Revealing cavities under a crown: What you need to know

How can crowned teeth get cavities?

Tooth decay is a common problem, and according to the CDC, almost 90% of adults have experienced at least one cavity.

When decay forms under or around a dental crown, we call them Recurrent or Secondary Cavities. If you're already prone to cavities, getting a crown can actually increase your risk even more unless you take some measures.

Recurrent cavities occur for the same reasons as regular tooth decay. It starts with acid-producing bacteria in your mouth thriving and forming plaque. These bacteria feed on sugars and starches, creating acids that attack your teeth.

You may be more prone to these cavity-causing bacteria if you have other risk factors, such as chronic dry mouth or overconsumption of sugary, acidic foods and drinks.

But why getting a crown can be a risk factor too? Well, before placing a dental crown, we trim the tooth to make it fit properly. The area where the crown borders meet the tooth (near the gum line) is called the Margin. And it's where decay is most likely to happen.

The margin attracts more plaque naturally, especially if you don't brush your teeth well or skip flossing.

Over time, this transition area can wear down, allowing saliva and oral bacteria to seep through. The result? More acid production and a higher risk of tooth decay.

When it's your dentist's fault

Secondary cavities are usually new lesions that develop slowly over time. Most of the time, it's not the dentist's fault. But what if your dentist hasn't completely removed the initial decay before placing your crown? That's what we call Residual Cavities.

These aren't new lesions and can appear anywhere under the crown, not just near the gum line. In other words, residual cavities happen when an old decay you already had reactivates and causes trouble again.

The tricky part is that these can hide under the crown, making them difficult to spot immediately. So you may not notice them until they've already done some serious damage.

What can cause cavities under crowns?

Various factors can contribute to cavities development. Understanding them can help you take proactive measures for your oral health.

Plaque, a white, soft film loaded with bacteria, is the main culprit. And as we already said, crowns create an environment that promotes more plaque buildup.

This is why maintaining rigorous oral hygiene practices becomes even more critical after receiving a dental restoration.

But, cavities (gum disease as well) are often a combination of various factors that interact, making some individuals more vulnerable. Here are the most involved:

1. The age of the crown: Crowns typically last between 15 to 20 years, with metal crowns being the most durable. However, over time, the crown's surface can become rough and worn, making it more prone to plaque buildup. Bacteria can then deeply penetrate the tooth, leading to tissue damage and decay. So, if your crown is showing signs of wear and tear, it may be time to consider getting a new one.


2. Poorly shaped crown: A poorly shaped crown that doesn't properly touch the neighboring teeth can create spaces where plaque can accumulate. This can result in cavities forming between the teeth. Additionally, a badly fitted crown can damage gum tissue, leading to inflammation and gum recession.


3. Gaps at the crown margin: One of the most challenging parts of making crowns is not leaving any gaps where bacteria and saliva can infiltrate. If you notice an unusual gap in the gum line area, it's crucial to consult your dentist. They may need to adjust or redo the crown to prevent cavities from developing.


4. Poor oral hygiene: Aside from the dentist's technique, it's your responsibility to keep the crown clean and free of plaque. Maintaining correct and regular oral hygiene will prolong the life of your crown for as long as possible.


5. Receding gums: When the gums recede, the tooth roots become exposed, leaving them vulnerable to plaque buildup and bacteria. Because roots are naturally more sensitive to acid attack, they can decay quicker than other parts of the tooth. (7)