Quaternary ammonium silane (k21) based intracanal medicament triggers biofilm destruction

Multispecies oral biofilm and identification of components as treatment target

Endodontic infections involve a multispecies biofilm, making it difficult to choose an antimicrobial treatment. Characteristics such as the pathogens involved and number of microorganisms, nutrients, material surface to develop the biofilm, flow and oxygenation conditions are important for biofilm development using in vitro models.

OBJECTIVE

To develop a standardized biofilm model, which replicates the main features (chemical, microbiological, and topographical) of an infected root canal tooth to detect components as treatment target.

DESIGN

Clinical strains of Enterococcus faecalis, Candida albicans, and Actinomyces israelii were isolated, and a multispecies biofilm was developed using continuous laminar flow reactors under anaerobic conditions in human dental roots. The microbiological composition was determined by counting colony-forming units and scanning electron microscope micrographs. In addition, the chemical composition of the exopolymeric matrix was determined by vibrational Raman spectroscopy and liquid chromatography of biofilm supernatant treated with enzyme.

RESULTS

E. faecalis turned out to be the main microorganism in mature biofilm, this was related to the presence of β-galactosidase detected by vibrational Raman spectroscopy. After the enzymatic treatment of the extracellular polymeric substance, the presence of mannose and glucose was established.

CONCLUSIONS

The present work contributes to better understanding of standard conditions to develop a multispecies biofilm in human dental roots, which could have an impact on the generation of new root canal disinfection techniques in endodontic pathologies.

Effect of a novel quaternary ammonium silane based cavity cleanser FiteBac 2% K21 QAS in comparison with other cavity disinfectants on the bond strength of resin-modified glass ionomer cement

Background

The application of cavity cleansers for cavity disinfection can be a crucial step in the longevity of restorations. The objective of the present study was to compare the effect of the application of a new quaternary ammonium silane (QAS)-based cavity cleanser (2% K21 QAS), with other commercially available cavity disinfectants on the bond strength of resin-modified glass ionomer cement (RMGIC).

Materials and Methods

The buccal surfaces of 40 extracted premolars were trimmed to obtain a flat dentinal surface and were randomly divided into four experimental groups depending on the cavity cleansers used before restoration. Group 1: 2% chlorhexidine (CHX), Group 2: QAS (FiteBac 2% K21 QAS), Group 3: silver diamine fluoride-potassium iodide (Riva Star, SDF-KI), and Group 4: 3% hydrogen peroxide (H2O2). Then, a predetermined dimension of RMGIC restoration was bonded to the treated dentin surfaces. Following this, each sample was tested for shear bond strength (SBS) using a universal testing machine at a crosshead speed of 0.5 mm/min.

Results

Among the experimental groups, SDF-KI has shown the highest mean SBS, followed by 2% K21 QAS, and 2% CHX, which have shown almost comparable results. The 3% H2O2 group has shown the lowest values.

Conclusion

According to the results of the present study, 2% K21 QAS has the potential to be used as an effective cavity cleanser before the placement of RMGIC restorations. Since its application does not affect the bond strength of restoration, it can be successfully used as an alternative to CHX and SDF-KI.

The effectiveness of newly synthesized quaternary ammonium salts differing in chain length and type of counterion against priority human pathogens

Quaternary ammonium salts (QAS) commonly occur as active substances in disinfectants. QAS have the important property of coating abiotic surfaces, which prevents adhesion of microorganisms, thus inhibiting biofilm formation. In this study, a group of nine monomeric QAS, differing in the structure and length of the aliphatic chain (C12, C14, C16) and the counterion (methylcarbonate, acetate, bromide), were investigated. The study included an analysis of their action against planktonic forms as well as bacterial biofilms. The compounds were tested for their anti-adhesion properties on stainless steel, polystyrene, silicone and glass surfaces. Moreover, mutagenicity analysis and evaluation of hemolytic properties were performed. It was found that compounds with 16-carbon hydrophobic chains were the most promising against both planktonic forms and biofilms. Tested surfactants (C12, C14, C16) showed anti-adhesion activity but it was dependent on the type of the surface and strain used. The tested compounds at MIC concentrations did not cause hemolysis of sheep blood cells. The type of counterion was not as significant for the activity of the compound as the length of the hydrophobic aliphatic chain.

Recent Update on Applications of Quaternary Ammonium Silane as an Antibacterial Biomaterial: A Novel Drug Delivery Approach in Dentistry

Quaternary ammonium silane [(QAS), codename – k21] is a novel biomaterial developed by sol-gel process having broad spectrum antimicrobial activities with low cytotoxicity. It has been used in various concentrations with maximum antimicrobial efficacy and biocompatibility. The antimicrobial mechanism is displayed via contact killing, causing conformational changes within the bacterial cell membrane, inhibiting Sortase-A enzyme, and causing cell disturbances due to osmotic changes. The compound can attach to S1' pockets on matrix metalloproteinases (MMPs), leading to massive MMP enzyme inhibition, making it one of the most potent protease inhibitors. Quaternary ammonium silane has been synthesized and used in dentistry to eliminate the biofilm from dental tissues. QAS has been tested for its antibacterial activity as a cavity disinfectant, endodontic irrigant, restorative and root canal medication, and a nanocarrier for drug delivery approaches. The review is first of its kind that aims to discuss applications of QAS as a novel antibacterial biomaterial for dental applications along with discussions on its cytotoxic effects and future prospects in dentistry.

Antibacterial and antibiofilm efficacy of k21-E in root canal disinfection

OBJECTIVES

The aim of the current project was to study the antimicrobial efficacy of a newly developed irrigant, k21/E against E. faecalis biofilm.

METHODS

Root canals were instrumented and randomly divided into the following groups: irrigation with saline, 6% NaOCl (sodium hypochlorite), 6% NaOCl+2% CHX (Chlorhexidine), 2% CHX, 0.5% k21/E (k21 - quaternary ammonium silane) and 1% k21/E. E. faecalis were grown (3-days) (1×10⁷CFU mL^-1), treated, and further cultured for 11-days. Specimens were subjected to SEM, confocal and Raman analysis and macrophage vesicles characterized along with effect of lipopolysaccharide treatment. 3T3 mouse-fibroblasts were cultured for alizarin-red with Sortase-A active sites and Schrödinger docking was performed. TEM analysis of root dentin substrate with matrix metalloproteinases profilometry was also included. A cytotoxic test analysis for cell viability was measured by absorbance of human dental pulp cells after exposure to different irrigant solutions for 24h. The test percentages have been highlighted in Table 1.

RESULTS

Among experimental groups, irrigation with 0.5% k21/E showed phase separation revealing significant bacterial reduction and lower phenylalanine 1003cm^-1 and Amide III 1245cm^-1 intensities. Damage was observed on bacterial cell membrane after use of k21/E. No difference in exosomes distribution between control and 0.5%k21/E was observed with less TNFα (*p<0.05) and preferential binding of SrtA. TEM images demonstrated integrated collagen fibers in control and 0.5%k21/E specimens and inner bacterial membrane damage after k21/E treatment. The k21 groups appeared to be biocompatible to the dental pulpal cells grown for 24h.

SIGNIFICANCE

Current investigations highlight potential advantages of 0.5% k21/E as irrigation solution for root canal disinfection.