Question: Antimicrobial agents: Are they necessary for successful endodontics?

Allen Ali Nasseh, DDS, MMSc | Barry Lee Musikant, DMD | Joseph Chikvashvili, DDS

Dr. Nasseh

All aspects of antimicrobial therapy are critical to endodontic success. In fact, the entire premise of endodontic therapy is addressing the microbial insult to the dental pulp and decontamination of the root canal space. Therefore, eliminating microbial mass through chemo-mechanical means remains the main goal of all endodontic therapy. The Kakehashi and Stanley study in 1965 demonstrated the role of microbes in the progression of endodontic disease and defined the critical factor of asepsis as the ultimate goal of prevention and treatment of endodontic disease. Once the sole, and unequivocal, role of microbes in the progression of endodontic disease was scientifically demonstrated, the entire field of endodontics became a body of methodologies developed to address the microbiological challenges of infectious agents to the dental pulp and the root canal space.

While consistent sterility may be impossible, given the anatomical complexity of the root canal space, chemo-mechanical techniques of shaping with files and irrigating with antimicrobial agents is currently our only hope in achieving clean canals before obturation. Therefore, all irrigants should be antimicrobial in order to more effectively clean the canals. The current standard of care for irrigation remains concentrations of sodium hypochlorite greater than 1% and as high as 6%; but because this chemical is highly cytotoxic, various means of delivery devices have recently been developed using negative pressure that allows safe and efficient delivery of this antimicrobial agents deep in the root canals.

All astute clinicians must be familiar with such devices in order to safely deliver a high volume of disinfectant into the deep recesses of the root canal and better clean necrotic canals before their obturation. Incomplete decontamination is a significant cause of endodontic failure and a high volume of antimicrobial agent delivered into the canals is one of the best ways to improve clinical success.

Dr. Musikant

Pulps die and periapical areas form because of the presence of bacteria and their toxic byproducts. Remove the bacteria and prevent their reoccurrence, and periapical healing occurs. Given these observations, it makes sense to reduce the bacterial presence when removing tissue and further ensure their absence by using cements that have an antibacterial component during the obturation phase of treatment.

Instrumentation involves the mechanical means to remove tissue and the bacteria associated with that tissue. Given the complex branch-like anatomy that pulp tissue can have in the body of the tooth, it is necessary to widen the main canals adequately to provide a space for the effective use of antibacterial irrigants. The irrigants have the task of removing the smear layer, opening up the dentinal tubules, penetrating these tubules, and killing any bacteria that might be present along with diluting and hopefully washing out all bacterial toxins that might be present. To accomplish these tasks, no one irrigant is sufficient. We use 17% EDTA to remove the smear layer and open up the tubules, followed by 6% sodium hypochlorite to digest any remaining tissue, break up, and kill the bacteria present in biofilms as well as penetrate into the tubules to kill bacteria that have taken up residence there. In addition to these two irrigants, 2% chlorhexidine is also recommended to kill the Enterococcus faecalis that is resistant to sodium hypochlorite and, if not removed, can lead to endodontic failure.

Without question, the use of these irrigants in canals enlarged enough to provide sufficient volume will dramatically reduce the bacterial count and dilute their toxic byproducts. They are even more effective if activated either sonically or ultrasonically. Insufficient canal enlargement reduces their effectiveness, something that might not produce failure in canals that originally contained vital tissue without the presence of bacteria, but will be critical in teeth that are already colonized with bacteria. Shaping and irrigation go hand in hand to produce a more predictable successful result.

Dr. Chikvashvili

Antimicrobial agents certainly must be used. This is very critical for necrotic teeth. Newer research continues to demonstrate how difficult it is to remove biofilm from infected root canals. With every year, more and more bacteria are discovered, indicating just how complex this disease process can be. Fortunately, recent innovations have helped to be able to better disinfect and medicate the root canal system.

Ultrasonics allow us to more effectively clean canals, allowing for fluids to better reach inside lateral canals and isthmuses. But in addition to these fantastic tools, we still need the irrigants themselves to help us thoroughly disinfect canals. While instruments can help scrape and shape those walls, irrigants must travel down to the apex to facilitate removal of debris. The best irrigant to use still remains full-strength sodium hypochlorite solution (6%) for removing debris in necrotic teeth as well as dissolving tissue in vital teeth.

More recently, other chemicals have had beneficial effects. Chlorhexidine 2% can also help to fight against E faecalis, one of the most prevalent bacterium in retreatment cases. Calcium hydroxide has been shown for years to have antimicrobial properties, helping to treat necrotic teeth, in particular. EDTA is routinely used to remove the smear layer from canal systems.

The prudent clinician will use these irrigants and devices to help facilitate complete cleaning and disinfecting of root canal systems. While they each have their individual purposes, there is certainly a place for all of them in root canal therapy. And despite having better devices to disinfect, we still must take the time and care to ensure that the canal system is always as clean and decontaminated as it can be for successful endodontics to occur.

About the Authors

Allen Ali Nasseh, DDS, MMSc
Clinical Instructor
Department of Restorative Dentistry and Biomaterial Sciences
Harvard University
School of Dental Medicine
Boston, Massachusetts

Barry Lee Musikant, DMD
Owner, President, and Co-Director of Research
Essential Dental Systems, Inc.
Hackensack, New Jersey

Joseph Chikvashvili, DDS
Director of Endodontics
Newark Beth Israel Medical Center, GPR Program
Newark, New Jersey