Osseointegration around titanium screws placed into the areas between guided bone augmented sites compared with osseointegration around guided bone graft augmented sites in rabbit tibia.

Abstract

The aim of this study was to compare the degree of osseointegration around titanium screws placed into the areas between guided bone augmented sites and guided bone graft augmented sites in 8 Japanese white rabbit tibia. The skin and periosteum were incised and lifted to expose the inner surfaces of both tibia. Eight rabbits were divided into 2 groups: 1) a guided bone augmentation (GBA) group of 2 rabbits, and 2) a guided bone graft augmentation (GBCA) group of 6 rabbits. In the GBA group, the bone marrow was penetrated several times in both tibial bones. Three titanium screws were inserted into the bone so that the top of each screw was 3 mm above the bone surface and covered with an expanded polytetrafluoroethylene membrane (ePTFE). In the GBGA group autogenous cortical bone (10 mm x 10 mm x 1 mm) was taken from the left tibia and grafted on the inner surface of the right tibial bone, titanium screws being similarly inserted. The surgical site was covered by ePTFE. After healing for 2 months, the animals were euthanatized, and the experimental area was prepared for histological investigation. New bone had formed on the surgical sites in the GBA group and grafted bone had survived in the GBGA group, with no sign of infection or membrane exposure. The degree of osseointegration around the screw was 67.6 +/- 11.2% (mean +/- SD) in the GBA group and 78.8 +/- 11.9% in the GBGA group. There was no significant difference between the groups (p = 0.29). The ratio of mineralized bone to bone marrow was 45.7 +/- 6.2% in the GBA group and 64.4 +/- 4.4% in the GBGA group. There was a significant difference between the groups (p < 0.05). Although there was no significant difference for osseointegration around the screw placed into the GBA and GBGA sites, the quality of newly generated bone or grafted bone was quite different. Therefore, we suggest that predictable bone augmentation beyond the bone surface can be achieved by either the GBA or the GBGA procedure with ePTFE. However, it was difficult to conclude which procedure was superior with respect to the osseointegration around the titanium screw.