Improving endodontic success through use of the EndoVac irrigation system

But what is referred to when we mention disinfection of the canal system? Disinfection comprises removal of the residual tissue in the canal system and the associated bacteria through flushing the canal system with irrigating solution. The key is to remove as much residual tissue as possible. The more thorough the irrigation process, the lower the remaining bacterial level.

The intricacies of the canal, with its fins, lateral canals and apical deltas, make it impossible for the instrumentation of the canals to reach all of the fine aspects of the anatomy. Irrigation of the canal system thus permits removal of residual tissue in the canal anatomy that cannot be reached by instrumentation of the main canals.

Cleansing the canal

No matter what obturation material is used, how well the sealer adheres to the canal walls is important. Smear layer can play a factor that may prevent sealer penetration into the dentinal tubules. The frequency of bacterial penetration through teeth obturated with intact smear layer (70 percent) was significantly greater than that of teeth from which the smear layer had been removed (30 percent). Removal of the smear layer enhanced sealability, as evidenced by increased resistance to bacterial penetration.[1] The incidence of apical leakage was reduced in the absence of the smear, and the adaptation of gutta-percha was improved no matter what obturation method was used later.[2–4]

 

What is used to obturate the canals is important, but the manner in which the canal was prepared prior to obturation also determines how well the canal is sealed when therapy is completed. Rotary instrumentation with NiTi files has shown less microleakage than hand-instrument-prepared canals, irrespective of what was used to obturate the canal.[5] The machining of the canal walls with NiTi rotary instruments provides smoother canal walls and shapes that are easier to obturate than can be achieved with stainless steel files. The better the adaptation of the obturation material to the instrumented dentinal walls, the less leakage is to be expected along the entire root length. The better the canal walls are prepared, the more smear layer and organic debris is removed, which is beneficial to root canal sealing.

Smear layer removal is best achieved by irrigating the canals with NaOCL (sodium hypochlorite) followed by 17 percent EDTA solution.[6] The NaOCL dissolves the organic component of the smear layer, exposing the dentinal tubules lining the canal walls. EDTA, a chelating agent, dissolves the inorganic portion of the dentin opening the dentinal tubules. Alternating between the two irrigants as the instrumentation is being performed will permit removal of more organic debris further into the tubules, increasing resistance to bacterial penetration once the canal is obturated.[7,8]

Studies suggest that regular exchange and the use of large amounts of irrigant should maintain the antibacterial effectiveness of the NaOCl solution, compensating for the effects of concentration.[9] So it seems that volume is more critical to canal disinfection during treatment than the concentration of the irrigant.[10]

Positive vs. negative apical pressure

Irrigation as it relates to endodontic treatment involves placement of an irrigating solution into the canal system and its evacuation for the tooth. Traditionally, this involved placement of an end-port or side-port needle into the canal and expressing solution out of the needle to be suctioned coronally. This creates a positive pressure system with force created at the end of the needle, which may lead to solution being forced into the periapical tissues. As some irrigating solutions, such as sodium hypochlorite, have the potential to cause tissue injury that may be extensive when encountering the periapical tissue and its communication with tissue spaces, positive pressure irrigation has its risks. Chow was able to show as early as 1983 that positive pressure irrigation has little or no effect apical to the needle’s orifice.[11] This is highlighted in his paradigm on endodontic irrigation, “For the solution to be mechanically effective in removing all the particles, it has to: (a) reach the apex, (b) create a current force and (c) carry the particles away.”

An apical negative pressure irrigation system, on the other hand, does not create a positive force at the needle’s tip, so potential accidents can be eliminated. In an apical negative pressure irrigation system, the irrigation solution is expressed coronally, and suction at the tip of the irrigation needle at the apex creates a current flow down the canal toward the apex and is drawn up the needle. But true apical negative pressure only occurs when the needle (cannula) is utilized to aspirate irrigants from the apical termination of the root canal. The apical suction pulls irrigating solution down the canal walls toward the apex, creating a rapid turbulent current force toward the terminus of the needle. Haas and Edson found, “The teeth irrigated with negative apical pressure had no apical leakage. While the teeth irrigated with positive pressure leaked an overage of 2.41 mL out of 3 mL.”[12] A recent study by Fukumoto found using [apical] negative pressure less extrusion of irrigant than needle irrigation (positive pressure) when both were placed 2 mm from working length.[13]

EndoVac endodontic irrigation system

Designed by Dr. G. John Schoeffel after almost a decade of research, the EndoVac irrigation system (Axis|SybronEndo, Anaheim, Calif.) was developed as a means to irrigate and remove debris to the apical constricture without forcing solution out the apex into the periapical tissue. The system utilizes apical negative pressure through the high-volume evacuation system, permitting thorough irrigation with high volumes of irrigation solution.

The EndoVac system consists of Multi-Port Adapter (MPA) assembly that connects to the high volume evacuation hose in the dental operatory (Fig. 2). To this connects the Master Delivery Tip (irrigation and suction together) with a disposable syringe filled with irrigation solution (Figs. 3,4). Either a MacroCannula or MicroCannula is attached and used simultaneously with the Master Delivery Tip during treatment. The plastic MacroCannula is placed on a handpiece, which is attached to tubing that connects to the MPA via a separate line. This is used for coarse debris removal. The MicroCannula is a metal suction tip available in either 21, 25 or 31 mm lengths with 12 micro holes in the terminal 0.7 mm of the tip, permitting removal of particles that are 100 microns or smaller to the apical constricture. This tip fits into a metal fingerpiece and is connected to the MPA in the HVE via tubing. The turbulent current forces developed by the MicroCannula rapidly flows to the micro holes at the terminus, which can reach within 0.2 mm of full working length. Quite simply, the vacuum formed at the tip of the MicroCannula is able to achieve each of Chow’s objectives in his irrigation paradigm.

Nielsen and Baumgartner found that the volume of irrigant delivered with the EndoVac system was significantly more than the volume delivered with needle irrigation over the same amount of time.14 Further, they reported significantly better debridement 1 mm from working length for the EndoVac system compared with needle irrigation.

EndoVac technique

Following removal of the chamber roof and exposure of the pulp, the Master Delivery Tip is used to provide frequent and abundant irrigation as the orifices are identified and explored. During instrumentation, the Master Delivery Tip is placed at the coronal to provide fresh irrigation solution and aid in debris removal that is brought coronally as the rotary file is used in the canal (Fig. 5). The benefit of the Master Delivery Tip is that with a single tip at the tooth’s access, visibility is not blocked and large volumes of irrigation solution can be utilized. The MacroCannula is utilized to remove coarse debris after instrumentation and is used in combination with the Master Delivery Tip, which delivers the irrigating solution. Apical negative pressure is created as irrigating solution is drawn down the canal toward the apex as it is expressed from the Master Delivery Tip and then is drawn up the MacroCannula (Fig. 6). The MacroCannula is taken to full working length and moved 2 mm with an up-and-down action every six seconds as each canal is flushed. This up-and-down action removes micro-gas bubbles formed during tissue hydrolysis. The MicroCannula is used with a combination of three rinse cycles using NaOCL.

The EndoVac will work in any canal configuration shaped at least to a size 35 with a 0.04 taper or greater (Fig. 7). To prevent plugging of the fine holes in the apical terminus, do not use the MicroCannula until thorough irrigation has been accomplished with the MacroCannula and all instrumentation has been completed.

Conclusion

Instrumentation, disinfection and obturation are important aspects of rendering quality endodontic care. Yet the instruments we use to prepare the canal, be they hand or mechanized, are unable to reach all aspects of the canal system. Irrigation is key to cleaning and disinfecting those areas that the instrument cannot reach.

The EndoVac irrigation system, with its apical negative pressure, is able to more thoroughly remove the micro debris at the apical constricture, thereby providing a better environment to be filled with sealer.

Note: This article was published in Endo Tribune U.S. Edition, Vol. 7 No. 3, April 2012. A complete list of references is available from the publisher. Please refer to Roots North America Edition, Vol. 2, No. 1, for a longer version of the article, which includes discussion on the safety of positive vs. negative pressure irrigation.