A dental crown is a custom-made, tooth-shaped cap placed over a damaged or weakened tooth structure. It completely encases the visible portion of the tooth, resting at or just below the gum line. The primary goal is to restore the tooth’s size, shape, and strength, allowing it to function normally under chewing forces. It also improves the tooth’s appearance, blending it with the rest of the smile.
Identifying the Signs of Failure
A patient’s first indication of a compromised crown often involves a change in sensation or a visible alteration. Persistent sensitivity, especially a sharp response to hot or cold temperatures, suggests a loss of the protective seal. This lingering discomfort signals that bacteria or irritants are reaching the dentin beneath the crown.
Physical changes include a visible crack, chip, or rough edge developing on the crown material. The crown may also feel loose, progressing until the restoration falls off. Patients might also notice inflammation or redness in the gum tissue surrounding the crown, sometimes accompanied by an unpleasant taste or odor.
Root Causes of Crown Malfunction
The most frequent cause of crown failure is secondary decay, a new cavity forming beneath the crown’s margin. Although the crown itself cannot decay, the junction where it meets the tooth is vulnerable to plaque accumulation. When plaque erodes the exposed tooth surface near the gum line, it creates a pathway for decay to spread underneath the cap, compromising the foundation.
Failure can also result from issues with the cementation process. The dental cement holding the crown in place can dissolve or wash out due to saliva and daily wear, leading to a loose fit and micro-leakage of bacteria. Physical trauma, such as sudden impact or chronic forces from bruxism (teeth grinding), can fracture the crown or dislodge it by overwhelming the adhesive bond.
A poor initial fit, where the crown margin does not precisely meet the prepared tooth structure, introduces an immediate weakness. This marginal gap traps debris and bacteria, accelerating decay and encouraging gum irritation. Chewing hard or sticky foods stresses these compromised areas, potentially cracking the crown or causing the restoration to become unseated.
Consequences of Untreated Failure
Ignoring a failing crown allows the problem to escalate from a simple restoration issue to a serious biological concern. When decay breaches the barrier, it progresses rapidly through the tooth, eventually reaching the pulp chamber where the nerve and blood vessels reside. This pulp infection, known as pulpitis, is often the source of severe pain.
If the infection remains untreated, bacteria can travel through the root canal system to the tip of the root, forming a periapical abscess. This pocket of pus forms within the jawbone, causing significant swelling and potentially spreading to adjacent facial spaces (cellulitis).
The chronic infection initiates a localized breakdown of the alveolar bone supporting the tooth. This bone loss weakens the tooth’s anchorage, increasing its mobility. The long-term consequence of an unaddressed failing crown is the complete structural compromise of the remaining tooth, often necessitating extraction to remove the source of infection.
Repair and Replacement Strategies
The treatment approach for a failed crown depends on the health of the underlying tooth structure and the crown’s condition. If a crown is simply dislodged but intact, and the tooth beneath shows no decay, a dentist can clean both surfaces and re-cement the existing restoration. This is the simplest and most conservative intervention.
If the crown is fractured, chipped, or if significant secondary decay is present, a complete crown replacement is necessary. The old crown must be removed, the decay cleaned out, and the tooth re-prepared for a new cap. If decay has reached the pulp, a root canal procedure must be performed before the new crown is placed.
If the underlying tooth is too extensively damaged by decay, fracture, or severe bone loss, it may be deemed unsalvageable. In this scenario, extraction is necessary, followed by replacement options such as a fixed dental bridge or a dental implant. An implant provides a stable foundation for a new crown and is often the preferred long-term solution.