TiN-coated abutment microtopographies promote gingival fibroblast-mediated soft-tissue sealing and reduce biofilm formation in vitro

The establishment of a stable peri-implant soft-tissue seal is critical for the long-term success of dental implants and is strongly influenced by abutment surface properties. This in vitro study systematically evaluated the combined effects of micro-topography and titanium nitride (TiN) coating on human gingival fibroblast (HGF) behavior and bacterial adhesion. Methods: Six TiN-coated surfaces with distinct micro-thread geometries—machined (M, M1, M2) and double-acid-etched (T, T1, T2)—were characterized for surface topography and wettability and assessed for HGF viability, adhesion, and mechanotransduction, alongside antibiofilm activity. Results: All surfaces were biocompatible and moderately hydrophilic. Among all conditions, the T1 surface (50 × 5 μm thread geometry with etching) demonstrated superior HGF viability and adhesion, confirmed by MTT, SEM, and immunofluorescence analyses. This surface may also enhance mechanotransduction, as suggested by increased activation of FAK, YAP, and TAZ and reduced levels of their phosphorylated forms. Additionally, TiN-coated surfaces significantly reduced biofilm formation across the bacterial species tested compared with uncoated surfaces, with T1 showing a marked reduction relative to M1 for most species. Conclusions: Collectively, these findings identify the T1 micro-topography as an optimal design for promoting HGF-mediated soft-tissue integration while limiting bacterial colonization, supporting its potential application in novel transmucosal abutments.