Dental crowns serve as protective caps over damaged or weakened teeth, restoring their shape, size, and function. While many assume a crowned tooth is immune to further issues, cavities can develop underneath, risking the underlying tooth structure. This article explains how decay forms under a crown, its signs, and steps for prevention and treatment.
Understanding Cavities Under Crowns
While a dental crown protects the visible portion of a tooth, the natural tooth structure underneath remains susceptible to decay. The area where the crown meets the natural tooth, known as the crown margin, is particularly vulnerable. Even with a seemingly perfect fit, microscopic gaps can exist at this margin, allowing oral bacteria and food particles to seep underneath the crown over time. This process, often referred to as microleakage, creates an environment where bacteria can thrive and produce acids. These acids then erode the tooth enamel and dentin beneath the crown, leading to a new cavity. The crown itself does not decay, but the underlying tooth material is still biological and vulnerable to the same processes that cause cavities in natural teeth. Once bacteria infiltrate this space, saliva, which normally helps neutralize acids and remineralize enamel, cannot effectively reach the affected area.
Factors Contributing to Decay
Several factors contribute to decay under a dental crown. Inadequate oral hygiene is a primary reason, as plaque and bacteria accumulate around crown margins if not consistently removed. A diet high in sugars and acids also fuels bacterial activity, increasing decay risk.
Gum recession can expose the tooth root surface, which is softer than enamel and more prone to decay, especially around the crown. An improper crown fit or seal creates spaces where bacteria easily gather. Old, worn, or damaged crowns with cracks or chips can compromise their seal, allowing bacteria to enter. Additionally, if decay was not entirely removed before the crown was initially placed, it can continue to progress underneath.
Identifying the Problem
Recognizing the signs of a cavity under a crown can be challenging because the crown covers the affected area. However, several symptoms may indicate an issue. Common indicators include increased sensitivity to hot, cold, or sweet foods and beverages, and persistent pain, especially when biting down. A bad taste or persistent foul odor in the mouth, despite good oral hygiene, can also signal bacterial activity and decay.
Visible changes might include swelling, redness, or tenderness of the gums around the crowned tooth. In some instances, dark spots or lines may become visible near the crown’s edge, or the crown itself might feel loose. A dentist diagnoses decay under a crown using a visual examination, dental probing to check for soft spots or gaps, and dental X-rays, which can reveal decay hidden beneath the crown.
Addressing and Preventing Recurrent Decay
Treatment for a cavity under a crown depends on the extent of the decay. If the decay is minor and accessible, a dentist might remove the crown, clean the decayed area, and place a new filling, then re-cement the existing crown if it is still sound. If the decay is extensive or the crown’s fit is compromised, replacing the entire crown is often necessary after the decay is removed. Should the decay reach the tooth’s pulp, root canal therapy will be required to save the tooth before a new crown is placed. In severe cases where the tooth structure is too compromised, extraction may be the only option.
Preventative measures are essential to maintain the longevity of a crowned tooth. Rigorous oral hygiene, including brushing twice daily with fluoride toothpaste and flossing around crown margins, is fundamental. Using an antimicrobial mouthwash can further reduce bacteria.
Regular dental check-ups, typically every six months, allow for early detection through professional cleaning and X-rays. A balanced diet, low in sugary and acidic foods, helps minimize decay risk. Addressing issues like teeth grinding with a nightguard and managing gum recession also contribute to long-term crown health.