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Web Exclusive | March 3, 2009
An adequate seal is key, even if only temporary
The literature clearly shows endodontic therapy is a viable and highly successful option that permits patients to maintain their natural dentition. In fact, a recent systematic review determined root canal therapy that has been restored with a crown is just as successful as single tooth implants.1
Still, some treatments fail. While several factors influence the overall success or failure of endodontic therapy, the majority of failures can be attributed to the presence of bacteria in the root canal system, and the most common route for the bacteria is coronal leakage.2 Therefore it is important for endodontic procedures to include techniques that remove bacteria already present within the root canal system and prevent further microbial ingress.3 Temporary seals Under most circumstances, it is ideal to place the permanent restoration immediately following endodontic therapy in order to decrease the likelihood of coronal leakage. However, this is not always feasible because of time constraints, or the sequencing between the restorative dentist and the endodontist. In these instances, a temporary restoration must be placed. It is extremely important for the temporary restorations to provide an adequate seal against fluids from the oral cavity entering the root canal system. Materials used for these temporary restorations also must be easy to place and remove, provide adequate esthetics and protect tooth structure during treatment.4 As providers of the majority of endodontic care, it is important for primary care dentists—as well as the endodontists to whom they may refer—to choose the appropriate temporary materials that will help ensure a good prognosis in endodontically treated teeth. Cavit 3M ESPE’s Cavit (3MESPE.com) is a premixed temporary material containing zinc oxide, calcium sulfate, zinc sulfate, glycol acetate, polyvinyl acetate resins, polyvinyl chlorine acetate, triethanolamine and pigments. It is available in several forms with multiple delivery methods and is uncomplicated to place and manipulate. Multiple studies show it to be a very effective temporary restorative material following endodontic therapy. Cavit also resists microleakage for up to two weeks longer than composite and other materials in a laboratory setting.5 However, it is important to note a minimum thickness of 3.5 mm of Cavit is necessary in order to obtain an accurate seal against leakage.6 IRM IRM or Interim Restorative Material from Dentsply Caulk (caulk.com) is zinc-oxide and eugenol cement reinforced with polymethyl methacrylate. It does not bond to the tooth structure; however it does provide better compressive strength than Cavit and has good sealing properties, but the sealing properties are not better than Cavit. A clinical study concluded IRM is superior in preventing coronal microleakage when compared to two brands of composite.7 Glass ionomer Glass ionomer cements bond chemically to tooth structure, are tooth-colored, biocompatible, and release fluoride.8 The coefficient of thermal expansion of conventional glass ionomer cements is close to that of dental hard tissues and has been cited as a significant reason for the material’s good marginal adaptation.9 Glass ionomer-based restorative materials can be used as temporary restorations during or after endodontic therapy, especially in cases that require longer temporization or increased strength. In a recent study, IRM, Cavit and Fuji II LC, Fuji IX and Fuji Triage from GC America (gcamerica.com) were used to coronally seal endodontically treated teeth against bacterial leakage. The results of this in vitro study show the glass ionomer and resin-modified glass ionomer restorative materials (Fuji II, IX and Triage) provide a better coronal seal against S. mutans than IRM in endodontic access preparations.10 Composite Composite, although normally used as an esthetic permanent restoration, may also be used for temporization of endodontically treated teeth. T.E.R.M.® from Dentsply Maillifer (maillefer.com) was introduced relatively recently as a temporary restorative material for endodontics. It is a single-component, light-cured resin, and like other composite resins, undergoes polymerization shrinkage.4 Cavit, IRM, and T.E.R.M. were tested for bacterial leakage in endodontically treated teeth in an in vitro study. On day four, thermocycling was introduced and on day eight, the teeth were longitudinally sectioned. Before thermocycling, IRM exhibited considerably more leakage than Cavit and T.E.R.M. After thermocycling, IRM and Cavit showed leakage and breakdown of marginal integrity, whereas T.E.R.M. remained leak proof.11 |
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The science behind endodontic failures,
