Endodontic sealers as biofilm prevention: facts and hypotheses

2025-05-07 13:13

M. Solomonov, Department of Endodontics, Sheba Medical Center, Tel Hashomer, Israel

Historically, the concepts regarding the use of sealers in endodontics have been polarized between the American and European schools.
The European approach emphasized sealers with active antibacterial properties, while the American scientific endodontic school preferred recommending inert sealers for obturation.
The reason is that antibacterial ingredients are active, leach out from the main material (the sealer), and thus disappear over time [1] — at which point the material loses both its antibacterial properties and its volume, thereby compromising its seal.
The process of losing active soluble ingredients is accelerated by apical percolation — the movement of periapical fluids into the apical part of the canal during mastication.

Modern disinfection techniques are unable to fully sterilize root canals [2], so researchers believe that high-quality obturation should serve to entomb the remaining microorganisms, thereby disrupting their life processes [3].
A crucial role in this is played by sealers that exhibit strong antibacterial properties during their setting phase and become inert after setting [4].
One of the most recommended groups is epoxy-based sealers, which have an antibacterial effect during setting and become completely inert afterward [4].

A major problem with current obturation materials is their inability to prevent the infiltration of new microorganisms from the oral cavity over the long term when coronal sealing is compromised [5].
Typically, within 3 months of exposure to the oral cavity, an obturated canal becomes re-infected and requires retreatment [6].

Since the discovery and realization that bacterial infections in our body — and particularly in root canals — occur mostly in the form of biofilms [7], there has been a search for new methods to combat them.
One of the newest directions involves the use of insoluble disinfecting macromolecules that kill bacteria upon direct contact without leaching or dissolving.
The mechanism is as follows: macromolecules carry a positive (+) electric charge, while microbes carry a negative (–) charge, and human cells are electrically neutral.
Upon contact between the macromolecule and the bacterium, the permeability of the microbial membrane is disrupted, leading to bacterial death [8].
A key property of these macromolecules is that they remain effective — they neither disappear, dissolve, nor lose their antibacterial properties [8], unlike traditional antibacterial agents such as NaOCl, CHX, Ca(OH)₂, or iodoform.

Several new approaches have emerged in the application of disinfecting macromolecules in endodontics. One such approach is the use of nanoparticles sized between 1 nm and 100 nm. For example, the natural nanoparticle chitosan, extracted from the chitin shells of small crustaceans [9].

The group led by Shrestha and Kishen attempted to use chitosan to eradicate biofilms [10], but did not achieve a significant improvement compared to classical Ca(OH)₂ and photoactivated disinfection methods [10]. Attempts were also made to use silver nanoparticles to eliminate biofilms, but again, no significant improvement was observed [11]. In my opinion, the issue lies in the electrical charge. Biofilms carry a negative (–) charge, so nanoparticles tend to adhere to the biofilm surface without penetrating the inner layers.
Of course, this hypothesis requires scientific verification.

At the same time, another direction emerged — the use of nanoparticles to prevent biofilm formation. At the Hebrew University of Jerusalem, a synthetic nanoparticle, Quaternary Ammonium Polyethyleneimine (QA-PEI), also known as I-ABN (Insoluble Antibacterial Nanoparticles), was developed [12].
In a series of experiments, these particles were incorporated into various dental materials [12, 14, 15, 18, 19]. As a result, biofilm formation on the surfaces of these materials was completely prevented for 1–3 months (the duration of the experiments). In control groups without the nanoparticle additives, biofilms formed within just 24 hours [13, 14, 15].

In endodontics, this led to the idea of creating a sealer with added nanoparticles.
A new epoxy-based sealer, BJM Root Canal Sealer, was developed.
This sealer, containing nanoparticles, has been shown to prevent biofilm formation for at least three months when in direct contact with infection [19].
Another research group tested the addition of nanoparticles to AH Plus and other root canal sealers, showing a pronounced anti-biofilm effect [20].

However, there is a critical concern: nanoparticles are able to cross all barriers in the human body, including the placental and blood-brain barriers [21, 22].
Researchers are unsure of the long-term biological consequences.
New testing protocols are being developed, and, as of now, health ministries in many countries have not authorized the use of materials containing nanoparticles [23, 24].

As a solution to this problem, another direction has emerged — using disinfecting macromolecules that are not nanoparticles.
One of the most widely used materials of this kind in general medicine is BioSafe, which is commonly added to plastics used for catheters and keyboard covers [25].
In endodontics, the addition of BioSafe is marketed under the name Immobilized Antibacterial Technology (IABT).
Today, BJM Root Canal Sealer is available with this additive.

Since BJM Root Canal Sealer is a new material, it was important to verify whether its properties meet ISO standards, whether its physical properties change after the addition of BioSafe, and, of course, its level of biocompatibility.
The study was conducted and is currently being prepared for publication [26].
The properties of the material were tested alongside classic epoxy sealers like AH Plus and MM-Seal.
BJM Root Canal Sealer was found to meet ISO standards and showed high biocompatibility.

There is still a need for further research to verify the duration of macromolecule activity when in contact with biofilms under conditions that closely simulate the oral cavity.
If it can be proven that their antibacterial effect is indeed unlimited, as chemists promise, we may be entering a fundamentally new era — where the prognosis for endodontic treatment will depend much less on the quality of the coronal seal!
Of course, this is still a hypothesis, and we await the results of further research.