A dental crown is a custom-made cap designed to cover a damaged or weakened tooth, restoring its strength, shape, and appearance. When a crown breaks, chips, or comes loose, the underlying tooth is vulnerable to further damage and decay. The good news is that a broken crown can almost always be replaced, but success depends entirely on the health and structure of the natural tooth underneath. This process involves a detailed assessment and a precise multi-step procedure.
Assessing the Tooth for Crown Replacement
Before a new crown can be placed, a dentist must perform a thorough evaluation to confirm the remaining tooth structure is sound enough for support. This assessment begins with a visual inspection and an X-ray, which helps detect hidden issues beneath the existing crown. The most common finding is recurrent decay, where bacteria have infiltrated the margin between the crown and the tooth, compromising the natural tooth material.
The dentist looks for sufficient healthy dentin and enamel, known as the ferrule effect, which is necessary for the new crown to resist chewing forces and remain secure. If the tooth is too fractured or has suffered extensive decay, a dental buildup may be required. This uses a strong material to replace the missing structure and create a stable foundation. The health of the tooth’s root and surrounding bone are also evaluated, as advanced gum disease or insufficient bone support can prevent successful crown placement. If the interior pulp is infected or inflamed, a root canal procedure must be completed first to stabilize the tooth before it can be crowned.
The Procedure for Replacing a Broken Crown
Replacing a broken crown is a routine dental procedure that usually requires two visits. The first step involves the careful removal of the existing crown, which may require the dentist to section or cut the old material with a small rotary tool to break the cement seal. Once the old restoration is removed, the underlying tooth is cleaned thoroughly to eliminate any decay, old cement, or debris.
The tooth is then reshaped or prepared to ensure the new crown fits precisely and does not interfere with the patient’s bite. New impressions, taken digitally or with traditional putty, are captured of the prepared tooth and surrounding teeth to serve as a blueprint for the permanent crown. A temporary crown, typically made of acrylic resin, is immediately placed over the prepared tooth to protect it while the custom-made permanent crown is fabricated in a dental laboratory. This fabrication process generally takes several weeks.
At the second appointment, the temporary crown is removed, and the permanent crown is checked for its fit, color match, and bite alignment. Crowns are made from various materials, including porcelain, metal alloys, or zirconia, depending on the tooth’s location and the patient’s preference. Once satisfied, the dentist permanently bonds the new restoration onto the prepared tooth, completing the replacement procedure.
Common Causes of Crown Failure
Understanding why a crown failed helps prevent the same issue from happening to the new restoration. The most frequent cause of failure is decay at the margin, where the crown meets the natural tooth structure, often due to inadequate cleaning. Plaque accumulation around the crown’s edge can lead to secondary decay in the vulnerable tooth material underneath, undermining the crown’s stability.
Physical forces are another common factor, including trauma or the stress of biting down on hard objects like ice or candy. Chronic teeth grinding or clenching (bruxism) places destructive pressure on the crown, leading to chips, cracks, or material fatigue. Crowns are not designed to last indefinitely; natural wear and tear can cause the material to weaken or the bonding cement to degrade after their expected lifespan of 5 to 15 years. Using a custom-fitted nightguard can reduce the damaging effects of bruxism and prolong the life of the crown.
Treatment Options When Replacement Is Not Feasible
If the damage found during the assessment is too extensive, the underlying tooth cannot support a new crown. If the remaining structure is severely compromised below the gum line or the root is fractured, the tooth may need to be extracted. Following extraction, the missing tooth can be replaced with a dental implant, which involves surgically placing a titanium post into the jawbone and topping it with a new crown. This option provides a stable, long-term solution that functions like a natural tooth.
Another alternative is a fixed dental bridge, which uses adjacent teeth to support an artificial tooth spanning the gap. This option requires the adjacent teeth to be prepared with crowns to anchor the prosthetic tooth. If the damage is too extensive for a simple filling but does not warrant a full crown, a dentist may recommend an inlay or onlay, sometimes called a partial crown. This restoration covers only the cusps or chewing surface of the tooth, preserving more natural tooth structure than a full crown.