Because of their pluripotency, these cells have been considered as a type of mesenchymal stem cells. It has been shown that when treated with BMPs, these cells readily upregulate many key osteoblast markers including RUNX2, OSX, osteocalcin, and alkaline phosphatase (ALPL). In the current study, we used C2C12 cells that were treated with BMP-2 or stably transfected with a BMP-2 expression vector.

MC3T3-E1 cells have been extensively used in numerous cell culture experiments as a model for osteoblasts. Under differentiating conditions, e.g., in the presence of ascorbic acid and β-glycerol phosphate, these cells upregulate the osteogenic markers and, more importantly, promote the deposition of calcium phosphate minerals within and around the collagen-rich extracellular matrix (ECM). In comparison to BMP2-treated C2C12 cells, MC3T3-E1 cells are considered to be at a more advanced stage of differentiation towards the osteogenic lineage.

Our cell culture system was compatible with both cell types as evident by the outcome of various functional studies, which include cell adherence, synthesis of alkaline phosphatase, and mineralization of the ECM. However, there was a clear difference in the degree of biocompatibility between the two types of implant surfaces; the 3M™ESPE™ MDI showed higher cell numbers and increased deposition of calcium phosphate minerals in comparison to Ankylos®.

The MDI surface was treated with sandblasting and passivation with an oxidizing acid whereas Ankylos® surface was sandblasted and acid etched. The scanning electron microscopic images showed rougher surface in MDIs in comparison to Ankylos®. The blasting process causes a moderate roughness (1–2 micron) to the implants.

The surface chemistry and topography of biomaterials seem to play an important role in the success or failure upon placement in a biological environment.

It has been established that alterations on the surface topography enhance the bone implant contact and biomechanical interaction of the interface during early implantation periods.