UNDERLYING MECHANISMS AT THE BONE-SURFACE INTERFACE DURING REGENERATION

The goal of regenerative therapy around teeth and implants is to creat e a suitable environment in which the natural biological potential for functional regeneration of periodontal ligament and/or bone can be ma ximized. In order For the regenerative process to be successful, the f ollowing factors must be addressed: prevention of acute inflammation f rom bacteria. mechanical stability of the wound, creation and maintena nce of blood clot-filled spacer isolation of the regenerative space fr om undesirable competing tissue types, and the creation of a desirable surface chemistry, energy, roughness and microtopography that can dir ectly influence cellular response, ultimately affecting the rate and q uality of new tissue formation and, therefore, the regeneration proces s. This paper will review how surface characteristics (chemistry and r oughness) call affect cell response and local Factor production. To ev aluate the effect of surface chemistry on cell proliferation and diffe rentiation costochoadral chondrocytes were grown on standard tissue cu lture plastic dishes sputter-coated with different materials. The resu lts indicate that surface materials can elicit differential responses in cell metabolism and phenotypic expression in vitro. In a second stu dy, the effect of varying titanium surface roughnesses on osteoblast-l ike cell behavior was examined. Surface roughness was found to alter o steoblast proliferation. differentiation and matrix production in vitr o. In addition, production of PGE(2) and TGF beta by these cells was a lso shown to increase with increasing surface roughness, indicating th at substrate surface roughness also affects cytokine and growth factor production. The role of surface roughness in determining cellular res ponse was further explored by comparing the response of osteoblasts gr own on new and previously used surfaces. The results of these latter s tudies showed that cell proliferation, expression of differentiation m arkers and overall matrix production are trot altered when cells are g rown on used vs. virgin surfaces. This suggests the possibility that i mplants may be re-used, especially in the same patient. if they are ap propriately treated. In this context, it should also be noted that rou gher titanium surfaces may require more extensive cleaning procedures. From a global perspective, these studies provide some insight into ho w bone regeneration can be optimized in the presence of an implant or tooth root residing at the site of a bony defect. Since the new bone b eing produced, during regeneration, grows from a distal area toward th e implant or tooth root surface, it is hypothesized that the osteoblas ts growing on the surface of the implant may produce local factors tha t can affect the bone healing process distally. In short, it appears t hat the surface characteristics of an implant, particularly roughness, may direct tissue healing and, therefore, subsequent implant success in sites of regeneration by modulating osteoblast phenotypic expressio n.