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This study evaluated the fluorescence of white zirconia immersed in coloring and fluorescence liquids, subjected to glass infiltration and aging. Sixty zirconia discs were machined and divided into groups. Ten discs received no treatment before sintering (Group NT), ten discs were immersed in a coloring liquid (Group A2), and ten discs were immersed in a fluorescent liquid (Group F). The other thirty discs were infiltrated with glass after the previous treatments (Groups NT + I, A2+I, and F + I). The composition of the liquids was characterized by X-Ray fluorescence. Additional superficial roughness and X-Ray diffraction measurements were made. Diffuse reflectance and total fluorescence were evaluated before and after aging, performed in an autoclave at 134 °C for 4 h. By X-Ray fluorescence analysis, a high concentration of Fe2O3 (80.7 at%) was found in the composition of the coloring liquid; Bi2O3 (54.2 at%) and Cl (45.2 at%) were found in the fluorescence liquid. Greater reflectance was observed in the glass infiltrated groups, in particular Groups NT + I and F + I. Mean values found for arithmetic average roughness (Ra) varied around 0.2 μm. The 3D Fluorescence maps of the groups submitted to immersion showed a higher total fluorescence value than Group NT, except for Group A2. Group F showed the highest fluorescence value that was 12.8 times higher than the value of Group NT. Fluorescence emission occurred in the region between 350 and 550 nm after excitation ranging between 290 and 360 nm. The presence of the glass infiltrated layer protected the samples from hydrothermal degradation.

In the piston ring-cylinder system, the surface topography is crucial to their tribological performance, emphasizing the relevance of the surface finishing processes. The present work studied the influence of different finishing processes in the surface roughness parameters of the coated compression piston rings. Three distinct surfaces’ finishing processes were used in the first approach: Option A, B, and C. Options D comprised the variation of different processing parameters. The piston rings with different surface topographies were tribologically evaluated using a tribometer developed explicitly for this industrial evaluation. Regarding the tribological performance, it was concluded that the use of the surface finishing processes fostered a decrease in the coefficient of friction. The surface finishing had also impacted the wear of the piston ring and in the counterbody. An increase in the piston rings’ surface roughness led to a rise in the surface's weight loss.

The main aim of this study was to assess the effect of ns-Nd:YAG laser structuring over zirconia green compacts on the adhesion of sintered zirconia to resin-matrix cements. Zirconia (3Y-TZP) compacts were divided according to the type of surface modification: GB – alumina grit-blasted sintered specimens; G8L – laser structured zirconia green compacts (square pattern 8 lines); G16L - laser structured zirconia green compacts (square pattern 16 lines); G8L/GB – alumina grit-blasted G8L specimens after sintering. Specimens of same group were cleaned, cemented using a dual cure resin-matrix cement and aged in distilled water for 24 h (37 °C). Afterwards, the tensile bond strength was measured using a universal test machine. Specimens were analyzed by field emission guns scanning electron microscopy (FEGSEM) and white light interferometry (WLI). Laser-structured surfaces showed higher roughness values and improved morphological aspects for adhesion to resin-matrix cements. Higher tensile bond strength mean values of zirconia to resin-matrix cements were recorded for G8L (16.7 ± 3.8 MPa) and G16L (13.6 ± 3.0 MPa) groups when compared to those recorded for ordinary grit-blasted zirconia surfaces to resin-matrix cements (10 ± 3.1 MPa). The highest tensile bond strength results were recorded for the G8L/GB group (24.2 ± 7.6 MPa). The laser texturing of green zirconia surfaces promoted an increase in roughness and changes in morphological aspects of sintered zirconia for improved adhesion to resin-matrix cements.

Despite the reported high success of dental implants, problems related to biofilm formation and peri-implantitis due to the entrance and proliferation of bacteria on the peri-implant zone have increasing attention. In this sense, this work proposes a new zirconia surface with micro-grooves aiming to develop an effective tight seal between artificial soft tissue and implant surface and thus, to protect from bacterial invasion. In this study, different laser and design parameters were tested to produce successive micro-grooves with different and variated depth, width and wall. The micro-grooves were produced by a Nd:YAG laser and were morphologically characterized by SEM. Higher marked depths were obtained for a high number of laser passages under low scan speed as a result of a high amount of laser energy density. The most adequate conditions were mechanically tested regarding their capacity to retain artificial soft tissue (mimicking natural gingiva) by mechanical tensile strength test. The strength of adhesion between soft tissue and the micro-grooved surface revealed to be strongly dependent on the depth and width. The obtained results showed that the production of successive micro-grooves on the zirconia surface increased the adhesion of artificial soft tissue to its surface, proving that laser technology is a promising approach for the manufacturing of implants with micro-grooves sites that can protect from bacterial invasion.

This systematic review and meta-analysis were made to evaluate the bond strength behavior and failure mode of zirconia surfaces treated by laser irradiation and to highlight the main characteristic...

During machining processes, a high temperature is generated in the cutting zone due to plastic deformation, resulting in an increase of wear and consequently reducing the lifetime of cutting tools. The addition of well-defined patterned surfaces with random or regular microfeatures to cutting tools can improve its wettability, providing an enhanced lubrication effect, a reduced tool-chip friction and a lower tool wear rate. In this sense, this work proposes a laser surface texturing approach of WC-Co green compacts to obtain different cross-hatched micropatterns, for enhancing these tools wettability. Results showed that laser surface texturing allowed to produce well-defined, reproducible and equally spaced cross-hatched micropatterns in WC-Co green compacts. A contact angle of 33.5° was obtained for the experiment with a groove and peak width of 250 μm and 3 laser passages, resulting in a 27% reduction, when compared with an untextured cutting tool (45.8°). This approach was found effective to improve the wettability of WC-Co cutting tools.

Magnesium (Mg) and its alloys are promising materials for a wide range of biomedical applications due to its biodegradability. Nevertheless, their rapid corrosion dictates the need to develop strat...

The aim of this work was the production and the characterization of a laser textured 316L stainless steel reinforced with CuCoBe-diamond composites by laser sintering. The composites were obtained ...

This work presents innovative zirconia surfaces functionalized with gold nanoparticles (Aunps) and silver microparticles (Agμps) through versatile laser technology where laser parameters and subtractive/additive strategies were combined to apply in dental implant surfaces regarding antibacterial potentialities. Aunps-functionalized zirconia surfaces were produced by a hybrid process starting with nanoparticles production by Nd:YAG laser ablation, followed by its deposition through spray system and its adhesion to the zirconia surface by the laser CO2 action, varying laser power and scan speed parameters. Agμps-functionalized zirconia surfaces were obtained through a hybrid laser process starting by laser texturing of the compacted zirconia surface, followed by allocation of Ag powder into the texture and its subsequent laser sintering, varying laser power. The functionalized zirconia surfaces were analyzed through SEM/EDS. In order to mimic the implant screwing effect, the samples were subjected to reciprocating friction tests against bone. It allows to evaluate the adhesion of the zirconia surface to the bone and the resistance to surface detachment. A purple colloidal solution of spherical gold nanoparticles with an average size of 5 ± 3 nm was successfully produced by laser. The friction tests revealed a good behavior of both functionalized zirconia surfaces indicating that their integrity is not affected during implant screwing insertion. A good dispersion of nanoparticles on the zirconia surface was observed indicating that the spray system is an effective way to deposit nanoparticles on the surface. A high amount of agglomerates was found for samples where low laser power (P = 11W) and scan speed (v = 1000 mm/s) were applied, probably due to the high density of energy (E). A decrease of defects on the sintered Ag layer with increasing laser power from 3 to 6 W was found, mainly related with the amount of laser energy density. The ion release showed to be strongly dependent on particle size.

The purpose of this systematic review is to report the characteristics and methods utilized in human lower limb or knee joint only biomechanical models to provide state-of-the-art knowledge on the topic. This review was conducted according to the preferred reporting items for systematic reviews and meta-analyses guidelines. PubMed, Scopus and Web of Science were searched up to 24th April 2018 to look for musculoskeletal models of the human lower limb or knee joint only without any associated pathology. A 15-item checklist was used to assess the methodological quality of the included studies. Twenty-one studies were included, with seventeen of them modelling the lower limb and four only the knee joint. The methodological quality of the studies varied considerably, with the reporting of model characteristics showing very low quality. Among studies including experimental setup, subjects were instructed to perform vertical jumping, running at different speeds, drop landing and isokinetic knee extension (5%), static conditions (9%), knee’s flexion/extension (14%) and walking at constant (29%) and different (33%) speeds. A great variety of modelling strategies was found for the reproduction of the human musculoskeletal system in terms of number of segments, muscles and muscle models. The reviewed musculoskeletal models were able to reproduce human movement dynamics similar to results present in literature and to experimentally measured records. However, standardized methods for reporting the characteristics and methods of these models are missing and should be addressed in future studies.

This paper exhibits an outline of the piston rings operational characteristics and consequently, of their main functional challenges. The basic geometrical shapes, materials and manufacturi...

Peri-implant diseases are one of the main causes of dental implant failure. New strategies for dental implants manufacturing have been developed to prevent the accumulation of bacteria and related inflammatory reactions. The main aim of this work was to develop laser-treated titanium surfaces covered with silver that generate a electrical dipole to inhibit the oral bacteria accumulation. Two approaches were developed for that purpose. In one approach a pattern of different titanium dioxide thickness was produced on the titanium surface, using a Q-Switched Nd:YAG laser system operating at 1064 nm. The second approach was to incorporate silver particles on a laser textured titanium surface. The incorporation of the silver was performed by laser sintering and hot-pressing approaches. The anti-biofilm effect of the discs were tested against biofilms involving 14 different bacterial strains growth for 24 and 72 hr. The morphological aspects of the surfaces were evaluated by optical and field emission guns scanning electronical microscopy (FEGSEM) and therefore the wettability and roughness were also assessed. Physicochemical analyses revealed that the test surfaces were hydrophilic and moderately rough. The oxidized titanium surfaces showed no signs of antibacterial effects when compared to polished discs. However, the discs with silver revealed a decrease of accumulation of Porphyromonas gingivalis and Prevotella intermedia strains. Thus, the combination of Nd:YAG laser irradiation and hot-pressing was effective to produce silver-based patterns on titanium surfaces to inhibit the growth of pathogenic bacterial species. The laser parameters can be optimized to achieve different patterns, roughness, and thickness of the modified titanium layer regarding the type and region of the implant. ispartof: JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART B-APPLIED BIOMATERIALS vol:109 issue:10 pages:1588-1600 ispartof: location:United States status: published

Yttria-stabilized zirconia (YSZ) is being proposed as an alternative material to Titanium for dental implants due to its aesthetic and biocompatibility properties. However, is it yet to define the optimal surface treatment to improve YSZ bioactivy. Texturization is a promising approach, but the biological role of patterned YSZ surfaces in cell cultures is yet to be determined. Thus, cellular behavior of osteoblasts and fibroblasts in contact with groove-texturized YSZ surfaces was investigated. YSZ discs were groove-textured by conventional milling and Nd:YAG laser. All samples including control were sandblasted and acid-etched. Human osteoblasts and fibroblasts were cultured on discs for 14 days. Morphology and cellular adhesion were observed. Cell viability, interleukin-1β, osteopontin, collagen type I prodution, alkaline phosphatase activity, and interleukin-8 were measured. YSZ texturization by conventional milling improved osteoblasts viability and differentiation when compared to laser texturization. Fibroblasts behavior did not seem to be influenced by the texturing technique. Compared to sandblasting and acid etching currently used as gold standard for zirconia dental implants no superiority of macrotexturization was found.

Recently, the production of well-defined patterned surfaces with random or regular micro and nano-features has brought new opportunities for research and development in the field of tissue engineering and regenerative medicine. Among advanced micro and nano processing technologies, laser surface texturing (LST) stands out due to its simplicity, flexibility, precision, reproducibility and relatively low cost. This work studies the development of patterned surfaces controlled by of LST into biomedical grade V titanium, Ti–6Al–4V–alloy. We present different cross-hatched micropatterns followed by the characterisation of surface morphology and topography. Structural integrity of the produced patterns is evaluated by friction tests against bone, mimicking the insertion of an implant. Wettability is studied as it is crucial for protein adsorption and cell adhesion. The results show that the surface topography obtained using different patterning plans influences the wetting behaviour and the coefficient of friction against bone.

This study intends to develop a novel zirconia scaffold design with a significantly lower Young's Modulus than zirconia bulk material (210 GPa) aiming to match this elastic property with that of the host bone, for application as endosseous implants. This scaffold with a complex interconnected structure can allow bone ingrowth, vascularization and provide a good initial stability. This novel thin-walled zirconia scaffold was manufactured by green machining and afterwards furnace sintered. The obtained YM of this zirconia scaffold was found significantly lower than zirconia bulk material due a less stiff geometry with small (walls and floors) dimensions. Insertion replication tests were performed for evaluating the fixation at the initial moment of implantation, being experimentally verified a high static initial coefficient of friction. The capillarity of these scaffolds was also assessed, revealing a very high rising speed of water inside these structures. This study proved that this novel ceramic scaffold design can be fabricated for several dimensions for obtaining desired elastic properties. The proposed fabrication strategy allows the fabrication of thin-walled structures unachievable by conventional machining.

Zirconia implants are becoming a preference choice for different applications such as knee, dental, among others. In order to improve osseointegration, implant's surfaces are usually coated with bioactive materials like hydroxyapatite (HAp) and beta-tricalcium phosphate (β-TCP) that are very similar to the calcium phosphates found in bones. However, due to the implantation process, these coatings can be detached from the zirconia surface, leading to implant premature failure. In this work, a new component materials design aiming to avoid this coating detachment problem is proposed. It is based on the use of a bioactive zirconia-calcium phosphate composite outer layer onto the zirconia bulk, where the zirconia bulk provides mechanical strength and the outer layer provides biological performance. In order to assess the potential of this new materials design, two types of bioactive zirconia outer composite layers (zirconia reinforced by 10 vol% of HAp and by 10 vol% of β-TCP) were produced by press and sinter process and the gradated samples were fully characterized concerning materials, mechanical resistance, fatigue resistance, and biological performance, as measured by different approaches. Results showed that the novel component materials design and the manufacturing process proposed for producing the bioactive zirconia samples with outer composite layers on zirconia bulk substrates are a promising solution for implants, with improved biological performance without substantially compromising their overall mechanical and fatigue properties.

Nowadays, conventional machining of WC-Co green compacts is used in industries in order to achieve desired dimensions, complex geometries and good surface quality. However, conventional machining presents some problems, namely tool wear, tool breakage, chatter, vibration and deflection besides mechanically induced damage to the compact. Laser machining is a promising approach to machine WC-Co green compacts, since it is performed without contact and allows great flexibility for producing several geometries, high material removal rate, good surface quality and precision, also for complex shapes. It also allows the production of details smaller than 0.2 mm, hardly manufactured by conventional machining, due to the brittle nature of cutting tools of very small dimensions. Due to the abovementioned reasons, laser machining presents a great potential for lowering the production costs of cemented carbide tools. This work addresses the laser machining of WC-Co green compacts, using a Nd:YAG laser and performing different strategies and combinations of laser parameters to obtain different types of profiles (grooves, areas and specific geometries). Results showed that an effective laser machining of WC-Co green compacts is attained when using laser power of 3 W, scan speed of 128 mm/s, 8 passages and line spacing of 0.08 mm. These parameters were effective for obtaining around 800 μm depth geometries, where the addition of a finishing step (1.5 W, 256 mm/s and 8 passages) improved the quality of the edge of the machined geometry. The laser machined compacts were sintered using a SinterHIP process and no undesirable phases were detected, as eta-phase or graphite.

Contrarily to conventional sintering (CS) method where longer cycles and high temperature (1400–1500 °C) are applied to sinter yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramics, this work presents a faster and low temperature (1175 °C) way through hot pressing (HP) to produce full densified zirconia with good mechanical and tribological properties. This work is concerned with the influence of sintering pressure on the microstructure and tribological properties of hot-pressed Y-TZP. For this purpose, four sintering pressures 5, 20, 60 and 100 MPa were tested. The wear tests were carried out by reciprocating ball-on-plate as a simplified test for tooth-to-restorative material contact under 37 °C using artificial saliva to mimic oral conditions. The results demonstrated that density, hardness and tribological properties are strongly influenced by the sintering pressure, namely an improvement with pressure increase was achieved. The highest density, hardness values and wear resistance were achieved for Y-TZP samples produced at P = 100 MPa. Furthermore, it was revealed that a smaller grain size for Z100 samples (full densification condition) was achieved comparatively to conventional-sintered Y-TZP. This work proves that it is possible to produce dense Y-TZP materials under low sintering temperature and faster cycles with reduced grain size without compromise mechanical and tribological properties.

Although hydroxyapatite coatings have been proven effective for obtaining uniform and continuous coatings on metallic endosseous implants, the detachment of these coatings during implantation can critically compromise the hydroxyapatite bioactive role. In order to overcome this problem, this work proposes a new integrated approach, starting with the laser machining of the Ti6Al4V implant, followed by the allocation of the hydroxyapatite and its subsequent laser sintering. In this study two different powder compaction/laser sintering methods were tested. Hydroxyapatite sinterability and adhesion to the metal was assessed for both methods, considering several conditions. Hydroxyapatite possible degradation due to the temperatures achieved during this process was also evaluated by means of Energy Dispersive Spectrometry (EDS) and X-ray diffraction (XRD). The better solution assured a significant retained volume of non-degraded hydroxyapatite. This work proves that laser technology is a promising approach for the manufacturing of implants with improved bioactivity sites that can overcome the detachment problems of coating-based solutions.

Osseointegration is defined by a stable and functional union between bone and a surface of a material. This phenomenon is influenced by the geometric and surface characteristics of the part where the bone cells will attach. A wide variety of studies proves that ceramic materials are strong competitors against conventional metals in the scope of bone tissue engineering. Ceramic scaffolds, porous structures that allow bone ingrowth, have been studied to enhance the osseointegration phenomenon. Geometric and dimensional parameters of the scaffold have influence in its performance as mechanical and structural supporter of bone growth. However, these parameters are conditioned by the manufacturing process by which these scaffolds are obtained. Several studies focusing on the production process of ceramic scaffolds have been developed, using 3D printing, stereolithography, selective laser sintering, green machining, robocasting, and others. The main purpose of this work is to evaluate and compare the different manufacturing processes by which ceramic scaffolds can be produced. This comparison addresses scaffold parameters like pore size, pore shape, porosity percentage, roughness, and so forth. Additionally, the different materials used in different manufacturing processes are also mentioned and discussed given its influence on a successful osseointegration while simultaneously displaying adequate mechanical properties. After making a screening on the available ceramic scaffolds manufacturing processes, several examples are presented, proving the potential of each of these manufacturing process for a given scaffold geometry.

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., This work has been supported by FCT (Fundação para a Ciência e Tecnologia -Portugal) in the scope of the projects UID/EEA/04436/ 2019 and NORTE-01-0145-FEDER-000018-HAMaBICo and Add.Additive_Manufacturing to Portuguese Industry_POCI-01-0247- FEDER-024533. I wish to thank the CNPq (205791/2014-0).

The aim of this work was to perform a statistical analysis in order to assess how the tribological properties of a laser textured 316L stainless steel reinforced with CuCoBe - diamond composites are affected by diamond particles size, type of technology (laser sintering and hot pressing) and time of tribological test. The analysis started with the description of all response variables. Then, by using IBM® SPSS software, the Friedman’s test was used to compare how the coefficient of friction varied among samples in five-time points. From this test, results showed that there was no statistically significant difference in the coefficient of friction mean values over the selected time points. Then, the two-samples Kolmogorov-Smirnov (K-S) test was used to test the effect of the diamond particles size and the type of technology on the mean of the coefficient of friction over time. The results showed that, for both sintering techniques, the size of the diamond particles significantly affected the values of the coefficient of friction, whereas no statistical differences were found between the tested sintering techniques. Also, the two-way ANOVA test was used to evaluate how these factors influence the specific wear rate, which conducted to the same conclusions drawn for the previous test. The main conclusion was that the coefficient of friction and the specific wear rate were statistically affected by the diamond particles size, but not by the sintering techniques used in this work.

This study presents experimental results on the mechanical behavior of aluminum alloy cellular structures filled with Polypropylene or ABS. Two types of base cell geometries were analyzed, having uniform cell structure and with a dual-size cell arrangement seeking optimized mechanical properties. The structures were manufactured by lost-wax casting using 3D printed components for internal structure definition. The polymer fill was introduced through a process of temperature assisted impregnation in a specially developed tool. Results for stiffness and energy absorption were obtained and compared on weight efficiency basis. The results are indicative of higher efficiency of the dual-size structures having PP/ABS filling that may be considered for energy absorption parts in compressive loading., This work has been supported by FCT – Fundação para a Ciência e Tecnologia within the R&D Units Project Scope: UIDP/04077/2020.

The high temperatures generated in the cutting zone during machining processes results in an increase of wear mechanisms, reducing the lifetime of cutting tools. In this sense, cutting tools industry is constantly looking for new ways to reduce this temperature. This work proposes a novel cemented carbide cutting tool design and fabrication process for enhancing these tools thermal conductivity. This design incorporates copper heat sinks in designated strategic locations, fabricated using innovative laser green compacts machining. A thermal conductivity of 127 W/m.K was obtained for WC-Co/Cu, considerably higher than that of WC-Co (36 W/m.K). This approach for obtaining WC-Co/Cu cutting tools was found effective for increasing locally the thermal conductivity, especially in the cutting zone vicinity., This work was supported by FCT (Fundação para a Ciência e a Tecnologia) through the project POCI-01-0145-FEDER-030353 (SMARTCUT) and also by the project NORTE 01-0145, FEDER-000018 (HAMaBICo). Additionally, this work is supported by FCT with the reference project UID/EEA/04436/2019. The authors would like to thank Miguel Ângelo Neto and Filipa Oliveira from University of Aveiro for helping in the 3D optical profilometry analysis.

Smart implants are endowed with functions of sensing, actuating and control to solve problems that may arise during their use. The assembly of these functions along the implant surface is still a challenge. However, with the advent of 3D printing, it is possible to print on implants’ surface, communication channels or micro-antennas or even sensoric/actuating areas. Hence, a positive impact on the long-term performance of the implants (including hip, dental and knee) may be expected with the proposed approach. Despite titanium and Ti6Al4V titanium alloy are the standard choice for implants fabrication, 3Y-TZP (tetragonal 3% mol yttria-stabilized zirconia) has emerged as a ceramic material suitable to overcome titanium alloy problems, due to its numerous advantages. In this sense, this work is concerned with the ability of printing silver-based communication system in zirconia substrates by using laser technology. For this purpose, micro-cavities were created on ZrO2 substrate, where the silver powder was placed and sintered into them. Through the laser approach, silver-based wires with great quality and low resistivity values were achieved. The flexural strength results showed that the mechanical resistance of zirconia disks was affected by laser micro-wire printing, which decreased as the laser passage was performed. Based on the results, it is believed that the proposed approach seems to be effective for the manufacturing of implants with intrinsic capacities, useful for smart implant applications., This work has been supported by FCT (Fundação para a Ciência e Tecnologia - Portugal) in the scope of the projects UID/EEA/04436/ 2019 and NORTE-01-0145-FEDER-000018-HAMaBICo and Add.Additive_Manufacturing to Portuguese Industry_POCI-01-0247- FEDER-024533. Thank the CNPq (205791/2014-0) and CAPES for the financial support.

The development of new approaches to improve the implant integration and subsequently its long-term maintenance is an actual challenge. In this way and trying to mimic natural bone composition, HAp-functionalized zirconia surfaces were produced by means of hybrid laser technique combining additive (laser sintering) and subtractive (laser machining) processes. Nd:YAG laser-generated textures were created to improve mechanical interlocking of hydroxyapatite (HAp) powder and consequently enhance its adhesion to zirconia surface. Different laser parameters and also different approaches were tested to optimize the textured line-patterning of zirconia surface. The created microtextures were characterized by Scanning Electron Microscopy (SEM). Furthermore, textured zirconia surfaces were functionalized with HAp by means of CO2 laser. Different power and scan speed laser parameters were tested to promote HAp retention inside of line-patterning. The results showed that it is possible to design the textured surface by changing energy density and atmosphere. Furthermore, high amount of retained and sintered bioactive material was found when high laser power and low scan speed were performed.

The main aim of this study was to perform a scoping review on the titanium electric stimuli approach to inhibit biofilm accumulation. An electronic search was conducted using key terms related to the incorporation of metal particles on the titanium surface for antibacterial purposes. The search identified 163 studies, of which 37 were considered relevant to this study. Previous studies reported the Ag-based modification of titanium surfaces to inhibit the bacterial adhesion considering that the Ag element has been used as an antimicrobial agent. Other metals such as Au, Zn, Cu, or Mg have been incorporated to titanium implant surfaces for antibiofilm proposal. Those metals are entrapped on the titanium surface and can speed up the exchanging of electrons within an increased electrical current flow. Reactive oxygen species or electron-depleted regions can arise from those interactions and disturb the normal regulation of bacterial functions. The proposed surface modifications showed some degree of antibacterial effect on Gram-positive and Gram-negative bacteria although further studies are required to access a potential cytotoxicity of the metal debris and ions.

The purpose of this study was to evaluate the mechanical properties of laser printed monolithic and laminated nano ceramic resins (NCR) for dental prosthetic applications. Three different types of discs were produced by laser printing: monolithic NCR discs and laminated NCR discs with 100 μm (laminate_100) and 500 μm (laminate_500) resin interlayers (n = 10). To assess the adhesion strength of the photosensitive resin used as interlayer to the NCR, cylindrical specimens were produced. The biaxial flexural strength and shear bond strength of the specimens were measured using a universal testing machine. Data was statistically analyzed by one-way ANOVA followed by Tukey HSD test (α = 0.05). The microstructure and fracture surfaces were analyzed by SEM/EDS. Results were rationalized with finite element analysis (FEA). Laminate_100 specimens showed significantly higher flexural strength (∼50%) than monolithic and Laminate_500 specimens (p

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.

Sealing the occlusal pits and fissures of molars and premolars is considered an effective therapy for the prevention of dental caries. However, such sealants have limited wear resistance, resulting in surface damage and sealant volume loss. The purpose of this study was to perform an integrative review of the literature on wear pathways of current tooth occlusal fissure sealants. A scoping review of the literature was performed based on database search (Medline/PubMed) using the following combination of key terms: “occlusal fissure sealant” OR “fissure sealant” OR “pit sealant” AND “degradation” OR “wear” OR “erosion” OR “aging”. The inclusion criteria involved articles published in the English language within the last 20 years on the dominant degradation mechanisms of occlusal sealant fissures. The literature search identified a total of 228 articles and then 21 studies were selected considering the scope of this study. Studies revealed a detrimental effect of acidic conditions on the wear of tooth occlusal fissure sealants. The corrosion effect of such acidic medium was higher on glass-ionomer materials when compared to resin-matrix composite sealants. Additionally, the content, size, and type of fillers in the materials affected their wear resistance. Unfilled sealants showed a higher damage by wear than filled sealants. An increase in fillers' size induced an increased wear rate while a decrease in the fillers' content exposed the organic matrix of the fissure sealant to the acidic medium and occlusal loading. The wear of resin-matrix sealants depends on the size, shape, volume, type of filler particles, filler content, the organic matrix type, and distance between the particles exposing the organic matrix.

This work presents a comprehensive study on the influence of three different processing technologies (Selective Laser Melting, Hot Pressing and conventional casting) on the microstructure, mechanical and wear behavior of an austenitic 316L Stainless Steel. A correlation between the processing technologies, the obtained microstructure and the mechanical and wear behavior was achieved. The results showed that the highest mechanical properties and tribological performance were obtained for 316L SS specimens produced by Selective Laser Melting, when compared to Hot Pressing and conventional casting. The high wear and mechanical performance of 316L Stainless Steel fabricated by Selective Laser Melting are mainly due to the finer microstructure, induced by the process. In this sense, Selective Laser Melting seems a promising method to fabricate customized 316L SS implants with improved mechanical and wear performance.

The aim of this work was to study the influence of the processing route on the microstructural constituents, hardness and tribological (wear and friction) behavior of Ti6Al4V biomedical alloy. In this sense, three different processing routes were studied: conventional casting, hot pressing and selective laser melting. A comprehensive metallurgical, mechanical and tribological characterization was performed by X-ray diffraction analysis, Vickers hardness tests and reciprocating ball-on-plate wear tests of Ti6Al4V/Al 2 O 3 sliding pairs. The results showed a great influence of the processing route on the microstructural constituents and consequent differences on hardness and wear performance. The highest hardness and wear resistance were obtained for Ti6Al4V alloy produced by selective laser melting, due to a markedly different cooling rate that leads to significantly different microstructure when compared to hot pressing and casting. This study assesses and confirms that selective laser melting is potential to produce customized Ti6Al4V implants with improved wear performance.

This study is concern with tribocorrosion behaviour of Ti6Al4V-HA biocomposites. The Ti6Al4V composites reinforced with different contents of hydroxyapatite (HA) particles 5–15%, vol%) were produced by hot pressing technique. The tribocorrosion tests were performed by using a ball-on-plate configuration in artificial saliva at 37 °C. The tests were carried out under open circuit potential (OCP), with a sliding duration of 1800 s, 1 N normal load and 1 Hz frequency. The open circuit potential and wear mechanisms for all tested biocomposites are presented and discussed. The results suggest that HA plays a relevant role on tribocorrosion behaviour of Ti6Al4V-HA composites. All composites samples presented better wear resistance and also a relatively lower tendency to corrosion with increasing HA content.

The development of high damping materials for noise reduction and attenuation of vibration on structural applications, such as automotive and aerospace industries, has been investigated. This experimental study is concerned with the damping capacity (tan delta) and dynamic Young's modulus (|E*|) of Silicon carbide (SiC) reinforced aluminium (Al) matrix composite. AlSi-SiCp composite was produced by hot pressing technique. Damping capacity and dynamic Young's modulus of composite and unreinforced AlSi alloy were studied using a dynamic mechanical analyser (DMA), over a temperature range of room temperature-400 °C (during heating and cooling phases), at 1 and 20 Hz. AlSi-SiCp composite showed higher damping capacity and dynamic Young's modulus than the AlSi unreinforced alloy. Furthermore, damping capacity was found to increase with temperature, while modulus decreases. The possible damping mechanisms are presented and discussed.

Aluminum-silicon (AlSi) composite reinforced with 20 wt% Ni particulates was produced by hot pressing and characterized using nanoindentation. Energy dispersive spectrometry and X-ray diffraction analyses showed that Al3Ni intermetallic was formed in the interface between Ni particulates and AlSi matrix. Chemical composition, hardness, and elastic modulus were studied along the interface from inner (near Ni) to outer (near AlSi) regions. A uniform composition was found throughout the interface, having 805.6 HV hardness and elastic modulus of 185.4 GPa. Interface properties have a crucial influence on the composite performance and their assessment is of paramount importance on composite properties estimation using predictive models.

This study is concerned with the influence of four metallic reinforcements on aluminum-silicon (AlSi) composites, with respect to wear behavior. AlSi-Ti; AlSi-Ti6Al4V; AlSi-1.4301 stainless steel and AlSi-Ni particulate reinforced composites were produced by a hot-pressing route. Microstructural characterization showed a uniform distribution of the reinforcing particles in the AlSi matrix. Reciprocating pin-on-plate wear tests were performed for AlSi and AlSi-based composites against gray cast iron plates. In order to compare the effect of different metallic particulates on the AlSi-based composites/gray cast iron tribopair wear performance, besides the pin, the counterface was also analyzed. The particle/matrix interface is analyzed in order to understand its influence on the tribopair behavior and on the controlling wear mechanisms. It was shown that the better compromise between both sliding surfaces performance was attained by AlSi-Ni/gray cast iron tribopair.

The corrosion and tribocorrosion behaviour of SLM-produced Ti6Al4V alloy was studied in comparison with its HP and commercial counterparts in 9 g/L NaClsolution at body temperature. Results showed that SLM processing route influenced the electrochemical response of the SLM-produced alloy by leading to a relatively lower quality for the passive film due to decreased beta phase and the formation of alpha' phase. However, after tribocorrosion, neither the total volume loss nor the volume loss under the influence of mechanical wear and wear accelerated corrosion showed any statistically significant difference between the processing routes., This study was supported by FCT with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 - Program Operacional Competitividade e Internacionalizacao (POCI) with the reference project POCI-01-0145-FEDER-006941, together with projects NORTE-01-0145-FEDER-000018-HAMaBICo and PTDC/EMS-TEC/5422/2014. The authors would also like to acknowledge Prof. Grata Minas for the provision of the profilometry.

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 on 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., Thank the CNPq (Conselho Nacional de Desenvolvimento Científico e Technológico, Brazil) (205791/2014-0) and CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brazil) for the financial support. Fundação para a Ciência e Tecnologia -Portugal) in the scope of the projects UID/EEA/04436/2019 and NORTE-01-0145-FEDER-000018-HAMaBICo. Add.Additive_Manufacturing to Portuguese Industry_POCI-01-0247-FEDER-024533

Objectives The aim of this study was to develop a novel design for implants surface functionalization through the production of HAp-coated zirconia structured surfaces by means of hybrid laser technique. The HAp-rich structured surfaces were designed to avoid hydroxyapatite (HAp) coating detachment from the zirconia surface during implant insertion, thus guaranteeing an effective osseointegration. Materials and methods The functionalization process of zirconia surface started by creating micro-textures using a Nd:YAG laser and subsequent deposition of a HAp coating on the designated locations by dip-coating process. Afterwards, a CO2 laser was used to sinter the HAp coating. The potential of the HAp-coated zirconia structured surfaces was inspected concerning HAp bioactivity preservation, surface wettability, HAp coating adhesion to the textured surfaces and mechanical resistance of zirconia, as assessed by different approaches. Results The functionalized surfaces exhibited a superhydrophilic behavior (2.30 ± 0.81°) and the remaining results showed that through the hybrid strategy, it is possible to maintain the HAp bioactivity as well as promote a strong adhesion of HAp coating to the textured surfaces even after high energy ultrasonic cavitation tests and friction tests against bovine bone. It was also verified that the flexural strength of zirconia (503 ± 24 MPa) fulfills the strict requirements of the ISO 13356:2008 standard and as such is expectable to be enough for biomedical applications. Significance The promising results of this study indicate that the proposed surface design can open the window for manufacturing zirconia-based implants with improved bioactivity required for an effective osseointegration as it avoids the coating detachment problem during the implant insertion.

In order to enhance osteointegration, prostheses surfaces are usually coated with bioactive materials like hydroxyapatite (HA), material found in teeth and bones. Traditional HA coatings were proven adequate for obtaining high-quality coatings on metal substrates. However, due to the implantation process, these coatings can be detached from the metal surface. In this work, a new materials design that aims to avoid this coating detachment scenario is proposed, based on composites of Ti6Al4V alloy reinforced with HA powder, with materials gradation from bulk to surface of the prosthesis, where the titanium bulk provides toughness and the outer regions provide biological performance. In order to assess the mechanical and biological performance of the prosthesis outer region, Ti6Al4V-HA composites with different HA contents were produced and characterized regarding microstructure and mechanical properties. Shear tests were performed and fracture surfaces were analysed. EDS and XRD analysis were performed in order to assess HA possible decomposition due to processing temperature and pressure during the hot pressing route. This work shows that the combination of hot pressing technique and an FGM design approach is a promising solution for manufacturing prosthesis with improved bioactivity that can overcome the detachment problems of solutions based on HA coatings. Keywords: Ti6Al4V, Hydroxyapatite, Hot pressing, Functionally graded material, Composite, Biomedical applications

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.

The aim of this paper was to study the interface reaction between an AlSi alloy reinforced with Ni coated Multi-Wall Carbon Nanotubes (MWCNTs). A powder metallurgy processing route was used to produce AlSi composites. SEM, DSC, XRD and TEM analysis showed the formation of Al3Ni due to the presence of Al from AlSi matrix and Ni from CNT coating. This contributes to stress transfer from matrix to CNT reinforcement and consequently to enhancement of mechanical properties of the composites. Also it was observed some dissolution of Ni to AlSi and that the CNTs are very stable as they maintain their integrity. The coating of CNTs seems to be a good solution for application of this reinforcement in commercial alloys.

Lightweight metal-matrix composites (MMC) are being applied in many fields such as aerospace and automotive, where detailed knowledge about their elastic and inelastic properties is required to make optimal design of the component. In this study the high-temperature damping capacity and dynamic Young’s modulus of hot-pressed AlSi-based hybrid composites reinforced with silicon carbide particles (SiC p ) and carbon nanotubes (CNTs) were experimentally measured and compared with AlSi–SiC p and AlSi–CNT composites. Results show that by reinforcing AlSi–SiC p with CNTs, the damping capacity is improved without reducing mechanical properties. The highest damping capacity value was attained by AlSi–(CNT–SiC p ) hybrid composite, for all the studied frequencies and temperatures, followed by AlSi–SiC p and AlSi–CNT composites. The possible damping mechanisms for all these produced composites are presented and discussed. Unlike to damping capacity, the dynamic Young’s modulus shows no substantial changes after adding CNTs to AlSi–SiC p . Results show that by using a proper combination of materials (including different types of reinforcements), scales (nano- and micro-sized reinforcements) and manufacturing processes, the design of a material with required damping capacity and mechanical properties is possible.

The effect of SiC particle size on the resultant damping capacity and dynamic modulus of aluminum metal matrix composites (AMMCs) was studied. Damping capacity, as well as dynamic Young's modulus, was measured at 1, 10 and 20 Hz, at room temperature. Image analysis and chemical composition were performed in order to investigate the AlSi–SiC interfacial reaction. The damping capacity of AlSi–SiCp composites, with three different particle size, was compared to AlSi unreinforced. The damping mechanisms involved were discussed in light of the results obtained from damping capacity. The results show that damping capacity and dynamic modulus of AlSi can be improved through the addition of SiC particles. Further, through a selection of specific sizes of SiC particles, it is possible to tailor the final composite stiffness and damping capacity.

The aim of this paper was to study the mechanical behavior of a hybrid AlSi–2 wt.%CNTs–5 wt.%SiCp composite. For comparison purposes the unreinforced AlSi alloy, AlSi–2 wt.%CNTs and AlSi–5 wt.%SiCp composites were used. A powder metallurgy processing route was used to produce the unreinforced AlSi alloy and AlSi composites. Tensile and fatigue tests were performed and the results showed that the hybrid composite AlSi–2 wt.%CNTs–5 wt.%SiCp proposed in the present paper, provided better overall properties than the single reinforcement composites. The improvement is attributed to the combined effects of two different reinforcements that act at different scales.

This work is concerned with understanding the influence of reinforcement mechanisms of carbon nanotubes (CNTs) on mechanical, wear, and fatigue tests on an Aluminium-Silicon (AlSi) alloy. The reinforcement mechanism is presented through the observation of fracture morphology of the different tests. Results of mechanical properties, fatigue life performance, and wear loss is presented and discussed. It is shown that the CNTs reinforcement effect is active simultaneously in all previous properties and the reinforcement physical mechanism seems to be essentially due to a reinforcement effect of the interface that seems to be similar in all mentioned mechanical solicitations.

In this study, the effect of the size of SiC particle on high temperature damping capacity and dynamic Young's modulus of hot-pressed AlSi–SiC composites has been investigated. SiC particles with sizes of 13 μm, 38.8 μm and 118 μm were added to AlSi matrix to prepare the hot-pressed AlSi–SiC composites. These composites were characterized using a dynamic mechanical analyser (DMA), over a temperature range of room temperature to 400 °C. Regarding damping capacity, all AlSi–SiCp composites exhibited higher damping capacity compared to unreinforced AlSi alloy (for all tested frequencies). AlSi–SiCp(118) composites exhibited the highest improvement in damping capacity. A damping peak was observed near 250 °C, as a result of a relaxation process. Regarding dynamic Young's modulus, it was observed that the addition of SiCp to the AlSi alloy improved the Young's modulus. It was also demonstrated that by increasing the SiCp size, a decrease in Young's modulus is attained, with the highest improvement in dynamic Young's modulus being obtained by AlSi–SiCp(13) composite. Keywords: Metal matrix composites, Powder metallurgy, Hot pressing, SiC

Background:Glass-ionomer cements perform a protective effect on the dentin-pulp complex considering the F ions release and chemical bonding to the dental structures. On the other hand, those materials have poor physic-mechanical properties in comparison with the restorative resin composite. The main aim of this work was to evaluate the influence of zirconia and/or alumina fillers on the microstructure and strength of a resin modified glass-ionomer cement after thermal cycling.Methods:Anin vitroexperimental study was carried out on 9 groups (n= 10) of cylindrical samples (6 x 4 mm) made from resin modified glass-ionomer (Vitremer, 3M, USA) with different contents of alumina and/or zirconia fillers. A nano-hybrid resin composite was tested as a control group. Samples were mechanically characterized by axial compressive tests and electron scanning microscopy (SEM) coupled to energy dispersive X-ray spectrophotometry (EDS), before and after thermal cycling. Thermal cycling procedures were performed at 3000, 6000 and 10000 cycles in Fusayama´s artificial saliva at 5 and 60oC.Results:An improvement of compressive strength was noticed on glass-ionomer reinforced with alumina fillers in comparison with the commercial glass ionomer. SEM images revealed the morphology and distribution of alumina or zirconia in the microstructure of glass-ionomers. Also, defects such as cracks and pores were detected on the glass-ionomer cements. The materials tested were not affected by thermal cycling in artificial saliva.Conclusion:Addition of inorganic particles at nano-scale such as alumina can increase the mechanical properties of glass-ionomer cements. However, the presence of cracks and pores present in glass-ionomer can negatively affect the mechanical properties of the material because they are areas of stress concentration.