Bioactive bone cement: Effect of surface curing properties on bone-bondingstrength

The fact that bisphenol-a-glycidyl methacrylate (bis-GMA)-based cements con tain an uncured surface is believed to play an important role when determin ing the surface curing properties of the cements. Threfore, in the present study, the bone-bonding strength of cement plates having an uncured surface on one side and a cured surface on the other side has been evaluated. Thes e cement plates were composites of a bis-GMA-based resin with either an apa tite- and wollastonite-containing glass-ceramic (AW-GC) powder or a hydroxy apatite (HA) powder, respectively designated AWC and HAC, The amount of eac h of these powders in a composite cement was 70 wt %. We formulate the hypo thesis that the uncured surface of a cement plate is bioactive having bone- bonding properties. The goal of the present study was to indicate the bone- bonding strength of the uncured surfaces of AWC and HAC and compare the str ength with the respective cured surfaces by a detaching in vivo test, as we ll as to histologically examine the bone-cement interface. Each plate has b een implanted into the tibiae of male Japanese white rabbits, taking care t o retain the surface properties, and the so-called "failure load" has been measured using a detaching test followed 8 weeks after implantation, The fa ilure load for AWC-plates at the uncured surface (2.05 +/- 1.11 kgf, n 8) w as significantly higher than AWC at its cured surface side (0.28 +/- 0.64 k gf, n = 8), The failure Load for MAC-plates at the uncured surfaces (1.40 /- 0.68 kgf, n = 8) was significantly higher than MAC at its cured surface (0.00 +/- 0.00 kgf, n = 8), Failure loads for AWC at its uncured and cured surfaces were both higher than for HAC, although not significantly. Direct bone formation has been observed histologically for both AWC and HAC on the uncured surfaces, and a Ca-P-rich layer was observed only at the uncured s urface of AWC, These findings strongly suggest that uncured surfaces are us eful for exposing a bioactive filler on a surface of composites, being very effective in inducing bone bonding. (C) 2000 John Wiley & Sons. Inc.