The Future of Zirconia as an Alternative Biomaterial for Dental Implant Systems: A Comprehensive Evaluation of Its Biological, Mechanical, and Surface Properties

Dental implants are some of the most common and successful implantable devices with approximately 800,000 procedures being performed annually in the US alone. Titanium has served as the material of choice for dental implants since the discovery of its ability to undergo osseointegration with bone tissue. However, titanium dental implants can inevitably fail for a plethora of reasons including bacterial infection, excessive cyclic loading, failure to achieve or loss of implant stability, surgical trauma, and patient-related complications. Many failure modes associated with titanium dental implants stem from the material itself which can degrade via corrosion-mediated mechanisms in the oral cavity. Ultimately, this can result in the generation and accumulation of toxic metal ions and debris in the host tissue, triggering an inflammatory cascade leading to eventual implant loss. To avoid problems associated with metallic biomaterials, zirconium oxide, also known as zirconia, has been explored as an alternative material comprising the entire dental implant system. As a ceramic, zirconia exhibits properties including mechanical strength and osseointegration desirable for dental implant applications while also possessing immunity to corrosion, an esthetically appealing ivory white color, and lower plaque accumulation as opposed to titanium. Despite these advantages and promising results from short-term clinical data, the material behavior and response of zirconia to the same oral environmental factors including bacterial adhesion and mechanical fatigue that deteriorate titanium surfaces remain understudied. Therefore, the goal of this study was to systematically assess the biological and mechanical properties of zirconia as compared to titanium when subjected to oral environmental factors including bacterial biofilm and fatigue-inducing cyclic stresses and their impact on zirconia surface degradation. Based on preliminary data, it was hypothesized that the biological response to zirconia would be equivalent to or better than that on titanium while the mechanical performance of zirconia would become compromised depending on prior surface treatment and environmental conditions. To test these hypotheses, this project was divided into two aims. Aim 1 investigated the “race-for-the-surface” between mammalian host tissue cell attachment and oral bacterial biofilm growth in mono- and co-culture on zirconia to understand its effect on the outcome for soft tissue healing and osseointegration of zirconia. Afterward, aim 2 focused on characterization of potential degradation conditions of zirconia after exposure to biological milieu, namely bacterial adhesion and cyclic mechanical loading under individual and synergistic test conditions simulating mastication (chewing) and oral environment, to determine which factors accelerate degradation of zirconia surfaces. Accomplishing the aims of this proposal yielded new knowledge about the material performance of zirconia which can provide guidance on the design of future zirconia-based dental and related implant systems.