While sometimes it seems that dental implants are all the rage, many clinicians firmly believe that there’s nothing like preserving natural tooth structure. These intrepid souls advocate root canal treatment (RCT) of a tooth, when possible, rather than extraction. The goal of RCT is to remove diseased or dead pulp tissue from a root canal, and to disinfect and fill the canal as thoroughly as possible.
In a perfect world, every nook and cranny of a canal is smoothly shaped, cleaned and disinfected, leaving canals sterile and ready for a complete fill and a hermetic seal. But in reality, complete disinfection and sterilization are recognized to be impossible in systems as complex as root canals, which are often curved and riddled with lateral offshoots. So clinicians simply have to come as close to complete disinfection and sterilization as they can.
After the shaping and cleaning step, what is left is a pulpless tooth — an empty void. But because bacteria can proliferate in such a vacant space, obturation is key prior to coronal restoration. Obturation involves sealing canal walls and thoroughly packing the canal three-dimensionally (every microscopic crevice) for an apical, coronal and lateral seal. This not only serves to shore up structure, but it can help prevent reinfection by eliminating voids with sealants and core materials.
But it’s not like you can just stuff anything in there. In fact, we’ve come a long way from the early days in endodontics, when everything from lead to arsenic was used to obturate canals. Nowadays, the ideal root canal filling material is not only biocompatible, but it should also be sterilizable, easy to handle, hydrophilic, bacteriostatic, radiopaque, nonstaining, able to seal laterally and vertically, offer low shrinkage upon setting, and, if necessary, easy to remove.
Obturation can be accomplished via a number of techniques. Of course, technique preferences vary widely among clinicians, and sometimes depend on the given situation. But here are some of the most popular:
• Cold lateral compaction involves the placement of an unheated gutta percha master cone into a canal to working length, after sealer has been applied either with the cone or with a lentulo spiral. Remaining spaces along the side of the master cone are filled with additional cones and compacted laterally with a spreader until a solid fill is achieved.
• Warm vertical compaction, or downpacking, is widely recognized as the “Schilder technique” — named for endodontic pioneer Herbert Schilder, DDS. The technique goes hand in hand with a continuously tapered funnel design in the canal. After sealer has been applied, a cone that corresponds to the last file used is inserted to working length. Following this, a heat carrier — typically a plugger that has been heated until it’s red hot — is used to vertically compact the gutta percha.
• Warm lateral compaction is similar, except that heated devices are placed beside the master cone to compress it laterally. The empty lateral space is then filled by subsequent cones that are also compacted laterally until the canal is filled.
• The continuous wave technique involves pushing a heat carrier, usually a commercially available device, through the gutta percha toward the apex. As it is pushed through, it spreads the material laterally, filling the canal. When it is close to working length, the heat is turned off, though downward pressure is continued, forcing material into accessory canals. When the carrier has reached its ultimate depth, after a final burst of heat, the carrier is used to separate the material from the apical plug, which is left in place and tamped down. The rest of the canal may be backfilled with thermoplastic material via injection.
• Carrier-based obturation employs what amounts to a gutta percha point with a handle and stopper. After sealer has been applied, and once working length is established, the stopper is adjusted to reflect working length, and the carrier is placed in an oven or heating device. Once the gutta percha is heated, it can be removed from the oven, the handle is broken off, and it is placed in a canal to working length.
• Hydraulic condensation is a new technique that involves the use of bioceramic sealer. After confirming working length, a clean file or cone is then dipped in bioceramic sealer to coat canal walls. Once the cone is re-inserted and its coronal excess seared off, a plugger is used to vertically condense the material. In this technique, the bioceramic sealer is key in that it behaves less like a sealer and more like a root canal filler with a single gutta percha cone.
Core obturation materials have centered mostly on an inert, thermoplastic material called gutta percha. This is a latex-like sap derived primarily from Palaquium gutta — trees found mostly in Southeast Asia. Used in dentistry since the 1800s, it remains the go-to material for root canal obturation. It’s not, however, a perfect obturation material — primarily due to a tendency to allow marginal leakage as a result of shrinkage and the fact that gutta percha does not stick or bond to anything.
This product category has not exactly been a hotbed of change, but that’s not for lack of trying. Industry efforts to improve upon and ultimately replace gutta percha led to a detour into resin as a core material a few years ago that turned out to be a dead end.
While resin-based formulations offered similar handling properties to gutta percha, and other benefits that gained them a fan base, many felt they didn’t live up to their claims. Some clinicians reported problems with voids, and accounts of debonding and disintegration of the material over the long term began to surface.
Therefore, gutta percha continues to reign supreme as an endodontic mainstay. Though there have been a few tweaks along the way. Gregori Kurtzman, DDS, a Silver Spring, Maryland-based practitioner, who has written extensively on the topic, notes, “With the boom in rotary nickel-titanium files, manufacturers have made cones available that match the files. This allows as low a sealer-to-cone ratio as possible, thereby giving more predictable results.”
James Gutmann, DDS, a Dallas-based endodontist, lecturer, and professor emeritus in restorative sciences at Texas A&M University College of Dentistry in Dallas, adds that while gutta percha remains the same, manufacturers have made some other improvements over the past few years. “Gutta percha points now allow more accurate fitting,” he says, “and core-carriers (once centered around plastic) are made of only gutta percha.”
Gutta percha is typically available from manufacturers as cones (also called points) that are color-coded according to size (thickness) and tapered to complement various sizes of files that have been used to shape canals. There is also what is known as a “core-carrier,” which is basically a cone with plastic handles. These carriers can be heated in an oven and transferred by their handles to the orifice for placement in the canal. The handles then can be broken off, leaving only gutta percha. Cones coated in materials such as resin or glass ionomer cements (GIC) are also available — a move to improve the seal between the core and the sealant on the canal wall.
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- The success of root canal treatments relies on complete obturation of the canal.
- Gutta percha remains the obturation material of choice — actually, it’s pretty much the only choice, but it is available in a range of configurations.
- Gutta percha cones may be used without heating, they may be heated by applying heated instruments, or core-carriers that are heated in an oven may be used.
- Warm gutta percha may also be injected into canals via a syringe.
- Sealers must be used with gutta percha to help plug gaps, provide lubrication and provide a bioactive and antimicrobial element.
- Techniques vary widely, but most rely on instrumentation that includes finger spreaders, pluggers, lentulo spirals, and various heating devices.
Prior to insertion of gutta percha core material, sealers are used to coat the canal walls, serving as lubricants and helping ensure that any voids within the core material or irregularities in the canal wall are adequately filled. They are available in a variety of delivery systems, such as automix syringes — in which the two-part mixing ratios are measured out to perfection. Some clinicians, however, prefer to apply sealers by hand via gutta percha cones or instruments.
Traditional sealers used with gutta percha include calcium hydroxide (CaOH), zinc oxide eugenol (ZOE), and GIC. Sealers resulting from more recent technology have also made an entrance into this product category and are gaining traction. Gutmann notes that over the past few years, resin-based sealers and bioceramic-based sealers have become available.
Bioceramics are inorganic, nonmetal compounds that incorporate materials such as alumina, zirconia, bioactive glass, composites, hydroxyapatite, and resorbable calcium phosphates into a stable, biocompatible substance. When exposed to oral fluids, these materials are also bioactive, in that they release calcium hydroxide, which is capable of forming hydroxyapatite — the main ingredient in dentition.
“The benefits of bioceramic sealers are that they set due to moisture, and are insoluble once set,” says Kurtzman. He adds that in regard to sealers, the current trend leans toward bioceramics and away from the ZOE- and CaOH-based sealers that have been used for many decades.
“ZOE- and CaOH-based sealers,” says Kurtzman, “can dissolve apically when infection recurs in the periapical area. In contrast, bioceramic sealers are very biocompatible and do not leach anything that could have localized inflammatory reactions like ZOE (in which eugenol is tissue irritating). Bioceramics have been used in orthopedics for decades as bone cement for fractures and voids, and have a well-documented history of biocompatibility.”
In fact, in the opinion of Boston-based endodontist Allen Ali Nasseh, DDS — an endodontic education and clinical instructor and lecturer at the Harvard School of Dental Medicine Post Doctoral Endodontics Program and president of the endodontic education and innovation group RealWorldEndo (RealWorldEndo.com) — the greatest change in the past decade has been the introduction of bioceramic sealers. “They have changed obturation dramatically by replacing originally resorbable hydrophobic sealers with dimensionally stable and nonresorbable hydrophilic fillers. The latter have helped simplify obturation significantly, and it has also become clear that hydrophilic cements can flow into oval parts of the canal better than hydrophobic cements.”
- Bioactive: Interacts with biological systems.
- Hydrophilic: Moisture friendly.
- Hydrophobic: Repelled by moisture.
- Inert: Does not interact with biological systems.
- Lentulo spiral: An instrument with a long, flexible, spiral wire. It’s used with a handpiece to apply sealer.
- Monoblock: A solid mass.
- Periapical: Surrounding the apex of the root.
- Plugger: An instrument used for downpacking material into the canal.
- Spreader: Instruments that feature a long taper, and look somewhat like tiny screwdrivers. They are used to compress gutta percha into the sides of the canal.
There is more than one way to obturate a canal, and, of course, each practitioner has a preference. But some methods are more well known than others. “There are basically three ways to go,” says Gutmann. “Lateral compaction, vertical compaction and core-carrier. The most effective may be the core-carrier, because it embodies heat-softened gutta-percha, vertical and lateral compaction and comes as close as you might get to a three-dimensional fill.”
Indeed, many clinicians advocate the use of heat in obturation. But others feel heat is a double-edged sword. Kurtzman, for instance, believes that techniques have moved toward the use of cold single cones from warm compaction obturation. “The problem with warm techniques is gutta percha shrinks about 7% when heated. When it cools, it’s open to the potential for leakage,” says Kurtzman. “With a cold, single-cone technique, when a cone is used that matches the shape of the final file, the ratio of sealer to cone is reduced and you get better adaption with less chance for leakage over time.”
Kurtzman notes that when setting, sealers also undergo shrinkage, losing a percentage of volume. “The lower the volume (less sealer to cone), the lower the overall shrinkage and leakage potential.”
For this reason, Nasseh favors the use of bioceramic sealers, which do not shrink. He also notes that, unlike gutta percha, bioceramic sealers are antimicrobial, hydrophilic, and capable of bonding to dentin. Bioceramic sealers also exhibit better flow properties and don’t harden as quickly as gutta percha upon cooling.
Nonetheless, in Nasseh’s estimation, most obturation techniques are effective as long as the canal has been properly cleaned and shaped. “The current thinking is shifting to the understanding that cleaning those spaces adequately is more important than merely filling them,” he reports.
In the final analysis, says Nasseh, “To obturate a root canal, only gutta percha and a sealing cement are needed in conjunction with a condensation and possibly a heat-delivery tool, depending on the kind of cement used. Some warm techniques may require additional tools but, for the most part, obturation requirements are not, and should not be, complicated.” He adds, “Success is a function of proper implementation of concepts of success, which include microbial control and disinfection, rather than obturation materials or methods alone.”
The holy grail of the hermetically sealed root canal may still be out of reach. But through various innovations, perhaps the day will come when endodontic obturation will involve a single material that will form a biocompatible monoblock fill, impervious to gap formation and leakage. Will bioceramics be the solution? The next time your customers need to “fill ‘er up,” will they stick with regular or go for an upgrade? Time will tell, but for now, the quest for the perfect obturation material continues.
Featured photo by WAKILA/E+/GETTY IMAGES PLUS
From MENTOR. June 2017;8(6): 24, 26,28-29.