Mechanical regulation of bone formation and resorption around implants in a mouse model of osteopenic bone.

Although mechanical stimulation is considered a promising approach to accelerate implant integration, our understanding of load-driven bone formation and resorption around implants is still limited. This lack of knowledge may delay the development of effective loading protocols to prevent implant loosening, especially in osteoporosis. In healthy bone, formation and resorption are mechanoregulated processes. In the intricate context of peri-implant bone regeneration, it is not clear whether bone (re) modelling can still be load-driven. Here, we investigated the mechanical control of peri-implant bone (re) modelling with a well-controlled mechano-biological experiment. We applied cyclic mechanical loading after implant insertion in tail vertebrae of oestrogen depleted mice and we monitored peri-implant bone response by in vivo micro-CT. Experimental data were combined with micro-finite element simulations to estimate local tissue strains in (re) modelling locations. We demonstrated that a substantial increase in bone mass around the implant could be obtained by loading the entire bone. This augmentation could be attributed to a large reduction in bone resorption rather than to an increase in bone formation. We also showed that following implantation, mechanical regulation of bone (re) modelling was transiently lost. Our findings should help to clarify the role of mechanical stimulation on the maintenance of peri-implant bone mass.