Influence of surface characteristics on bone integration of titanium implants.  A histomorphometric study in miniature pigs. 
The purpose of the present study was to evaluate the influence of different surface characteristics on bone integration of titanium implants.  Hollow-cylinder implants with six different surfaces were placed in the metaphyses of the tibia and femur in six miniature pigs.  After 3 and 6 weeks, the implants with surrounding bone were removed and analyzed in undecalcified transverse sections.  The histologic examination revealed direct bone-implant contact for all implants.  However, the morphometric analyses demonstrated significant differences in the percentage of bone-implant contact, when measured in cancellous bone.  Electropolished as well as the sandblasted and acid pickled (medium grit; HF/HNO3) implant surfaces had the lowest percentage of bone contact with mean values ranging between 20 and 25%.  Sandblasted implants with a large grit and titanium plasma-sprayed implants demonstrated 30-40% mean bone contact.  The highest extent of bone-implant interface was observed in sandblasted and acid attacked surfaces (large grit; HCl/H2SO4) with mean values of 50-60%, and hydroxylapatite (HA)-coated implants with 60-70%.  However, the HA coating consistently revealed signs of resorption.  It can be concluded that the extent of bone-implant interface is positively correlated with an increasing roughness of the implant surface.