We report on the structural transformations of Bioglass ® during thermal treatments. Just after the glassy transition, at 550 °C, a glassy phase separation occurs at 580 °C, with the appearance of one silicate-and one phosphate-rich phase. It is followed by the crystallization of the major phase Na 2 CaSi 2 O 6 , from 610 to 700 °C and of the secondary phase, silicorhenanite, at 800 °C. The latter evolves from the phosphate-rich glassy phase, which is still present after the first crystallization. In order to control the processing of glass-ceramic products from Bioglass ® , crystallization kinetics were studied via differential scanning calorimetry measurements in the range of 620-700 °C and temperature-timetransformation curves were established.

Sintering and crystallisation phenomena in powders of a typical bioactive glass composition (45S5 Bioglass) have been investigated in order to gain further understanding of the processes involved in the fabrication of Bioglass, based glass-ceramic scaffolds for tissue engineering applications. In situ experiments in an environmental scanning electron microscope with a heating stage were carried out to follow the morphology of Bioglass particles during sintering and crystallisation. Optimal processing parameters for the manufacture of Bioglass based glass-ceramic scaffolds by the foam-replica technique were determined. To assess the in vitro performance and bioreactivity of Bioglass -derived glass-ceramic scaffolds, the biodegradation of samples in simulated body fluid (SBF) was investigated using various techniques, including SEM, TEM, XRD and EDX. The mechanism of interaction of the glass-ceramic surface with SBF was determined, which involves (i) preferential dissolution at glass/crystal interfaces, (ii) break-down of crystalline particles into very fine grains through preferential dissolution at crystal structural defects, and (iii) amorphisation of the crystalline structure by introduction of point defects produced during ion exchange. The present report thus offers for the first time a complete assessment of the processing parameters, microstructure, and in vitro performance of Bioglass derived glass-ceramic scaffolds intended for bone tissue engineering.

No abstract

No abstract

No abstract

Porous metals (sintered beads and meshes) have been used for many years for different orthopedic applications. Metal foams have been recently developed. These foams have the advantage of being more porous than the traditional coatings. Their high porosity provides more space for bone ingrowth and mechanical interlocking and presents more surface for implant‐bone contact. The objective of this study was to evaluate in vivo bone ingrowth into Ti implants covered with a novel Ti foam coating. This foam contains 50% in volume of interconnected pores and a higher surface area compared to dense Ti. Both coated implants and dense Ti controls were placed transcortically in the rat tibia. The animals were sacrificed at 2 weeks after implantation, and the amount of bone in the implants was determined using backscattered electron imaging and X‐ray microtomography. Already at this time interval, the pores within the Ti foam showed 97.7% bone filling, and the bone‐implant contact area was significantly increased compared to dense Ti controls. These initial results indicate that this novel Ti foam is biocompatible, has the capacity to sustain bone formation, and can potentially improve osseointegration. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010

Objective: This study aimed at investigating the influence of the porous titanium (Ti) structure on the osteogenic cell behaviour. Materials and methods: Porous Ti discs were fabricated by the powder metallurgy process with the pore size typically between 50 and 400 μm and a porosity of 60%. Osteogenic cells obtained from human alveolar bone were cultured until subconfluence and subcultured on dense Ti (control) and porous Ti for periods of up to 17 days. Results: Cultures grown on porous Ti exhibited increased cell proliferation and total protein content, and lower levels of alkaline phosphatase (ALP) activity than on dense Ti. In general, gene expression of osteoblastic markers–runt‐related transcription factor 2, collagen type I, alkaline phosphatase, bone morphogenetic protein‐7, and osteocalcin was lower at day 7 and higher at day 17 in cultures grown on porous Ti compared with dense Ti, a finding consistent with the enhanced growth rate for such cultures. The amount of mineralized matrix was greater on porous Ti compared with the dense one. Conclusion: These results indicate that the porous Ti is an appropriate substrate for osteogenic cell adhesion, proliferation, and production of a mineralized matrix. Because of the three‐dimensional environment it provides, porous Ti should be considered an advantageous substrate for promoting desirable implant surface–bone interactions.

No abstract