Implant placement in bone formed beyond the skeletal envelope by means of guided tissue regeneration: an experimental study in the rat

Objectives: The aim of the present study was to evaluate whether the placement of implants in bone formed by means of guided tissue regeneration (GTR) beyond the skeletal envelope may influence bone volume and/or structure.

Material and Methods: Rigid, hemispherical, Teflon capsules were placed with their open part facing the lateral surface of the ramus in both sides of the mandible in 18 rats. After 1 year, the capsules were removed by a re-entry operation, and a custom-made titanium implant was placed in the augmented ramus in only one side of the jaw. Six animals were sacrificed shortly after implant surgery, another six after 3 months, and the last six after 6 months. Histological specimens of the augmented sites including the implants were prepared, and the volumes of (1) the newly formed bone (mineralized bone and marrow) (2) the soft connective tissue, and (3) the implant, in the space originally created by the capsule were estimated by a point-counting technique. Additionally the height of the augmented bone was measured.

Results: One year after capsule placement, the major portion of the space originally created by the capsules was filled with newly formed bone. In the test specimens, implant placement seemed to result in a denser arrangement of the augmented bone, but this event did not influence its long-term stability. Although some resorption occurred after 3 and 6 months, the vast portion of the generated bone remained stable over time in both tests and controls, and there were no differences between tests and controls at any observation periods.

Conclusion: It is concluded that large amounts of bone can be formed beyond the skeletal envelope by means of GTR, and that this bone remains stable on a long-term basis both with and without the placement of titanium implants.