Future directions in dental implant materials research

There are literally thousands of published accounts of the performance of medical and dental implants that employ metals and ceramics for which little or no materials characterization has been accomplished. Before the current decade, the level of sophistication of research was such that many materials did not even receive postprocessing analysis of the "bulk" composition, a minimal characterization we now realize is inadequate. Instead, research focused upon mechanical properties and corrosion studies at the macroscopic level, along with the search for a mythical property called biocompatibility. There were sound scientific reasons for this focus. The state of knowledge of the biology associated with implants did not allow the creation of experiments at the cellular or molecular level. Experiments progressed slowly from clinical observations to histologic observations, from which inferences of past events were made. The complete characterization of implant surfaces was virtually impossible because the analytical instrumentation and the associated understanding of physical and chemical processes occurring at surfaces were lacking. Materials were selected because of their apparently inert state, as defined by corrosion studies and histological examination of implant specimens. The focus in the 1970s was on micron-sized surface features. Porosity, grooves, textures, etc., were emphasized along with the macroscopic design features. A proliferation of designs, many of which were based on inspiration, rather than experimentation and optimization, were brought to the marketplace. Perhaps the exception to this lack of surface analysis was the development of the surface-active biomaterials based on calcium phosphates, the tricalcium phosphates, hydroxylapatites, and surface active glasses. Unfortunately, investigators did not pursue the same analyses for the "inert" materials.(ABSTRACT TRUNCATED AT 250 WORDS)