TRANSFORMING GROWTH-FACTOR-BETA STIMULATES BONE ONGROWTH - HYDROXYAPATITE-COATED IMPLANTS STUDIED IN DOGS

Unloaded cylindrical grit-blasted titanium (Ti-6A-4V) implants (6 x 10 mm) coated with hydroxyapatite ceramic were inserted into the proxima l part of the humerus of 20 skeletally mature Labrador dogs. The impla nts were initially surrounded by a 2 mm gap. In 10 dogs, HA-coated imp lants without growth factor were inserted in one humerus and implants with 0.3 mu g rhTGF-beta 1 adsorbed onto the HA coating were inserted in the contralateral humerus. In another group of 10 dogs, a dose of 3 .0 mu g rhTGF-beta 1 was tested in a similar design. All dogs were kil led at 6 weeks after treatment. Results were evaluated by histomorphom etry and mechanical push-out testing. Bone ongrowth was increased by o ne third, using the 0.3 mg rhTGF-beta 1 stimulation. Bone volume in th e gap and mechanical testing showed no statistically significant diffe rences between control and rhTGF-beta 1 stimulated implants. RhTGF-bet a 1 only moderately enhanced bone ongrowth to hydroxyapatite-coated im plants.