A dental crown is a custom-made, tooth-shaped cap placed over a damaged tooth to restore its shape, size, strength, and appearance. Crowns are typically recommended to protect a tooth weakened by extensive decay, fracture, or following root canal treatment. While durable, crowns do not last indefinitely and often require replacement due to normal wear, chipping, or new decay forming at the margin. If the underlying tooth structure is compromised beyond repair, however, a new crown cannot be successfully placed, and the tooth must be removed.
Severe Loss of Remaining Tooth Structure
The primary reason a crown cannot be replaced is a lack of sufficient healthy tooth material remaining above the gum line. A new crown requires sound tooth wall to securely grip and stabilize the restoration against the forces of chewing. This necessary support is a protective band of tooth structure that encircles the prepared tooth, distributing stress and preventing fracture.
If the tooth structure is extensively damaged, often by recurrent decay beneath the existing crown margin, there may be inadequate height or width left for proper retention. Dentists typically require a continuous wall of 1.5 to 2 millimeters in height for stabilization. Without this minimum dimension, the crown will be prone to loosening, or the remaining tooth root may fracture under normal chewing pressure. Even procedures like building up the tooth with a core material will not succeed if the surrounding dentin walls are too short or thin to provide the necessary mechanical resistance for the new restoration.
Unrepairable Root and Periodontal Problems
Limitations for crown replacement can also stem from irreversible damage occurring beneath the gum line, making the entire tooth unit non-viable. A vertical root fracture is a catastrophic issue, involving a crack that runs from the crown down into the root structure. This type of fracture cannot be reliably repaired with restorative materials and creates a pathway for bacteria to infect the bone and surrounding tissues.
A chronic infection beneath the tooth, often resulting from failed root canal therapy, can also lead to irreversible damage if it cannot be resolved through re-treatment. An unresolvable periapical lesion signals a failure of the tooth’s internal environment, making it unsuitable for a long-term crown. Severe, localized bone loss from aggressive periodontal disease also compromises the tooth’s support structure. When the bone holding the tooth is significantly diminished, the tooth becomes loose and unstable, forcing its removal regardless of the crown’s condition.
Treatment Options When Crown Replacement Fails
When a dentist determines that the tooth is unsalvageable due to structural or root failure, extraction is the mandatory first step. This removes the source of infection or instability and prepares the area for tooth replacement.
The most preferred solution for replacing a single extracted tooth is a dental implant, which involves surgically placing a titanium post into the jawbone. Once the implant fuses with the bone, a new crown is attached, creating a replacement that is stable, functions like a natural tooth, and helps preserve the surrounding bone density.
Another option is a fixed bridge, which replaces the missing tooth by anchoring a false tooth to crowns placed on the healthy teeth adjacent to the gap. This procedure requires reshaping the neighboring teeth, even if they are otherwise sound. A third, more cost-effective alternative is a removable partial denture, which is a prosthetic appliance that offers less stability and comfort than the fixed options.