Larry L. Hench

An Introduction to bioceramics

Alumina and zirconia, S. Hulbert bioactive glasses - materials science, L. Hench and O. Andersson bioactive glasses-materails science, L. Hench and O. Anderson applications, J. Wilson and R.P. Happonen A/W glass-ceramic - processing and properties, T. Kokubo A/W glass ceramic - clinical applications, T. Yamamuro bioactive glass-ceramics - ceravital, U. Gross et al machineable glass-ceramics, W. Holland and W. Vogel hydroxyapotite, R. LeGros and J. LeGros porous ceramics, R. Holmes and E. Schors resorbable calcium phosphates, C.P.A.T. Klein et al hydroxyapatite coatings, W. Lacefield bioactive glass coatings, L. Hench and O. Andersson pyrolytic carbon coatings, R.H. Dauskardt and R.O. Ritchie bioceramic composites, P. Ducheyne polyethylene-HA composites, W. Bonfield radiotherapy glasses, D. Day characterization of bioceramics, L. Hench regulation of medical devices, E. Horowitz and E. Mueller summary, L. Hench and J. Wilson appendices ASTM standards, J. Lemons and D. Greenspan.

Gene-expression profiling of human osteoblasts following treatment with the ionic products of Bioglass® 45S5 dissolution

The effect of the ionic products of Bioglass 45S5 dissolution on the gene-expression profile of human osteoblasts was investigated by cDNA microarray analysis of 1,176 genes. Treatment with the ionic products of Bioglass 45S5 dissolution increased the levels of 60 transcripts twofold or more and reduced the levels of five transcripts to one-half or less than in control. Markedly up-regulated genes included RCL, a c-myc responsive growth related gene, cell cycle regulators such as G1/S specific cyclin D1, and apoptosis regulators including calpain and defender against cell death (DAD1). Other significantly up-regulated genes included the cell surface receptors CD44 and integrin beta1, and various extracellular matrix regulators including metalloproteinases-2 and -4 and their inhibitors TIMP-1 and TIMP-2. The identification of differentially expressed genes by cDNA microarray analysis has offered new insights into the mode of action of bioactive glasses and has proven to be an effective tool in evaluating their osteoproductive properties.

Ultrastructure processing of ceramics, glasses, and composites

A presentation of the proceedings and papers of the International Conference, this volume examines the state of the science of producing ceramic, glass, and composite materials using the new methods of chemical micromorphology, and transformation based processing, along with practical applications. Discusses the potential for producing materials with unique properties and the possibility of controlling long-term reliability.

Biomaterials : a forecast for the future

The survivability half-life of prostheses made with current bio-inert materials is approximately 15 years, depending upon clinical applications. Bioactive materials improve device lifetime but have mechanical limitations. This paper proposes that biomaterials research needs to focus on regeneration of tissues instead of replacement. Alternatives are: use hierarchical bioactive scaffolds to engineer in vitro living cellular constructs for transplantation, or use resorbable bioactive particulates or porous networks to activate in vivo the mechanisms of tissue regeneration.

Bioglass ®45S5 Stimulates Osteoblast Turnover and Enhances Bone Formation In Vitro: Implications and Applications for Bone Tissue Engineering

Abstract. We investigated the concept of using bioactive substrates as templates for in vitro synthesis of bone tissue for transplantation by assessing the osteogenic potential of a melt-derived bioactive glass ceramic (Bioglass® 45S5) in vitro. Bioactive glass ceramic and bioinert (plastic) substrates were seeded with human primary osteoblasts and evaluated after 2, 6, and 12 days. Flow cytometric analysis of the cell cycle suggested that the bioactive glass-ceramic substrate induced osteoblast proliferation, as indicated by increased cell populations in both S (DNA synthesis) and G2/M (mitosis) phases of the cell cycle. Biochemical analysis of the osteoblast differentiation markers alkaline phosphatase (ALP) and osteocalcin indicated that the bioactive glass-ceramic substrate augmented osteoblast commitment and selection of a mature osteoblastic phenotype. Scanning electron microscopic observations of discrete bone nodules over the surface of the bioactive material, from day 6 onward, further supported this notion. A combination of fluorescence, confocal, transmission electron microscopy, and X-ray microprobe (SEM-EDAX) examinations revealed that the nodules were made of cell aggregates which produced mineralized collagenous matrix. Control substrates did not exhibit mineralized nodule formation at any point studied up to 12 days. In conclusion, this study shows that Bioglass 45S5 has the ability to stimulate the growth and osteogenic differentiation of human primary osteoblasts. These findings have potential applications for tissue engineering where this bioactive glass substrate could be used as a template for the formation of bioengineered bone tissue.

Effect of crystallization on apatite-layer formation of bioactive glass 45S5

The bioactive glass 45S5 was crystallized to 8-100 vol % of crystals by thermal treatments from 550-680 degrees C. The micro-structure of the glass-ceramics had a very uniform crystal size, ranging from 8 to 20 microns. Fourier-transform infrared (FTIR) spectroscopy was used to determine the rate of hydroxycarbonate apatite (HCA) formation that occurs on bioactive glass and glass-ceramic implants when exposed to simulated body fluid (SBF) solutions. Crystallization did not inhibit development of a crystalline HCA layer, but the onset time of crystallization increased from 10 h for the parent glass to 22 h for 100% crystallized glass-ceramic. The rate of surface reactions was slower when the percentage of crystallization was > or = 60%.

Physical chemistry of glass surfaces

Abstract Six typical problem areas requiring improved understanding of glass surfaces are identified. Results obtained from several surface-analysis instruments show that five types of surfaces are characteristic of a silicate glass at any time in its history. The type of surface is dependent on the environmental history of the glass and may be defined in terms of surface compositional profiles. Several important glass surface topics of current interest are discussed. These include: corrosion mechanisms; mixed-alkali effect; surface passivation with solution ions; protective film formation; the role of CaO, R 2 O/SiO 2 and Al 2 O 3 in glass corrosion; glass surface area to solution volume ratio; relevance of autoclave procedures in durability tests; and bioglass-bone bonding mechanisms.

Chemical processing of advanced materials

Sol-Gel Science A Sol-Gel Route to Very High Porosity Silica Aerogels Kinetics and Equilibrium of Acid-Catalyzed Tetraethoxysilane Hydrolysis NMR Studies of the Sol-Gel Process Various Oxide and Multicomponent Systems The Preparation and Characterization of Sn-Si-O Gels Raman Spectroscopy of Phosphorous-Doped Silica Gels Sol-Gel Applications New Group 2 Organometallic Precursors to Metal Oxides Optical and Thermal Properties of Silica Aerogels Thin Films and Coatings: Ultrastructure Processing of Thin Crystalline Films Size Effects in Ferroelectric Thin Films Micromorphology Science Ultrastructural Polymers Chemically Processed Fibres and Composites Microwave Syntheses of Materials and Their Precursors Advanced Optical Materials Nanomodulated Ceramic Superlattices by Electrodeposition Future Directions.

Development and in vitro characterisation of novel bioresorbable and bioactive composite materials based on polylactide foams and Bioglass® for tissue engineering applications

Bioactive and bioresorbable composite materials were fabricated using macroporous poly(DL-lactide) (PDLLA) foams coated with and impregnated by bioactive glass (Bioglass) particles. Stable and homogeneous Bioglass coatings on the surface of PDLLA foams as well as infiltration of Bioglass particles throughout the porous network were achieved using a slurry-dipping technique in conjunction with pre-treatment of the foams in ethanol. The quality of the bioactive glass coatings was reproducible in terms of thickness and microstructure. Additionally, electrophoretic deposition was investigated as an alternative method for the fabrication of PDLLA foam/Bioglass composite materials. In vitro studies in simulated body fluid (SBF) were performed to study the formation of hydroxyapatite (HA) on the surface of PDLLA/Bioglass composites. SEM analysis showed that the HA layer thickness rapidly increased with increasing time in SBF. The high bioactivity of the PDLLA foam/Bioglass composites indicates the potential of the materials for use as bioactive, resorbable scaffolds in bone tissue engineering.

Comparative bone growth behavior in granules of bioceramic materials of various sizes

Various bioceramic materials were implanted into 6-mm-diameter holes made in the femoral condyles of mature Japanese white rabbits using different-sized granules to find an optimal material and granule diameter for use as a bone graft. Bioceramics include a bioinert ceramic (Alumina), surface-bioactive ceramics [hydroxyapatite (HAp) and Bioglass(R)], and resorbable bioactive ceramics [alphatricalcium phosphate (alpha-TCP), beta-TCP, tetracalcium phosphate (TeCP), Te. DCPD, Te. DCPA, and low-crystalline HAp]. Granule sizes were 100-300, 10, and 1-3 microm. Bone growth behavior varied with the kind of bioceramic and the size used. For surface-bioactive ceramics, 45S5 Bioglass(R) led to more rapid bone proliferation than synthetic HAp. In resorbable bioactive ceramics, the order of resorption was: low-crystalline HAp and OCP > TeCP, Te DCPD, Te DCPA > alpha-TCP, beta-TCP. In terms of biocompatibility, alpha-TCP was better than beta-TCP.