Abstract
Nanoscale surface modifications influence peri-implant cell fate decisions and implant loading generates local tissue deformation, both of which will invariably impact bone healing. The objective of this study is to determine how loading affects healing around implants with nanotopography. Implants with a nanoporous surface were placed in over-sized osteotomies in rat tibiae and held stable by a system that permits controlled loading. Three regimens were applied: (a) no loading, (b) one daily loading session with a force of 1.5N, and (c) two such daily sessions. At 7 days post implantation, animals were sacrificed for histomorphometric and DNA microarray analyses. Implants subjected to no loading or only one daily loading session achieved high bone-implant contact (BIC), bone-implant distance (BID) and bone formation area near the implant (BFAt) values, while those subjected to two daily loading sessions showed less BFAt and BIC and more BID. Gene expression profiles differed between all groups mainly in unidentified genes, and no modulation of genes associated with inflammatory pathways was detected. These results indicate that implants with nanotopography can achieve a high level of bone formation even under micromotion and limit the inflammatory response to the implant surface.
Highlights
Surface modification strategies at all scales have been proposed for improving the osseointegration of implants, in situations where bone quality is an issue or immediate loading is clinically indicated
In previous studies using the loading system in mice and in rats [20,24], we have demonstrated that multiple daily loading sessions create interfacial stress and strain conditions around machined-surface, screw-shaped implants that can significantly disrupt bone healing and cause fibrous tissue formation
In the present study using similar screw-shaped implants with nanotopography, we show that doubling the number of loading sessions induces major changes at the bone–implant interface but to a lesser degree than similar implants with a machined surface
Summary
Surface modification strategies at all scales have been proposed for improving the osseointegration of implants, in situations where bone quality is an issue or immediate loading is clinically indicated. Reports by several groups [12,13,14,15,16,17] have shown the efficiency of nanoscale surface modification of implants placed in the complex environment of the body. These reports dealt with unloaded implants and comparative information on how nanotopographic implants perform under ‘acceptable’ and ‘detrimental’ loading conditions is still lacking. When implants are placed in function, the imparted forces will cause some degree of micromotion, which generates local strain and stress conditions that deform interfacial tissues, which can influence the bone healing response [18,19]
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