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Polymer-infiltrated ceramic network (PICN) materials have gained considerable attention as tooth-restorative materials due to their mechanical compatibility with human teeth, especially with computer-aided design and computer-aided manufacturing (CAD/CAM) technologies. However, the designed geometry affects the mechanical properties of PICN materials. This study aims to study the relationship between manufacturing geometry and mechanical properties. In doing so, zirconia-based PICN materials with different geometries were fabricated using a direct ink-writing process, followed by copolymer infiltration. Comprehensive analyses of the microstructure and structural properties of zirconia scaffolds, as well as PICN materials, were performed. The mechanical properties were assessed through compression testing and digital image correlation analysis. The results revealed that the compression strength of PICN pieces was significantly higher than the respective zirconia scaffolds without polymer infiltration. In addition, two geometries (C-grid 0 and C-grid 45) have the highest mechanical performance. [ABSTRACT FROM AUTHOR]

The objective of this study is to explore and compare the mechanical response of AlCrSiN coatings deposited on two different substrates, namely, WC-Co and cBN. Nano-indentation was used to measure the hardness and elastic modulus of the coatings, and micro-indentation was used for observing the contact damage under Hertzian contact with monotonic and cyclic (fatigue) loads. Microscratch and contact damage tests were also used to evaluate the strength of adhesion between the AlCrSiN coatings and the two substrates under progressive and constant loads, respectively. The surface damages induced via different mechanical tests were observed using scanning electron microscopy (SEM). A focused ion beam (FIB) was used to produce a cross-section of the coating–substrate system in order to further detect the mode and extent of failure that was induced. The results show that the AlCrSiN coating deposited on the WC-Co substrate performed better in regard to adhesion strength and contact damage response than the same coating deposited on the cBN substrate; this is attributed to the lower plasticity of the cBN substrate as well as its less powerful adhesion to the coating. [ABSTRACT FROM AUTHOR]

The influence of sustained and cyclic loading on the crack growth behavior of a multilayered alumina–zirconia composite exhibiting high internal compressive stresses is investigated. The study was conducted on precracked notched samples and focused on evaluating the static and cyclic fatigue resistance to crack extension beyond the first arresting interface (threshold) as well as the mechanisms involved during stable crack growth through the layered structure for each loading condition studied. Although it is found that the layered composite is prone to subcritical crack growth, the effectiveness of operative toughening mechanisms, i.e., compressive residual stresses as well as crack bifurcation and delamination at interfaces, is observed to be independent of the loading conditions. As a consequence, fatigue degradation of the multilayered ceramics studied is restricted to the intrinsic environmental-assisted cracking of the individual layers, pointing them out as toughened composites practically immune to variable stresses and much less static and cyclic fatigue sensitive than other structural ceramics. [ABSTRACT FROM AUTHOR]

The aim of this work was to prepare and characterize polymer–ceramic composite material for dental applications, which must resist fracture and wear under extreme forces. It must also be compatible with the hostile environment of the oral cavity. The most common restorative and biocompatible copolymer, 2,2-bis(p-(2′-2-hydroxy-3′-methacryloxypropoxy)phenyl)propane and triethyleneglycol dimethacrylate, was combined with 3D-printed yttria-stabilized tetragonal zirconia scaffolds with a 50% infill. The proper scaffold deposition and morphology of samples with 50% zirconia infill were studied by means of X-ray computed microtomography and scanning electron microscopy. Samples that were infiltrated with copolymer were observed under compression stress, and the structure's failure was recorded using an Infrared Vic 2DTM camera, in comparison with empty scaffolds. The biocompatibility of the composite material was ascertained with an MG-63 cell viability assay. The microtomography proves the homogeneous distribution of pores throughout the whole sample, whereas the presence of the biocompatible copolymer among the ceramic filaments, referred to as a polymer-infiltrated ceramic network (PICN), results in a safety "damper", preventing crack propagation and securing the desired material flexibility, as observed by an infrared camera in real time. The study represents a challenge for future dental implant applications, demonstrating that it is possible to combine the fast robocasting of ceramic paste and covalent bonding of polymer adhesive for hybrid material stabilization. [ABSTRACT FROM AUTHOR]

Porous zirconia scaffolds manufactured using polymer-infiltrated ceramic network (PICN) and additive manufacturing technologies are emerging as promising alternatives to traditional ceramic materials in dental restorations. However, incomplete osseointegration and bacterial infections still represent challenges for the long-term performance of this new composite material. To address this, the present study aims to investigate the effect of peptide biofunctionalization on the biological performance of infiltrated zirconia scaffold surfaces. The samples used in the work consisted of a 3D-printed zirconia scaffold infiltrated with a dimethacrylate copolymer. Surface biofunctionalization was achieved using a synthetic platform containing the cell-adhesive sequence RGD and the antibacteria LF1-11 peptide (RGD-LF). The attachment of the molecule was characterized through fluorescence confocal laser scanning microscopy and X-ray photoelectron spectroscopy. The biological performance of the samples was evaluated in terms of human mesenchymal stem cell adhesion and early attachment of S. aureus. The physicochemical characterization verified the successful anchoring of the biomolecule to the surface, leading to a peptide density of 288 pmol/cm2. The biological assays confirmed the potential of RGD-LF to improve cell adhesion and spreading. In this sense, the average cell area increased fourfold in the biofunctionalized surface. Regarding bacterial adhesion, it was demonstrated that RGD-LF significantly inhibited it, reducing early adhesion by half compared to the untreated surface. Overall, this study provides valuable insights into the biofunctionalization of polymer-infiltrated 3D scaffolds for the development of cell-instructive and antibacterial surfaces tailored for dental applications. [ABSTRACT FROM AUTHOR]

Additive manufacturing of ceramics has attracted large interest due to its unique ability to rapidly prototype, low cost, and increased geometric complexity. Material extrusion technique is often considered for processing and shaping fine and dense ceramic structures because of the high solid loading in ink. In this work, 8 mol.% yttria-stabilized zirconia ink with 70 wt% ceramic loadings was prepared to print zirconia samples in horizontal and vertical directions, following two different filament orientations: 0/90° and ±45°. The study's main objective was to evaluate printing design influences on mechanical properties. This was assessed through flexural testing and digital image correlation analysis. Experimental findings showed that samples printed horizontally with ±45° filament orientation displayed the highest strength. A detailed inspection of fracture surfaces revealed that printing defects were the critical failure location sites formed after sintering and intimately related to printing design issues. After that, a conductive sensor was integrated into the surfaces of 3D-printed specimens by screen-printing silver-based conductive ink to analyze the structural health of zirconia samples. The sensing capabilities of printed conductive patterns were investigated using the four-point bending tests. The results demonstrated that the electrical resistance of the printed silver patterns increased as the applied load on zirconia substrates rose. It indicates that hybrid material extrusion and screen printing techniques are favored ways to manufacture sensors for structural detection of advanced 3D-printed ceramics. [ABSTRACT FROM AUTHOR]

Advanced ceramics with complex geometry have become indispensable in engineering applications. Due to limitations of traditional ceramic fabrication processes, additive manufacturing represents a revolution for shaping and consolidation because of its unique capabilities for increasing shape complexity and reducing waste material. Among the additive manufacturing techniques, robocasting is often considered to yield fine and dense ceramic structures with geometrically complex morphology and high strength. Within this context, it is the objective to attain dense 8 mol% yttria-stabilized zirconia (8Y-ZrO 2) by evaluating the influence of solid loading and filament orientation on the physical and mechanical properties of sintered parts. In doing so, a printable ink was developed using an inverse-thermoresponsive hydrogel. Results revealed that ceramic charges of 67.5 and 70 wt% achieved the best balance regarding density, hardness, and compression strength. Furthermore, rectilinear geometry with a filament orientation at 45º displayed higher mechanical response than 0/90º and cylindrical ones. [ABSTRACT FROM AUTHOR]

There is a growing interest in zirconia ceramics due to their high flexural strength, excellent corrosion resistance and good biocompatibility. The assembly of advanced zirconia material with functions of sensing, actuation and controlling to solve the problems that may arise during its use is critical to ensure long-term service and performance. Within this context, the objective of this work is to analyse the structural health of zirconia samples by screen-printing silver-based conductive ink on the surface subjected to maximum load under flexural testing. In doing so, silver conductive ink was formulated using silver nanoparticles where polyvinyl pyrrolidone acted as the capping agent. Silver ink was then screen-printed onto zirconia samples and sintered at 200 °C. The resistance of the sensors was measured and the sensing capabilities of printed conductive patterns were investigated using the four-point probe method. Experimental findings displayed a reproducible direct correlation between electrical resistance change and strain resulting from surface displacement under applied load in four-point bending. [ABSTRACT FROM AUTHOR]