After cleaning and shaping the inside of a tooth during a root canal, a material called an endodontic sealer is used. It is a therapeutic, paste-like cement designed for the unique environment inside a tooth’s root. This material is not the primary filling substance but works in concert with it. Its role is to ensure the space is completely and permanently sealed off from the rest of the body.
The Purpose of Sealers in Root Canal Therapy
The main objective of a root canal is to remove infected tissue and bacteria and then seal the cleaned space to prevent future problems. The primary filling material, a rubber-like substance called gutta-percha, is shaped to fit the main canal. However, a tooth’s internal anatomy is complex, featuring microscopic fins, webs, and lateral canals that the solid gutta-percha cannot fill on its own. This is where the sealer performs its function.
Sealers are introduced in a paste consistency to flow into these tiny irregularities, creating a complete, three-dimensional seal. This function is often compared to the grout used between tiles; the gutta-percha acts as the tile, and the sealer is the grout that fills every gap. By filling these voids, the sealer eliminates empty space where bacteria could survive and lead to reinfection.
Beyond filling gaps, the sealer acts as a binding agent. It provides adhesion between the gutta-percha and the dentin, the hard tissue of the tooth wall, creating a unified and fluid-tight filling.
Composition and Categories of Sealers
Endodontic sealers are grouped into categories based on their chemical makeup, with each type offering different handling properties and biological interactions. The choice of sealer depends on the clinical situation and the dentist’s preference, as these materials are designed to be stable and long-lasting. While all sealer types are formulated to provide a complete seal, their different compositions offer unique advantages.
There are four primary categories of sealers:
- Zinc oxide-eugenol (ZOE) based sealers are a traditional type valued for their natural antibacterial properties, derived from eugenol (an oily liquid from cloves), and their long track record.
- Resin-based sealers are prized for their excellent sealing ability and strong adhesion to the dentin walls. They are also characterized by low solubility, meaning they resist breaking down when exposed to tissue fluids.
- Calcium silicate-based sealers, often called “bioceramics,” have become a preferred option in modern endodontics. These advanced materials are highly biocompatible and are considered bioactive, interacting with tissues to support healing.
- Glass ionomer sealers are noted for their ability to chemically bond to dentin and their capacity to release fluoride, which can help strengthen the surrounding tooth structure.
The Sealer Application Procedure
The application of an endodontic sealer is a precise step during the final phase of a root canal, known as obturation. Before the sealer is introduced, the root canal system is completely cleaned, shaped, and disinfected. This preparation is fundamental to the long-term success of the treatment.
Once the canal is clean, it must be thoroughly dried. The presence of moisture can interfere with some sealers, so tiny, absorbent paper points are used to wick away any remaining fluid. A dry canal ensures the sealer can properly adhere to the dentin walls.
With the canal prepared, the sealer is mixed to a smooth, paste-like consistency. It can be applied by coating the canal walls directly or by coating the primary gutta-percha cone with the sealer before placing it.
The final step involves placing the gutta-percha points into the sealer-coated canal. As the gutta-percha is compacted, it pushes the sealer to flow into all microscopic irregularities and lateral canals, creating the fluid-tight, three-dimensional seal.
Biocompatibility and Healing
A primary consideration for any material placed inside the body is its biocompatibility, which is the ability of a material to exist in harmony with living tissue. An ideal endodontic sealer should not only be tolerated by the body but should actively support the healing of the tissues surrounding the tooth root.
The concept of bioactivity is relevant to the newer generation of calcium silicate-based, or bioceramic, sealers. These materials are not inert; they interact with the body’s natural processes. When a small amount of bioceramic sealer is extruded past the root tip, it can stimulate the regeneration of bone and the periodontal ligament. This happens because the sealer releases calcium and hydroxide ions, creating an alkaline environment that promotes hard tissue formation.
This contrasts with some older sealer formulations, which could cause a mild inflammatory response in the surrounding tissues. While the body can manage this minor irritation, bioactive materials represent an advancement in promoting more predictable healing.
Although modern sealers are safe, rare instances of allergic reactions can occur. Some individuals may have a sensitivity to components like the eugenol in ZOE-based sealers or ingredients in resin-based formulations. Dentists consider a patient’s medical history to select the most appropriate material.