Apical negative pressure irrigation advances endodontic treatment

Dr. Brett E. Gilbert answers some questions about advances in irrigation

Why do we need more advanced endodontic irrigation?
Endodontics has seen vast developments and innovative advances in rotary instruments, ultrasonics, imaging, and the biocompatibility of filling materials over the past 2 decades. However, innovations in technology to irrigate the canals have been more delayed in development. Today, we are finally seeing a surge in advanced irrigation technology. These advances will help us in the ongoing battle of improving upon the classic irrigation technique to accomplish more effective apical cleansing while minimizing the risks of irrigating at the working length of the root canal.

The ultimate goal of endodontic treatment is to clean the root canal system. The apical third of this system (the last 3 mm of the root) is the most critical area to clean as this anatomy is a highly complex network of canal space, apical deltas, and fins. A 2006 study by Kim and Kratchman showed that the apical 3 mm of the root canal system contains over 98% of the canal ramifications and 90% of lateral canals as compared to the middle and coronal thirds of the root.

Our ability to clean the apical third with mechanical instruments alone is quite limited. After completed rotary instrumentation, Peters, et al. (2001), showed that only 35% of the canal space walls have actually been contacted by the instruments. The rotary instruments we use are effective in creating a pathway within the canal space which allows us to flow our solutions to the end of the canal. We depend on the chemical action of sodium hypochlorite solution to clean this complex canal space by antibacterial
action, tissue dissolution, and biofilm removal capability (Clegg, et al., 2006). The classic technique of positive pressure needle irrigation is the dispensing of solution into the pulp chamber or coronal/middle third of the root canal with a syringe tip. This method does not allow the solutions to reach the full working length of the canal effectively.

Historically, we have been ultraconservative with the volume and placement of our sodium hypochlorite solution in an effort to prevent the traumatic incidence of the solution getting past the apex of the root. However, in this effort to reduce or eliminate the incidence of a sodium hypochlorite accident, we have neglected to clean our apical anatomy to a sufficient level. Even in the instance of placement of the irrigating syringe into the apical third of the canal, the presence of the apical vapor lock is problematic. The apical vapor lock is a bubble that forms apically blocking the flow of the solution from reaching the working length of the canal. A study by Chow (1983) describes that for a solution to be mechanically effective, it must create a current force, reach the apex, and carry particles away. These criteria are simply not met with the classic positive pressure irrigation technique.

What is the apical negative pressure technique, and how can it lead the way to more advanced canal cleansing?
The advent of the apical negative pressure technique has changed the game of effective apical irrigation. This technique allows for a large volume of sodium hypochlorite and EDTA to be delivered to the full working length of a mechanically prepared root canal. The technique is performed using the Endovac™ Pure. This technology uses negative pressure to pull the irrigating solution from a reservoir in the pulp chamber to the working length by using high-speed suction through small apertures in the cannulas of the unit. Sodium hypochlorite is neutralized quickly in the root canal system by tissue and dentin debris.

Apical negative pressure can deliver 188 cycles of fresh solution to the full working length of the canal every 30 seconds, allowing for a constant and fresh exchange of solution (Fanibunda, 1966). Thereby, you are getting fresh delivery and replenishment of full-powered antibacterial and tissue-dissolving solution to the most critical part of the root canal system. As the flow of irrigation reaches the full working length of the canal, you simultaneously have a high-powered evacuation of the solution along with debris and particles out of the canal.

The Endovac Pure unit delivers a controlled flow of irrigation into the pulp chamber. A macrocannula is placed into the canal to the level of the middle third. The macrocannula has the ability to pull the solution from the pulp chamber down into the canal by a negative pressure force to the level of the open aperture at the end of the cannula. Thereby, a negative pressure current force is placed on the solution to flow down the canal and into the high-speed suction opening for evacuation. The larger size of the macrocannula aperture allows for larger pieces of debris to be removed quickly and effectively from the canal.

A second cannula, the microcannula, is then placed to full working length in the canal. Again, the high-speed suction at the end of the cannula has a negative pressure pulling force on the fresh solution in the pulp chamber. The irrigant is able to flow down the canal by the negative pressure to reach the level of the high-speed suction apertures at the tip of the microcannula.

The solution is then evacuated through the high-velocity suction openings, creating an irrigation flow from crown to apex. As the solution flows down the canal from the pulp chamber to the apical working length and suctioned out, you have a continuous current force of fresh irrigation reaching the apical third. This technique is streamlined and ergonomic as the Endovac Pure unit is operated by one hand through a hand controller, which dispenses the stored solutions (NaOCl and EDTA) by the touch of a button. The two suction cannulas extend right from the disposable apex cartridge into the canals.

How does apical negative pressure irrigation help minimize risk and maximize effectiveness?
The inherent lack of risk of this technique is simple. The negative pressure current force on the irrigation solution is driven by the high-speed suction at the tip of the cannulas. If the cannula gets blocked, or the suction force is otherwise disturbed, no solution will be present in the apical third of the canal. This is because it relies on the suction force to deliver the solution to the working length of the canal. In a similar way, if the cannula is extended beyond the apex, the negative pressure is no longer created because the cannula will be suctioning outside of the root, and there is no pulling force to pull the solution down into the canal.

As clinicians, our highest priority is to assure that our treatments do not harm or pose risk to our patients. Desai and Himel (2010) showed “that the Endovac did not extrude irrigant after deep intracanal delivery and suctioning the irrigant from the chamber to full working length.” The protection of the periapical tissue is fundamentally built into the technique by relying on the high-velocity suctioning force to deliver the flow of solution to the apex. Any interruption of the high-velocity suction will stop the flow of irrigant.

Once we have determined that a technique helps protect our patients, we then turn our attention to the efficacy of the technique. Nelson and Baumgartner (2009) showed that there was significantly better cleaning of canals 1 mm from the apex in comparison to needle irrigation (positive pressure) alone. In regards to clinical outcomes, a study by Gondim, et al. (2010), showed that there was less postoperative pain with use of apical negative pressure by Endovac as compared to needle irrigation alone.

What is the clinical impact of advanced apical irrigation?
Advances in dental technology continue to increase the efficiency and efficacy of our dental treatments. The delivery of the apical negative pressure irrigation technique with the Endovac Pure is a technique that provides clinicians with the answer to the significant limitations of the classic endodontic irrigation techniques. We are always striving to raise the bar in endodontic success. By irrigating more effectively in the apical third of our root canal systems, we can reach the next level of success in endodontics.

This information was provided by Kerr Endodontics.