Antimicrobial Activity of a Colloidal AgNP Suspension Demonstrated In Vitro against Monoculture Biofilms: Toward a Novel Tooth Disinfectant for Treating Dental Caries.

A novel silver nanoparticle (AgNP) formulation was developed as a targeted application for the disinfection of carious dentine. Silver nitrate (AgNO3) was chemically reduced using sodium borohydrate (NaBH4) in the presence of sodium dodecyl sulfate (SDS) to form micelle aggregate structures containing monodisperse 6.7- to 9.2-nm stabilized AgNPs. AgNPs were characterized by measurement of electrical conductivity and dynamic light scattering, scanning electron microscopy, transmission electron microscopy, and inductively coupled plasma mass spectrometry. Antimicrobial activity of AgNPs was tested against planktonic cultures of representative gram-positive and gram-negative oral bacteria using well diffusion assays on tryptic soy broth media and monoculture biofilms grown with brain heart infusion ± sucrose anaerobically at 37°C on microtiter plates. Biofilm mass was measured by crystal violet assay. Effects were compared to silver diamine fluoride and chlorhexidine (negative controls) and 70% isopropanol (positive control) exposed cultures. In the presence of AgNPs, triplicate testing against Streptococcus gordonii DL1, C219, G102, and ATCC10558 strains; Streptococcus mutans UA159; Streptococcus mitis I18; and Enterococcus faecalis JH22 for planktonic bacteria, the minimum inhibitory concentrations were as low as 7.6 µg mL-1 and the minimum bacteriocidal concentrations as low as 19.2 µg mL-1 silver concentration. Microplate readings detecting crystal violet light absorption at 590 nm showed statistically significant differences between AgNP-exposed biofilms and where no antimicrobial agents were used. The presence of sucrose did not influence the sensitivity of any of the bacteria. By preventing in vitro biofilm formation for several Streptococcus spp. and E. faecalis, this AgNP formulation demonstrates potential for clinical application inhibiting biofilms.

An in vivo study of the plaque control efficacy of Persica: a commercially available herbal mouthwash containing extracts of Salvadora persica.

AIM: This study compared the oral health efficacy of Persica mouthwash (containing an extract of Salvadora persica) with that of a placebo. DESIGN: In a double-blind, cross-over trial, participants were randomly allocated to use either the Persica mouthwash or a placebo for a three-week period. Plaque accumulation, gingival bleeding and the salivary concentrations of mutans streptococci (MS) were measured before and immediately following the experimental period. After an eight-week 'washout' period, the study was repeated with participants using the alternative mouthwash. PARTICIPANTS: Twenty-eight healthy students (aged between 18 and 42 years) volunteered to take part in this investigation. RESULTS: Compared with the pre-treatment values, both placebo and experimental groups demonstrated significantly reduced gingival bleeding (p < 0.01). Plaque scores were not significantly reduced following use of either Persica or the placebo. However, the use of Persica, but not the placebo, resulted in significant reduction in the carriage of MS (p < 0.05). CONCLUSION: Use of Persica mouthwash resulted in improved gingival health and lower carriage rate of cariogenic bacteria when compared with the pre-treatment values. The placebo (vehicle control) also improved gingival health significantly. Neither the Persica nor the placebo reduced the accumulation of dental plaque.