EFFECT OF POLYMERIZATION REACTION INHIBITOR ON MECHANICAL-PROPERTIES AND SURFACE REACTIVITY OF BIOACTIVE BONE-CEMENT

We introduced an inhibitor to the polymerization reaction of bioactive bone cement (AWC) consisting of MgO-CaO-SiO2-P2O5-CaF2 apatite and wo llastonite containing glass-ceramic powder and bisphenol-alpha-glycidy l methacrylate based resin , together with an increased amount of acce lerator but without any prolongation of its setting time in order to i mprove the degree of polymerization and decrease the amount of incompl etely polymerized monomers on the cement surface. A comparison was mad e between the AWC containing the inhibitor [AWC(I+)] and the AWC witho ut it [AWC(I-)] with regard to setting: parameters, mechanical propert ies, and surface reactivity in vitro and in viva, The proportion of gl ass-ceramic powder added to the AWC was 70% (w/w), The total amount of f heat generation and the peak temperature of the AWC(I+) during polym erization were slightly greater than those of the AWC(I-), The mechani cal strength of AWC(I+) was higher than that of the AWC(I-) under wet conditions, In simulated body Amid, the width of the Ca-P rich layer o n the surface of the AWC(I+) was less than that on the AWC(I-) after 2 8 days of immersion, although the rate of apatite formation on the top surface of the AWC(I+) was almost identical to that on the AWC(I-) su rface. Histological examination using sat tibiae up to 26 weeks reveal ed that the bioactivity of the AWC(I+) was equivalent to that of the A WC(I-). Scanning electron microscopy and energy-dispersive X-ray micro analysis demonstrated that the Ca-P rich layer in the AWC(I+) was sign ificantly narrower than that in the AWC(I-) at the same time points. T hese results indicate that introduction of the inhibitor improved the mechanical properties of the AWC and made the Ca-P rich layer narrower , but it had no adverse effect on bioactivity. (C) 1998 John Wiley & S ons, Inc.