Scaffold-based rhBMP-2 therapy in a rat alveolar defect model: Implications for human gingivoperiosteoplasty

Background: Primary alveolar cleft repair has a 41 to 73 percent success rate. Patients with persistent alveolar defects require secondary bone grafting. The authors investigated scaffold-based therapies designed to augment the success of alveolar repair. Methods: Critical-size, 7 × 4 × 3-mm alveolar defects were created surgically in 60 Sprague-Dawley rats. Four scaffold treatment arms were tested: absorbable collagen sponge, absorbable collagen sponge plus recombinant human bone morphogenetic protein-2 (rhBMP-2), hydroxyapatite-tricalcium phosphate, hydroxyapatite-tricalcium phosphate plus rhBMP-2, and no scaffold. New bone formation was assessed radiomorphometrically and histomorphometrically at 4, 8, and 12 weeks. Results: Radiomorphometrically, untreated animals formed 43 ± 6 percent, 53 ± 8 percent, and 48 ± 3 percent new bone at 4, 8, and 12 weeks, respectively. Animals treated with absorbable collagen sponge formed 50 ± 6 percent, 79 ± 9 percent, and 69 ± 7 percent new bone, respectively. Absorbable collagen sponge plus rhBMP-2-treated animals formed 49 ± 2 percent, 71 ± 6 percent, and 66 ± 7 percent new bone, respectively. Hydroxyapatite- tricalcium phosphate treatment stimulated 69 ± 12 percent, 86 ± 3 percent (p < 0.05), and 87 ± 14 percent new bone, respectively. Histomorphometry demonstrated an increase in bone formation in animals treated with hydroxyapatite-tricalcium phosphate plus rhBMP-2 (p < 0.05; 4 weeks) compared with empty scaffold. Conclusions: Radiomorphometrically, absorbable collagen sponge and hydroxyapatite-tricalcium phosphate scaffolds induced more bone formation than untreated controls. The rhBMP-2 added a small but significant histomorphometric osteogenic advantage to the hydroxyapatite- tricalcium phosphate scaffold.