A dental crown is a tooth-shaped cap used to restore a damaged, decayed, or weakened tooth. This cap covers the entire visible portion of the tooth above the gum line, providing protection and structural integrity. Although crowns are durable and designed to withstand chewing forces, the natural tooth structure underneath can still be compromised. When the underlying tooth breaks, it is a serious dental issue that compromises the restoration and requires immediate professional attention.
Recognizing the Signs of Failure
Failure of the tooth structure beneath a crown presents with several symptoms. Patients frequently report a sudden, sharp pain when biting down or chewing, caused by pressure moving the fractured pieces. This sensation is often intermittent, occurring only when the tooth is stressed, though a chronic, dull ache may also develop.
The exposed inner layers of the tooth often lead to increased sensitivity to hot, cold, or sweet foods. Over time, the structural failure can cause the crown itself to feel loose or wiggly. Swelling, tenderness, or redness of the gum tissue around the crowned tooth may indicate the fracture has extended below the gum line or that an infection has begun.
Common Reasons for Structural Failure
The most frequent cause of a tooth breaking beneath a crown is recurrent decay. If the seal between the crown margin and the natural tooth is compromised, bacteria can leak underneath the restoration. This leads to a cavity that weakens the remaining tooth structure. Decay can progress silently until the tooth is too weak to withstand normal chewing forces and fractures.
Excessive trauma or stress applied to the tooth is also a cause of failure. Habits like bruxism (involuntary clenching or grinding) subject the crowned tooth to high, repetitive forces that cause hairline cracks to propagate into a full fracture. Biting down on hard objects, such as ice or popcorn kernels, creates acute pressure that can instantly split the compromised tooth structure. Teeth that have undergone root canal therapy are more brittle and susceptible to fracture under these stresses.
Clinical Assessment and Prognosis
Diagnosing a break beneath a crown requires a thorough clinical assessment, since the crown hides the underlying damage. The dentist usually begins by removing the existing crown for a direct visual inspection of the remaining tooth structure. Dental explorers are used to probe the exposed tooth and locate the precise path of any cracks or fracture lines.
Standard two-dimensional X-rays, such as periapical radiographs, are taken to evaluate the bone level and look for signs of infection at the root tip. However, these traditional images may not always reveal a fracture, especially if it is vertical. For a more definitive diagnosis, the dentist may utilize specialized tools. These include transillumination, which shines a light through the tooth to reveal the crack, or a three-dimensional cone-beam computed tomography (CBCT) scan to precisely map the crack’s depth and proximity to the pulp and bone. The likelihood of saving the tooth is determined by how far the fracture extends, particularly whether it reaches below the bone line.
Treatment Pathways for the Damaged Tooth
Treatment depends entirely on the location and severity of the fracture determined during assessment.
Minor Damage
For minor damage, such as a localized cusp fracture or a small area of decay, the tooth may be salvageable without extensive procedures. The dentist can clean out decay, repair the remaining structure with a filling or a core buildup, and then cement a new crown over the reinforced tooth.
Moderate Damage
If the fracture or decay has progressed into the pulp (nerve center) of the tooth, a more involved procedure is necessary. This requires root canal therapy to remove the infected or inflamed pulp tissue and seal the root canals. Following the root canal, a post and core buildup is often placed inside the tooth to create a solid foundation for a new crown. This sequence restores function and prevents future infection.
Severe Damage and Extraction
In cases of severe damage, such as a vertical root fracture that extends far below the gum line, the tooth is often deemed non-restorable. When the fracture involves the root and supporting bone, the tooth must be extracted to prevent the spread of infection. Following extraction, the two main options for replacement are a fixed partial denture (bridge) or a dental implant. A dental implant is often considered the optimal long-term solution as it replaces the root and provides independent stability for the new crown.