• ANTIMICROBIAL EFFECTS IN VITRO OF SILVER DIAMINE FLUORIDE AGAINST SELECTED HUMAN RED AND ORANGE COMPLEX PERIODONTAL PATHOGENS

      Rams, Thomas E.; Whitaker, Eugene J.; Page, Lawrence (Temple University. Libraries, 2019)
      Objectives: Silver diamine fluoride is approved by the United States Food and Drug Administration for intraoral human treatment of tooth hypersensitivity, and it has also been employed world-wide as an emerging method to arrest tooth decay. A 38% silver diamine fluoride formulation, comprised of 25% silver, 5% fluoride, and 8% ammonia as a solvent, is commercially available in the United States. One of the main mechanisms underlying the dental caries arrest potential of silver diamine fluoride is the silver component, which exerts pronounced antimicrobial activity against cariogenic bacteria. Interestingly, studies initiated in the late 1990s demonstrated marked susceptibility of periodontal bacterial pathogens to silver nitrate. However, efforts to develop silver-based, slow-release biodegradable wafers for subgingival placement into periodontal pockets were not commercially successful. At present, no commercial products are available which employ silver ions to combat periodontal bacterial pathogens in periodontal disease treatment. It is not known whether the 38% silver diamine fluoride product commercially available in the United States possesses antimicrobial activity against periodontal bacterial pathogens, and potentially, have application in periodontal therapeutic regimens. As a result, the objective of this study was to test the in vitro antimicrobial effects of silver diamine fluoride on freshly-isolated red and orange complex periodontal pathogens from severe human periodontitis lesions. Methods: Paper point subgingival biofilm samples from 24 adults with severe periodontitis that were to be discarded after microbiological analysis at the Temple University School of Dentistry Oral Microbiology Testing Service Laboratory were secondarily employed in this study. Dilution aliquots from each subgingival specimen were mixed with either 38% or 19% silver diamine fluoride, inoculated onto enriched Brucella blood agar plates, and incubated anaerobically for 7 days at 37°C. Bacterial species growing subsequent to the silver diamine fluoride exposure were considered to be resistant to that concentration of silver diamine fluoride. Total viable counts in silver diamine fluoride-exposed subgingival specimens were quantitated, and established phenotypic criteria employed to identify the following red and orange complex periodontal pathogens: Porphyromonas gingivalis, Tannerella forsythia, Prevotella intermedia/nigrescens, Parvimonas micra, Campylobacter rectus, Fusobacterium nucleatum group species, and Streptococcus constellatus. Other cultivable isolates recovered from silver diamine fluoride-exposed subgingival specimens were identified using matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF) mass spectrometry and Bruker MALDI Biotyper analytic software. Subgingival sample dilution aliquots not exposed to silver diamine fluoride were similarly processed as controls for comparison with silver diamine fluoride-exposed specimens Paired t-tests compared mean total subgingival viable counts, and mean total subgingival proportions of the evaluated anaerobic red and orange complex periodontal pathogens per patient, between subgingival biofilm samples exposed and not exposed in vitro to 38% or 19% silver diamine fluoride, with a P-value of < 0.05 required for statistical significance. Results: Subgingival specimens exposed in vitro to either 38% or 19% silver diamine fluoride yielded significantly lower total subgingival viable counts per patient than those not exposed to silver diamine fluoride (P < 0.001, paired t-test), with no statistically significant differences found between 38% and 19% silver diamine fluoride exposures (P = 0.370, paired t-test). All evaluated red and orange complex periodontal pathogens were suppressed below detection levels in 21 (87.5%) of subgingival samples after in vitro exposure to 38% silver diamine fluoride. Three other patient specimens treated with 38% silver diamine fluoride each had persistence of P. micra. Similarly, 21 (87.5%) of subgingival specimens also were culture-negative for red and orange complex periodontal pathogens after 19% silver diamine fluoride exposure, with two other patient samples showing persistence of P. micra, and a third sample persistence of S. constellatus. Total subgingival proportions of red and orange complex periodontal pathogens averaged 0.6% per patient in subgingival specimens exposed in vitro to 38% silver diamine fluoride, and 0.5% per patient in those exposed to 19% silver diamine fluoride, which were both significantly lower than 25.9% mean proportions detected in subgingival biofilms not exposed to silver diamine fluoride (P < 0.0001, paired t-test). No statistically significant differences were found between 38% and 19% silver diamine fluoride relative to suppression of total red and orange complex periodontal pathogen proportions (P = 0.345, paired t-test). Various Streptococcus species, particularly Streptococcus oralis, were the most frequently recovered microorganisms in subgingival biofilm specimens after exposure to both 38% and 19% silver diamine fluoride, indicative of their in vitro resistance to silver diamine fluoride. Conclusions: Silver diamine fluoride demonstrated substantial antimicrobial activity against fresh clinical isolates of red and orange complex periodontal pathogens, and total viable counts, in subgingival biofilm specimens from severe periodontitis patients, with no statistically significant differences found between silver diamine fluoride concentrations of 38% and 19%. The dramatic in vitro suppression of red and orange complex periodontal pathogens in subgingival biofilm specimens by silver diamine fluoride, along with its selection of silver diamine fluoride-resistant species of Streptococcus that are associated with periodontal health, suggests a new therapeutic use for silver diamine fluoride in the management of human periodontal infections.