IntroductionBisphenol-a-glycidyl dimethacrylate (bis-GMA) resins have been studied in orthopedic applications since the late 1970s [21]. Various formulations were developed in efforts to reduce the amount of leachable unreacted monomer, to avoid high local temperatures during polymerization, to improve mechanical properties, and to enhance direct bone contact [4,19]. Current formulations of bis-GMA resins have achieved these goals of improved mechanical, chemical, and biologic properties [14,18]. One such formulation is Cortoss synthetic cortical bone void filler, a biocompatible, bone-bonding, terpolymer cortical bone substitute containing bisphenol-a-glycidyl dimethacrylate (bis-GMA), bisphenol-a-ethoxy dimethacrylate (bis-EMA), and triethylene glycol dimethacrylate (TEGDMA) resins reinforced with synthetic combeite glass-ceramic particles to stimulate bone apposition at the interface, barium boroaluminosilicate glass for radiopacity and strength, and silica for improved viscosity.For more than 20 years, polymethyl methacrylate (PMMA) bone cement has been used to reconstruct vertebral bodies that have collapsed as a result of trauma or tumor invasion [8,9,12]. Long-term studies report that these treatments are highly durable and that significant failAbstract A newly formulated and reinforced bisphenol-a-glycidyl dimethacrylate (bis-GMA) resin (Cortoss/Orthovita, Malvern, Pa.) was compared with Simplex P polymethyl methacrylate (Stryker Howmedica Osteonics, East Rutherford, N.J.) in rabbits for up to 52 weeks and in sheep for up to 78 weeks. As seen in scanning electron microscopy and histology examinations, both implant materials were surrounded by bone at late time periods, with fibrous layers of connective tissue seen in half the Simplex P specimens. No clinically significant safety differences between implant materials were apparent. Interfacial bond strengths between the implant and bone generally increased with time, but were 4.5-fold greater with Cortoss than Simplex P at 24 weeks, and 100-fold greater at 52 weeks. Forces required to displace 316SS rods held in place with Cortoss were consistently greater than forces to displace rods held in place with Simplex P. No statistically significant differences in displacement forces were found between rods held in place with Cortoss polymerized in situ and rods held with prepolymerized Cortoss. Interfacial bond strengths were greater for Simplex P that was polymerized in situ than for prepolymerized polymethyl methacrylate specimens. Cortoss synthetic cortical bone void filler is a good candidate material to fix implants in bone. It has characteristics consistent with longterm safety and has a better ability to bond to bone than Simplex P.

No abstract

IntroductionBisphenol-a-glycidyl dimethacrylate (bis-GMA) resins have been studied in orthopedic applications since the late 1970s [21]. Various formulations were developed in efforts to reduce the amount of leachable unreacted monomer, to avoid high local temperatures during polymerization, to improve mechanical properties, and to enhance direct bone contact [4,19]. Current formulations of bis-GMA resins have achieved these goals of improved mechanical, chemical, and biologic properties [14,18]. One such formulation is Cortoss synthetic cortical bone void filler, a biocompatible, bone-bonding, terpolymer cortical bone substitute containing bisphenol-a-glycidyl dimethacrylate (bis-GMA), bisphenol-a-ethoxy dimethacrylate (bis-EMA), and triethylene glycol dimethacrylate (TEGDMA) resins reinforced with synthetic combeite glass-ceramic particles to stimulate bone apposition at the interface, barium boroaluminosilicate glass for radiopacity and strength, and silica for improved viscosity.For more than 20 years, polymethyl methacrylate (PMMA) bone cement has been used to reconstruct vertebral bodies that have collapsed as a result of trauma or tumor invasion [8,9,12]. Long-term studies report that these treatments are highly durable and that significant failAbstract A newly formulated and reinforced bisphenol-a-glycidyl dimethacrylate (bis-GMA) resin (Cortoss/Orthovita, Malvern, Pa.) was compared with Simplex P polymethyl methacrylate (Stryker Howmedica Osteonics, East Rutherford, N.J.) in rabbits for up to 52 weeks and in sheep for up to 78 weeks. As seen in scanning electron microscopy and histology examinations, both implant materials were surrounded by bone at late time periods, with fibrous layers of connective tissue seen in half the Simplex P specimens. No clinically significant safety differences between implant materials were apparent. Interfacial bond strengths between the implant and bone generally increased with time, but were 4.5-fold greater with Cortoss than Simplex P at 24 weeks, and 100-fold greater at 52 weeks. Forces required to displace 316SS rods held in place with Cortoss were consistently greater than forces to displace rods held in place with Simplex P. No statistically significant differences in displacement forces were found between rods held in place with Cortoss polymerized in situ and rods held with prepolymerized Cortoss. Interfacial bond strengths were greater for Simplex P that was polymerized in situ than for prepolymerized polymethyl methacrylate specimens. Cortoss synthetic cortical bone void filler is a good candidate material to fix implants in bone. It has characteristics consistent with longterm safety and has a better ability to bond to bone than Simplex P.