Tissue compatibility to different surfaces of dental implants: in vitro studies

Factors affecting cell and tissue responses to dental implant biomaterials are typically characterized as spatial and temporal. Spatially, a dental implant must form an interface with both bone tissue for the development and maintenance of biomechanical stability and soft tissue for the prevention of microbial infection that can lead to peri-implantitis. There is a developing body of knowledge regarding the reactions of host tissues to implant materials, although the specific mechanisms by which these responses are not yet totally understood. From a temporal standpoint, there seems to be a sequence of events after placement of an implant that involves cell attachment, migration, and differentiation. These early wound healing responses appear to be influenced significantly by the properties of the underlying implant surface. Our laboratory has focused its attention on the first cellular event, i.e., cell attachment at the interface between bone and the implant surface. An in vitro primary cell model has been developed and used to study the influence of materials selection (Ti, Ti-6Al-4V, hydroxyapatite-like coatings), surface topography (smooth to rough), and surface chemistry (as a function of preparation treatments) on the cellular events that occur at implant surfaces. Currently, we believe that both uncoated Ti implants and those fabricated with calcium phosphate or hydroxyapatite-like coatings are capable of supporting initial cellular attachment, although they probably occur by different and incompletely understood mechanisms. The initial interactions of the host tissues with the implant surface remain key for long-term acceptance and must be understood if new generations of tissue engineered devices are to be developed and used clinically.