A common misunderstanding is that a tooth with both a crown and a root canal is immune to cavities. While dental crowns protect the visible tooth and root canal therapy addresses the internal pulp, decay can still develop. Understanding how and why this occurs is important for maintaining oral health.
Understanding the Vulnerability
A tooth that has undergone root canal therapy and received a crown remains susceptible to decay. While a crown covers the visible tooth, it does not create a hermetic seal. Over time, the dental cement bonding the crown can degrade or wash out, leading to microscopic gaps at the crown margin, where it meets the natural tooth structure. These tiny openings can serve as entry points for oral bacteria.
Root canal treatment involves removing the infected pulp, including the nerve and blood vessels, from inside the tooth. This procedure eliminates the tooth’s ability to sense hot, cold, or pain from decay, as the nerve is no longer present. However, the outer layers of the tooth, including remaining enamel and dentin, are still natural tooth structure. This structure remains vulnerable to bacterial acid attacks, similar to any other tooth.
How Decay Develops
Decay under a crown on a root-canaled tooth begins when oral bacteria and food particles, particularly sugars, accumulate in microscopic gaps at the crown margin. These areas are often difficult to clean effectively with routine brushing and flossing. Bacteria thrive on these trapped food residues and metabolize the sugars.
As bacteria metabolize sugars, they produce acids as a byproduct. These acids demineralize the exposed tooth structure (enamel and/or dentin) underneath the crown, leading to cavity formation. Because the tooth no longer has a living nerve due to the root canal, decay can progress silently and extensively without causing pain or sensitivity. This lack of sensation means significant damage can occur before detection, often only during a routine dental examination.
Recognizing the Signs
Detecting a cavity under a crown on a root-canaled tooth is challenging due to the absence of nerve sensation. However, certain subtle indicators may suggest decay. These include persistent bad breath or a foul taste from the affected tooth, as bacteria and decay produce unpleasant odors. Sensitivity to pressure or discomfort when chewing, even without a nerve, can also occur because surrounding tissues and ligaments are still intact and can react.
Other signs might include visible discoloration, such as dark spots, around the crown margin, indicating underlying decay. A change in the crown’s fit or a feeling it is pulling away can also signal a problem. Often, these cavities are only identified during regular dental check-ups, where a dentist can perform a thorough clinical examination or use X-rays, which can reveal demineralization or gaps beneath the crown.
Managing and Preventing Recurrence
If a cavity is identified under a crown on a root-canaled tooth, treatment options vary depending on the extent of the decay. For minor, accessible decay, a dentist might remove the crown, clean the decayed area, and place a new filling before reattaching or replacing the crown. If the decay is extensive or the crown’s fit is compromised, replacing the entire crown may be necessary to ensure a proper seal and protect the tooth. In severe situations where the tooth structure is too damaged, extraction could be the only viable solution.
Preventing recurrence involves consistent oral hygiene practices. Brushing teeth twice daily with fluoride toothpaste and flossing daily are important, with particular attention to the gum line around the crown to remove plaque and food particles. Limiting sugary and acidic foods and drinks can also reduce the risk of decay. Regular dental check-ups, typically every four to six months, including professional cleanings and X-rays, are crucial for early detection. Avoiding habits that could damage the crown, such as chewing on hard objects, further helps maintain its integrity.