Natural structural materials are built at ambient temperature from a fairly limited selection of components. They usually comprise hard and soft phases arranged in complex hierarchical architectures, with characteristic dimensions spanning from the nanoscale to the macroscale. The resulting materials are lightweight and often display unique combinations of strength and toughness, but have proven difficult to mimic synthetically. Here, we review the common design motifs of a range of natural structural materials, and discuss the difficulties associated with the design and fabrication of synthetic structures that mimic the structural and mechanical characteristics of their natural counterparts.

Bioinspired structural materials

Calcium phosphate (CaP) bioceramics are widely used in the field of bone regeneration, both in orthopedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The aim of this article is to review the history, structure, properties and clinical applications of these materials, whether they are in the form of bone cements, paste, scaffolds, or coatings. Major analytical techniques for characterization of CaPs, in vitro and in vivo tests, and the requirements of the US Food and Drug Administration (FDA) and international standards from CaP coatings on orthopedic and dental endosseous implants, are also summarized, along with the possible effect of sterilization on these materials. CaP coating technologies are summarized, with a focus on electrochemical processes. Theories on the formation of transient precursor phases in biomineralization, the dissolution and reprecipitation as bone of CaPs are discussed. A wide variety of CaPs are presented, from the individual phases to nano-CaP, biphasic and triphasic CaP formulations, composite CaP coatings and cements, functionally graded materials (FGMs), and antibacterial CaPs. We conclude by foreseeing the future of CaPs.

Calcium Phosphate Bioceramics: A Review of Their History, Structure, Properties, Coating Technologies and Biomedical Applications.

This review discusses and summarizes the recent developments and advances in the use of biodegradable materials for bone repair purposes. The choice between using degradable and non-degradable devices for orthopedic and maxillofacial applications must be carefully weighed. Traditional biodegradable devices for osteosynthesis have been successful in low or mild load bearing applications. However, continuing research and recent developments in the field of material science has resulted in development of biomaterials with improved strength and mechanical properties. For this purpose, biodegradable materials, including polymers, ceramics and magnesium alloys have attracted much attention for osteologic repair and applications. The next generation of biodegradable materials would benefit from recent knowledge gained regarding cell material interactions, with better control of interfacing between the material and the surrounding bone tissue. The next generations of biodegradable materials for bone repair and regeneration applications require better control of interfacing between the material and the surrounding bone tissue. Also, the mechanical properties and degradation/resorption profiles of these materials require further improvement to broaden their use and achieve better clinical results.

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Biodegradable Materials for Bone Repair and Tissue Engineering Applications

https://nano.tu-dresden.de/pubs/reprints/2011_Acta_Biomaterialia_7_2644.pdf

Three-dimensional printing of hierarchical and tough mesoporous bioactive glass scaffolds with a controllable pore architecture, excellent mechanical strength and mineralization ability

The impact of bone diseases and trauma in the whole world has increased significantly in the past decades. Bioactive glasses are regarded as an important bone regeneration material owing to their generally excellent osteoconductivity and osteostimulativity. A new class of bioactive glass, referred to as mesoporous bioglass (MBG), was developed 7 years ago, which possess a highly ordered mesoporous channel structure and a highly specific surface area. The study of MBG for drug/growth factor delivery and bone tissue engineering has grown significantly in the past several years. In this article, we review the recent advances of MBG materials, including the preparation of different forms of MBG, composition–structure relationship, efficient drug/growth factor delivery and bone tissue engineering application. By summarizing our recent research, the interaction of MBG scaffolds with bone-forming cells, the effect of drug/growth factor delivery on proliferation and differentiation of tissue cells and the in vivo osteogenesis of MBG scaffolds are highlighted. The advantages and limitations of MBG for drug delivery and bone tissue engineering have been compared with microsize bioactive glasses and nanosize bioactive glasses. The future perspective of MBG is discussed for bone regeneration application by combining drug delivery with bone tissue engineering and investigating the in vivo osteogenesis mechanism in large animal models.

https://royalsocietypublishing.org/doi/pdf/10.1098/rsfs.2011.0121

Mesoporous bioactive glasses: structure characteristics, drug/growth factor delivery and bone regeneration application

Despite its apparent simplicity, spreading of liquid metals at high temperatures has defi ed description and generalization. Wetting at high temperature is usually accompanied by interdiffusion and chemical reaction, but the forces that drive reactive spreading and the mechanisms that control its kinetics have been very poorly understood. The unsolved challenge has been to link macroscopic measurements such as the dynamic contact angle or the speed of a moving liquid front to phenomena occurring at the microscopic and even atomic level in the vicinity of the triple solid‐liquid‐vapour junction. We have taken a big step towards meeting this challenge. Our systematic analysis of the spreading of metal‐metal systems with varying degrees of mutual solubility allows us to report on the fundamental differences between the mechanisms controlling spreading of organic liquids and liquid metals and on formation of Marangoni fi lms driven by surface-tension gradients in high-temperature systems.

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Atomic dynamics and Marangoni fi lms during liquid-metal spreading

An electric-current-assisted method was used to mineralize dense hydrogels and create hydroxyapatite/hydrogel composites with unique hierarchical structures. The microstructure of the final material can be controlled by the mineralization technique and the chemistry of the organic matrix. A hydroxyapatite/hydrogel composite was obtained with a large inorganic content (approximately 60% of the weight of the organics). After being heated to 1050 degrees C, the sintered inorganic phase has a very uniformly distributed porosity and its Brunauer-Emmett-Teller (BET) surface area is 0.68 m(2)/g.

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Three-dimensional biomimetic mineralization of dense hydrogel templates.

-Tricalcium phosphate (-TCP) scaVolds with designed, three-dimensional (3-D) geometry and mesoscale porosity have been fabricated by direct-write assembly (robocasting) techniques. Concentrated -TCP inks with suitable viscoelastic properties were developed to enable the fabrication of the complex 3-D structures. A comprehensive study of the sintering behavior of TCP as a function of the calcium content in the starting powder was also carried out, and the optimal heat treatment for fabricating scaVolds with dense -TCP rods has been determined. Such analysis provides clues to controlling the microstructure of the fabricated structures and, therefore, enabling the fabrication by robocasting of TCP scaVolds with tailored performance for bone tissue engineering applications.

Sintering and robocasting of -tricalcium phosphate scaVolds for orthopaedic applications

Provided are methods and compositions relating to a dental bonding composition useful in bonding a dental resin composite.

Dental bonding compositions and methods useful in inhibition of microleakage in resin-bonded dentin

L'invention porte sur un materiau composite fait d'un polymere souple d'hydrogel obtenu par melange d'une phase organique et d'une composition minerale, la phase organique consistant en un hydrogel monomere un agent reticulant, un initiateur de radicaux et/ou un solvant. On forme ainsi un melange polymerisable que l'on polymerise en un article de la forme et de la taille souhaitees.

Antoni P. Tomsia

Papers

Atomic dynamics and Marangoni fi lms during liquid-metal spreading

Three-dimensional biomimetic mineralization of dense hydrogel templates.

Sintering and robocasting of -tricalcium phosphate scaVolds for orthopaedic applications

Dental bonding compositions and methods useful in inhibition of microleakage in resin-bonded dentin

Materiaux composites fonctionnels souples a base d'hydrogel-