A dental crown functions as a cap placed over a damaged or weakened tooth to restore its shape, size, strength, and appearance. While a crown provides durable protection, it is not a permanent fixture and will eventually require replacement due to wear, damage, or changes in the underlying tooth structure. Understanding the process of replacing an old crown is helpful for patients, as it involves several distinct steps designed to ensure the long-term health and function of the tooth.
Identifying the Need for Replacement
A crown replacement often becomes necessary when the integrity of the restoration or the underlying tooth is compromised. One of the most common issues is recurrent decay, which occurs when bacteria penetrate the margin—the border where the crown meets the natural tooth structure—leading to new cavities beneath the cap. This marginal leakage can be identified by a dark line around the gumline or detected on dental X-rays.
Physical damage, such as a fractured or chipped crown, also necessitates replacement, as the break can expose sensitive dentin and pulp or create rough edges that irritate the mouth. General wear and tear from years of chewing forces, especially in patients who grind their teeth (bruxism), can thin the crown material. This wear compromises the structural support the crown provides.
Another sign of failure is the crown feeling loose or if the patient experiences persistent pain or increased sensitivity when biting down. When a crown becomes loose, the bonding cement has failed, allowing bacteria and fluids to seep into the preparation space, increasing the risk of infection and decay. If the crown’s fit is no longer precise, often due to gum recession or changes in the underlying tooth, a gap is created that harbors plaque and makes replacement unavoidable.
The Process of Removing the Existing Crown
The replacement procedure begins with a careful assessment and the administration of local anesthesia to ensure patient comfort. The dentist must first gain access to the crown’s material to section it, typically involving a high-speed dental bur. This instrument is used to create grooves through the crown’s surface until the underlying tooth structure is reached.
Once the crown is grooved, the dentist uses a specialized instrument, often a crown remover or ultrasonic tool, to gently fracture the remaining cement seal and lift the old restoration off the tooth. This technique minimizes trauma to the abutment, which is the prepared natural tooth or core structure underneath. Preserving the existing tooth structure reduces the need for extensive re-preparation.
After removal, the dentist cleans and evaluates the exposed tooth surface for any signs of decay or structural cracks. If decay is detected, it must be completely removed, which may alter the shape of the remaining tooth. If the remaining tooth structure is insufficient to support a new crown, a core build-up is performed, where a restorative material is bonded to the tooth to rebuild the necessary bulk and shape.
The underlying tooth structure must be shaped to hold the new crown securely against dislodging forces, ensuring adequate retention and resistance form. This preparation ensures the new restoration will have a long and stable fit.
Fabrication and Seating of the New Crown
With the tooth prepared, the next phase involves capturing a precise record of the prepared tooth and the surrounding dentition. This is accomplished either through traditional impression materials or increasingly through modern digital scanning technology. Digital scanners create a highly accurate three-dimensional optical impression of the mouth, which is then sent electronically to a dental laboratory.
The impression or digital file serves as the blueprint for the dental laboratory to fabricate the new permanent crown. While the permanent crown is being made—a process that typically takes one to two weeks—a custom-fitted temporary crown is placed on the prepared tooth. This temporary restoration protects the exposed dentin, prevents adjacent teeth from shifting, and maintains the proper bite relationship.
Material selection balances strength, aesthetics, and location in the mouth. Common materials include porcelain-fused-to-metal (PFM), which offers a strong metal sub-structure with a tooth-colored porcelain exterior, and all-ceramic options. Zirconia is known for its durability and is often selected for molars, while lithium disilicate provides excellent translucency for highly visible front teeth.
When the permanent crown returns, the patient returns for the try-in appointment. The dentist checks the crown’s fit, ensuring the margins are seamlessly sealed and the crown integrates properly with the gum tissue. The crown’s occlusion, or bite, is verified and adjusted so that it does not interfere with the opposing teeth.
Aesthetics are also confirmed, ensuring the shade and contour match the adjacent natural teeth. Once the fit, function, and appearance are satisfactory, the final cementation process begins. A permanent dental cement or resin bonding agent is applied, and the crown is firmly seated onto the tooth preparation.
The permanent cement forms a strong bond between the crown and the underlying tooth structure. Any excess cement that extrudes around the margins is carefully removed and polished. This final step prevents gum irritation and ensures the newly replaced crown offers a smooth, plaque-resistant surface at the gum line.
Post-Replacement Care and Longevity
Immediately following the seating of the permanent crown, patients may experience transient sensitivity to hot or cold temperatures, which usually subsides within a few days. Patients should avoid chewing sticky or hard foods for the first 24 hours to allow the cement to fully cure. The dentist will also provide instructions on managing any temporary soreness or changes in bite perception.
Long-term maintenance relies on consistent oral hygiene practices. Proper brushing, including angling the bristles toward the gumline, is important for removing plaque, especially around the crown margins where recurrent decay is most likely. Flossing removes debris from between the teeth and beneath the contact points of the crown.
The expected lifespan of a well-maintained replacement crown generally ranges between 10 to 15 years, though many restorations last longer depending on the material and patient habits. Crowns made of gold alloys or zirconia often exhibit greater resistance to wear than some all-porcelain options. Regular dental check-ups and professional cleanings allow the dentist to monitor the crown’s margins and the integrity of the underlying tooth structure.
Patients should contact their dental office immediately if they notice issues, such as the crown feeling loose, experiencing sharp, persistent pain when chewing, or if the crown fractures. Prompt attention to these symptoms can prevent more serious complications, such as a deep infection. Diligent care is the primary factor influencing the long-term success of the crown replacement.