Manual polishing of Ti6Al4V produces minimal changes in oral bacterial adhesion and osteogenic cell behavior

Surface characteristics of titanium implants influence both bacterial colonization and host cell responses. However, the specific contribution of surface roughness within clinically relevant low-roughness ranges remains incompletely understood, particularly when isolated from other surface modifications. This study aimed to determine whether controlled variations in Ti6Al4V surface roughness Ra = 0.27-0.60 µm) induced by mechanical polishing are sufficient to influence early oral bacterial adhesion and osteoblast-like cell responses.

Ti6Al4V samples were either manually polished or left unpolished, and surface roughness parameters were quantified by stylus profilometry. Biological performance was assessed using the early colonizer Streptococcus gordonii, the late pathogen Porphyromonas gingivalis, and MG-63 osteoblast-like cells. Bacterial adhesion and biofilm formation were evaluated by ATP bioluminescence, scanning electron microscopy (SEM), and RT-qPCR targeting adhesion-related genes. Osteogenic responses were measured through Alizarin Red staining, SEM, and RT-qPCR of osteogenic markers.

Mechanical polishing reduced surface roughness from 0.60 to 0.27 µm without markedly altering peak profiles. For both bacterial species, adhesion levels, SEM biofilm morphology, and expression of adhesion-associated genes showed no significant differences between polished and unpolished surfaces. MG-63 cell adhesion, mineral deposition, and osteogenic gene expression were likewise unaffected by surface polishing.

Within the low-roughness range tested, manual mechanical polishing of Ti6Al4V had no significant effect on early bacterial adhesion or osteogenic cell responses. This study highlights that polishing alone is insufficient to modulate early biological interactions at the implant interface, underscoring the need of advanced surface modification strategies to enhance implant biofunctionality.