Histomorphometric and fluorescence microscopic analysis of bone remodelling after installation of implants using an osteotome technique.

The influence of the osteotome technique on the osseointegration of rough-surfaced stepped cylinder implants (Frialit)-2) was compared to conventional preparation of the implant site in an animal model. A total of 104 implants were placed into the distal femoral condyle of 52 New Zealand white rabbits. This region contains sufficient trabecular bone for implant placement. The implant site was prepared either by the osteotome technique or by conventional technique with drills as a control group. During the healing period polychromatic fluorescence labelling was performed with four different fluorescent dyes. After 2, 4 and 8 weeks, the implants were removed with the surrounding bone. The sample preparation was done using the 'sawing and grinding' technique. Ground sections 100 microm thick were used for fluorescence microscopic analysis; 30- microm-thick ground sections were examined histomorphometrically. After 2 weeks the bone-to-implant contact ratio was 55.0 +/- 7.1% for the osteotome technique and 29.2 +/- 4.8% for the control group (P < 0.0005). After 4 weeks, the bone-to-implant contact ratio was still significantly better for the osteotome technique (bone-to-implant contact ratio osteotome technique 71.1 +/- 7.2%, bone-to-implant contact ratio control 59.0 +/- 6.3%, P = 0.003). Eight weeks after implant placement the bone-to-implant contact ratio was still better for the osteotome technique compared to the conventional implant placement. However it was no longer statistically significant. The qualitative fluorescence microscopic examination showed an earlier and stronger signal for the osteotome technique than the control group. With the latter, the zone of mineralization moved slowly towards the implant surface. Implant sites prepared by the osteotome technique showed a pronounced signal in the whole compressed area already by the second day. In conclusion, the osteotome technique increases new bone formation and leads to an enhanced osseointegration of dental implants in trabecular bone. However, more experimental trials have to be carried out on higher mammals that show a metabolic rate of bone that is more comparable to humans.