Effect of recombinant human bone morphogenetic protein-2 in an absorbable collagen sponge with space-providing biomaterials on the augmentation of chronic alveolar ridge defects

Background: Recombinant human bone morphogenetic protein-2 (rhBMP-2) in an absorbable collagen sponge (ACS) carrier has been shown to support significant bone formation in the craniofacial skeleton. When used as an onlay, however, rhBMP-2/ACS may become compressed with limited resulting bone formation. The objective of this study was to evaluate the effect of two space-providing biomaterials, bioactive glass (BG) and demineralized/mineralized bone matrix (DMB), on rhBMP-2/ACS induced alveolar ridge augmentation. Methods: Bilateral alveolar ridge defects were produced in the mandible in six mongrel dogs. rhBMP-2/ACS with biomaterials was surgically implanted into contralateral defects in four animals. Treatments were alternated between jaw quadrants in consecutive animals. Two animals received rhBMP-2/ACS or sham-surgery in contralateral defects. The animals were injected with fluorescent bone labels to monitor bone formation. Clinical evaluations were made at ridge augmentation and 12 weeks post-implantation when the animals were euthanized and block biopsies collected for histopathologic evaluation. Results: Sham-surgery produced limited horizontal alveolar augmentation (0.1 +/- 0.6 mm). Implantation of rhBMP-2/ACS resulted in alveolar augmentation amounting to 2.2 +/- 1.8 mm. Alveolar augmentation in sites receiving rhBMP-2/ACS with DMB or BG was 2-fold greater compared to rhBMP-2/ACS alone averaging 4.4 +/- 1.3 and 4.6 +/- 1.5 mm, respectively. The DMB biomaterial appeared substituted by newly formed bone. The BG particles were observed imbedded in bone or encapsulated in dense connective tissue without associated bone metabolic activity. Fluorescent light microscopy suggested that the new bone was formed within 4 weeks. Conclusion: The bioglass and demineralized/mineralized bone matrix biomaterials utilized in this study in combination with rhBMP-2/ACS supported clinical and histological ridge augmentation.