Effect of Propolis Nanoparticles against Enterococcus faecalis Biofilm in the Root Canal

Abstract

To determine the antibacterial effect of propolis nanoparticles (PNs) as an endodontic irrigant against Enterococcus faecalis biofilm inside the endodontic root canal system. Two-hundred-ten extracted human teeth were sectioned to obtain 6 mm of the middle third of the root. The root canal was enlarged to an internal diameter of 0.9 mm. The specimens were inoculated with E. faecalis for 21 days. Following this, specimens were randomly divided into seven groups, with 30 dentinal blocks in each group including: group I—saline; group II—propolis 100 µg/mL; group III—propolis 300 µg/mL; group IV—propolis nanoparticle 100 µg/mL; group V—propolis nanoparticle 300µg/mL; group VI—6% sodium hypochlorite; group VII—2% chlorhexidine. Dentin shavings were collected at 200 and 400 μm depths, and total numbers of CFUs were determined at the end of one, five, and ten minutes. The non-parametric Kruskal–Wallis and Mann–Whitney tests were used to compare the differences in reduction in CFUs between all groups, and probability values of p < 0.05 were set as the reference for statistically significant results. The antibacterial effect of PNs as an endodontic irrigant was also assessed against E. faecalis isolates from patients with failed root canal treatment. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were also performed after exposure to PNs. A Raman spectroscope, equipped with a Leica microscope and lenses with curve-fitting Raman software, was used for analysis. The molecular interactions between bioactive compounds of propolis (Pinocembrin, Kaempferol, and Quercetin) and the proteins Sortase A and β-galactosidase were also understood by computational molecular docking studies. PN300 was significantly more effective in reducing CFUs compared to all other groups (p < 0.05) except 6% NaOCl and 2% CHX (p > 0.05) at all time intervals and both depths. At five minutes, 6% NaOCl and 2% CHX were the most effective in reducing CFUs (p < 0.05). However, no significant difference was found between PN300, 6% NaOCl, and 2% CHX at 10 min (p > 0.05). SEM images also showed the maximum reduction in E. faecalis with PN300, 6% NaOCl, and 2% CHX at five and ten minutes. CLSM images showed the number of dead cells in dentin were highest with PN300 compared to PN100 and saline. There was a reduction in the 484 cm−1 band and an increase in the 870 cm−1 band in the PN300 group. The detailed observations of the docking poses of bioactive compounds and their interactions with key residues of the binding site in all the three docking protocols revealed that the interactions were consistent with reasonable docking and IFD docking scores. PN300 was equally as effective as 6% NaOCl and 2% CHX in reducing the E. faecalis biofilms.

Nanostructures as Targeted Therapeutics for Combating Oral Bacterial Diseases

“…A study investigated the antibacterial activity of propolis NPs (300 µg/mL) with an average size of 117.6 nm as a root canal irrigant against a root canal infected with E. faecalis biofilm. Results confirmed propolis NPs were equally effective as NaOCl (6%) and chlorhexidine (2%) in reducing the E. faecalis biofilm [35]. Interestingly, an in vitro study exhibited promising results on root canal surfaces treated with cationic antibacterial NPs such as ZnONP, CS/ZnONP, or CS-layer-ZnONP.…”

Propolis in Oral Healthcare: Antibacterial Activity of a Composite Resin Enriched With Brazilian Red Propolis

“…The use of propolis on technological development in dentistry and oral health has been frequent because it is a nontoxic raw material, with traditional use in natural medicine and that shows some known pharmacological activities as antimicrobial, anti-inflammatory and wound healing ( Koo et al, 2002 ; Freires et al, 2016 ; Oliveirados et al, 2017 ; de Carvalho Furtado et al, 2018 ; Bezerra et al, 2020 ; da silva Barboza et al, 2021 ). It has been reported in scientific literature the use of propolis on development of varnish ( De Luca et al, 2014 ; Neto et al, 2020 ), toothpaste ( Wiatrak et al, 2017 ; Peycheva et al, 2019 ), total-etching adhesive system ( Porto et al, 2021 ), cavity cleaning agent ( Celerino de Moraes Porto et al, 2018 ) and endodontic irrigant ( Parolia et al, 2021 ). The use of propolis was not found in the development of composite resins in scientific literature and in technological literature.…”

“…Propolis has been used in dentistry and oral healthcare due to its pharmacological properties and absence of toxicity ensured even by its use in traditional medicine ( Sforcin and Bankova, 2011 ; da silva Barboza et al, 2021 ; Zulhendri et al, 2021 ). Among the possibilities of propolis use in dentistry and oral healthcare are: in inhibition of adhesion and biofilm formation of Candida species in dentistry materials ( Bezerra et al, 2020 ), on development of endodontic irrigants ( Parolia et al, 2021 ), on development of varnishes ( De Luca et al, 2014 ), on development of total-etching adhesive system ( Porto et al, 2021 ), as cavity cleaning agent ( Celerino de Moraes Porto et al, 2018 ), on mouthwash development ( Santiago et al, 2018 ), on gel formulation development ( González-Serrano et al, 2021 ) and on oromuco-adhesive films development ( Arafa et al, 2018 ).…”

Studies Regarding the Antibacterial Effect of Plant Extracts Obtained from Epilobium parviflorum Schreb

“…Several studies have evaluated the antimicrobial efficacy of endodontic irrigants such as sodium hypochlorite (NaOCl), ethylene diamine tetra acetic acid (EDTA) and chlorhexidine (CHX) against E. faecalis biofilms [13]. In general, the aim of any disinfection strategy is to reduce the bacterial load to a subcritical level so that the patient's immune response allows healing by itself [14].…”

“…NaOCl can disrupt the biofilm, disintegrating the dental pulp which is a built-in organ, but it is a well-known irritant to periapical tissues. Therefore, identification of natural products in the disinfection of root canals can be interesting [13,15,16].…”