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

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 (SDF T ) and 31.3%, Riva Star (SDF R ), KI alone, and KI in combination with SDF R (SDF R+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 (SDF T and SDF R ) 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, (SDF T v SDF R/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.

The effect of the combined use of silver diamine fluoride and potassium iodide in disrupting the plaque biofilm microbiome and alleviating tooth discoloration: A systematic review

“…Abdullah et al [ 59 ] tested the antimicrobial efficacy of SDF, KI, and SDF/KI on in-situ biofilms. Five participants were instructed to wear a maxillary intraoral appliance, each having six removable wells for biofilm collection, which were removed after 6 hours.…”

“…It is unclear whether the sample size in those studies was sufficiently large to capture the clinical difference of application of KI post-SDF on tooth color. The studies by Karched et al [ 60 ] and Abdullah et al [ 59 ] were also limited in their sample size, each having only five participants.…”

“…While it has previously been hypothesized that application of KI may reduce the antimicrobial efficacy of SDF by reducing the concentration of silver ions [ 47 ], studies reviewed here generally indicate that there is no significant difference between the antimicrobial actions of SDF in isolation, and SDF/KI combination, indicating that KI does not affect the microbicidal action of SDF. Thus, three studies [ 59 , 62 , 64 ] revealed that KI does not exhibit any antimicrobial activity, while one study [ 65 ] showed some degree of antimicrobial action of KI.…”

“…A single in-vitro study has thus far used a natural in-situ biofilm [ 59 ] to evaluate SDF/KI’s anti-cariogenic effect, although the biofilm was collected from caries-free individuals. It is known that biofilms of carious lesions have a different composition compared to healthy sites due to a shift towards acidophilic and aciduric bacterial species [ 77 ].…”

“…However, only routine microbiological culture assessments were used, hence enabling the analysis of cultivable bacteria only. A major shortcoming of the studies of Abdullah et al [ 59 ] and Karched et al [ 60 ] is the small sample size of less than ten individuals in each study. Since the composition of plaque biofilm varies within individuals and between individuals, a larger sample size is required to illuminate the true in-vivo antimicrobial effect of SDF/KI.…”