Principles of Cell Behavior on Titanium Surfaces and Their Application to Implanted Devices

Abstract

The term “tissue engineering” has become a catchall phrase that generally describes the use of materials that are specifically designed to restore, maintain or improve the function of human tissues or, as in the case of dental implants, to replace them. The materials may be combined with cells cultured outside the body or implanted directly. Tissue engineering is an interdisciplinary field that in theory should apply the principles of biology and engineering to the solution of the thorny problems of interfacing artificial devices to living tissues. In fact however, while the engineering and material principles are well known, the more subtle biological principles are often unknown or obscure. The net result is that, as noted in Dr. Buddy Ratner’s Presidential address to the American Biomaterials Society in 1996, current biomaterials have been developed as the result of trial and error optimization rather than specific design [1]. Yet to design materials to achieve specific responses from tissues is a difficult prospect if the biological principles governing cell interaction with implant materials are not established or understood. The consequence is that the engineering part of the tissue engineering equation has taken precedence. For example, it was recognized that the mechanical retention of dental implants might be improved by the incorporation of macroscopic features such as screw threads or vents for bone ingrowth, or micro features such as using sandblasted or plasma-sprayed surfaces. Many implant surfaces varying in macroscopic and microscopic topography were developed and some of these have been successful [2], but their design generally did not proceed from a knowledge of cell response to surfaces.