Osteoconductivity and bone-bonding strength of high- and low-viscous bioactive bone cements

A study was conducted to evaluate the osteoconductivity and bone-bonding ab ility of two types of bioactive bone cement, both consisting of apatite and wollastonite containing glass-ceramic powder (AW-P), fused silica glass po wder (SG-P), submicron fumed silica as an inorganic filler, and bisphenol-a -glycidyl methacrylate (Bis-GMA) based resin as an organic matrix. The ceme nts had two kinds of formulas: one (dough-type cement; designated DTC) comp osed of 85 % (w/w) filler and 15 % resin, which was developed for fixation of the acetabular component in total hip arthroplasty and could be handled manually; and one (injection-type cement; designated ITC) composed of 79 % (w/w) filler and 21 % resin. ITC was developed for fixation of the femoral component and, because it had a lower viscosity than DTC, could be injected . The DTC and ITC both contained 73 % AW-P, 25 % SG-P, and 2 % fumed silica in the weight ratio of the filler component. Two other types of cement, bo th of which consisted of 83.3 % AW-P or SG-P, 1.7 % fumed silica, and 15 % resin, were used as reference material (designated AWC or SGC) for a detach ing test. Following the packing of bone defects in the rat tibiae with eith er DTC or ITC, histological examination revealed that the DTC and ITC had b oth directly contacted the bone and were almost completely surrounded by bo ne by 16 weeks after the surgery and that no marked biodegradation had occu rred at 52 weeks postimplantation. Rectangular plates (2 x 10 x 15 mm) of A WC, DTC, ITC, and SGC were implanted into the metaphysis of the tibia of ma le rabbits and the failure load was measured by a detaching test at 10 and 25 weeks after implantation. The failure loads of AWC, DTC, ITC, and SGC we re 3.65, 2.21, 2.44, and 0.04 kgf at 10 weeks and 4.87, 2.81, 2.82, and 0.1 3 kgf at 25 weeks, respectively. Observation of the bone-implant interface by scanning electron microscopy and energy dispersive X-ray microanalysis r evealed that all the samples except SGC formed direct contact with the bone and that only AWC-implanted tibiae had a layer of a low calcium and phosph orus level at the bone-implant interface. Results showed that DTC and ITC h ave excellent osteoconductivity and bone-bonding ability under non-weight-b earing conditions. (C) 1999 John Wiley & Sons, Inc.