Written by G. John Schoeffel, DDS, MMS Sunday, 31 May 2009 19:00
Although the EndoVac's safety and efficacy were previously discussed, newly published studies have further validated these benefits. A safety study designed on previous protocols1-4 that examined the "worse case clinical situation" has again demonstrated that intracanal positive pressure systems always produce substantial apical extrusion of the irrigant. However, in the same study, the EndoVac system extruded nothing.5 In terms of total canal cleanliness, a recent SEM study has shown that the EndoVac can completely remove smear layer at 1 mm from the working length in a "closed system" (Figure 1),6 with the same efficacy previously reported in an "open system."7 Finally, a recent microbiological study published in 2008 again proved the EndoVac efficacy by producing 100% negative cultures compared to a 33% failure rate with positive pressure.8
This article will conclude the discussions presented in the previous 3 parts by describing the clinical warnings, precautions, considerations, setup, and use of the EndoVac to achieve deep debridement and evacuation of the entire root canal from apical foramen to canal orifice during endodontic irrigation (Figure 2).
GENERAL PRECAUTIONS AND CONSIDERATIONS
|Figure 1. SEM (5,000X)—Traditional versus EndoVac irrigation, demonstrating the EndoVac's ability to clear the canal walls of smear layer and to dissolve the intratubular organic components at 1 mm from working length in a "closed root canal system." (Note: A "closed root canal system" means the root canal system is totally sealed and irrigants cannot freely flow out portals of exit thereby producing a false positive result.)|
Figure 2. Postoperative radiograph after using EndoVac irrigation, demonstrating 4 portals of exit in the last 2 mm.
Figure 3. The master delivery tip (MDT) is used to maintain a brim-full pulp chamber. (A) It concurrently delivers irrigant and (B) aspirates the excess. The operator must never direct this stream at (or towards) a canal orifice.
Prior to EndoVac irrigation, the clinician needs to take every precaution to ensure that the integrity of the rubber dam seal and any potential communication from the pulp chamber to the oral cavity are absolutely secure. An example of the latter would be deep caries below the level of the rubber dam that could result in irrigants leaking into the oral cavity via the pulp chamber. In this example, the caries would be removed and replaced with a temporary sealing material.
It is also important to always protect the patient's eyes with safety glasses and their clothing from sodium hypochlorite splatter or spill, and to never place the master delivery tip (MDT) (Figure 3) closer than 5 mm from the orifice of any pulp canal.
Another thing to remember is that the correct clinical use of the EndoVac system requires a minimum canal shape of a No. 35 instrument at a 4% taper at full working length (WL); or in the case of nontapered instruments, a No. 45 at WL. Always use the EndoVac system in the sequence described herein. Skipping or deviating from the following steps can cause the EndoVac's cannulae to clog (discussed later) and the clinician to become unnecessarily frustrated. Prefill the various syringes: 20 cc syringes with 5% to 6% sodium hypochlorite, 3 cc syringes with 15% to 17% EDTA, and optional syringes with irrigants of the clinician's choice as described in step No. 3 (Micro Evacuation; Microcycle Technique). Make sure no air bubbles are trapped in the prefilled syringes, as this will cause uncontrolled irrigant extrusion after releasing the plunger pressure.
Finally, the EndoVac's fluid mechanics depend on an intact clinical crown with an access opening measuring at least 6 to 8 mm from cavosurface angle to the pulp floor. If the clinical crown is compromised, create a temporary one using a composite material.
MASTER DELIVERY TIP SETUP AND CLINICAL METHOD
Figure 4. Setup of MDT begins in the operatory by (a) attaching the HiVac adapter tube assembly (left arrow) into the office's high-volume evacuation that is set to full-on. Note: The white cap shown (right arrow) is NOT removed until Macro evacuation. The red Luer fittings are connected (b) and the MDT is connected to the sodium hypochlorite syringe (c). During treatment, the syringe plunger is held against the palm to reduce "thumb fatigue" during irrigant extrusion (d).
Refer to Figure 4 for assembly instructions. MDT is connected to the office high-vacuum system via the HiVac adapter tube assembly (HATA). This tube has an adapter at one end that fits in the office's HiVac while the other end consists of a "T-connector" with 2 Luer ports and a clip to attach the T-connector to the patient's garments.
There are 3 phases of EndoVac irrigation/evacuation: (1) Gross evacuation during orifice expansion and between instrument changes, (2) Macro evacuation after complete instrumentation, and (3) Micro evacuation at full WL.
Gross Evacuation—During Instrumentation
The MDT provides both a constant source of fresh sodium hypochlorite from its metal delivery tip into the pulp chamber, and the immediate removal of any excess irrigant via the plastic evacuation hood surrounding the delivery tip (Figure 3). This dual action provides a method of maintaining a pulp chamber brim full with fresh sodium hypochlorite. The delivery tip is placed just inside the access opening while the evacuation hood remains on the outside. A stream of irrigant is directed from the delivery tip at an axial wall and never towards a pulp canal orifice. The rate of irrigant delivery through the MDT varies according to each phase of irrigation.
Caution: It is possible to create positive pressure in the pulp canal if the MDT is misused, creating the risk of a sodium hypochlorite accident. Although previously discussed, the following points are mentioned again with emphasis to help prevent clinical failures:
- Always discharge the irrigant from the MDT into a natural or temporary intact access opening measuring at least 6 to 8 mm from cavosurface angle to pulp floor.
- Always direct the irrigant stream at an axial wall approximately 45º from the pulp canal's axial plane in molars (Figure 3), 60º in premolars, and 90º in anteriors.
- Never place the MDT's delivery tip closer than 5 mm from the coronal opening of any pulp canal.
Macro Evacuation:Setup and Clinical Method
Figure 5. Prior to treatment, the MacroCannula/Handpiece assembly begins in the sterilization area during tray setup by inserting the MacroCannula into the handpiece with light pressure (a); the male Luer fitting from the "white connection tube is inserted into the back of the fingerpiece with firm pressure (b); in the clinic, after complete instrumentation, the white Luer cap is removed from the T-connector (c); and lastly, the previously assembled MicroCannula/Handpiece/Tube are attached white-to-white (d).
Refer to Figures 5a to 5d for assembly instructions. After all instrumentation has been completed, remove the white Luer cap on the HATA T-Connector (Figure 5c) and connect the white Luer connector from the Handpiece (Figure 5d). The opposite end should have already been inserted in the Handpiece during the tray setup (Figure 5b). Note: Do not discard the white Luer cap from the T-Connector, as it will be replaced upon completion of EndoVac irrigation.
The clinician places the blue MacroCannula into the pulp canal and constantly moves it up and down from a point where it starts to bind apically to a point just below the orifice, all the while the assistant uses the MDT to deliver sodium hypochlorite at the rate of 10 cc over 30 seconds. Each pulp canal is Macro evacuated in this manner for 30 seconds.
After the last pulp canal has been Macro evacuated, remove the cannula quickly from the pulp canal—and then—remove the MDT. This order of device removal ensures the pulp canal(s) stay loaded ("charged") with fresh sodium hypochlorite. Then a 30 second passive wait begins in order to allow further chemical reactions to occur, during which time patency should be rechecked and/or re-established with a small instrument.
Figure 6. Cannulae Clogging: During instrumentation, the tip of a Ni-Ti rotary instrument (center of circle) caught in an intracanal anastomosis and twisted off. However, during Macro evacuation, the separated tip was sucked into and lodged in the MacroCannula. Most debris evacuated by the MacroCannula is easily removed with a 2 x 2 gauze, or by blowing air in the Luer fitting via the office 3-way syringe. In the rare event that the MicroCannula becomes clogged, only the 3-way syringe clearing method is used.
In the infrequent event that the Macro becomes clogged, simply remove the MacroCannula from the pulp canal and wipe the tip with gauze or blow air in the Luer end via the office 3-way syringe. This topic is further addressed in the "clogging" section (Figure 6).
Micro Evacuation: Setup and Clinical Method
|Figure 7. The MicroCannula and Fingerpiece are assembled in the sterilization area, during tray setup. Using the MicroCannula's protective cover, force it into the Fingerpiece with extremely strong pressure (a) to avoid separation between the Fingerpiece and the MicroCannula when using the MicroCannula at full working length in difficult anatomical configurations. After Macro evacuation the white Luer fitting is removed from the Handpiece and inserted into the Fingerpiece with firm pressure (b). The protective cover is removed (c) and working length(s) is/are marked (d) with a waterproof marker. (Although a depth stopper can be used for length control, this is discouraged due to possible stopper slippage. Even though the MicroCannula fits into the handpiece, this is discouraged because the clinician loses the critical proprioceptive feeling necessary to navigate the MicroCannula down narrow and curved canals.)|
Refer to Figure 7 for assembly instruction and setting WL. At the conclusion of the passive wait following Macro evacuation, the clinician places the MicroCannula into the pulp canal to full WL as the assistant delivers 5% to 6% sodium hypochlorite from the MDT at a rate of 3 cc over 30 seconds. At this point, the last of the organic debris on the walls in the apical one-third begins to dissolve and to form microgas bubbles of ammonia and carbon dioxide; thus necessitating that the MicroCannula be constantly repositioned 2 mm up and down the pulp canal in order to evacuate these micro bubbles and to ensure a constant irrigant exchange. This constant up-down motion (active irrigation) lasts 30 seconds and is followed by a 60-second passive wait. Together the active evacuation and passive wait are referred to as a "Microcycle."
MICRO EVACUATION TECHNIQUE
Three Microcycles are required to complete the associated chemical reactions and to evacuate the residual debris. The first Microcycle dissolves and removes organic debris from the pulp canal walls using 5% to 6% sodium hypochlorite. The second Microcycle disassociates and removes the smear layer (Figure 1), thereby exposing the dentinal tubules by using 15% to 17% EDTA. The third and final Microcycle again employs 5% to 6% sodium hypochlorite to dissolve and remove the contents of the now exposed dentinal tubules.
The precise placement and movements of the MicroCannula during the 30 second active irrigation period are as follows: (1) seconds 0 to 6 at WL, (2) seconds 7 to 12 at WL minus 2 mm, (3) seconds 13 to 18 at WL, (4) seconds 19 to 24 at WL minus 2 mm, and finally (5) seconds 25 to 30 at WL. As with the MacroCannula—at the conclusion of 30 seconds—the MicroCannula is quickly withdrawn before the MDT in order to leave a charged canal. If the tooth is single-rooted, the clinician must passively wait for 60 seconds. If it is a multirooted tooth, the other pulp canal(s) may be treated during the passive wait of the first pulp canal.
The MDT is changed from a sodium hypochlorite syringe to an EDTA syringe for the second Microcycle (to remove the smear layer). At the conclusion of the second Microcycle, the sodium hypochlorite syringe is re-attached to the MDT and the final Microcycle is performed to remove the intratubular organic debris. Upon finishing the third Microcycle, the clinician may choose to use different irrigants or solutions such as chlorhexidine or ethanol. The canal(s) are then dried with paper points.
(Note: In the case of retreatment, all pulp canals must be fully prepared, then as clean and dry of gutta-percha solvent as possible before proceeding to both Macro and Micro evacuation. Both cannulae may still clog; however, this is the very nature of retreatment. When this occurs, both cannulae can be quickly cleared with air from the 3-way syringe as described in the next section.)
MacroCannula clogging occasionally occurs and is, in fact, a testament to the power of the macroevacuation phase of EndoVac irrigation. For example, Figure 6 demonstrates the tip of a broken Ni-Ti instrument that was sucked into a MacroCannula and clogged the tip—this was good.
Sometimes pulpal remnants that were trapped in anastomoses and cul-de-sacs during instrumentation are also sucked into the MacroCannula causing blockage. This is rectified by wiping the tip with a 2 x 2 gauze or blowing air in the Luer end via the office 3-way syringe. It also gives the clinician a feeling of satisfaction after removing that which would have been otherwise entombed in the root canal system. If macroevacuation is executed according to the above instructions, MicroCannula clogging very, very rarely occurs. In this event, remove the fingerpiece at the white Luer connector and then blow air in the Luer end via the office 3-way syringe.
STERILIZATION AND MAINTENANCE PROCEDURES
After treatment, discard all disposable items, ultrasonically clean and sterilize both the titanium handpiece and fingerpiece. Replace the white Luer cap back on the T-Connector and wipe the entire HATA with a surface disinfectant.
- Lambrianidis T, Tosounidou E, Tzoanopoulou M. The effect of maintaining apical patency on periapical extrusion. J Endod. 2001;27:696-698.
- Tinaz AC, Alacam T, Uzun O, et al. The effect of disruption of apical constriction on periapical extrusion. J Endod. 2005;31:533-535.
- Brown DC, Moore BK, Brown CE Jr, et al. An in vitro study of apical extrusion of sodium hypochlorite during endodontic canal preparation. J Endod. 1995;21:587-591.
- Myers GL, Montgomery S. A comparison of weights of debris extruded apically by conventional filing and Canal Master techniques. J Endod. 1991;17:275-279.
- Desai P, Himel V. Comparative safety of various intracanal irrigation systems. J Endod. 2009; 35(4):545-549.
- Schoeffel GJ. Endodontic Irrigation via Apical Negative Pressure. Presented at: AAE Annual Session. May 2, 2009; Orlando, Fla.
- Torabinejad M, Cho Y, Khademi AA, et al. The effect of various concentrations of sodium hypochlorite on the ability of MTAD to remove the smear layer [published correction appears in J Endod. Jun 2003;29:424]. J Endod. Apr 2003;29:233-239.
- Hockett JL, Dommisch JK, Johnson JD, et al. Antimicrobial efficacy of two irrigation techniques in tapered and nontapered canal preparations: an in vitro study. J Endod. 2008;34:1374-1377.
Disclosure: Dr. Schoeffel holds 2 United States Patents on the EndoVac and receives a royalty from Discus Dental based on sales.
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