BONE-REPLACEMENT WITH POROUS HYDROXYAPATITE BLOCKS AND TITANIUM SCREW IMPLANTS - AN EXPERIMENTAL-STUDY

The aim of this experimental study was to examine whether porous hydroxyapatite (HA) blocks, fixed with titanium screw implants, could be used as a bone graft substitute. Twenty minipigs received coralline HA blocks for augmentation of surgically created defects in edentulous mandibles. Each block was fixed with two titanium screw implants. Two types of porous HA blocks that differed in pore diameter were used. A high rate of HA loss occurred in the group of animals that had received the HA block with small pore sizes, and fractures of the block occurred in the vicinity of the titanium implants in 12 of the remaining 13 cases. Histologic examination showed that the HA blocks with larger pore size were homogenously penetrated by bone that extended into the central pores and even incorporated the dislocated block fragments. The titanium implants were in close contact with the newly formed bone in these blocks. Little contact between bone and implants was seen in the HA blocks with the smaller pore size. The results indicate that, with improved mechanical properties, a combined augmentation with porous HA blocks and screw implants may be useful in primary reconstruction of bone defects. © 1991.