What is the ideal endodontic interappointment medicament, and what are its most effective placement and removal techniques?

Drs. Carlos A.S. Ramos, Richard D. Tuttle, and Mr. Daniel C. White explain the benefits of UltraCal^® XS

Due to the central role of microbes in the pathogenesis of primary apical periodontitis, it is logical that eradication of the microorganisms from the infected tooth is regarded as the key to healing. The technical and biological goal of root canal treatments is to shape the root canal(s) in such a way that complete disinfection can be achieved and the root canal system can be prepared for successful obturation. 

If eradication of the infection cannot be successfully completed and if the residual microbes communicate with host tissues, healing will be compromised. Furthermore, the new ecological environment may contribute to the development of a more resistant facultative microflora.

The most common sites for bacteria to remain after root canal therapy are in the apical portion of the main canal and in the apical delta (the apical lateral canals). In teeth affected with apical periodontitis, the bacteria residing in the dentinal tubules can develop a biofilm on the external root surface. In such teeth, there is a strongly increased possibility that invasion of dentin by microbes from the main root plays a major role in the development and resistance to treatment of endodontic infections. This will usually result in the development of a resistance to future treatments for endodontic infections.

There are several necessary elements in the control of endodontic infection, each of which could be the cause of treatment failure or prolong the healing process. These elements include complete canal instrumentation, adequate irrigation during the procedure, and the proper placement of a medicament in the canal between appointments. The presence of biofilm in these situations makes the proper chemo-mechanical preparation paramount in any endodontic treatment. 

The biofilm and the surface layer of infected dentin must be eliminated during the instrumentation and chemical irrigation of the canal. Complex internal anatomy such as canal fins, wings, recesses, or isthmuses make absolute cleaning and disinfection nearly impossible. The popular engine-driven instrumentation techniques currently used can only reach the central body of the canal. These techniques will leave areas of the canal untouched because their design prohibits them from reaching and removing the microbes residing in the irregular recesses and apical ramifications of the canals. These are the same bacteria associated with apical periodontitis that are found in the dentinal tubules. 

Proper use of chemical irrigation will help disinfect these areas, but the antibacterial irrigants are not  left in the canal long enough for them to reach effective concentrations that would kill bacteria harbored in these anatomic complexities. 

An interappointment medication is used so that the prolonged exposure will allow the chemical to have the proper antibacterial effect in those areas inaccessible to instruments and/or irrigants. The most effective interappointment dressing is a material that is not easily dissolved and replaced by tissue fluid and that can remain relatively intact over weeks or months.

A calcium hydroxide paste combines several attractive features of a good canal dressing. It is strongly alkaline (pH 12.5) and dissociates into calcium and hydroxide ions in an aqueous solution without completely dissolving. The released hydroxide ions are absorbed into the surrounding tissues, elevating the pH, which provides the antimicrobial effect. Because of the fairly low solubility of the paste, it may be left in the canals for relatively long periods of time. Calcium hydroxide is also effective in arresting inflammatory root resorption and promotes the reparative process of periapical tissues resulting in the formation of hard tissues.  

One of the advantages of calcium hydroxide is that it has an effect on microorganisms even when not in direct contact. This is because of the high pH environment created and because it absorbs the CO₂ required by bacteria for growth. Therefore, the most effective formulation of the Ca(OH)₂  material will allow the hydroxyl ions to escape and diffuse into the dentinal tubules or pass through the apical foramen and reach surrounding tissues. 

The best technique for using calcium hydroxide is to place and condense the paste into the canals. Historically, this has been done with the same instrumentation files or engine-driven paste carriers, and can be difficult to execute—especially when working with very narrow or curved canals. 

One canal dressing currently on the market is UltraCal^® XS from Ultradent Products, Inc. It is an aqueous, radiopaque formulation of nonsetting calcium hydroxide paste with a pH of 12.5. This premixed paste is delivered or “injected” from a syringe through a 29ga NaviTip^® delivery tip directly into the canal. 

The alternative to this technique is mixing a calcium hydroxide paste in the operatory and then using a spiral instrument to place the material into the canals. The syringe-delivered UltraCal XS technique is faster and more dependable for less-experienced operators or those practitioners not performing this treatment on a regular basis. 

The quality of the placement of calcium hydroxide in the canal system during the early stages after extirpation/debridement can be affected by the degree of remaining adherent tissue within the canal and possible persistent exudation. In such situations, the properties of the UltraCal XS paste when used as an interappointment medicament allow the inflammatory symptoms to subside and allow better fill at the second visit.

As well as producing a more reliable result, especially in posterior teeth, the placing of Ca(OH)₂ with a 29ga NaviTip eliminates the possibility of separating a spiral instrument during the procedure. When there is instrument separation in the canal, it is troublesome for the treating dentist and may possibly require the involvement of a specialist. UltraCal XS allows the operator to deliver the correct amount of Ca(OH)₂ to the working length, preventing any material from being inadvertently extruded past the open apex into the periradicular tissues, especially if a chronic or large lesion is present.

UltraCal XS formulation has been shown to have good antibacterial activity starting in as quickly as 12 hours. Studies have shown it is more effective over longer periods of time when compared with camphorated paramonochlorophenol (CPMC) and less toxic than formocresol. The prolonged antibacterial activity of UltraCal XS is the result of its ability to destroy bacterial cytoplasmic membranes by releasing hydroxyl ions, and the activation of tissue enzymes such as alkaline phosphates.

Studies have shown that up to 35% of 16-year-old males have suffered either primary or secondary dentition trauma. This demonstrates how common this trauma occurs in adolescents and how important it is that there is a reliable product and quick and simple technique available on the market. When a treatment requires apexification, the Ca(OH)₂ must be placed into the open-ended canal to provide a favorable environment for the formation of a hard-tissue barrier.

A paste preparation containing nonsetting calcium hydroxide can be difficult to completely remove from the canal walls without the proper materials and technique. The paste is difficult to remove because of the irregular surfaces of the canal walls. It has been shown that UltraCal XS can be removed by using 20% citric acid and the NaviTip^® FX^® tip. This is a strong but flexible delivery tip with small fibers attached to the last few millimeters, making it look like a miniature bottle brush. The citric acid is expressed into the canal and used to “scrub” away the paste from the canal walls. After approximately 60 seconds, the citric acid has softened and broken down the UltraCal XS so it can then be easily rinsed away.

Once the canal has been adequately rinsed, it is ready for obturation. 

References

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Zmener O, Pameijer CH, Banegas G. An in vitro study of the pH of three calcium hydroxide dressing materials. Dental Traumatol. 2007;23(1):21-25.

Haapasalo M, Shen Y. Current therapeutic options for endodontic biofilms. Endod Topics. 2010;22(1):79-98.

Gibson R, Howlett P, Cole BO. Efficacy of spirally filled versus injected non-setting calcium hydroxide dressings. Dental Traumatol. 2008;24(3):356-359.

Pérez F, Franchi M, Péli JF. Effect of calcium hydroxide form and placement on root dentine pH. Int Endod J. 2001;34(6):417-423.