A dental post is a stabilizing rod or pin placed inside the root of a tooth that has previously undergone root canal therapy. Its purpose is to help rebuild a tooth that has lost a significant amount of its natural structure due to decay, trauma, or the treatment itself. The post creates an internal anchor, serving as a foundation upon which a final restoration can be securely constructed. This underlying structure is only necessary when there is insufficient remaining tooth material above the gum line to support a dental crown directly.
The Structural Role of the Dental Post
Teeth that have received root canal treatment often have compromised internal structure, making them more susceptible to fracture under the normal forces of chewing. The removal of the central pulp tissue and the necessary access preparation weaken the tooth walls, requiring internal support. The dental post acts not to strengthen the root itself but rather to provide a means of retaining the material used to replace the missing coronal tooth structure.
The post functions like a foundation, securing the restorative material placed above it. Without this internal anchor, the new material and the final crown would be at high risk of loosening or dislodging. The post’s primary mechanical purpose is to achieve retention for the subsequent “core buildup” before the protective crown is placed.
Placement and Anatomy Inside the Root
To visualize a dental post inside a tooth, understand that it occupies the space where the nerve and blood vessels once resided, known as the root canal. A dentist prepares this canal by gently removing some of the rubber-like filling material, called gutta-percha, which was used to seal the canal during the root canal procedure. The post is designed to fit snugly into this prepared space, extending deep into the root for maximum stability.
Proper placement requires the post to be long enough to achieve retention, often extending into the apical third of the root. A specific amount of the original gutta-percha filling must remain undisturbed at the tip of the root to maintain the biological seal and prevent bacterial leakage. It is recommended that at least 3 to 5 millimeters of the original filling material is left in place. The post itself is typically cylindrical, tapered, or a combination of both shapes.
How Different Materials Affect the Appearance
The material composition of the post significantly influences its appearance, particularly when viewed on a dental X-ray. Metal posts, which can be prefabricated or custom-cast from alloys like titanium or stainless steel, appear highly opaque. On an X-ray, these posts show up as bright white, sharply defined rods that clearly contrast with the surrounding darker tooth structure. While they offer high strength, their rigidity can sometimes transfer stress unevenly to the root walls.
Fiber posts, made from materials such as fiberglass or carbon fiber, present a different image. These posts are designed to have flexibility closer to that of natural dentin, potentially reducing the risk of root fracture. On an X-ray, fiber posts appear less opaque, often blending more subtly with the natural density of the tooth structure. Their translucent nature is an aesthetic advantage, especially when the final restoration is an all-ceramic crown, as the underlying post will not cast a dark shadow.
Completing the Structure: Core Buildup and Crown
The post is the first step in rebuilding the tooth, acting as a foundation for the next component: the core buildup. The core buildup is a body of restorative material, commonly a strong composite resin or dental amalgam, bonded around the portion of the post protruding from the root. This material replaces the missing tooth structure, restoring the original shape of the prepared crown portion of the tooth.
The core buildup is then shaped to create the ideal form for receiving the final dental crown. This prepared shape, often referred to as a “stump,” ensures that the crown can be seated precisely and securely, distributing chewing forces across the foundation. Once the crown is permanently cemented over the core buildup and post complex, the final restoration mimics the function and appearance of a natural tooth.