THE ROLE OF IMPLANT SURFACE CHARACTERISTICS IN THE HEALING OF BONE

The surface of an implant determines its ultimate ability to integrate into the surrounding tissue. The composite effect of surface energy, composition, roughness, and topography plays a major role during the i nitial phases of the biological response to the implant, such as prote in adsorption and cellular adherence, as well as during the later and more chronic phases of the response. For bone, the successful incorpor ation (and hence rigid fixation) of an alloplastic material within the surrounding bony bed is called osteointegration. The exact surface ch aracteristics necessary for optimal osteointegration, however, remain to be elucidated. This review will focus on how surface characteristic s, such as composition and roughness, affect cellular response to an i mplant material. Data from two different culture systems suggest that these characteristics play a significant role in the recruitment and m aturation of cells along relevant differentiation pathways. In the cas e of osteointegration, if the implant surface is inappropriate or less than optimal, cells will be unable to produce the appropriate complem ent of autocrine and paracrine factors required for adequate stimulati on of osteogenesis at the implant site. In contrast, if the surface is appropriate, cells al the implant surface will stimulate interactions between cells at the surface and those in distal tissues. This, in tu rn, will initiate a timely sequence of events which include cell proli feration, differentiation, matrix synthesis, and local factor producti on, thereby resulting in the successful incorporation of the implant i nto the surrounding bony tissue.