Antimicrobial activity of silver nitrate against periodontal pathogens

Metal ions were evaluated as potential antimicrobial agents suitable for lo cal delivery in the oral cavity for the treatment of periodontitis, Silver nitrate. copper chloride, and zinc chloride were tested for antimicrobial a ctivity in in vitro killing assays conducted in phosphate buffered saline w ith a series of oral bacteria including gram-negative periodontal pathogens and gram-positive streptococci. Copper and zinc salts failed to exhibit st rong and consistent activity against periodontal pathogens. Zn contrast, si lver at a concentration of 0.5 mug/mL produced a 3 log(10) reduction in col ony forming units (CFU)/mL or greater against all periodontal pathogens tes ted including Porphyromonas gingivalis, Prevotella intermedia, Prevotella d enticola, Bacteroides forsythus, Fusobacterium vincentii. Campylobacter gra cilis, Campylobacter rectus, Eikenella corrodens, and Actinonbacillus actin omycetemcomitans. In comparison, substantially higher concentrations of sil ver nitrate failed to kill oral streptococci. A silver nitrate concentratio n of 25 mug/mL produced log(10) reductions in CFU/mL of 3.5-5 in killing as says performed in human serum against P. gingivalis, demonstrating the abil ity of silver to retain activity in a biological medium similar to that enc ountered in vivo in the periodontal pocket. These results identify silver n itrate, an antimicrobial that may possess advantages over traditional antib iotics, as a potential agent for controlled release local delivery in the o ral cavity for the treatment of periodontitis.