Development of Multifunctional Polyphenolic Coatings for Improved Peri-Implant Healing

Abstract

Bone-anchored implants, such as dental implants, are implants with a direct anchorage between the implant surface and the surrounding tissues. To fully function, these implants are dependent on the foreign body reactions, which determines how cells react to the surface. For a firm anchorage, bone cells need to adhere to the implant surface and form new bone tissue fixing the implant into the existing bone. However, the function and long-term stability of these implants can be jeopardized by the presence of bacteria. Dental implants are particularly vulnerable since they extend into the oral cavity and face a variety of different microbes. Microbial infections around implants are often very persistent and difficult to treat. With the increasing threat of antibiotic resistant bacteria and fungi, current treatment strategies for infected implants are likely to be even less effective in the future. Florian's PhD project focused on tackling microbial infections and inflammation around implant surfaces using plant polyphenols, a group of antioxidant and antibacterial compounds that are found in several plant-based foods, such as tea, chocolate and wine. The goal is to prevent painful and disturbing replacement surgeries, which are often necessary to remove the affected implant and to clear the infection in the surrounding tissues. In contrast to common approaches to alter the bone tissue integration, the focus was put on creating a close seal between the gingival soft tissue and the implant surface to prevent bacteria from entering peri-implant pockets. Therefore, thin polyphenolic coatings were developed, which change the surface properties of titanium dental implant surfaces and release active molecules into the surrounding tissue. Studies of the assembly mechanism of the coatings in different chemical environments led to the establishment of a novel coating process using tannic acid and silicic acid. Thereafter, an evaluation of the inflammatory reaction showed that the developed coatings alter the protein adsorption, which reduced the activation of the immune response. Further, the antioxidant properties of polyphenolic coatings lowered the oxidative stress in gingival fibroblasts. This is expected to lead to a faster relief of the inflammation after surgery and increase the patient comfort. Contrary to many reports of the antimicrobial properties of polyphenolic molecules, fungal colonisation could not be prevented. These antimicrobial properties are, however, highly dependent on the type of bacteria or fungi and further efforts are required to obtain infection-resistant implant surfaces.