Direct bone formation on alumina bead composite

Abstract

We have developed a composite (designated ABC), consisting of alumina bead powder as an inorganic filler and bisphenol-alpha-glycidyl methacrylate (Bis-GMA)-based resin as an organic matrix, which allows direct bone formation on its surface in vivo. Alumina bead powder was manufactured by fusing crushed alpha-alumina powder and quenching it. The beads took spherical form 3 microns in average size. According to powder X-ray diffraction and Fourier transform infrared spectroscopy, the alumina bead powder was composed of amorphous and delta-crystal phases of alumina in its main crystal structure. Fused-quenched silica glass-filled composite (SGC) was used as a control. The proportion of filler added to the composites was 70% w/w. Mechanical testing of the ABC indicated that it would be strong enough for use under weight-bearing conditions. No apatite formation was detected on the surfaces of either composite after soaking in simulated body fluid for 28 days in vitro. Histological examination of rat tibiae for up to 8 weeks revealed that ABC bonded to bone directly via a layer of calcium, phosphorus, and alumina with no interposed soft-tissue layer. Moreover, the amount of bone directly apposed to the ABC surface increased with time, whereas with SGC there was poor direct bone formation even at 8 weeks. The precise mechanism of direct bone formation on ABC is as yet unknown but it is possible that changes in the crystallinity of alumina, which is known to be highly biocompatible, contribute to its excellent osteoconductivity in vivo. Although bioactive materials such as Bioglass or apatite and wollastonite-containing glass-ceramic have previously been reported to form bone-like apatite on their surfaces under acellular conditions via simple chemical reactions, ABC does not have such characteristics, and presenting favorable conditions for osteoconduction and tissue calcification may lead to direct bone formation on its surface in vivo.

Aluminosilicates and biphasic HA-TCP composites: studies of properties for bony filling

“…The kinetics of biomineralization and bioconsolidation was studied with the PIXE method (particle-induced x-ray emission). Swabs of blood were taken from implanted rabbits to detect the eventual release of Al from composites to the organism [14,15]. Ten samples of extracted swabs at different delays after implantation were taken.…”

PMMA‐based bioactive cement: Effect of glass bead filler content and histological change with time

“…A cortical bone defect measuring 2 × 5 mm was created at the medial aspect of the proximal metaphysis of both tibiae, and the bone marrow was curetted. The intramedullary canals of both bone defects were irrigated with physiological saline, a paste‐form cement was inserted at random, and each paste was allowed to solidify in situ to evaluate osteoconductivity 6–8, 10–12, 15–18, 21–23. A total of 42 rats (84 legs) were used, of which 18 legs received GBC40, 24 received GBC50, 24 received GBC60, and 18 received GBC70.…”

“…To calculate an affinity index, the length of bone in direct contact with the cement surface, as measured in an SEM photograph, was divided by the total length of the cement surface, and this value was multiplied by 100 6–8, 10–12, 15–18, 21–23. Measurements were taken using an integrated image analyzer (Tectron, Kyoto, Japan) 6–8, 10–12, 15–18, 21–23. When measuring the total length of the cement surface, the area outside the tibia (i.e., the area of the cortical bone defect) was excluded because the cement was in contact with soft tissue in that region, and our intention was to examine the reaction of the cement with bone.…”