An Alternative to Gutta-Percha for Root Canal Obturation

Obturation of the cleaned and shaped root canal space has been performed for many years using a core of gutta-percha rubber cones combined with various formulations of sealer cements. This step in root canal treatment is an effort to create a root canal system that is sealed from reinfection resulting from coronal leakage, and to entomb residual bacteria and their by-products remaining in the roots following cleaning and shaping procedures. The gutta-percha cones can be manipulated into the root canal with either cold lateral condensation, or through a method which involves softening the core filling material with the application of heat, which was introduced more than 40 years ago by Dr. Schilder.1 The gutta-percha and sealer filling material has been the most popular and most tested filling material throughout the history of nonsurgical endodontic procedures.

THERMOPLASTIC FILLING MATERIALS INTRODUCED

Despite significant advances in materials science over the past 50 years, it was just recently that an alternative filling material for root canal obturation was introduced and studied in an attempt to improve upon the successful history of gutta-percha. A new a polycaprolactone resin-based thermoplastic filling material (Resilon [Resilon Research LLC]) has been introduced that differs from gutta-percha—the rubber in the gutta-percha material has been replaced with a urethane-based resin. A dual-cured methacrylate resin sealer cement (Epiphany [Pentron Clinical Technologies]) was developed to be utilized with a self-etching primer in association with Resilon in an attempt to create a root filling material that is of a single, solid, bonded material. This system differs from the gutta-percha sealer-based obturation material because it has the ability, through dentin adhesive resin-bonding technology, to bond the root canal walls to the sealer cement, which in turn bonds to the core filling material. This has the potential to strengthen roots and to improve the leakage resistance of the obturated root, hopefully improving nonsurgical endodontic outcome success over the long term. The Resilon and Epiphany obturation material is available under different names: Resilon/Epiphany (Pentron Clinical Technologies), Resinate (Obtura Spartan), and RealSeal (SybronEndo).
In the past 4 years, sponsored and independent research has been busy determining if the new Resilon material is an acceptable alternative to the time-tested gutta-percha and sealer. Factors that have been tested include the cement’s cellular toxicity, bacterial leakage in filled roots, fluid filtration leakage comparisons, microscopic bonding visual analyses, bond strength to root dentin studies, periapical inflammation evaluations, and clinical outcome comparisons. Based on the majority of the current research through 2008 covering the various aspects of the new material, studies show that the new filling material is a viable alternative to the gutta-percha-sealer technique for filling roots in nonsurgical endodontic treatment. Furthermore, future research and development may eventually reveal that it has the potential to be a better material than gutta-percha.

NEW MATERIAL CHALLENGES: HANDLING

Despite significant amounts of published research, there is little information about the handling difference between this new root-filling material compared to its traditional alternative. While the dispensing of the Resilon/Epiphany system comes in similar standardized (ISO) cone forms, or pellet form for use in heated syringable dispensing systems (ie, Obtura II [Obtura Spartan] or the Hot Shot [Discus Dental]); the newer material handles differently in several ways. The Resilon core-filling material has less body stiffness and cohesion when compared to a standard gutta-percha cone. This translates into a cone that is softer (less stiff) and can be pulled apart easier. For example, if a master cone does not match the instrumentation size precisely, a cone that fits 0.5 mm short of the desired length cannot be “pushed” that extra distance with pressure on the cone itself. This is because the softer cone will buckle under pressure and will not slide apically like a gutta-percha cone might have a tendency to do. Additionally, if a Resilon cone is placed into a canal where it has very firm “tug-back,” if the cone is pulled on to withdraw it, there is a risk that the cone can be pulled apart upon withdrawal leaving the firm-fitting apical fragment in place. Of course, the flipside of this situation is that less tugback is required to successfully perform various obturation procedures. For example, when using a single master cone warm vertical obturation technique and there is inadequate tug-back present, the master cone could be withdrawn attached to the heated plugger. This is more difficult to do with a softer Resilon cone. Although the cone feels different in this subtle way, its flow characteristics and adaptability to the root canal walls have been studied and found to perform comparably to heated gutta-percha with sealer techniques in replicating anatomic depressions and filling lateral canals.2-4 In lateral condensation filling techniques, the softer cone does lead to an increased spreader-depth penetration versus gutta-percha cones.5 As a result, this permits further spreader penetration, which is essential for better master cone adaptation.6

Figure 1. Tooth No. 18 is obturated with Resinate (A brand of Resilon [Obtura Spartan]) obturation material. Note the greater radiopacity of this filling material compared to the gutta-percha filling in tooth No. 19.

Not only does the higher contrast increase the possibility of a void showing up, but the consistency of Resilon may also encourage void formation. This is especially the case when back-filling the root canal in bulk using an injectable filling device like an Obtura gun. When using gutta-percha, the Obtura gun dispensing needle can be placed in the canal, and when the gutta-percha is extruded from the gun, the tip of the gun will back out of the root canal from pressure of the stiff bodied gutta-percha material. The Resilon material, even though it is used at a much lower temperature, does not have the body and firmness to back the Obtura gun out, and instead can flow around the sides of the needle without backing out the gun’s tip. By filling not with a single increment, but 2 to 3 smaller amounts that are individually condensed, this problem can be successfully avoided.
The Resilon material seems to be “stickier” as well. When a large amount of the warmed material is injected into the root canal, if a condensation plugger (Figure 3) is inserted in deeply to vertically condense the material into the root canal, the Resilon material will have a tendency to stick to the plugger. As a result, it can be completely or partially withdrawn instead of remaining in the canal space. Once again, this problem can be avoided by injecting multiple smaller backfilling increments that do not require deep condenser penetration.
Greater filling material radio-pacity also means that overfilling becomes more apparent. While it takes large amounts of ZOE sealer extruded beyond the root apex to visualize the overfilling on a radiograph, it takes very little extruded Epiphany sealer to be visible on radiographs. Pumping a master cone to distribute the Epiphany cement in a patent root canal will frequently result in significant sealer extrusion; and while studies show that extruded Epiphany and Resilon is biocompatible and tolerated as well as other gutta-percha-sealer type root filling materials9, keeping the root filling confined to the spaces of the root canal is an objective of nonsurgical endodontic therapy. Therefore, the technique of pumping master cones or precoating the canal with sealer is not recommended.
Since the Resilon-Epiphany root filling material is a composite resin-based system, it will not pose a deleterious effect upon the subsequent resin-bonding procedures often used for coronal restorations. On the other hand, it has been shown that these bonding procedures can be affected by eugenol-containing root fillings, especially eugenol-containing sealers.10,11 The Resilon root filling can be light-cured to a coronal depth of 2 mm (according to the manufacturer). However, due to the unfavorable root canal C-factor and inherent polymerization shrinkage that is exacerbated when curing rapidly with a light, this is not a required step.12 The Resilon/Epiphany self-curing time is approximately 30 minutes in the deep areas that are unreachable by light curing.5

Figure 3. S-Kondensors (Obtura Spartan).

Technically there are a few differences involving the use of the new material that are easily incorporated into the obturation steps, as mentioned earlier. When looking at the bigger picture, there are significant hurdles that a root canal filling material must overcome to produce a completely sealed root canal due to the bonding difficulties encountered within the root canal system.13,14 The largest and potentially negative issues are as follows: the presence of intracanal moisture and its effect on bonding agents; the unfavorable bonding surface configuration of the root canals; the microscopic root surface characteristics; and the flexing during tooth function that potentially leads to root filling debonding. Despite these issues, Resilon has performed favorably in various leakage comparisons when compared to other filling materials. Current studies show that the Resilon/Epiphany root filling material performs favorably in the presence of intracanal moisture, even when residual calcium hydroxide is left behind in the canals.15 Clinically, outcome studies show that the success rate between gutta-percha filled cases and Resilon filled cases are comparable.16,17 Even though the type of material that fills the roots of endodontically-treated teeth is not an essential factor to permit the healing of apical periodontitis in the absence of coronal leakage,18 recurrent caries and restorative failures do occur. Therefore, a root canal filling that seals totally is needed.
It is well known that when a gutta-percha and sealer is in contact with saliva in the oral cavity, complete reinfection of the root canal can occur in a short amount of time.19 This is an indication that the current popular choice of root filling materials does not always perform as expected, and a newer filling material is needed that can perform with even better results.

CONCLUSION

In the past 4 years, Resilon, and its other brand names Resinate (Figure 4) and RealSeal, have been shown to be an effective alternative to gutta-percha for filling the roots of endodontically treated teeth. With further studies, research, and development, this material may evolve to eventually retire gutta-percha as the endodontic root filling of choice.

References

Dr. Guess is a Diplomate of the American Board of Endodontics and maintains his private endodontic practice in La Jolla, California. He is an associate clinical professor at the University of Pennsylvania, in the Department of Endodontics. He is the technology editor for the San Diego County Dental Society newsletter, and has published numerous research papers in the Journal of Endodontics. He can be reached by e-mail at endo@drguess.com.

Disclosure: Dr. Guess has no financial interest in any of the companies mentioned in this article.