The antibacterial efficacy of silver diamine fluoride (SDF) is not modulated by potassium iodide (KI) supplements: A study on in-situ plaque biofilms using viability real-time PCR with propidium monoazide.

Nizam Abdullah,Lakshman Perera Samaranayake,Suharni Mohamad,Hien Chi Ngo,Koippallil Gopalakrishnan Aghila Rani,Normastura Abd Rahman,Farah Al Marzooq,Ove A Peters

doi:10.1371/journal.pone.0241519

Abstract

Silver diamine fluoride (SDF) is commonly used to arrest caries lesions, especially in early childhood caries. Recently, it was suggested that SDF can be combined with potassium iodide (KI) to minimize the discoloration of demineralized dentine associated with SDF application. However, the antibacterial efficacy of SDF alone or combined with KI on in-situ biofilm is unknown. Hence, we compared the anti-plaque biofilm efficacy of two different commercially available SDF solutions, with or without KI, using an in-situ biofilm, analysed using viability real-time PCR with propidium monoazide (PMA). Appliance-borne in-situ biofilm samples (n = 90) were grown for a period of 6 h in five healthy subjects who repeated the experiment on three separate occasions, using a validated, novel, intraoral device. The relative anti-biofilm efficacy of two SDF formulations; 38.0% Topamine (SDFT) and 31.3%, Riva Star (SDFR), KI alone, and KI in combination with SDFR (SDFR+KI) was compared. The experiments were performed by applying an optimized volume of the agents onto the biofilm for 1min, mimicking the standard clinical procedure. Afterwards the viability of the residual biofilm bacteria was quantified using viability real-time PCR with PMA, then the percentage of viable from total bacteria was calculated. Both SDF formulations (SDFT and SDFR) exhibited potent antibacterial activities against the in-situ biofilm; however, there was non-significant difference in their efficacy. KI alone did not demonstrate any antibacterial effect, and there was non-significant difference in the antibacterial efficacy of SDF alone compared to SDF with KI, (SDFT v SDFR/KI). Thus, we conclude that the antibacterial efficacy of SDF against plaque biofilms is not modulated by KI supplements. Viability real-time PCR with PMA was successfully used to analyze the viability of naturally grown oral biofilm; thus, the same method can be used to test the antimicrobial effect of other agents on oral biofilms in future research.

Highlights

Dental caries, in childhood, is a rampant, global health problem that affects millions [1]
To determine the lowest inhibitory volume of SDF formulations; 38.0% Topamine (SDFT) that significantly inhibits the plaque biofilm, each of a serial dilution (0.5, 1, 2, 5 and 10μl) of SDFT and negative control were applied onto 4 insitu biofilm samples
Biofilm treated with PMAxx dye is shown in the (Fig 2A and 2B), and it represents amplification from viable bacteria, while total bacteria including both viable and dead bacteria were amplified from samples not treated with PMAxx

Summary

Introduction

In childhood, is a rampant, global health problem that affects millions [1]. A variety of evidence-based approaches for caries prevention strategies have been reported [3]. These include pharmacologic and chemotherapeutic modalities to arrest and halt the caries process [4,5,6,7]. One of these noteworthy approaches that has gained recent popularity is the topical application of silver diamine fluoride (SDF), for early childhood caries (ECC) management [8,9]. Numerous clinical trials have demonstrated the effectiveness of SDF arresting both childhood and adult dental caries [1,4,10]

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