A dental post is a supporting rod placed inside a tooth’s root canal after a root canal procedure to secure a final restoration, such as a crown. It is used when a significant portion of the natural tooth structure is missing, providing an anchor to rebuild the core. While posts are intended to be permanent, they can sometimes fail or require removal. A dental post can often be safely replaced, though the procedure is delicate and requires specialized care.
Reasons a Dental Post Fails
A primary reason for post and crown failure is recurrent decay. This decay occurs at the margin where the crown meets the underlying tooth structure, allowing bacteria to penetrate the remaining tooth and root surface. This compromises the foundation holding the post in place, leading to failure.
Another common issue is the loosening or mobility of the post itself, which happens due to the degradation of the dental cement. When the cement seal fails, the post loses retention inside the root canal, causing the entire restoration to become unstable. This loosening can be compounded by constant biting forces and tooth grinding.
Fractures can also necessitate removal, including a fracture of the post itself or a vertical root fracture. Finally, if the original root canal treatment develops a new infection or was not fully successful, the existing post must be removed to allow access to the root canal system for retreatment.
Safe Removal Techniques
The safe removal of a dental post is a technically demanding procedure designed to preserve the remaining root structure. Dentists employ specialized tools and high magnification, such as a dental operating microscope, to visualize the root canal space. The initial approach for many posts, particularly cemented metal types, involves using specialized ultrasonic devices.
These ultrasonic tips vibrate the post at a high frequency, transmitting energy to the surrounding cement. The vibration gradually breaks the adhesive bond between the post and the internal wall of the tooth, allowing for non-traumatic removal. A constant water coolant must be applied to prevent excessive heat buildup, which could damage the tooth’s ligament and bone.
If ultrasonic vibration is not sufficient, a specialized post removal kit may be used. These systems employ a trephine bur to create space around the post, followed by a tap that screws onto the post for purchase. Once engaged, an extractor applies controlled, axial pulling force to elevate the post out of the canal. The goal of any removal technique is to avoid lateral forces that could cause an irreparable root fracture.
Restoring the Tooth After Removal
Once the failed post is removed, the focus shifts to treating any underlying issues and preparing the tooth for a new restoration. If the failure was due to an infection, the root canal system is thoroughly cleaned and disinfected through endodontic retreatment. The root canal is then sealed with a permanent filling material.
A new post is placed into the prepared canal space to provide retention for the core buildup. Contemporary dentistry utilizes fiber posts, which are preferred over older metal posts because their elasticity is closer to that of the natural tooth structure. This similarity reduces the risk of future root fracture. The fiber post is bonded into the canal using strong adhesive resin cements.
The core buildup material, typically a composite resin, is placed around the post to reconstruct the missing coronal tooth structure. This rebuilt portion serves as the foundation upon which the new crown will be seated. Impressions are taken of this prepared tooth structure to allow a dental laboratory to fabricate a permanent crown.
When Replacement is Not Possible
There are situations where replacing a dental post is not a viable option for saving the tooth. The most common reason is a vertical root fracture, where a crack runs down the length of the root. This type of fracture is often irreparable because bacteria can colonize the crack, making it impossible to sterilize the root canal system.
Post replacement may also be impossible if the removal procedure or initial failure resulted in the loss of too much surrounding tooth structure. If the remaining root walls are too thin, the tooth is susceptible to fracture and cannot reliably support a new post and crown. Extensive decay that extends deep below the gum line also compromises the tooth’s prognosis.
In these circumstances, the tooth is considered unrestorable, and the recommended treatment is extraction to prevent further complications like bone loss or infection. Following extraction, the patient must consider alternatives for tooth replacement, such as a traditional fixed dental bridge or a dental implant. A dental implant replaces the entire root structure and is often the most conservative long-term solution.