Laser Microtexturing of Implant Surfaces for Enhanced Tissue Integration

Dental and orthopaedic implants rely on combinations of bone and soft tissue integration for mechanical support. While polished metal surfaces have been shown to encourage fibrous tissue encapsulation, roughened surfaces encourage bone integration. It is an accepted practice to roughen or texture regions of implants to encourage bone integration and produce smooth regions to promote soft tissue integration. We have developed a laser microtexturing technique that can be used to produce precision microtextured surfaces. Several techniques are commonly used to produce texturing. These include machining, surface blasting, acid etching, and plasma spraying techniques. These techniques produce a range of surface microstructures of varying sizes and shapes, from sub-micron to more than 50 /an in size. None of these techniques allow micron-tolerance control of microstructure size and placement, and blast texturing, which is usually produced using glass bead for matte finishes and alumina grit for surface roughening, can cause significant surface contamination with embedded fragments of blast medium. Newer blast methods use resorbable or soluble blast medium to avoid this problem. Blasting is often followed by acid etching, which removes the embedded material and produces a fine microtexture of its own. We have developed a computer-controlled Excimer laser micromachining method for producing surface microtexturing on metal implants. This method produces clean, controlled microstructural patterns in defined regions, with micron resolution and reproducibility. We have tested bone response to these surfaces in three animal models, an implantable chamber system, an intramedullary rod model, and a dental implant model. The results indicate that controlled microstructural patterns such as microgrooves in an 8-12 micron size range suppress fibrous encapsulation, microintegrate directly with bone, and control regional integration of bone and soft tissue. These surfaces organize attached cells, causing production of oriented extracellular matrix. The end result is surface microstructural control of the organization of attached tissue. We have applied these surfaces to dental implants and are conducting human clinical trials. We are also developing surfaces for guided tissue regeneration membranes, transcutaneous prosthetic fixation systems, and other biomedical applications. This project was supported by grants from the Orthopaedic Research and Education Foundation, the New Jersey Center for Biomaterials, The New Jersey Commission on Science and Technology, NSF grant DMI-9304020, and NIH grant 1R41 NS351551-01 to Orthogen Corporation. Dental implants were produced in collaboration with BioLok International.