It is important that treatment procedures in endodontics include techniques that remove bacteria already present and prevent further microbial entry into the root canal system.¹ Trials have demonstrated that the success rate of initial endodontic treatment is between 85% and 96%.^2-4 Endodontic therapy is a viable and highly successful option that allows patients to maintain their natural dentition.

Several factors influence the success or failure of endodontic therapy. Most failures can be attributed to the presence of bacteria; the most common route is through the coronal portion.⁵ In 1991, Vire examined the cause of failure of endodontically treated teeth that were extracted over a 1-year period.⁶ Of these, 59.4% were prosthetic failures primarily caused by crown fracture, which led to coronal recontamination. Teeth that had been crowned had significantly greater longevity than the teeth without crowns. A more recent study by Lazarski and colleagues showed that over 3.5 years, 95% of endodontically treated teeth remained functional, and teeth that were not restored after endodontic therapy were significantly more likely to be extracted than adequately restored teeth.³

In an investigation by Swanson and Madison, it was concluded that a significant amount of coronal leakage is evident when a root canal has been exposed to artificial saliva for as little as 3 days.⁵ Also, Torabinejad and colleagues found that 50% of single-rooted teeth that were obturated using lateral condensation and exposed to a microbial challenge were contaminated with bacteria along the entire length of the root canal after 19 to 42 days (dependent on the microorganism).⁷ In a cross-sectional study, Siqueira and colleagues demonstrated that endodontically treated teeth with sufficient endodontic treatment and coronal restoration had a 23% higher rate of success when compared with effectively obturated endodontically treated teeth with no restorations.⁸

Because coronal leakage is a major contributor to endodontic failure and most permanent restorations are not placed immediately after endodontic therapy, it is important that temporary restorations provide a seal against fluids from the oral cavity to the root canal system. Also, these materials must be easy to place and remove, provide adequate esthetics, and protect tooth structure during the treatment.⁹ 

A variety of materials have been used to achieve a coronal seal after endodontic treatment. Some include gutta-percha, zinc oxide-eugenol preparations, glass ionomers, and composite resins. Previous studies have focused on the efficacy of these materials to adhere to the criteria. Because primary care dentists provide the majority of endodontic care, it is important they choose the appropriate materials to help ensure a good prognosis for the teeth they have endodontically treated. Primary dental care providers also should be familiar with various alternative materials that they may wish to use or that may be used by the endodontists to whom they refer.

Cavit
Cavit^a is a premixed temporary material that contains zinc oxide, calcium sulfate, zinc sulfate, glycol acetate, polyvinyl acetate resins, polyvinyl chlorine acetate, triethanolamine, and pigments. It comes in several delivery methods and is simple to place and manipulate. Studies have shown it to be an effective temporary restorative material after endodontic therapy. Sauaia and colleagues determined that it was superior to both a glass ionomer and a composite in preventing coronal leakage.¹⁰ Cavit also has been shown to resist microleakage for up to 2 weeks when compared with a composite and with Interim Restorative Material^b (IRM) in a laboratory setting.¹¹ However, it is important to note that a minimum thickness of 3.5 mm of Cavit is necessary to obtain an accurate seal against leakage.¹²

IRM
IRM is a zinc oxide-eugenol cement reinforced with polymethyl methacrylate. It does not bond to the tooth structure; however, it does provide compressive strength. IRM differs from Cavit because it requires mixing a powder and liquid preparation. This may be accomplished through trituration (capsule form) or traditional hand mixing (vials of powder and liquid).

IRM also has strength and good sealing properties. Zaia and colleagues demonstrated that it was superior in preventing coronal microleakage when compared with 2 brands of composite.¹³ Seventy-five percent of specimens remain sealed with IRM vs 54% that were sealed with composite.¹³ Hagemeier and colleagues showed that a Cavit and IRM “sandwich” provided excellent coronal-sealing properties.¹⁴ Although this may not be clinically feasible, this technique capitalizes on the best attributes of both materials to provide a resilient seal.

Glass Ionomer
Glass ionomer cements bond chemically to tooth structure. They are tooth-colored, biocompatible, and release fluoride. Glass ionomer cements are derived from polyacrylic acid and a glass component that is usually a fluoroaluminosilicate.¹⁵ The coefficient of thermal expansion of a conventional glass ionomer cement is close to that of dental hard tissue and has been cited as a significant reason for the material’s good marginal adaptation.¹⁶ 

Glass ionomer–based restorative materials can be used as temporary restorations during or after endodontic therapy, especially in cases that require longer temporization. In fact, according to the manufacturer, the purpose of Fuji Triage^c is to fill endodontic accesses. In a recent study by Seiler, 5 restorative materials (IRM, Cavit, Fuji II LC^c, Fuji IX^c, and Fuji Triage) were used to coronally seal endodontically treated teeth against bacterial leakage.¹⁷ The results of this in vitro study showed that the glass ionomer and resin-modified glass ionomer restorative materials (Fuji II, Fuji IX, and Triage) provided a better coronal seal against Streptococcus mutans than zinc oxide-eugenol in endodontic access preparations. In a study by Chailertvanitkul and colleagues, the floor of the root canal chamber and the access were covered or filled with a resin-modified glass ionomer and monitored for bacterial leakage for 60 days.¹⁸ At the end of the period, none of the teeth that were restored with the glass ionomer showed any leakage.

Although the above studies yielded good results for glass ionomers in preventing coronal microleakage, other materials may perform better. For instance, in a 1993 study, 3 materials were examined for the best prevention of dye penetration into an obturated root canal space. Of them, the glass ionomer allowed the greatest amount of leakage into the canal space; the composite performed significantly better.¹⁹

Composite Resin
Composite, although normally used as an esthetic permanent restoration, also may be used as a temporary restoration of endodontically treated teeth. TERM^d was introduced relatively recently as a temporary restorative material for endodontics. It is a single-component, light-cured resin and undergoes polymerization shrinkage similar to other composite resins.⁹

Cavit, IRM, and TERM were tested for bacterial leakage in endodontically treated teeth in an in vitro study by Deveaux and colleagues.²⁰ On day 4, thermocycling was introduced, and on day 8, the teeth were longitudinally sectioned. Before thermocycling, IRM exhibited considerable more leakage than Cavit and TERM. Thermocycling appeared to aggravate percolation in IRM and decrease the tightness of Cavit, but TERM remained leak proof. In 1993, Hansen and Montgomery compared the leakage rate of TERM in different thicknesses (1 mm, 2 mm, 3 mm, and 4 mm) and different time intervals.²¹ Their findings showed that TERM created an adequate seal at each thickness and may be suited for clinical situations where less than 4 mm of restorative space exists.

Intraorifice Barriers
Traditionally, coronal leakage prevention by general practitioners and endodontists has been accomplished by the temporary restorative materials previously mentioned. Most of the materials are temporary by design and will eventually lose their marginal integrity; therefore, the idea of a permanent intraorifice barrier placed in contact with gutta-percha 2 mm to 4 mm into the canal orifice has become favorable. The depth of these barriers has been evaluated to determine if there is a minimum amount of space that would provide a better seal.

In a recent evaluation, Jenkins and colleagues evaluated several different materials used at various depths (1 mm, 2 mm, 3 mm, and 4 mm).²² There was no statistically significant difference between any of the test materials and orifice depths or main effect of orifice depth. Pisano and colleagues noted that canals with an intraorifice barrier, despite the material used (Cavit, IRM, or Super EBA^e) were more resistant to coronal leakage than their unsealed counterparts.²³ The Cavit group had the lowest percentage of leakage at 15%; IRM leaked 35% of the time.

In a study published by Wolcott and colleagues, it was again determined that teeth without an intraorifice barrier leaked significantly more than teeth with an intraorifice barrier.²⁴ From that study, the following criteria for a good intraorifice barrier were developed:
• can be easily placed
• bonds to tooth structure
• seals effectively against coronal microleakage
• is easily distinguished from the natural tooth structure
• does not interfere with the final restoration of the access preparation

Cotton Beneath Restorations
It is usually customary, regardless of the temporary restoration used, to place a cotton pellet directly over canal orifices. The purpose of the cotton pellet is to aid in removal of the temporary restoration without risking removal of intact tooth structure.⁹ However, by using a layer of cotton, the potential for coronal leakage increases because the thickness of the temporary restoration decreases. There is also an increased risk of leakage through the exposed lateral canals.⁹ It is for these reasons that it is extremely important to remove the temporary restoration and the cotton pellet in its entirety before placing the final restoration.

Conclusion
Endodontic therapy is a viable and successful option to save a natural tooth. Research has demonstrated that the coronal seal, both temporary and permanent, is one of the most crucial factors in achieving a successful treatment outcome. Many materials are available for temporary fillings; it is important for the practitioner to assess the length of time until the permanent restoration placement when making a decision. In cases where the permanent restoration is going to be delayed, using an intraorifice barrier in addition to a more resilient type of temporary may be prudent. The use of a cotton pellet makes the removal of a temporary restoration easier; however, it may not be indicated in cases where an adequate depth of temporary cannot be obtained.

There are many alternatives to temporary restorations, and correct placement is important to ensure the success of treatment. However, it is critical to remember that the best temporary is still only that: temporary, and nothing is more critical to the success of endodontic treatment than a well-placed permanent restoration.

References
1. Abbott PV. Recognition and prevention of failures in clinical dentistry. Endodontics. Ann R Australas Coll Dent Surg. 1991; 11: 150-166 Review.

2. Peak JD. The success of endodontic treatment in general dental practice: a retrospective clinical and radiographic study. Prim Dent Care. 1994; 1:9-13.

3. Lazarski MP, Walker WA 3rd, Flores CM, et al. Epidemiological evaluations of the outcome of nonsurgical root canal treatment in a large cohort of insured dental patients. J Endod. 2001; 27:791-796.

4. Friedman S, Abitbol S, Lawrence HP. Treatment outcome in endodontics: the Toronto Study. Phase 1: initial treatment. J Endod. 2003; 29:787-793.

5. Swanson K, Madison S. An evaluation of coronal microleakage in endodontically treated teeth. Part I. Time periods. J Endod. 1987; 13:56-59.

6. Vire DE. Failure of endodontically treated teeth: classification and evaluation. J Endod. 1991; 17:338-342.

7. Torabinejad M, Ung B, Kettering JD. In vitro bacterial penetration of coronally unsealed endodontically treated teeth. J Endod. 1990; 16:566-569.

8. Siqueira JF Jr, Rocas IN, Alves FR, et al. Periradicular status related to the quality of coronal restorations and root canal fillings in a Brazilian population. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2005; 100: 369-374.

9. Naoum HJ, Chandler NP. Temporization for endodontics. Int Endod J. 2002;35:964-978.

10. Sauaia T, Gomes BP, Pinheiro ET, et al. Microleakage evaluation of intraorifice sealing materials in endodontically treated teeth. Oral Surg Oral Med Oral Pathol Oral Radio Endod. 2006; 102: 242-246.

11. Balto H. An assessment of microbial coronal leakage of temporary filling materials in endodontically treated teeth. J Endod. 2002; 28:762-764.

12. Webber RT, del Rio CE, Brady JM, et al. Sealing quality of a temporary filling material. Oral Surg Oral Med Oral Pathol. 1978; 46:123-130.

13. Zaia A, Nakagawa R, De Quadros I, et al. An in vitro evaluation of four materials as barriers to coronal microleakage in root-filled teeth. Int Endod J. 2002; 35:729-734.

14. Hagemeier MK, Cooley RL, Hicks JL. Microleakage of five temporary endodontic restorative materials. J Esthetic Dent. 1990;2:166-169.

15. Wilson AD, McLean JW. Glass Ionomer Cement. Chicago, Ill: Quintessence; 1988.

16. Burgess J, Norling B, Summitt J. Resin ionomer restorative materials: the new generation. J Esthet Dent. 1994; 6:207-215.

17. Seiler KB. An evaluation of glass ionomer-based restorative materials as temporary restoration in endodontics. Gen Dent. 2006; 54:33-36.

18. Chailertvanitkul P, Saunder WP, Saunder EM, et al. An evaluation of microbial coronal leakage in the restored pulp chamber of root-canal treated multirooted teeth. Int Endod J. 1997; 30:318-322.

19. Beckham BM, Anderson RW, Morris CF. An evaluation of three materials as barriers to coronal microleakage in endodontically treated teeth. J Endod. 1993; 19:388-391.

20. Deveaux E, Hildelbert P, Neut C, et al. Bacterial microleakage of Cavit, IRM, and TERM. Oral Surg Oral Med Oral Pathol. 1992; 74:634-643.

21. Hansen SR, Montgomery S. Effect of restoration thickness on the sealing ability of TERM. J Endod. 1993; 119:448-452.

22. Jenkins S, Kulild J, Williams K, et al. Sealing ability of three materials in the orifice of root canal systems obturated with gutta-percha. J Endod. 2006; 32:225-227.

23. Pisano DM, DiFiore PM, McClanahan SB, et al. Intraorifice sealing of gutta-percha obturated root canals to prevent coronal microleakage. J Endod. 1998; 24:659-662.

24. Wolcott JF, Hicks ML, Himel VT. Evaluation of pigmented intraorifice barriers in endodontically treated teeth. J Endod. 1999; 25:589-592.

^a 3M ESPE, St Paul, MN 55144; (800) 216-9502
^b DENTSPLY Caulk, Milford, DE 19963; (800) 532-2855
^c GC America, Alsip, IL 60803; (800) 323-7063
^d DENTSPLY Maillefer, Tulsa, OK 74135; (800) 924-7393
^e Harry J Bosworth Company, Skokie, IL 60076; (800) 323-4352