Previously, we reported that application of 10 microg recombinant human TGF-beta2 (rhTGF-beta2) enhanced peri-implant bone formation and bone-implant contact in a rat model. To further investigate the dose effect, the present experiment evaluated doses of rhTGF-beta2 bracketed around 10 microg (5, 10, 20 microg) using the same model. Four groups (including buffer-only control) received femoral implantation of hydroxyapatite/tricalcium phosphate-coated titanium implants. Four weeks post-surgery, all femurs were collected and analyzed by micro computed tomography followed by a mechanical test or histology. Compared with control, all rhTGF-beta2-treated groups had significantly higher bone volume. Bone-implant contact was not different between the control, 5, and 10 microg groups; however, the 20 microg group had less contact than the control. There were significant decreases in the strength of fixation in all rhTGF-beta2 treated groups compared with the control. In particular, while rhTGF-beta2 was able to enhance bone formation in the vicinity of the implant, the relative lack of bone-implant contact in the 20 microg group depressed the strength of fixation, suggesting that the location as well as the amount of new bone formed is important for implant fixation.
(c) 2009 Wiley Periodicals, Inc.