When you visit the dentist for treatment that includes dental restorations like crowns or fillings, you usually trust that the restoration has fixed the problem of caries (or cavities) in that tooth. This may not always be the case. Recurrent caries can occur after dental restoration.

What are recurrent caries?

Recurrent caries are caries (also commonly known as cavities) that occur underneath a dental restoration. In the case of a filling or a crown, this means that even if the previous decay that prompted the application of the crown (or filling) was removed, more decay occurred after the filling or crown.

Composite fillings are most often affected by this, but over time any type of filling or crown material will degrade. This can allow recurrent caries to form.

People sometimes confuse recurrent caries with secondary caries. Although recurrent caries are located underneath dental restorations, secondary caries are new caries that occur at the margins of a restoration. These are most commonly found at the places where the dental restoration meets the gumline, as in the case of a crown or a fixed denture.

What causes tooth decay under a filling?

Bacteria causes tooth decay of all kinds.

For better or for worse, bacteria is present in everyone’s mouth. The bad kind of bacteria grows and thrives on high-acid, high-fat diets. This is why people who consume large amounts of acidic foods (e.g., soda, coffee, and sour candy) and high-fat foods (e.g., sugar, white pastas, and processed foods) have a higher incidence of caries in general.

In the case of recurrent caries, this bacteria enters the space underneath the dental restoration through micro-cracks of 50 microm or more in the material. Once the bacteria enters the area underneath the dental restoration, it is very difficult, if not impossible, to prevent recurrent caries formation. The trapped bacteria has nothing to do but eat at the tooth material and, eventually, the dental pulp.

As with regular caries, poor dental hygiene is a common cause. Additionally, dry mouth can increase the chances of developing recurrent caries, as can cracked or failing dental restorations. Dental restorations that weren’t properly fitted in the first place can also lead to the development of recurrent caries.

How are recurrent caries diagnosed?

Your dentist can diagnose recurrent caries in one of three ways (or any combination of the three).

Visual exam

When recurrent caries have progressed to a certain point, there may be discoloration on the tooth. The tooth may also appear obviously pocked or pitted.

Tooth color can range from yellowish to brown to grey-black.

Physical exam

Your dentist will use a dental tool called an explorer to check each tooth for issues. If the fine tip of the explorer sticks, recurrent caries may be present.

X-rays and other imaging devices

An X-ray can pick up recurrent caries that are not obvious from a visual or physical exam, specifically those that occur between teeth and under dental restorations. In many cases, this is the only way your dentist can diagnose recurrent caries.

Your dentist may also use a laser fluorescence caries detection device. Decayed or decaying teeth will glow in proportion to the amount of bacteria present. Your dentist will measure the amount of fluorescence to identify potential issues.

What are recurrent caries symptoms?

Recurrent caries symptoms are similar to regular cavity symptoms. They can include:

  • Tender gums that bleed easily: A sign of both cavity and gingivitis, bleeding gums in the area surrounding a dental restoration can be a first sign that excess bacteria is present and causing inflammation.
  • Sensitivity to hot and cold: Even if the dental restoration is a crown, recurrent caries can cause sensitivity to hot or cold food and drink. Some patients even experience sensitivity to food that is high in sugar.
  • Bad breath: Bad breath is another clear sign that unhealthy bacteria is present in the mouth.

How will a dentist treat recurrent cari