Effect of titanium on selected oral bacterial species in vitro

Titanium granules were tested for their antibacterial effect on strains of Streptococcus sanguis, Streptococcus mitis, Actinomyces naeslundii, Haemophilus parainfluenzae, Fusobacterium spp. and Prevotella intermedia in comparison with amalgam and two of its components, copper and tin. Glass beads were used as controls. The number of viable bacteria was estimated in samples exposed to the various materials for 1, 3, 6 and 24 h, respectively, and the viable counts were related to the baseline value. Titanium showed low antibacterial effect on the species tested. Copper and amalgam showed an expressed toxicity to all species and differed significantly from titanium and glass particles. Gram positive Streptococcus spp. and A. naeslundii showed a lower susceptibility to the metals than the Gram negative species. The antibacterial effect of copper and amalgam test particles on S. sanguis and P. intermedia was significantly decreased in the presence of serum. This study showed that some metals have a toxic effect in vitro on oral bacteria, a fact that may play a role in plaque formation when these materials are used for dental restorations. Titanium did not have a similar antibacterial effect.