Once a tooth is compromised beyond the point that it can be directly restored, the next recommendation may be a root canal. With today’s emphasis on minimally invasive treatment, this option versus implant placement can make a lot of sense.
Filling the Void
Root canal treatment involves cavity preparation, shaping and cleaning canals, and obturation, or the placement of filling material — typically gutta percha. For root canal treatment applications, it is mixed with zinc oxide, heavy metal salts and wax or resin, and is usually available in the shape of cones of various sizes. 1Stone R. Bridging the canal. Mentor. 2018;9(1):22–24,26,28.
Gutta percha is biocompatible, and can be softened with heat to facilitate compaction into the canal and to enhance anatomical adaptation. Unfortunately, it does not bond to tooth structure. This is where sealers come in. Ranging from zinc oxide-eugenol, resins, silicone, glass ionomer or bioglass, they are capable of bonding to dentin as well as to gutta percha. And voila! A seal is born. 2Stone R. Bridging the canal. Mentor. 2018;9(1):22–24,26,28.
On the Cusp
New sealers are constantly emerging, offering improved characteristics for intracanal placement, including improved dimensional stability, hydrophilicity, and adhesive qualities. Some sealers, such as those that are bioceramic, are not only biocompatible, but also bioactive, offering healing and protective properties. Such formulations release calcium hydroxide when they come into contact with fluids. This interacts with phosphates to form hydroxyapatite, the primary building block of dentition. 3Stone R. Bridging the canal. Mentor. 2018;9(1):22–24,26,28.
Bioceramic materials include alumina, zirconia, bioactive glass, glass ceramic, hydroxyapatite and calcium phosphates, as well as bioaggregates and some calcium silicates. Sealers incorporating these materials include mineral trioxide aggregate (MTA) as well as several commercial brands of sealers, some of which comprise nanoparticles for enhanced penetration into dentinal tubules. 4Stone R. Bridging the canal. Mentor. 2018;9(1):22–24,26,28. 5AL-Haddad A, Aziz Z. Bioceramic-based root canal sealers: a review. Int J Biomater. 2016;9753210.
In addition to creating a seal, the goal of obturation in RCT is to affect a three-dimensional fill, wherein the interface between canal anatomy and filler/sealer is complete, with no voids. But one of the trickiest things about canals is that they may be contorted in multiple directions and feature any number of lateral offshoots that are easy to miss and hard to reach.
Experts agree that it is currently impossible to completely sterilize root canals. Instead, the aim is to disinfect as thoroughly as possible prior to thorough obturation, which should entomb any remaining bacteria.
Obturation Techniques for Root Canal Treatment
Some obturation methods rely on the placement of a single gutta percha master cone, coated in bioceramic sealer, whose size corresponds to that of the last instrument used in the canal. This technique is reported to help prevent excessive dentin removal, while resulting in a tight seal. 6 Inside Dentistry. Successful Single Cone-Obturation. Available here. Accessed September 18, 2018.
Another method of creating a three-dimensional fill is through heat. Use of ovens or heated delivery devices to compress master cones, is thought to facilitate the flow of material into the nether reaches of the canal. 7Mentor. Obturation Techniques. Available here.
In each case, once a master cone, and sometimes accessory cones, has been condensed, excess removed and compaction verified, thermoplasticized gutta percha is extruded, backfilling the rest of the canal. 8Advanced Endodontics. Continuous Wave and Hybrid Techniques. Available here. Accessed September 18, 2018.
Isolation and Root Canal Treatment
Also among the challenges when performing root canal treatment is that of keeping the field isolated. Because bacteria-laden saliva can reinfect the canal the clinician is working so hard to disinfect, this is critical. Isolation also prevents instruments and other materials from being swallowed or inhaled.
The American Association of Endodontists considers the use of isolation devices such as rubber dams to be the standard of care. But while rubber dams can be difficult to place, systems such as the Isolite, which also provides illumination, suction and retraction, can facilitate the process. 9Anabtawi MF, Gilbert GH, Bauer MR, et al. Rubber dam use during root canal treatment: findings from the Dental Practice-Based Research Network. J Am Dent Assoc. 2013;144:179–186.
Each clinician must determine his or her own technical preference. It is by finding what works best in his or her hands, that the best chance for RCT success can be realized.