Evaluation of a novel alloplast for osseous regeneration in the rat calvarial model

Background: Alloplasts are inert foreign bodies acting as osteoconductive space maintainers during osseous wound healing. They may also function as carriers for growth factors that are known to enhance neovascularization and osteoinduction; human recombinant transforming growth factor beta (rhTGF-β1) is one such factor. The purpose of this study was to evaluate di-vinyl styrene beads (DVSb) and rhTGF-β1 effects on osseous regeneration in the rat calvaria critical-sized defect model. Methods: Di-vinyl styrene beads (DVSb) with and without rhTGF-β1 were placed between gelfilm membranes in a critical-sized defect in the rat (Rattus norvegicus) calvaria. Actual bone fill; percentage bone fill; bone formation rate (BFR); and mineralization at 3, 6, and 12 weeks postsurgery were measured using densitometry, histomorphometry, scanning electron microscopy (SEM), and vital staining with tetracycline-HCI. Results: Mean radiographic density and percentage fill were statistically greater for DVSb treatment groups as compared with controls (P ≤0.05). BFR was consistently between 3 and 7 μm per day for all groups; alloplast group BFR was significantly greater than controls or the rhTGF-β1 groups at 6 weeks (P ≤0.05); however, at 3 and 12 weeks, the control BFR was greater than treatment groups (P ≤0.05). Membranes often collapsed and little bone fill or mineralization occurred in defects without DVSb. Mineralization appeared to occur adjacent to the alloplast by 12 weeks in the histologic and SEM sections. While DVSb fibrous attachment occurred in some specimens, there was no evidence of an inflammatory response. Conclusion: Di-vinyl styrene beads, with or without rhTGF-β1, significantly enhance bone regeneration in the rat calvaria defect model.