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

Abstract

A new bioactive bone cement (designated GBC), which is a polymethyl methacrylate (PMMA)-based composite consisting of bioactive glass beads as an inorganic filler and high molecular-weight PMMA as an organic matrix, has been developed. The purpose of the present study was to evaluate the effect of the filler content on the mechanical properties and osteoconductivity of GBC, to decide the most suitable filler proportion, and to evaluate the degree of cement degradation with time. The bioactive beads, consisting of MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) glass, were added to the cement in various proportions (40-70 wt %). The bending strength of GBC did not differ among the proportions (approximately 136 MPa), but the elastic modulus of bending of GBC increased as the glass bead filler content increased (approximately 4.1-7.2 GPa). The all types of GBC were packed into the intramedullary canals of rat tibiae to evaluate osteoconductivity, as determined by an affinity index calculated as the length of bone in direct contact with the cement surface expressed as a percentage of the total length of the cement surface. Rats were sacrificed at 4, 8, 25, and 39 weeks after implantation, and the affinity index was calculated for each type of GBC at each time point. Histologically, new bone had formed along the surface of all types of GBC within 4 weeks, even in GBC containing only 40 wt % of glass beads. The affinity indices of GBC tended to increase as the proportion of glass bead filler increased and as the implantation period increased. In GBC containing 60 or 70 wt % of glass beads, significant rapid increases in the affinity indices were found from 4 to 8 weeks, and the high values (approximately 70%) were maintained up to 39 weeks. A sign of glass bead degradation was observed at the bone-cement interface in the rat tibiae at 39 weeks. We conclude that, when mechanical properties and osteoconductivity are both taken into consideration, GBC containing 60 or 70 wt % of glass beads is the most suitable formulation, but that further studies are needed to investigate and overcome the degradation.

PMMA‐based bioactive cement: Effect of CaF2 on osteoconductivity and histological change with time

“…A low-signal layer, which may be a sign of degradation, as reported previously, 7,15 was observed in SEM photographs of the cementbone interface with both GBC(F ϩ) and GBC(F Ϫ . SEM photographs of (a) GBC(F ϩ) at 4 weeks after implantation, (b) GBC(F Ϫ) at 4 weeks, and (c) hPMMA at 4 weeks in rat tibiae.…”

“…7,8 The bending strength of GBC (approximately 130 MPa) 7,11,15 became higher than that of conventional PMMA cement (92 MPa). 21 A further important advantage is that the handling properties of GBC are as good as those of PMMA bone cement.…”

“…Previous studies have shown that, in terms of both osteoconductivity and mechanical properties, the most suitable proportions of the glass-bead filler content mixed into GBC are 60 or 70 wt.%. 11,15 In this study, 60 wt.% of filler was used.…”

In vivo aging test for a bioactive bone cement consisting of glass bead filler and PMMA matrix

“…Moreover, the Young's moduli of GBC50 and GBC60 were significantly higher than those of CMW-1 at all time points. Although high Young's modulus values are not in themselves an advantage, because high elastic moduli can be associated with uneven stress distribution or load transmission between a prosthesis and the bone, 11,15,23 GBC was believed to retain its ductility. In a previous study, GBC was packed into the intramedullary canals of rat tibiae and found found to have excellent osteoconductivity.…”

“…After soaking in phosphate-buffered saline solution (PBS) for one day, their bending strength was tested on a materials testing machine (model AG-10TB; Shimadzu Co., Kyoto, Japan), run at a cross-head speed of 0.5 mm/min, with the use of the three-point bending method. 7,[11][12][13][14][15][16][17] The values for Young's modulus were derived from the stress-strain curves obtained from the bending test results.…”