Advances in technology have improved the use and quality of tooth-canal instrumentation. Available irrigants such as NaOCl, chlorhexidine, EDTA, and MTAD provide antibacterial, tissue solvent, and smear-removing capabilities that aid in cleaning the root canal system of tissue remnants, bacteria, bacterial products, and dentinal debris. In spite of this, root canals with nonvital pulps often retain viable bacteria after instrumentation (Figure 1).^1,2 The complexity of the root canal system and the inability of instruments or irrigants to eradicate all bacteria contribute to this result. To decrease the bacterial count in teeth of patients whose treatment plans include a series of appointments, a wide range of materials have been sealed in the tooth between appointments as intracanal medicaments.

Volatile Medicaments

A number of volatile aldehydes and phenolic compounds, such as formocresol, camphorated parachlorophenol (CMCP), and cresatin, have been promoted for years as intracanal medicaments. They were usually applied on a cotton pellet and sealed within the pulp chamber. Although these materials posses obvious antibacterial qualities in vitro, their clinical efficacy has not been finalized conclusively. Because they are volatile in nature, the duration of these materials is limited,³ and the potential exists for a spread into the body.^4,5 As a result, there is little emphasis on  the use of volatile medicaments.

Calcium Hydroxide

Currently, calcium hydroxide is the most commonly used intracanal medicament. It can be prepared as a paste by mixing calcium hydroxide powder with sterile water, saline, or anesthetic. Commercially available preparations are also available, which contain glycerine or methyl cellulose to give a viscosity suitable for delivery into the canal (Figures 2-3-4-5-6).

Calcium hydroxide pastes may be placed into the canal by injection, the use of pluggers, or with a lentulo spiral. Placement to the full length of the canal is important to maximize the effects of the calcium hydroxide.

The pH of calcium hydroxide mixed with saline is 12.5⁶. This high pH is believed to contribute to its antibacterial and biologic effects. Using calcium hydroxide as an intracanal medicament for one week has been proved to substantially decrease the bacterial count as compared with canals instrumented in the same way but without the use of calcium hydroxide.⁷

Endotoxin is a component of the cell wall of gram-negative bacteria, which is released upon cell death and has been shown to be a potent initiator of inflammation. Calcium hydroxide can hydrolyze the endotoxin molecule, and it has been suggested that this neutralization of its inflammatory effects may be an important benefit to using calcium hydroxide as an intracanal medicament.⁸ Other evidence has shown that calcium hydroxide is also capable of removing tissue remnants that may remain on canal walls after instrumentation.⁹ This may aid in providing a cleaner canal for obturation.

Chlorhexidine

Chlorhexidine gluconate is an antibacterial material that has been used for years as an oral rinse for plaque control and has more recently received support as an endodontic irrigant and intracanal medicament. Chlorhexidine is less effective against gram-negative bacteria than it is against gram-positive bacteria; there is one gram-positive specie, Enterococcus faecalis, that has frequently received attention as being isolated from persistent infections associated with previously root-filled teeth. Chlorhexidine has proven superior for in vitro antibacterial effectiveness against E. faecalis as compared with calcium hydroxide; the in vivo comparisons are less conclusive.¹⁰

Chlorhexidine is noted for its substantivity, in which its antibacterial effects persist for days or perhaps weeks after placement. This is due to its affinity for and slow release from the hydroxyapatite of dentin. As an intracanal medicament, chlorhexidine can be used as a 2% liquid or gel. The increased viscosity of the gel is thought to aid in its adaptation to the canal walls and provide a more persistent effect. Delivery of chlorhexidine gel can be performed with a file or lentulo spiral.

Conclusion

While a variety of intracanal medicaments are currently available for use during endodontic procedures, selection of the appropriate materials should be based on the material’s predictability, the patient’s condition, and the operator’s comfort with the material’s delivery method. It is imperative that an antibacterial agent be applied immediately following instrumentation to limit the growth of microorganisms within the canal and to reduce the potential of bacterial activity following root canal treatment and crown restoration. As in any other restorative procedure, the patient’s overall medical background should be verified prior to the delivery of intracanal medicaments in order to avoid potential side effects.

*This piece was adapted from an article written by Dr. Robert Scott Gatewood in the Winter 2007 edition of Endodontic Therapy Magazine. Dr. Gatewood is an associate professor and chairman of the department of Endodontics at the University of Mississippi Medical Center School of Dentistry.  

References:

1. Bystrom A, Sundqvist G. The antibacterial action of sodium hypochlorite and EDTA in 60 cases of endodontic therapy. Int Endod J 1985;18(1):35-40.
2. McGurkin-Smith R, Trope M, Caplan D, et al. Reduction of intracanal bacteria using GT rotary instrumentation, 5.25% NAOCl, EDTA, and Ca9OH)₂. J. Endod 2005;31(5):359-363.
3. Messer H, Shepard C, Chen RS. The duration of effectiveness of root canal medicaments. J Endod 1984;10(6):240-245.
4. Hata G, Nishikawa I, Kawazoe S, Toda T. Systemic distribution of 14C-labeled formaldehyde applied in the root canal following pulpectomy. J. Endod 1989;15(11):539-543.
5. Fager FK, Messer HH. Systemic distribution of camphorated monochlorophenol from cotton pellets sealed in pulp chambers. J Endod 1986;12(6):225-230.
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