, Fabiana Villela da; Carvalho, Oscar; Henriques, Bruno
Objectives: The purpose of this study was to evaluate the shear bond strength of veneering feldspathic porcelain to zirconia substrates modified by CNC-milling process or by coating zirconia with a composite interlayer. Methods: Four types of zirconia–porcelain interface configurations were tested: RZ – porcelain bonded to rough zirconia substrate (n1⁄416); PZ – porcelain bonded to zirconia substrate with surface holes (n1⁄416); RZI – application of a composite interlayer between the veneering porcelain and the rough zirconia substrate (n1⁄416); PZI – application of a composite interlayer between the porcelain and the zirconia substrate treated by CNC-milling (n1⁄416). The composite interlayer was composed of zirconia particles reinforced porcelain (30%, vol%). The mechanical properties of the ceramic composite have been determined. The shear bond strength test was performed at 0.5 mm/min using a universal testing machine. The interfaces of fractured and untested specimens were examined by FEG-SEM/EDS. Data was analyzed with Shapiro–Wilk test to test the assumption of normality. The one-way ANOVA followed by Tukey HSD multiple comparison test was used to compare shear bond strength results (α1⁄40.05). Results: The shear bond strength of PZ (100715 MPa) and RZI (96711 MPa) specimens were higher than that recorded for RZ (control group) specimens (89715 MPa), although not significantly (p40.05). The highest shear bond strength values were recorded for PZI specimens (138719 MPa), yielding a significant improvement of 55% relative to RZ specimens (po0.05)
The effect of surface treatment on the friction and wear behavior of dental Y-TZP ceramic against human enamel
(Elsevier, 2017-12) Martinelli, Antonio Eduardo; Buciumeanu, Mihaela; Queiroz, José Renato Cavalcanti; Silva, Filipe Samuel; Henriques, Bruno
The aim of this paper was to study the influence of different surface treatments procedures on tribological behavior of Yttria-tetragonal zirconia polycristals (Y-TZP) against human enamel. The Y-TZP plates were divided into four areas and each area was subjected to a surface treatment according to the groups: GC - no surface treatment, GM – unidirectional milling with high speed tapered bur, GPK – polishing kit Kenda and GPD – polishing kit Diacera. The results demonstrated that the surface treatments play a relevant role on wear behavior of zirconia. In all cases the tooth suffered a greater wear than the Y-TZP plates. In the case of the polished groups it was obtained an improvement on the wear resistance of the tribopair
Tribological behaviour of glass-ceramics reinforced by Yttria Stabilized Zirconia
(Elsevier, 2016) Santos, Rafaela Luiz Pereira; Buciumeanu, Mihaela; Silva, Filipe Samuel; Souza, Júlio César Matias de; Nascimento, Rubens Maribondo do; Motta, Fabiana Villela da; Carvalho, Oscar; Henriques, Bruno
The aim of this study was to evaluate the tribological behaviour of a dental glass-ceramic (GC) reinforced by 20% (vol.) Yttria-Stabilized Zirconia. Two types of particles were tested: zirconia agglomerates (ZA) and pre-sintered zirconia particles (ZP). The wear tests were carried out using a ball-on-plate configuration. The wear mechanisms were characterized by field emission guns scanning electron microscope. Results revealed an improvement of wear behaviour for GC reinforced by ZP. The improvement on wear resistance was attributed to the effect of reinforcement, by the action of the uniformly distributed ZP that allowed the load transfer reinforcing mechanism through the matrix and reinforcement phase. Dental glass-ceramic reinforced by ZP can constitute a promising alternative to conventional glass-ceramics to produce prosthetic restorations

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Navegando por Autor "Silva, Filipe Samuel"