Key Engineering Materials Vol. 377

Abstract: The research on ceramic scaffolds for bone tissue engineering is, nowadays, one of the newest and most attractive topics in the field of materials for biomedical applications. These scaffolds are aimed to provide supporting or even enhance the reparative capacity of body. Biphasic calcium phosphates (BCPs) and silicon doped BCP are very interesting candidates to be used as materials for scaffolds fabrication in bone tissue engineering. BCPs and silicon doped BCP consist of a mixture of hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) or HA and α-tricalcium phosphate (α-TCP), respectively. For the regenerative purposes BCPs show better performance than HA because of the higher solubility of β-TCP compound, which facilitate the subsequent bone ingrowth in the implant. On the other, silicon doped BCP involve silicon that substituted into the apaptite crystal lattice for phosphorous with the subsequent charge imbalance. HA/α-TCP based bioceramics exhibits an important improvement of the bioactive behaviour with respect to non-substituted apatites. This work reviews the procedures to synthesise and fabricate scaffolds based on HA/β-TCP and silicon stabilised HA/α-TCP. Special attraction has been paid in the different synthesis methods and to the shaping of final scaffolds. By knowing the scaffold features at the crystallinity and macrostuctural level, the biocompatibility and clinical performance can be better understood, which will be also considered in this review.

Abstract: Autogenous bone grafts are considered to be the gold standard in maxillo-facial surgery. However, drawbacks of donor site morbidity and unpredictable rates of resorbtion often limit their use. In vivo tests have shown that 45S5 bioactive glass particles placed in critical size bone defects lead to regeneration of new bone that has the structural characteristics and architecture of mature trabecular bone. In vitro tests using primary osteoblast cultures have shown that the bioactive glass particles release ionic dissolution products that provide genetic stimuli that control osteoblast cell cycles and lead to rapid growth of mineralized bone nodules. These in vitro and in vivo results led to approval of use of bioactive glass particles and monolithic bioactive glass implants for use in maxillo-facial reconstructions after removal of bone cysts and trauma, as described by several case histories.

Abstract: The integration of drugs and devices is a growing force in the medical industry. The incorporation of pharmaceutical products not only promises to expand the therapeutic scope of device technology but to access combination products whose therapeutic value stem equally from both the structural attributes of the device and the intrinsic therapy of the drug. For example, the orthopedic industry is exploring drug-coated hip, knee and bone reconstruction implants capable of promoting healing as an added therapeutic benefit for device recipients. In this context, the drug is eluted locally, being targeted in a specific site of interest, thus offering a convenient strategy to avoid adverse effects commonly observed for systemic treatments of some diseases, as an additional benefit. In addition, these new technologies are generally well adapted to the development of minimally invasive surgery for their implantation. In this context, given the wide use of calcium phosphates (CaPs) and bisphosphonates (BPs) for the therapy of bone-related affections, there was great interest to investigate the chemistry taking place when combining the two systems since: (i) it could provide better insight in the mechanism of BP fixation on bones (ii) such combination could act as efficient BP delivery systems when implanted in bone defects.

Abstract: Bioactive ceramic coatings have been widely applied to ensure direct chemical implant-bone contact, thus reducing the time required for osseointegration. In this respect the plasma-sprayed CaP coatings are the most widely applied, although the composition, structure and the adhesion to the substrate are difficult to control. Despite the success in preparing a large variety of bioactive ceramics, metal implants are still widely used in load-bearing orthopedic and dental applications. Regardless, that the inert metallic materials do not form a chemical bond with tissues, in both hard and soft tissue environments, but rather a fibrous tissue capsule is formed. In order for a material to chemically attach to bone, spontaneous formation (or ready-made presence) of bone-mineral like calcium phosphate (CaP) on the materials’ surface in physiological environments is needed. In this review both conventional and sol-gel derived ceramics are discussed as well as the recent attempts to ensure implant fixation. Special focus is put on the use of sol-gel derived titania coatings and their applications including the newest findings in soft tissue environment.

Abstract: Much research effort has been committed to the development of bioceramics that promote bone tissue regeneration and this is still one of the greatest challenges for the scientific community. In this sense, silica-based ordered mesoporous materials constitute a new generation of bioceramics that combine the intrinsic properties of bioceramics, such as bioactive behavior, together with the capability to host and controlled release biologically active molecules that promote new bone formation, i.e. drug delivery systems. In this chapter, the recent advances aimed at tailoring ordered mesoporous materials for biomedical applications will be tackled and critically discussed.

Abstract: Historically the function of biomaterials has been to replace diseased, damaged and aged tissues. First generation biomaterials, including bio ceramics, were selected to be as inert as possible in order to minimize the thickness of interfacial scar tissue. Bioactive glasses provided an alternative from the 1970’s onward; second generation bioactive bonding of implants with tissues and no interfacial scar tissue. This chapter reviews the discovery that controlled release of biologically active Ca and Si ions from bioactive glasses leads to the up-regulation and activation of seven families of genes in osteoprogenitor cells that give rise to rapid bone regeneration. This finding offers the possibility of creating a new generation of gene activating bioceramics designed specially for tissue engineering and in situ regeneration of tissues.