Understanding the bone/implant interface

In order to better understand how implant surfaces modulate bone formation, we developed a cell culture model. Cells in the osteoblastic lineage (fetal rat calvarial cells [FRCs]: multipotent osteoprogenitor cells; human osteoblast-like MG63 cells: immature osteoblasts; mouse OCT-1 cells: mature osteoblasts; and mouse MLO-Y4 cells: osteocyte-like cells) were cultured on cpTi disks with either smooth (R(a) = 0.5 μm) or rough (R(a) = 5 μm) surfaces. The effects of surface roughness on proliferation, matrix synthesis, differentiation, local factor production, cell morphology, and response to 1,25-(OH)₂D₃ were determined. The interaction of surface roughness and surface chemistry in cell response was also examined by culturing MG63 cells on smooth and rough surfaces prepared by machining disks of cpTi or Ti-6Al-4V alloy (Ti-A). The results show that cell differentiation and local factor production are enhanced with increasing surface roughness, whereas proliferation is decreased. Response to 1,25-(OH)₂D₃ increases with increasing surface roughness. Both surface roughness and 1,25-(OH)₂D₃ mediate their effects through PGE₂, explaining, in part, the synergistic effects of these two variables. While surface chemistry plays a role in determining cell response, surface roughness may be a more important variable with respect to bone formation.