A dental crown is a custom-made cap placed over a damaged or weakened tooth to restore its shape, strength, and appearance. It is designed to encase the entire visible portion of the tooth, providing mechanical protection and sealing the underlying structure. While durable, a crown is not permanent; its materials or the cement securing it can wear down over time. Neglecting to replace a crown when it shows signs of failure leaves the vulnerable prepared tooth exposed to progressive damage.
Decay and Structural Damage to the Underlying Tooth
The most immediate and common risk of not replacing a failing crown is the breakdown of the marginal seal, which is the junction where the crown meets the natural tooth structure. This seal is maintained by dental cement, which can slowly dissolve or fracture over many years of use, creating microscopic gaps. Once a gap forms, it allows oral bacteria, food particles, and saliva to seep underneath the crown, a process known as marginal leakage.
Bacteria trapped in this space cause secondary decay on the natural tooth structure, often progressing silently because the crown covers the area. The underlying tooth, which is softer near the margins, is particularly susceptible to rapid decay once bacteria penetrate. This decay erodes the foundation of the tooth, which can lead to the crown becoming loose, shifting, or falling off entirely.
Structural failure can also occur within the crown itself, such as a fracture or a chip. This damage compromises the protective shell, allowing bacteria to directly access the tooth below and accelerating the decay process. If the remaining tooth structure is severely undermined by decay or a fracture extends below the gum line, the tooth may become non-restorable, ultimately requiring extraction instead of a crown replacement.
Progression to Internal Infection and Abscess
When secondary decay beneath a failing crown progresses inward, it breaches the dentin layer and reaches the pulp chamber. Once exposed to bacteria, the pulp (which contains the tooth’s nerves and blood vessels) becomes inflamed, a painful condition called pulpitis. This stage often manifests as persistent, severe pain that may linger after exposure to hot or cold temperatures.
If the pulp infection is not treated, bacteria multiply and spread through the root canals to the tip of the root. This results in a periapical abscess, a localized pocket of pus and infection in the surrounding bone. Symptoms can include localized swelling, fever, and a dull, throbbing pain that is difficult to manage with over-the-counter medication.
Treating this advanced stage of infection is more complex than replacing a crown earlier in the process. An internal infection typically necessitates a root canal procedure, which involves drilling through or removing the crown to clean out the infected pulp and seal the root canals. If the decay or infection has destroyed too much tooth structure or bone, the tooth cannot be saved and must be extracted.
Impact on Surrounding Oral Health
A failing crown compromises not only the tooth it covers but also adjacent oral structures, particularly the gums. A crown with a poorly fitting margin or damaged edge can mechanically irritate the gingiva, leading to localized inflammation or gingivitis. Over time, this chronic irritation and plaque accumulation can contribute to gum recession and periodontal disease around the crowned tooth.
Receding gums expose the root surface of the tooth, which is not protected by enamel and is highly vulnerable to decay and sensitivity. Furthermore, a crown that is worn down or fractured can disrupt the way the upper and lower teeth meet, known as the occlusion. This uneven contact can place undue force on the jaw joint, potentially leading to strain on the temporomandibular joint (TMJ) and associated discomfort or headaches.
The altered bite alignment caused by a damaged crown forces neighboring and opposing teeth to bear excessive pressure during chewing. This abnormal distribution of force accelerates wear on other healthy teeth, increasing their risk of chipping, fracturing, or developing sensitivity. Timely crown replacement is necessary for maintaining the functional harmony of the entire chewing system.