Oral Health Group
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Bonded Endodontic Obturation: Another Quantum Leap Forward for Endodontics

July 1, 2004
by Rich Mounce, DDS and Gary Glassman, DDS, FRCD(C)


The surgical operating microscope and the advent of rotary nickel titanium instrumentation have both provided a quantum leap forward towards a higher standard of endodontics. Adhesion has done much the same for restorative dentistry. Blending the best of adhesion into endodontic obturation has now become reality. In the authors’ opinion, adhesion in canal obturation represents another quantum leap forward for the specialty. Recently, Resilon Research LLC, (Madison, CT) has introduced Resilon obturating points (a soft resin) and resin sealer which when used in combination with a self etch primer after smear layer removal, allow creation of a solid “monoblock” (a material which is contiguous from its resin tags in cleared dentinal tubules through sealer to the core canal filler). The material not only fully obturates canal anatomy (especially through the compaction possible with warm obturation techniques); it diminishes coronal microleakage through bonding to the cleared dentinal tubules. Resilon Products (RP) are marketed as RealSeal (SybronEndo, Orange, CA). and Epiphany (Pentron, Wallingford, CT) (Figs. 1-2). The authors experience is with the RealSeal brand and will reference it throughout the report. It is hard to overstate the advance that this represents (detailed in this paper) relative to gutta percha.

Gutta percha, despite its many advantages (non toxic, biocompatible, thermoplastic and retreatable) and status as a time honored standard for endodontic obturation possesses one significant limitation. Gutta percha cannot prevent coronal microleakage which places the entire procedure at risk in the event of recurrent caries or subsequent microleakage if either the patient does not have the tooth restored or the subsequent restoration is not satisfactory (and microleakage occurs). Gutta percha (with or without sealer) provides a relatively poor to non existent barrier to prevent the coronal to apical migration of bacteria after obturation as gutta percha (with and without sealer) does not bond to canal walls, it can only adapt1-4 (Fig. 3). In addition, even if the standard of endodontic therapy is excellent, a lack of coronal seal or recurrent decay significantly diminish the possibilities for endodontic success over the long term as bacteria can migrate in a coronal to apical direction and initiate failure. Ironically, coronal seal is a major indicator of the potential for endodontic success or failure aside from the quality of the endodontic treatment or the presence of gutta percha.5,6 As a result, gutta percha has been more of a “filler” that took up space within the root canal system. While imperfect, gutta percha has been the best material clinicians have had up to this point in time.

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These significant limitations are overcome by RealSeal. By removal of the smear layer (Figs. 4-5), produced during instrumentation, it is now possible to bond the obturating material into the dentinal tubules and create (as mentioned above) a “monoblock” of resin sealer and resin core filling material (Figs. 6-11). The root canal system can now be sealed to some degree (technique and clinician dependent) along the entire length of the canal (from orifice to apex) preventing microbial migration. One strategic advantage that this gives the clinician is that if the patient does not get a coronal restoration as they should (assuming that the treatment has been performed correctly), Resilon is significantly resistant to leakage along its length and one of the key factors responsible for endodontic failure has been eliminated or dramatically reduced. A recent study by Shipper, et al found that comparing bacterial leakage using Streptococcus mutans and Enterococcus faecalis through both gutta percha and Resilon over a 30 day period demonstrated that Resilon showed minimal leakage which was statistically significant compared to gutta percha.7 In essence, now, Resilon endodontic obturating material can significantly diminish microleakage, a property not possessed by gutta percha.

RealSeal is a thermoplastic synthetic resin material based on the polymers of polyester and contains a difunctional methacrylate resin, bioactive glass and radio opaque fillers. RealSeal sealer contains UDMA, PEGDMA, EBPADMA and BisGMA resins, silane treated barium borosilicate glasses, barium sulfate, silica, calcium hydroxide, bismuth oxychloride with amines, peroxide, photo initiator, stabilizers and pigment. RealSeal Primer is an acidic monomer solution in water. RealSeal is non toxic, FDA approved and non mutagenic. With its radio opaque fillers, RealSeal is a highly radio opaque material. The sealer is resorbable. Aside from its capacity to be thermoplasticized, RealSeal can be dissolved with chloroform and retreated. There are unsubstantiated statements on the internet that RealSeal shrinks substantially less than gutta percha but this fact cannot be verified from the literature at this time.

One remarkable feature about RealSeal is that in virtually all handling characteristics, it handles and feels like gutta percha. In other words, it can be used with all the common present forms of endodontic obturation (vertical compaction of warm gutta percha, cold lateral condensation, lateral/vertical combinations) and there is virtually no learning curve to its use. This allows the clinician to use this new technology with only two added steps relative to common endodontic treatment regimens, clearing the smear layer and placing the self etch primer (to be described). RealSeal points are available in introductory kits of various configurations and as individual components (.02, .04, .06 tapered cones with a variety of tip sizes along with accessory points ranging in size from x-fine to large). RealSeal cones are very flexible and pellets of the material are available for the Obtura gun (Spartan Obtura, Fenton, MO). At present, no carrier based product exists that possesses Resilon technology and none is on the horizon to the authors knowledge.

Because root canal therapy removes some amount of dentin within the tooth, the potential exists to weaken the tooth to some degree and make the tooth more susceptible to vertical root fracture. Gutta percha has no potential to strengthen the roots after treatment. RealSeal in contrast has the potential to strengthen roots. In vitro, Teixeira, et al. found that the resistance to root fracture found with Resilon was superior (P=0.037) to gutta percha/AH 26 sealer (Dentsply Maillefer) using both lateral and vertical condensation.8 In essence, Resilon used in the manner tested increased the fracture resistance of single canal endodontically treated teeth as compared to other common gutta percha techniques. While this might be considered a secondary benefit as compared to its potential to reduce coronal to apical leakage of bacteria, it is not in any way inconsequential.

CLINICAL TECHNIQUE

Canal Preparation: The canal is prepared with the protocol normally used. Canal preparation techniques do not need to be altered to facilitate the use of the material.

Smear Layer Removal: Throughout the entire instrumentation protocol an alternating sequence of 17% EDTA and sodium hypochlorite must be used to remove the smear layer. The smear layer is the layer of organic and inorganic debris that is created along the walls of the canals during instrumentation. While 17% liquid EDTA can be used as a final canal rinse, the author recommends SmearClear (SybronEndo, Orange, CA) as a final rinse where the liquid is allowed to soak into the tubules throughout the entire canal system for 1-2 minutes. SmearClear contains surfactants which enhance wetting of the canal walls and provide optimal smear layer removal. It is important not to use either sodium hypochlorite or absolute alcohol as the final rinse to dry the canal after the smear layer is removed. Sodium hypochlorite will disrupt the sealer bond and absolute alcohol will act as a drying agent. The walls need not be completely dry as the sealer is hydrophilic.

Placement of the Primer: After the canal is dried with paper points, a brush provided by the manuf
acturer can be used to bring the self etch primer into the coronal third of the canal. Alternatively, a paper point of an appropriate taper can be super saturated with the adhesive that has been introduced into a plastic bonding well. The primer should be dispersed evenly on the canal walls yet not extrude apically. Under a surgical operating microscope, one may see if any primer remains in the canal or if the excess has been removed.

Mixing of the Resin Sealer: Next, the dual syringe (containing the sealer) is used to express the sealer onto the mixing pad. The dual syringe has tips which mix the sealer as it is expressed. As an aside, it is possible to forgo the use of the mixing tip provided in the kits and hand mix the sealer with a spatula (express a small amount of both sealer components onto the pad without the mixing tip) and save a significant amount of sealer from every dual syringe although the mixing tips eliminate one step relative to hand spatulation. Cone fit (Fig. 12) and placement of the sealer can be performed as per the clinician’s present technique. While preferred methods for sealer placement vary widely, the author is not in favor of use of a lentulo spiral to introduce sealer of any type and this personal preference extends to the resin sealer used with RealSeal due to the unwarranted risk of apical extrusion as well as potential for lentulo separation.

Obturation: Stainless steel Schilder pluggers (Tulsa/Dentsply, Tulsa, OK), Obtura pluggers (Obtura/Spartan, Fenton, MO),or Buchanan Hand Pluggers (SybronEndo, Orange, CA) are prefit into the canals to their binding point. Rubber stoppers are adjusted on these pluggers to the occlusal reference point corresponding to 2 mm short of the apical binding point. These pluggers are placed aside to be used later in the back fill phase of canal obturation (Figs. 13A, B & C). The The System-B Buchanan plugger is prefit to its binding point in the canal, and the rubber stop is adjusted adjacent to the appropriate reference point (Fig. 14a,b). The canal is dried and measured one last time with feather-tipped paper points, and the master RealSeal cone is cemented in the canal with sealer (Fig. 15).

The omni directional trigger switch on the System B handpiece is made active. The plugger is driven through the center of the RealSeal cone in a single motion (about one second), to a point about 3-4 mm shy of its apical binding point (Figs. 16 & 17). While maintaining pressure on the plugger, the trigger switch is released and the plugger slows its apical movement as the plugger tip cools (about one second) to within 2 mm from its apical binding point. After the plugger stops, short of its binding point apical pressure on the plugger is sustained until the apical mass of RealSeal has set (five to ten seconds), taking up any shrinkage that occurs upon cooling (Fig. 18).

After the apical mass has set, the touch switch is made active again, for a one-second surge of heat. Pause for one-second after this separation burst, and then remove the heated plugger and the surplus RealSeal (Fig. 19 & 20). Because these pluggers heat from their tips, this separation burst of heat allows for quick, sure severance of the plugger from the already condensed and set apical mass of RealSeal, minimizing the possibility of pulling the master cone out. Be certain to limit the length of this heat burst, as the goal is separation from the apical mass of RealSeal without reheating it. Clinicians must be very alert during the first second of the downpack so that the binding point is not reached before completion of the downpack. If heat is held for too long, the plugger drops to its binding point in the canal and then cannot maintain condensation pressure on the apical mass of gutta-percha during cooling, possibly allowing it to pull away from the canal walls. If binding length is reached by mistake, the heat plugger should be removed immediately and the small end of the nickel-titanium Buchanan hand plugger (Sybron Endo, Orange, CA), or Obtura pluggers (Obtura/Spartan, Fenton, MO) should be used to condense the apical mass of gutta-percha until set. A final downpacking nuance is required for ovoid or canals that join into a common apical foramen (apically contiguous). These two canal forms can allow for venting of condensation backpressures during a Continuous Wave downpack and less then ideal filling of canal irregularities. In both canals, a secondary RealSeal cone is first to butt into the master cone short of the canal terminus and the fat end of the hand plugger is used to hold it in place during the downpack. For ovoid canals, the hand plugger is placed at the orifice alongside the heat plugger. For apically contiguous canals, the hand plugger is held at the orifice of the other canal.

BACKFILLING

The Obtura II (Obtura/Spartan, Fenton, MO) thermosoftened injection molded delivery system is used to backfill the canal space at a temperature of between 150C-175C. A 23 gauge applicator tip is suitable for most root canals (Fig. 21). A thin layer of sealer is applied to the root canal walls with a paper point before backfilling. The applicator tip is placed into the root canal space until it penetrates the coronal aspect of the apical plug of RealSeal. A bolus of 5 to 6 mm of RealSeal is then deposited. As thermosoftened RealSeal is extruded from the applicator tip, the viscosity gradient of the back pressure produced will push the tip coronally from the root canal space.The technique sensitivity requires that when this sensation occurs, the operator must sustain pressure on the trigger mechanism as the applicator tip moves from the canal. The prefit hand condensers are then used in sequence to maximize the density and homogeneity of the compressed gutta-percha mass. This sequence of thermosoftened gutta-percha injection and progressive compaction is continued until the obturation of the entire root canal space is achieved (Figs. 22-28).

Post Preparation or Curing the Coronal third: If required, a post space may be prepared at the time of obturation only after the canals are first filled to the level of the orifices. If any lateral/accessory canals and/or dentinal tubules have not been sealed during the down pack, perhaps they may be sealed on the back fill. If post space needs to be prepared after the material has set up and the monoblock created, ideally, a small amount of chloroform can be introduced and the RealSeal dissolved to the desired depth in the canal and post preparation accomplished. A curing light can also be used to help cure several mm of the material in the coronal third and the material will self cure within one hour.

Empirically, the authors have found the transition from gutta percha to RealSeal to be virtually seamless and without a learning curve and are using this material exclusively. The added step of placing the primer is virtually negligible with regard to the amount of time it takes in the context of the entire procedure and the benefits derived (Figs. 29A & B).

With certainty, this material will be extensively studied, tested and reported in the literature in the years to come. Technique nuances with regard to its handling and creation of the greatest possible efficiency in its use may emerge. This said, in the authors’ opinion, over the next decade, as studies in all probability will continue to validate this material, it is very possible that gutta percha will become obsolete until another material can be found which will give greater clinical benefit with less patient risk than RealSeal. In the authors’ opinion, this material truly is a quantum leap forward in the modern era of endodontics and worthy of consideration for use as an obturating material in place of gutta percha.

Dr. Mounce is in private endodontic practice in Portland, OR.

Dr. Glassman in a Fellow of the Royal Endodontic in Canada, endodontic consultant for Oral Health Dental Journal and is in a group endodontic practice in Toronto, ON. Drs. Mounce and Glassman have no commercial interests in products in this article.

Resilon, Epiphany and RealSeal have received regulatory clea
rance from the FDA and has the proper documentation to allow placement of the CE mark for European sales. At the time of this publication Resilon, Epiphany and RealSeal are undergoing the approval process by Health Canada.

Oral Health welcomes this original article.

REFERENCES

1.Barrieshi KM, Walton RE, Johnson WT, Drake DR. Coronal leakage of mixed anaerobic bacteria after obturation and post space preparation. Oral Surg 1997;84:310-4.

2.Torabinejad M, Ung B, Kettering JD In vitro bacterial penetration of coronally unsealed Endodontically treated teeth, J. Endod. 1990 Dec; 16(12):566-9.

3.Saunders WP, Saunders EM Assessment of leakage in the restored pulp chamber of Endodontically treated multirooted teeth Int. Endod J. 1990 Jan;23(1):28-33.

4.Chailertvanitkul P, Saunders WP, Saunders EM, MacKenzie D, An evaluation of microbial coronal leakage in the restored pulp chamber of root canal treated multirooted teeth Int Endod. J 1997 Sept;30(5):318-22.

5.Swartz DB, Skidmore AE, Griffin JA. Twenty years of Endodontic success and failure. J Endod. 1983;9: 198-202.

6.Ray HA, Trope M. Periapical status of Endodontically treated teeth in relation to the technical quality of the root filling and the coronal restoration. Int Endod. J 1995;28:12-18.

7.Shipper G, Orstavik D, Teixeira FB, Trope M, An evaluation of microbial leakage in roots filled with a thermoplastic synthetic polymer based root canal filling material (Resilon), J Endod, 2004 May; 30(5):342-7.

8.F.B. Teixeira, E.C. Teixeira, J. Y. Thompson, M. Trope. IADR/AADR/CADR 82nd General Session, March 10-13, 2004.


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