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

• Published in: Journal of biomedical materials research 2003-05, Vol.65B (2), p.262-271
• Main Authors: Shinzato, Shuichi, Nakamura, Takashi, Kawanabe, Keiichi, Kokubo, Tadashi
• Format: Article
• Language: English
• Subjects: Animals; bioactive cement; Biological and medical sciences; Bone Cements - chemical synthesis; Bone Cements - chemistry; Bone Cements - classification; CaF2; Calcium Fluoride - chemistry; Cementation - instrumentation; Cementation - methods; Equipment Failure Analysis; glass; Glass - chemistry; Male; Manufactured Materials; Medical sciences; Microscopy, Electron, Scanning; Osseointegration - physiology; osteoconductivity; Polymethyl Methacrylate; polymethyl methacrylate (PMMA); Rats; Rats, Wistar; Surface Properties; Tibial Fractures - pathology; Tibial Fractures - therapy
• ISSN: 1552-4973; 0021-9304; 1552-4981; 1097-4636
• DOI: 10.1002/jbm.b.10008

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 (hPMMA) as an organic matrix, has been developed. The bioactive glass beads consist of MgO‐CaO‐SiO2‐P2O5‐CaF2 glass. The purpose of the present study was to evaluate the effect of CaF2 on osteoconductivity and to evaluate the degree of cement degradation with time. Three different types of cement were prepared. GBC(F +), which has been previously described, consisted of CaF2‐containing bioactive glass beads and hPMMA. GBC(F −) consisted of CaF2‐free bioactive glass beads and hPMMA. The third cement was hPMMA itself (as a reference material). These three types of cement 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 killed at 4, 8, 25, and 52 weeks after implantation, and the affinity index was calculated for each type of cement at each time point. Histologically, new bone had formed along the surface of both GBC(F +) and GBC(F −) within 4 weeks, whereas hPMMA had little contact with bone, and an intervening soft tissue layer between bone and cement was detected. No significant difference in affinity index was found between GBC(F +) and GBC(F −) at any of the time points studied, although GBC(F −) showed higher affinity indices than GBC(F +) at 8, 25, and 52 weeks. The affinity indices for GBC(F +) and GBC(F −) were significantly higher than those for hPMMA at all time points. With GBC(F +) and GBC(F −), significant increases in the affinity indices were found as the implantation period increased, and the affinity index values at 52 weeks reached more than 70%. In hPMMA, no significant increase in affinity index was observed up to 52 weeks, and the value at 52 weeks was less than 30%. Although no significant difference in affinity index was found between GBC(F +) and GBC(F −), GBC(F −) is conclusively better than GBC(F +) because diseases such as chronic fluorosis might be caused by CaF2‐containing glass beads. Regarding the cement degradation of both GBC(F +) and GBC(F −), the degree of the degradation at 25 weeks was the same as that at 52 weeks. Therefore, the cement degradation does not appear to proceed rapidly. Further studies are ne