Surface characteristics of dental implants: A review

During the last decades, several changes of paradigm have modified our view on how biomaterials' surface characteristics influence the bioresponse. After becoming aware of the role of a certain microroughness for improved cellular contact and osseointegration of dental titanium implants, the likewise important role of surface energy and wettability was increasingly strengthened. Very recently, synergistic effects of nanoscaled topographical features and hydrophilicity at the implant/bone interface have been reported.

Questions arise about which surface roughness and wetting data are capable to predict the bioresponse and, ultimately, the clinical performance. Current methods and approaches applied for topographical, wetting and surface energetic analyses are highlighted. Current knowledge of possible mechanisms explaining the influence of roughness and hydrophilicity at the biological interface is presented.

Most marketed and experimental surfaces are based on commonly available additive or subtractive surface modifying methods such as blasting, etching or anodizing. Different height, spatial, hybrid and functional roughness parameters have been identified as possible candidates able to predict the outcome at hard and soft tissue interfaces. Likewise, hydrophilic implants have been proven to improve the initial blood contact, to support the wound healing and thereby accelerating the osseointegration.

There is clear relevance for the influence of topographical and wetting characteristics on a macromolecular and cellular level at endosseous implant/biosystem interfaces. However, we are still far away from designing sophisticated implant surfaces with the best possible, selective functionality for each specific tissue or cavity interface. Firstly, because our knowledge of the respective surface related reactions is at best fragmentary. Secondly, because manufacturing of multi-scaled complex surfaces including distinct nanotopographies, wetting properties, and stable cleanliness is still a technical challenge and far away from being reproducibly transferred to implant surfaces.