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Sealing Endodontic Access Cavities

The elimination of bacteria from the root canal system of a tooth is one of the primary goals of endodontic treatment.1,2 Instrumentation and irrigation are designed to achieve this outcome, but what happens after it is completed? Even if the root canal system is obturated, how does one prevent microleakage, especially if a temporary restorative material is used? The key is to assess the physical properties of the temporary material by looking at its depth of cure as well as its ability to bond to tooth structure on an interim basis. Often, the ideal solution would be to immediately place a full-coverage restoration at the completion of endodontic treatment. However, this may not be practical for a number of reasons.
At times, endodontic treatment may involve multiple appointments, and one needs to balance the need to place a strong durable restoration with the need to be able to easily remove the restoration without marring or altering any of the anatomy on the pulpal floor. To achieve this, one can turn to a wide range of materials, including a class of temporary composite resins. One such example is Interval LC (Temrex). This composite resin material is designed for use as a light-cured temporary restoration. It is based upon a diurethane dimethacrylate polymer, making it a very biocompatible restoration. This material has physical properties, making it an ideal restorative material for use in temporarily sealing endodontic access openings: a compressive strength of 10,000 psi, a diametral tensile strength (after curing) of 1,500 psi, water solubility less than 0.1%, and a depth of cure of up to 10.0 mm in 40 seconds.

In this clinical situation, the patient was seen in clinic for emergency treatment of the maxillary left first molar. Endodontic therapy was initiated, and due to limited time and a need to ensure that the acute infection had been brought under control, it was decided to place an interim temporary restoration in the access opening. The canals were cleaned and dried and the margins of the access cavity were examined to ensure that they were sound with no caries evident (Figure 1). This would ensure the creation of a good seal.

Figure 1. The access opening as seen after endodontic instrumentation was completed. Figure 2. The access cavity was bulk-filled with the light-cured composite resin. Bonding resin was then applied and light-cured to seal the margins.
Figure 3. The occlusion was adjusted immediately after light-curing the interim restoration. Figure 4. The interim restoration, as seen 2 weeks later. The margins were intact, with no clinical signs of microleakage or staining.
Figure 5. Interval LC (Temrex).

A small cotton pellet was then placed at the bottom of the access preparation, ensuring that the root canal orifices were covered. Interval LC was placed into the access cavity so that it completely filled the hole (Figure 2). A layer of bonding resin was placed over the top of the material to help adapt it to the tooth walls. Next, it was light-cured for 40 seconds and then checked to be sure that the material was set completely. The occlusion was adjusted with a bur (SS White Finishing Bur FG7379) and the patient was dismissed (Figure 3).
When the patient returned in 2 weeks, the restoration margins appeared intact. There were no clinical signs of microleakage or staining along the interface between the walls of the preparation and the interim composite resin restoration (Figure 4).
Interval LC (Figure 5) was able to create a strong, durable bond to the tooth structure that withstood occlusal forces for a 2-week period. The literature indicates that, if the temporary filling materials are more than 3.0 mm in depth, they should create an adequate interim restoration.3,4 Interval LC, with its ability to bulk cure up to 10.0 mm in depth, allows for the creation of a strong interim restoration.
Removal of Interval LC is very easy. Once the initial occlusal portion is removed with a bur, the remainder can even be removed with an ultrasonic instrument, if there is concern about removing additional tooth structure. This interim composite material is softer than the surrounding tooth structure and slightly more transparent so it is easy to identify when re-entering the access preparation.

This brief case report has demonstrated a solution for creating a durable temporary seal for endodontic access preparations. The material used here is easily placed, seals to a depth of 10.0 mm in 40 seconds, can be immediately polished, and is easily removed to complete treatment.


  1. Siqueira JF Jr, Rôças IN, Favieri A, Abad EC, Castro AJ, Gahyva SM. Bacterial leakage in coronally unsealed root canals obturated with 3 different techniques. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2000;90:647–650.
  2. Siqueira JF Jr. Aetiology of root canal treatment failure: why well-treated teeth can fail. Int Endod J. 2001;34:1–10.
  3. Barkhordar RA, Kempler D. Microleakage of endodontic access cavities restored with composites. J Calif Dent Assoc. 1997;25:215–218.
  4. Zaia AA, 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.

Dr. Abrams is a general dental practitioner with more than 33 years of clinical experience. Upon graduation from the University of Toronto Faculty of Dentistry in 1980, he established a group practice in Toronto that has grown to involve general dentists and dental specialists. He is a Fellow of the Pierre Fauchard Academy the Academy of Dentistry International, and American College of Dentistry. He is a member of the European Association for Caries Research and International Association of Dental Research. He has published more than 90 articles in various international publications on topics such as early caries detection, prevention, removable prosthetics, and restorative dentistry. In 2002, Dr. Abrams was awarded the Barnabus Day Award from the Ontario Dental Association for 20 years of distinguished service to the dental profession. He can be contacted at (416)-265-1400 or at This email address is being protected from spambots. You need JavaScript enabled to view it..

Disclosure: Dr. Abrams is a paid consultant for Temrex Corporation.

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