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Multi-scale BiOmechanical characterization of peri-iMplant Bone tissue: influence of the environment

Periodic Reporting for period 1 - BOMB (Multi-scale BiOmechanical characterization of peri-iMplant Bone tissue: influence of the environment)

Reporting period: 2018-10-01 to 2020-09-30

Osseointegration of metallic implants is key for long-term lasting dental and orthopaedic prostheses. Bone ingrowth onto and around a metallic foreign body happens during a healing period, creating a bone-implant interface which biomechanical properties will condition implant stability. During this healing phase, any disruption may lead to implant failure, which is still frequent, difficult to anticipate and have dramatic consequences for the patient. The effectiveness of long-term implant anchorage plays a central role in public-health, as highlighted by more than 500 000 dental implants and 150 000 hip prostheses implanted every year just in France, as well as the rise in osteoporosis occurrence, deemed responsible for 3.5 million fractures in the European Union in 2010. The overall objectives of the project are to study the biomechanical properties of regenerated bone tissue around implants, implementing a multi-scale and multi-modal framework.
To investigate the properties of the interface, we setup a multi-modal structural and mechanical characterisation. As bone is a complex and hierarchical material, spanning all the scales from nano to macro, the project involved a wide range of high-resolution techniques including micro-tomography, small-angle x-ray scattering, light microscopy and nanoindentation.
A bone-chamber animal model allowed us to distinguish newly-formed bon from mature existing tissue. The new tissue is still young and immature, with a composition and organization changing along healing, especially close to the interface. At the nanoscale, bone crystals are thinner and more oriented close to the implant surface, as probed by x-rays diffraction (SAXS). This suggests that the implant mostly affects the bone ultrastructure within the first 100µm, potentially due to difficulty in binding to the metal. At the microscale, we observed an increase in bone contact with healing time and in presence of rougher surfaces, thanks to a non-destructive ultrasounds technique (QUS). Locally, the mechanical properties of the new bone tissue were lower than the mature tissue, suggesting an ongoing mineralisation and maturation of the tissue at the interface, especially affected by the presence of the implant.
The results and findings generated in this project were communicated via research conferences and have several potential socio-economic impacts. Data is relevant to the development of new implant design and surfaces to enhance bone integration. Results can also help develop new devices to be used during surgery to help the surgeon evaluate primary stability and the evolution of the osseointegration. This research adds knowledge onto the biomechanics of the bone-implant interface, to reach the clinical goal of maximising the life-time of implants, to ensure patients comfort and restoration of their daily life activity, particularly relevant nowadays in the aging but active population.