MacDonald et al. have shown that wettability, i.e., hydrophilic surfaces support cell interactions and biological fluids better than the hydrophobic surfaces. It has also been shown that roughening the titanium surface improves hydrophilicity. In addition, many authors have stated that rougher surfaces promote differentiation, growth and attachment of bone cells, and higher production of growth factors and augment mineralization. However, an in vitro study has demonstrated that osteoblastic cells attach, spread, and proliferate faster on smooth surfaces than on rough surfaces.

ALPL is a late osteogenic marker, which is essential for normal bone mineralization. ALPL-deficient osteoblasts fail to mineralize in culture. Considering that there was no significant difference in the relative ALPL activity in cells grown on two surfaces, it is unlikely that the surface property of the disks affected cell differentiation. This observation does not support the findings of Davies that BMPs, alkaline phosphatase and osteocalcin, the important markers of osteogenic differentiation and bone tissue formation, were express at higher levels on rougher surfaces. In addition to surface topography, surface chemistry is also a very strong variable. Therefore, the different surface chemistry of the implant materials used by Davies and our group might have contributed to this discrepancy. Regardless, there is a general agreement that roughening the implant surface greater than the degree seen by machining only leads to a stronger bone formation as shown in a systematic review.

Our data suggest that the increased cell number is the primary reason why cultures grown on 3M™ESPE™ MDI deposited more minerals in comparison to those grown on Ankylos®. Taken together, we reject the null hypothesis, since our data demonstrates that MDIs have a superior surface quality that promotes cell proliferation, facilitating osseointegration. However, this needs to be tested in vivo.

Our results demonstrate that both implant surfaces are conducive for osteoblastic cell attachment, proliferation, and mineralization. However, 3M™ESPE™ MDI surface shows more pronounced effects on cell proliferation, which may in turn facilitate better osseointegration by enhancing ECM mineralization. Our ongoing research will provide further information on how implant surfaces may affect cell behavior at the implant-tissue interface.