Effect of a bioactive rapidly resorbing silica containing calcium alkaliphosphate bone grafting material on osteo-, angiogenesis and micromechanic bone properties in biopsies 6 months after sinus floor augmentation as compared to tricalcium phosphate and

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Over the last few decades there has been an ever increasing search for adequate bone grafting materials in implant dentistry for use for sinus floor augmentation (SFA) and alveolar ridge augmentation. For most clinically available bone grafting materials, however, data which would provide a detailed characterization of the cell and tissue responses to these materials including data derived from clinically representative large animal models and clinical studies are extremely scarce. An ideal bone grafting material should be highly bioactive and stimulate osteogenesis, while resorbing rapidly at the same time, thereby facilitating copious and expeditious bone formation and bone regeneration with fully functional bone, which then in its turn facilitates earlier implant placement and shorter treatment durations. As a result, a former DFG funded project succeeded in developing a highly bioactive silica containing calcium alkali orthophosphate (Si-CAOP) bone grafting material and in demonstrating greater bone formation and biodegradability as well as a greater stimulatory effect on osteogenesis, when compared to tricalcium phosphate (TCP), in the context of a clinically representative large animal model and in vitro. When using TCP for SFA, high clinical success rates were achieved. TCP, however, resorbs within 1-2 years in humans. Since Si-CAOP was cleared by the FDA and received the CE mark on the basis of the data generated in the previously funded DFG projects, the proposed project aims at confirming the excellent osteogenic properties of Si-CAOP and greater stimulatory effect on bone formation when compared to TCP, which were demonstrated in the context of these previous projects, in human tissue, so as to obtain successful translation into the clinical arena. To this end, the correlation between the signal transduction data as well as the data generated in the context of the large animal sheep study and data obtained by analyzing patient biopsies and radiological data will be established in order to facilitate the evidence-based use of Si-CAOP in patients (on the basis of robust comprehensive data sets). As a result, the effect of Si-CAOP on osteogenesis and angiogenesis will be characterized in biopsies obtained from 30 patients 6 months after SFA at implant placement, and compared to that of TCP, utilizing comprehensive, cutting-edge hard tissue histologic, immunohistochemical and synchrotronmicrotomographic and micromechanic analyses. This is in addition to evaluating the volume stability of the grafted region on the basis of cone beam CT data. Hence, the proposed project aims at testing the hypothesis that the superior osteogenic properties, which were previously demonstrated in vitro and in vivo, will also result in markedly enhanced bone formation in patient tissue when using Si-CAOP for SFA as compared to TCP. If this hypothesis will be confirmed, earlier implant placement after 4 instead of 6 months after SFA can be justified ethically.