Bone tissue response to BMP-2 adsorbed on amorphous microporous silica implants

Aim To evaluate bone regeneration potential of bone morphogenetic protein‐2 (BMP‐2) adsorbed on amorphous microporous silica (AMS). Materials & Methods Four implants [titanium as control (CTR); AMS‐coated titanium (AMS), BMP‐2 adsorbed on titanium (CTR+BMP) and AMS (AMS+BMP)] were implanted randomly in the tibiae of 20 New Zealand white rabbits. Bone specimens with implants were retrieved 2/4 weeks post implantation and analysed histologically and histomorphometrically. Bone fraction was measured in initial bone‐free area (bone regeneration area, BRA) and in the area with initial bone–implant contact [bone adaptation area (BAA)] (BFBRA & BFBAA). Bone–implant contact was measured in BRA (BICBRA). In vitro BMP‐2 release profiles were determined to evaluate the impact of the carrier surface. Mixed models were used for statistical analysis. Results BMP‐2 release profiles were different for CTR+BMP and AMS+BMP. BICBRA and BFBRA were significantly increased after 4 weeks compared to 2 weeks for AMS, CTR+BMP and AMS+BMP. However, no differences between the implant types were observed within both healing periods. BFBAA for CTR+BMP was smaller than that for CTR and AMS+BMP after 4 weeks. Despite slower BMP‐2 release, AMS+BMP did not stimulate bone regeneration. CTR+BMP caused bone resorption at the bone–implant interface. Conclusions BMP‐2 functionalized implant surfaces failed to stimulate bone regeneration and osseointegration.