Cytotoxic effects of titanium particles and implantoplasty-treated surfaces exposed to bacterial biofilm

Objectives This study evaluated the cytotoxicity and metabolic activity of human fibroblasts and osteoblasts in the presence of metallic particles and on implant surfaces subjected to implantoplasty (IP), previously contaminated with a multispecies biofilm. It also assessed the potential for biofilm formation on these particles. Methods Titanium alloy (Ti6Al4V) particles were collected to assess their cytotoxic potential and interactions with human cells and bacterial biofilms. Cytotoxicity assays were performed using fibroblasts (HFF-1) and osteoblast-like cells (SaOs-2) through an indirect lactate dehydrogenase (LDH) assay. Biofilm formation was evaluated using Streptococcus oralis, Actinomyces viscosus, Veillonella parvula, and Porphyromonas gingivalis, quantified by colony-forming units (CFUs) and metabolic activity. Fibroblasts and osteoblasts were co-cultured with biofilm-contaminated particles for 2, 4, and 6 hours. Cell morphology and biofilm association were examined by phase-contrast microscopy, while metabolic activity was measured spectrophotometrically. Results IP-treated implants did not show significant cytotoxicity in HFF-1 or SaOs-2, with metabolic activities above 92% and cytotoxicity below 20%. Ti6Al4V particles, however, promoted Actinomyces viscosus and Veillonella parvula growth, increasing metabolic activity by 192.36% and 202.89%, and CFUs to 1.41 × 10⁹ and 7.10 × 10⁸, compared to 4.27 × 10⁶ and 2.33 × 10⁶ in controls. In multispecies biofilm, overall metabolic activity showed no significant differences (94.34% vs. 100%). Co-culture with infected particles drastically reduced fibroblast and osteoblast activity (< 25% and < 10%). In the absence of bacteria, fibroblasts reached 266.2% and osteoblasts 90% viability. Conclusions Contaminated particles from IP markedly reduced cytocompatibility of osteoblasts and fibroblasts and promoted specific bacterial growth, whereas IP-treated implant surfaces did not impair cell viability. Clinical relevance: Biofilm-contaminated titanium particles released during implantoplasty reduce cell viability and promote bacterial growth, unlike the treated implant surface.