Evaluation of Antimicrobial Efficacy and Adaptability of Bioceramic Sealer Containing Nanoparticles

The main purpose of endodontic therapy is to clean and shape the root canals. This is done by means of instruments and chemical irrigants in order to effectively control the pulpal and periapical infection. That chemomechanical preparation aims to reduce the microorganisms count but cannot completely eliminate it. This is mainly due to (i) anatomical complexity and access limitations (ii) incompetent chemomechanical preparations leaving surfaces untouched (iii) ineffectual irrigation. Besides, despite an accurate chemomechanical preparation, infection may persist in 20-33% of cases, even if intracanal medicament is used.

Treatment failure may also occur due to microleakage, which occurs due to interfacial gaps between the gutta-percha and the sealer, the sealer and the dentin, or through voids within the sealer. Fifty eight percent of treatment failures happen due to incomplete obturation and that's why, hermetic seal is the main factor associated with the success of root canal treatment . Therefore, disinfection, gap-free, three dimensional obturation are the main requisites for treatment standards in endodontics.

Another reason for treatment failure is presence of persisting bacteria. Enterococcus faecalis is a resistant bacterium commonly retrieved from obturated root canals with post treatment disease (apical periodontitis). This pathogen is believed to be highly virulent; it can invade dentinal tubules, adhere, overcome environmental challenges and form biofilm.. Besides, it can resist intracanal disinfectants and medicaments. Therefore, the best approach to resolve this is by using a sealer with broad spectrum antibacterial action.

Ideal root-canal sealer should be able to kill microorganisms on direct contact on the dentinal walls and those present deep inside the dentinal root canals. That means that it should be able to diffuse inside the dentinal tubules to entomb and kill surviving bacteria. Besides, it should be capable of perfectly sealing the prepared canal to block any space and nutrients needed for bacterial growth. Finally, endodontic sealers that retain flowability and antimicrobial properties may help eliminate microorganisms in the root canal system.

Dspite the fact that most sealers have antibacterial constituents, their antibacterial activity is eventually lost after setting. Besides, even if it doesn't, these constituents have to be liberated from the set sealer matrix to fulfill their function. Then again, their release would be accompanied by disintegration of the sealer, interfacial gaps and later on bacterial recolonization.

Moreover,the current root filling materials aren't enough for reaching a complete, gap-free obturation. That would be due to the dimensional changes and lack of adhesion between Gutta percha and dentin. And that is why endodontic sealers are used. Thus, the adaptability of the sealer to the dentin is the main factor influencing microleakage and reinfection.

Nanotechnology is the science of producing materials in nano-dimensions by re-location and re-arrangement of atoms to prepare materials with better properties. It is considered a great advancement in the field of medicine. It can be beneficial in producing material with superior properties by enhancing surface to volume ratio. Besides, having antibacterial nanoparticles are shown to have better antibacterial action than their powder counterparts. That would be due to their higher surface area and charge density which favor their interaction with the negatively charged bacterial surface.

Resistance in pathogens is a major challenge in field like biomedicine. Chemical antimicrobial agents depend on binding to specific receptor for their antimicrobial action, which by time lead to multidrug resistance. . On the other hand, antibacterial nanoparticles such as nanosilver interact with multiple targets in the bacterial cell. Therefore, providing the bacteria with the least chance of gaining resistance.

The mechanism of action of silver ions. Silver ions are highly reactive. They start by binding to proteins on the bacterial cell leading to structural changes, which leads to cell distortion and death. Silver ions also can inhibit the bacterial replication, by binding and denaturing its DNA. Moreover, they can react with thiol group of proteins, followed by DNA condensation resulting in the cell death.

Although, silver nanoparticle's potential disadvantage is its toxicity towards mammalian cells. A number of studies proved that silver is safe as long as it's used in small concentrations. A study assessed the tissue response of silver nanoparticles dispersion embedded in fibrin sponge and implanted in polyethylene tubes. They concluded that silver nanoparticles dispersion was biocompatible at low concentrations. Another study stated that silver nanoparticles at low concentrations are effective against microorganisms without any toxic effect on eukaryotic cells.

Furthermore, there is a natural cationic biopolymer which can overcome the silver nanoparticles shortcomings and still provide an antibacterial efficacy. Chitosan (CS) is usually obtained by the alkaline deacetylation of chitin, which is the main component of the exoskeleton of crustaceans. CS has an excellent antibacterial, antiviral and antifungal properties, as an antibacterial, it works better on gram negative than gram positive. Besides, the addition of CS nanoparticles into zinc-oxide eugenol sealer in a membrane restricted assay. They proved that CS improved the antibacterial property suggesting that it can diffuse and penetrate dentinal tubules and anatomical complexities.

The mechanism of action of CS and stated that it's contact-mediated killing. It starts by electrostatic attraction of positively charged CS with negatively charged bacterial cell membrane. That is followed by altered cell permeability, resulting in rupture of cells and leakage of the intracellular components.

Finally, as reflected earlier, successful endodontic treatment depend on disinfecting the canals and providing a hermetic seal. That's why; this study's target is to assess the antibacterial efficacy and adaptability of bioceramic sealer when incorporated with nanosilver and chitosan respectively.