Virulence modulation of Streptococcus mutans biofilms by metal ions released from orthodontic appliances.

OBJECTIVES: To evaluate the impact of metal ions commonly shed from orthodontic appliances on the virulence of Streptococcus mutans ATCC(R)25175 biofilms. MATERIALS AND METHODS: Biofilms were grown in the presence of Ni(2+), Fe(3+), Cr(3+), Co(2+), and a metal ion pool at concentrations similar to those released in saliva of orthodontic patients for 72 hours. Once mature, biofilms were treated for up to 12 hours with 5% glucose. RESULTS: Ions interfered with the growth of S mutans by reducing its biomass (Ni(2+), Fe(3+), Cr(3+)), raising its rates of sugar metabolism (Ni(2+), Fe(3+), Cr(3+)), and raising its secretion of lactate (Ni(2+), Fe(3+), Cr(3+), pool). CONCLUSION: The laboratory data presented here point to the possibility of virulence increase of S mutans by metal ions commonly released during orthodontic therapy.