On implant surfaces: a review of current knowledge and opinions

The aims of the present review are (1) to identify essential surface parameters; (2) to present an overview of surface characteristics at the micrometer and nanometer levels of resolution relevant for the four most popular oral implant systems; (3) to discuss potential advantages of nanoroughness, hydrophilicity, and biochemical bonding; and (4) to suggest a hypothetical common mechanism behind strong bone responses to novel implant surfaces from different commercial companies. Oral implants from four major companies varied in average surface roughness (Sa) from 0.3 to 1.78 microm and in the developed surface area ratio (Sdr) from 24% to 143%, with the smoothest implants originating from Biomet 3i and the roughest from Institut Straumann. The original Branemark turned, machined surface had an Sa of 0.9 microm and an Sdr of 34%, making it clearly rougher than the smoothest implants examined. When evaluated for nanometer roughness, there was a substantial variation in Sa in the different implants from the four major companies. Novel implants from Biomet 3i, AstraTech, and Straumann differed from their respective predecessors in microroughness, physicochemical properties, and nano_roughness. When examined with scanning electron microscopy at high magnification, it was noted that these novel implant surfaces all had particular nanoroughness structures that were not present in their respective predecessors; this finding was suggested as a possible common mechanism behind the demonstrated stronger bone responses to these implants compared to adequate controls.