Recent progress made in biomaterials and their clinical applications is well known. In the last five decades, great advances have been made in the field of biomaterials, including ceramics, glasses, polymers, composites, glass-ceramics and metal alloys. A variety of bioimplants are currently used in either one of the aforesaid forms. Some of these materials are designed to degrade or to be resorbed inside the body rather than removing the implant after its function is served. Many properties such as mechanical properties, non-toxicity, surface modification, degradation rate, biocompatibility, and corrosion rate and scaffold design are taken into consideration. The current review focuses on state-of-the-art biodegradable bioceramics, polymers, metal alloys and a few implants that employ bioresorbable/biodegradable materials. The essential functions, properties and their critical factors are discussed in detail, in addition to their challenges to be overcome.

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In the last five decades, there have been vast advances in the field of biomaterials, including ceramics, glasses, glass-ceramics and metal alloys. Dense and porous ceramics have been widely used for various biomedical applications. Current applications of bioceramics include bone grafts, spinal fusion, bone repairs, bone fillers, maxillofacial reconstruction, etc. Amongst the various calcium phosphate compositions, hydroxyapatite, which has a composition similar to human bone, has attracted wide interest. Much emphasis is given to tissue engineering, both in porous and dense ceramic forms. The current review focusses on the various applications of dense hydroxyapatite and other dense biomaterials on the aspects of transparency and the mechanical and electrical behavior. Prospective future applications, established along the aforesaid applications of hydroxyapatite, appear to be promising regarding bone bonding, advanced medical treatment methods, improvement of the mechanical strength of artificial bone grafts and better in vitro/in vivo methodologies to afford more particular outcomes.

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Strongly distorted RNiO 3 (R ) Gd, Dy) perovskites, containing Ni 3+ , have been prepared under high-pressure conditions: 90 MPa of O 2 pressure (R ) Gd) or 2 GPa of hydrostatic pressure in the presence of KClO 4 (R ) Dy). These materials have been characterized by X-ray diffraction, neutron powder diffraction (NPD) (for DyNiO 3 ), DSC, magnetic measurements, and specific heat measurements. In contrast with the next member of the series, HoNiO 3 , which shows a subtle monoclinic distortion at room temperature, DyNiO 3 exhibits orthorhombic symmetry, as shown by NPD data. A noticeable distortion is observed in NiO 6 octahedra, at variance with the almost regular octahedra exhibited by the first members (R ) La, Pr, Nd) of the series: it is interpreted as a manifestation of the Jahn-Teller character of the Ni 3+ cation, enhanced in the RNiO 3 perovskites with heavier rare earths, showing weaker, less covalent Ni-O bonds. DSC measurements show sharp endothermic peaks at 510.9 K (Gd) and 564.1 K (Dy) in the heating run, which have been assigned to the corresponding metal-insulator transitions of both charge-transfer perovskites, based on the analogous behavior observed for the precedent members of the RNiO 3 series. Subtle slope variations in the susceptibility vs T curves, highly dominated by the strong paramagnetic signal of Gd 3+ and Dy 3+ , indicate the onset of antiferromagnetic ordering of the Ni 3+ sublattice, confirmed by specific heat measurements, below T N values of 185 and 154 K, respectively. Additionally, the Dy 3+ sublattice becomes ordered below 8 K.