Organo-chemical modification of titanium alloy and zirconia surfaces to achieve tight gingival adhesion (GingiSeal)

• Applicants: Professor Dr.-Ing. Horst Fischer; Professor Dr. Stefan Wolfart
• Subject Area: Dentistry, Oral Surgery ; Biomaterials
• Term: from 2019 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 418670251

Oral rehabilitation using dental implants provides several options for treating patients with tooth loss, thereby offering them better quality of life. In addition to the integration of the implant into the alveolar bone, the attachment of the surrounding soft tissue to the material surface of the implant's supraconstruction (abutment) plays an essential role. However, the peri-implant mucosa exhibits significant differences compared to that of a natural tooth. The natural ”seal” at the interface between mucosa and tooth, which is ensured by the so-called junctional epithelium, is missing in an implant-supported restoration. Thus, bacteria can easier penetrate into the interface and can subsequently provoke pathological processes at the interface between implant and alveolar bone. In the first phase of the research project GingiSeal, the abutment materials zirconia (Y-TZP) and the established titanium alloy (Ti6Al4V) were modified by self-assembled monolayers (SAM) and further functionalized with proteins of the extracellular matrix (ECM) with the help of a suitable cross linker. In-vitro experiments with human gingival fibroblasts have shown significantly enhanced cell adhesion, cell proliferation, cell spreading, and integrin expression on the organo-chemically modified surfaces compared to untreated surfaces. In addition to the mimicry of oral conditions in-vitro, which are tasks still to be completed within the first phase of the project, important further questions have arisen. In the second phase of the project, the exact adhesion mechanisms between the functionalized abutment surfaces and gingival epithelial cells is of importance. Furthermore, mass spectrometry will be used to determine how the crosslinker interacts with the proteins of the ECM. Furthermore, the bacterial DNA content on the differently modified surfaces will be determined via qPCR. In addition, a three-dimensional in vitro model of a gingival mucosa will be fabricated using bioprinting technology. A biofilm consisting of various bacteria strains is then applied to the interface between the modified/unmodified abutment material and the bioprinted mucosa substitute. The 3D model will be used to determine whether increased adhesion of the printed soft tissue to the modified abutment materials is impermeable to bacteria. For this purpose, live-dead staining will be performed, cytokine release from the printed gingival mucosa will be investigated by ELISA, and biofilm-induced cytotoxicity will be analyzed using a lactate dehydrogenase (LDH) assay. If the project progresses positively, the findings from the experiments with the bioprinted in vitro 3D model will form the foundation for a clinical pilot study envisaged after the two years.

• DFG Programme: Research Grants