Direct laser interference patterning of bioceramics: a short review

Bioceramics are a great alternative to use in implants due to their excellent biocompatibility and good mechanical properties. Depending on their composition, bioceramics can be classified into bioinert and bioactive, which relate to their interaction with the surrounding living tissue. Surface morphology also has great influence on the implant biological behavior. Controlled texturing can improve osseointegration and reduce biofilm formation. Among the techniques to produce nano- and micropatterns, laser texturing has shown promising results due to its excellent accuracy and reproducibility. In this work, the use of laser techniques to improve surface morphology of biomaterials is reviewed, focusing on the application of direct laser interference patterning (DLIP) technique in bioceramics.This study was funded by FCT-Portugal through the following projects-UID/EEA/04436/2013, COMPETE 2020 with the code POCI-01-0145-FEDER-00694 and LaserMULTICER (POCI-01-0145-FEDER-031035) and by Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Brazil through the project-CNPq/UNIVERSAL/421229/2018-7. B.H. acknowledges the support of the Alexander von Humboldt Foundation

Adhesion behavior of conventional and high‐translucent zirconia: Effect of surface conditioning methods and aging using an experimental methodology

Objective: Evaluate the adhesive behavior of conventional and high-translucent zirconia after surface conditioning and hydrothermal aging. Materials and methods: Conventional (ZrC) and high-translucent zirconia (ZrT) specimens were divided into six groups: without surface treatment (ZrC and ZrT), air-borne particle abrasion with 50-μm Al2 O3 sized particles (ZrC-AO and ZrT-AO), and tribochemical treatment with 30-μm silica modified Al2 O3 sized particles (ZrC-T and ZrT-T). Zirconia specimens were treated using an MDP-containing universal adhesive and bonded to two resins blocks with an adhesive luting cement. Microbar specimens with cross-sectioned areas of 1 mm2 were achieved. Half of the microbars were subjected to hydrothermal aging. Bond strength was evaluated by microtensile bond strength test and statistically evaluated by the Weibull analysis. Results: Roughness of the ZrC-AO and ZrT-AO groups were statistically higher. Bond strength analysis revealed higher bond strength for ZrC-AO and ZrC-T groups compared to ZrT-AO and ZrT-T, respectively. Mixed failure was the most frequent for the mechanically treated groups, while no cohesive failures were obtained. Conclusion: Lower values of bond strength were obtained for the mechanically treated high-translucent zirconia groups when compared to their conventional zirconia counterparts. Mechanical surface treatment significantly improved the bond strength to conventional and high-translucent zirconia. Clinical significance: Mechanical surface treatment (air-borne particle abrasion or tribochemical treatment) associated with the use of universal adhesives containing MDP could provide a durable bonding to conventional and high-translucent zirconia. Keywords: adhesive cementation; high-translucent zirconia; microtensile bond strength

Chitosan-based hierarchical scaffolds crosslinked with genipin

Osteochondral defects present significant challenges for effective tissue regeneration due to the complex composition of bone and cartilage. To address this challenge, this study presents the fabrication of hierarchical scaffolds combining chitosan/β-tricalcium phosphate (β-TCP) to simulate a bone-like layer, interconnected with a silk fibroin layer to mimic cartilage, thus replicating the cartilage-like layer to mimic the native osteochondral tissue architecture. The scaffolds were produced by freeze-drying and then crosslinking with genipin. They have a crosslinking degree of up to 24%, which promotes a structural rearrangement and improved connection between the different layers. Micro-CT analysis demonstrated that the structures have distinct porosity values on their top layer (up to 84%), interface (up to 65%), and bottom layer (up to 77%) and are dependent on the concentration of β-tricalcium phosphate used. Both layers were confirmed to be clearly defined by the distribution of the components throughout the constructs, showing adequate mechanical properties for biomedical use. The scaffolds exhibited lower weight loss (up to 7%, 15 days) after enzymatic degradation due to the combined effects of genipin crosslinking and β-TCP incorporation. In vitro studies showed that the constructs supported ATDC5 chondrocyte-like cells and MC3T3 osteoblast-like cells in duo culture conditions, providing a suitable environment for cell adhesion and proliferation for up to 14 days. Overall, the physicochemical properties and biological results of the developed chitosan/β-tricalcium phosphate/silk fibroin bilayered scaffolds suggest that they may be potential candidates for osteochondral tissue strategies.This study was partially financed by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES)—Finance Code 001 and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), PVE 407035/2013-3. This work is also financially supported by Portuguese FCT (PD/BD/135247/2017, SFRH/BPD/93697/2013, DL 57/2016/CP1377/CT0054 (https://doi.org/10.54499/DL57/2016/CP1377/CT0054), CEECINST/00018/2021), PhD programme in Advanced Therapies for Health (PATH) (PD/00169/2013), FCT R&D&I projects with references PTDC/BII-BIO/31570/2017, PTDC/CTM-CTM//29813/2017, and PTDC/CTM-BIO/4706/2014- (POCI-01-0145-FEDER-016716). The authors would like to thank the contributions to this research from the project “TERM RES Hub—Scientific Infrastructure for Tissue Engineering and Regenerative Medicine”, reference PINFRA/22190/2016 (Norte-01-0145-FEDER-022190), funded by the Portuguese National Science Foundation (FCT) in cooperation with the Northern Portugal Regional Coordination and Development Commission (CCDR-N), for providing relevant lab facilities, state-of-the-art equipment, and highly qualified human resources

Influence of ns-Nd:YAG laser surface treatment on the tensile bond strength of zirconia to resin-matrix cements

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

The potential use of oyster shell waste in new value-added by-product

Calcium carbonate is one of the most used raw materials in various industries, such as construction materials, food supplement, pharmaceutics, animal feed, plastic production, and others. Calcium carbonate can derive from marine wastes, like crustaceans and bivalve’s shells. The worldwide demand for new sources of food has increased exponentially, and following that tendency, the mariculture—especially the oyster culture—has been increasingly resorting to farming techniques. In 2016, 438 billion tons of oysters were produced. The majority of the shells were unduly discarded, presenting a public health problem. This article offers a solution based on the reuse and recycling of oyster shell residues in the production region of Florianópolis, SC, Brazil. The presented solution is an oyster shell by-product developed by a local company which produces artificial stone. The main component of the artificial stone is a composite material made of oyster shells incorporated in a polymeric resin. The mechanical properties, such as its flexural strength, hardness, Weibull modulus, and fracture analysis, were held in the artificial stone. The mechanical results of the new artificial stone were compared with other natural stones, such as granite and marble, and other commercial artificial stones. This material owns suitable mechanical properties for table tops and workbenches. Using this product as an artificial stone represents an innovation in the development of a new product and adds commercial value to local waste. This product is an excellent example of a circular economy for local producers who care about the environment, and it encourages the reduction of extraction of natural stone, such as granite and marble.This research was funded by National Council for Scientific and Technological Development - PVE/CAPES/CNPq 407035/2013-3 UFSC/UMinho (Portugal) “Development of High-Performance Bioinspired Functionally Graded Materials for Oral Rehabilitation” and NORTE-01-0145-FEDER-000018- HAMaBICo “Hybrid Additive Manufacturing for Bio-Inspired Components”.info:eu-repo/semantics/publishedVersio

Moldagem por injeção de pós cerâmicos: remoção da parafina e do polipropileno utilizados como veículo orgânico Ceramic injection molding: removal of pafafin and polypropylene used as organic binder

A moldagem por injeção de pós cerâmicos tem se tornado um processo altamente atrativo por aliar a versatilidade e a produtividade da moldagem por injeção convencional às propriedades inerentes aos materiais cerâmicos. A remoção do ligante, usado como veículo orgânico nesse processo, é uma das etapas críticas para a produção de peças cerâmicas sem defeitos. Neste trabalho avaliou-se a influência da geometria das peças injetadas na remoção do ligante, tanto por imersão em solvente como por decomposição térmica. Alumina em pó foi misturada fisicamente a um ligante composto por polipropileno [PP], parafina [PW] e ácido esteárico [AE]. As peças com diferentes geometrias foram mantidas imersas em hexano, secas sob vácuo e acompanhada a variação de massa devido à solubilização do PW e AE. A determinação da porosidade das peças, realizada por meio das isotermas de adsorção/desorção de nitrogênio, mostrou um aumento de porosidade de 0,5% volume para aproximadamente 20% volume após a imersão em solvente. A remoção térmica do PP remanescente produziu hidrocarbonetos alifáticos e compostos insaturados, determinados e quantificados por espectroscopia de infravermelho, que permearam a estrutura porosa da peça. A geometria das peças tem grande influência na remoção do ligante, podendo afetar não só a qualidade do produto final, mas também as etapas subseqüentes do processo.Powder injection molding [PIM] has become highly attractive as it combines the versatility and productivity of conventional injection molding processes with the intrinsic properties of metallic and ceramic materials. The removal of organic binder, used as vehicles during the process, is one of the most critical stages in the production of ceramic devices in this process. In this work, the influence from the geometry of the injected part on the removal of the organic binder was evaluated for both solvent immersion and thermal degradation processes. Alumina powder was mixed with an organic binder, comprising polypropylene [PP], paraffin wax [PW] and stearic acid [SA], and injection molded in different geometries. Immersion of ceramic parts in hexane induced the solubilization of PW and SA, confirmed by weight variation. Parts porosity, determined through nitrogen adsorption isotherm, showed an increase from 0.5 v% before immersion to ca. 20 v% after immersion. PP burnout produced aliphatic hydrocarbons and unsaturated compounds that flow through a porous structure produced in early stages of this process. Parts geometry plays an important role in binder removal, affecting the quality of the sintered part as well as the remaining stages of the process