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Recommendations for occlusal schemes for single implants or fixed partial denture supported by implants include a mutually protected occlusion with anterior guidance and evenly distributed contacts with wide freedom in centric relation. Suggestions to reduce occlusal overload include reducing cantilevers, increasing the number of implants, increasing contact points, monitoring for parafunctional habits, narrowing the occlusal table, decreasing cuspal inclines, and using progressive loading in patients with poor bone quality. Protecting the implant and surrounding peri-implant bone requires an understanding of how occlusion plays a role in influencing long-term implant stability.

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Recombinant human platelet-derived growth factor-BB (rhPDGF-BB) promotes soft tissue and bone healing, and is FDA-approved for treatment of diabetic ulcers and periodontal defects. The short half-life of topical rhPDGF-BB protein application necessitates bolus, high-dose delivery. Gene therapy enables sustained local growth factor production. A novel gene activated matrix delivering polyplexes of polyethylenimine (PEI)-plasmid DNA (pDNA) encoding PDGF was evaluated for promotion of periodontal wound repair in vivo. PEI-pPDGF-B polyplexes were tested in human periodontal ligament fibroblasts (hPLFs) and gingival fibroblasts (hGFs) for cell viability and transfection efficiency. Collagen scaffolds containing PEI-pPDGF-B polyplexes at two doses, rhPDGF-BB, PEI-vector, or collagen-alone were randomly delivered to experimentally-induced tooth-supporting periodontal defects in a rodent model. Mandibulae were harvested at 21-days for histologic observation and histomorphometry. PEI-pPDGF-B polyplexes were biocompatible to cells tested and ELISA confirmed the functionality of transfection. Significantly greater osteogenesis was observed for collagen-alone and rhPDGF-BB versus the PEI-containing groups. Defects treated with sustained PDGF gene delivery demonstrated delayed healing coupled with sustained inflammatory cell infiltrates lateral to the osseous defects. Continuous PDGF-BB production by non-viral gene therapy could have delayed bone healing. This non-viral gene delivery system in this model appeared to prolong inflammatory response, slowing alveolar bone regeneration in vivo.

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