Bone disorders are of significant concern due to increase in the median age of our population. Traditionally, bone grafts have been used to restore damaged bone. Synthetic biomaterials are now being used as bone graft substitutes. These biomaterials were initially selected for structural restoration based on their biomechanical properties. Later scaffolds were engineered to be bioactive or bioresorbable to enhance tissue growth. Now scaffolds are designed to induce bone formation and vascularization. These scaffolds are often porous, biodegradable materials that harbor different growth factors, drugs, genes or stem cells. In this review, we highlight recent advances in bone scaffolds and discuss aspects that still need to be improved.

measured results indicated that the infill shape did not greatly affect the dielectric properties.Although sample E had no infill, the inclusion of the lid and base made up 33% of the total volume. To examine the effects of the external walls, sample F was printed with the same honeycomb infill with thinner bottom base but without the top lid. The thicknesses of the base and the honeycomb infill part of sample F were 0.2 mm and 2.2 mm, respectively. The measured results showed that sample F had a lower permittivity and loss tangent value than sample E, due to its lower PLA volume fraction. CONCLUSIONThis letter has presented the feasibility of creating low loss dielectric substrates with various relative permittivities and loss tangent values using conventional 3D printing. Voids were introduced inside the substrates which were printed in one process. The volume fraction of air in the host material affected the dielectric properties more significantly than the infill shape. The permittivity and loss factor of the substrate were reduced by the increasing air volume fraction. Therefore, the permittivity and loss tangent of the dielectric substrate can be tailored to the desired values by extrapolating from the sample results produced here.These highly customisable dielectric materials will improve the flexibility of antenna design and related EM applications. The automatic fabrication process also allows the dielectric properties to be graded within one structure. ance evaluations.

No abstract

Calcium phosphates (CaPs) are the most widely used bone substitutes in bone tissue engineering due to their compositional similarities to bone mineral and excellent biocompatibility. In recent years, CaPs, especially hydroxyapatite and tricalcium phosphate, have attracted significant interest in simultaneous use as bone substitute and drug delivery vehicle, adding a new dimension to their application. CaPs are more biocompatible than many other ceramic and inorganic nanoparticles. Their biocompatibility and variable stoichiometry, thus surface charge density, functionality, and dissolution properties, make them suitable for both drug and growth factor delivery. CaP matrices and scaffolds have been reported to act as delivery vehicles for growth factors and drugs in bone tissue engineering. Local drug delivery in musculoskeletal disorder treatments can address some of the critical issues more effectively and efficiently than the systemic delivery. CaPs are used as coatings on metallic implants, CaP cements, and custom designed scaffolds to treat musculoskeletal disorders. This review highlights some of the current drug and growth factor delivery approaches and critical issues using CaP particles, coatings, cements, and scaffolds towards orthopedic and dental applications.

The general trends in synthetic bone grafting materials are shifting towards approaches that can illicit osteoinductive properties. Pharmacologics and biologics have been used in combination with calcium phosphate (CaP) ceramics, however, recently have become the target of scrutiny over the safety. The importance of trace elements in natural bone health is well documented. Ions, e.g. lithium, zinc, magnesium, manganese, silicon, strontium etc. have shown to increase osteogenesis and neovascularization. Incorporation of dopants into CaPs can provide a platform for safe and efficient delivery in clinical applications where increased bone healing is favorable. This review highlights use of trace elements in CaP biomaterials, and offers an insight into the mechanisms of how metal ions can enhance both osteogenesis and angiogenesis.