Short-term effects of povidone iodine and sodium fluoride therapy on plaque levels and microbiome diversity.

OBJECTIVES: The objective of this study is to evaluate the effect of short-term changes in the oral microbial ecology of dental plaque and plaque levels after topical treatment of a combination of 10% povidone iodine (PI) and 5% sodium fluoride varnish (FV). MATERIALS AND METHODS: A single group design intervention study on 12 pediatric patients, who underwent two baseline plaques samplings before the intervention, were enrolled in the study. A modified mixed dentition Silness-Löe plaque index score was used to assess plaque accumulation and microbial composition was assessed by amplicon sequencing analysis of the 16S rRNA V4 region. RESULTS: Dental plaque accumulation (P = 0.0424) was reduced after 1 week using PI/FV application. This reduction was not observed between the two double-baseline visits. 16S rRNA analysis showed that the single PI/FV therapy did not have dramatic shifts in the plaque microbiome community depicted by hierarchical cluster and principle component analysis. More subtle changes were found when analyzing the Shannon diversity index after the application of PI/FV vs two baselines prior to combination therapy. CONCLUSIONS: The bacteria within the dental biofilms showed resilience in maintaining the overall community diversity but reduced biofilm accumulation following PI/FV therapy. Repeated uses of PI/FV may augment plaque control during dental rehabilitation in children.

N-Acetyl-l-cysteine effects on multi-species oral biofilm formation and bacterial ecology.

UNLABELLED: Future therapies for the treatment of dental decay have to consider the importance of preserving bacterial ecology while reducing biofilm adherence to teeth. A multi-species plaque-derived (MSPD) biofilm model was used to assess how concentrations of N-acetyl-l-cysteine (NAC) (0, 0·1, 1, 10%) affected the growth of complex oral biofilms. Biofilms were grown (n = 96) for 24 h on hydroxyapatite discs in BMM media with 0·5% sucrose. Bacterial viability and biomass formation was examined on each disc using a microtitre plate reader. In addition, fluorescence microscopy and Scanning Electron Microscopy was used to qualitatively examine the effect of NAC on bacterial biofilm aggregation, extracellular components and bacterial morphology. The total biomass was significantly decreased after exposure of both 1% (from 0·48, with a 95% confidence interval of (0·44, 0·57) to 0·35, with confidence interval (0·31, 0·38)) and 10% NAC (0·14 with confidence interval (0·11, 0·17)). 16S rRNA amplicon sequencing analysis indicated that 1% NAC reduced biofilm adherence while preserving biofilm ecology. SIGNIFICANCE AND IMPACT OF THE STUDY: As a compound with a wide safety margin, N-acetyl-l-cysteine (NAC) has the potential to be used as a long term anti-plaque bacteriostatic agent for managing chronic dental decay without substantially altering biofilm's bacterial ecology. The potential anti-caries benefit of NAC is directly related to reducing the biofilm coverage which reduces the degree of acid generation and the amount of time that the surface is exposed to a lower pH.