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Home » Tooth Decay Under Crowns: What To Do?

Tooth Decay Under Crowns: What To Do?

Detecting tooth decay under crowns can be an upsetting experience for anyone, especially when we know that crowns protect damaged teeth and restore their functionality. Any decay under the crown tells us that it may not have done its job perfectly.

The truth could not be further from that. Although crowns are strong, they can crack and break down with time. Besides, the tooth under the crown is still subject to decay like any other tooth. Without good oral hygiene, teeth underneath their crowns can have cavities.

In this article:

  • What are the symptoms of tooth decay under crowns?
  • Why may you have tooth decay under a crown?
  • How to treat cavities under crowns?
  • What happens when tooth decay is left untreated?

And much more.

What are the symptoms of tooth decay under crowns?

Decay under crowns may be followed by one or more of the following:

  • Pain in or around your crowned tooth
  • Persistent pain at the root of the tooth
  • The pain has spread to your jaw, face, and other teeth
  • Sore gums
  • Sensitive gums
  • Bleeding from the gums
  • Bad breath
  • Constant bad taste in the mouth
  • Pain when chewing
  • Loose crown
  • Loose tooth
  • Misaligned tooth
  • A black line around the crown
  • Tooth discoloration

It is likely that any tooth decay under the crown will remain undetected to you for some time. But it will be easy for your dentist to determine if you have cavities under the crown from various symptoms you may have.

Besides, your dentist has access to x-ray equipment. If they suspect that you have cavities, they will x-ray your mouth for a thorough examination.

What can cause tooth decay under a crown?

Decay in crowned teeth can happen for many reasons.

Gum recession

The margin of the gum tissues around your tooth may pull back, exposing the tooth and its root to food debris and bacteria. The bacteria can grow in what is called a ‘pocket.’ It is the space between your tooth and gum.

You may hurt your gum by brushing your teeth repeatedly and aggressively. The problem can be acute if you do not choose a soft-bristled brush.

Plaque build-up

Plaque causes tooth decay or cavities, gum disease, and bad breath.

Bacteria grow fast in the plaque. They produce acid that damages your tooth enamel. Plaque can form under the gums and gradually reach the root of your tooth to damage your tooth and jawbone.


According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), uncontrolled diabetes raises the glucose level in your saliva, which catalyzes high bacterial growth. A high sugar level in the blood also lowers your body’s ability to fight infection.

Diabetes Canada says, ‘people with diabetes are at higher risk for tooth decay, gum inflammation and disease, and periodontitis.’

Hormonal imbalance

Hormonal changes in women affect the blood supply to the gum tissue. They also direct the body not to respond adequately to the toxins from plaque buildup.

During pregnancy, more estrogen and progesterone cause more blood to flow to a woman’s gums, thus making them more sensitive. Other dental risks during pregnancy include gingivitis, dry mouth, and tooth decay.

Root canal failure

Your root canal treatment may have failed. It is not impossible for bacteria to find a way to the root of your tooth through any damage or crack in the root canal sealant. The root canal failure rate is between 2% and 14%.

Root canal failure may lead to infection in the pulp chamber of your tooth. This is a complication that cannot be treated without removing your crown.

Cracked or fractured tooth or crown

If you have cracked your tooth, bacteria may find their way to the pulp through the cracks, thus creating tooth infection. You do not need a long period to decay your tooth this way.

The impact can be sudden, and the tooth may have to be extracted in favor of a dental implant because it may not be suitable for a new crown.

The same can be said about your crown. Crowns can crack if you have bruxism


According to The Well Project, HIV weakens one’s immune system and causes oral complications like gingivitis or periodontal disease, mouth infections, and sores.

According to the National Institute of Dental and Craniofacial Research, HIV can cause the following dental problems:

  • Chronic dry mouth
  • Gingivitis
  • Bone loss around the teeth
  • Canker sores
  • Oral warts
  • Fever blisters
  • Oral candidiasis
  • Hairy leukoplakia
  • Dental caries

It will not be a surprise if your crowned tooth also becomes a victim of HIV.


Excessive smoking may result in gum disease, a bad taste in the mouth, and mouth cancer. Smoking also creates an imbalance of blood pressure in your body, ultimately impacting your gum tissues. Besides, smoking reduces your healing capacity, which is why any infection at the root of your tooth does not want to heal easily.

Family history of gum disease

If you have a family history of gum disease, most likely you will get gum disease too. Some genetic factors can increase the likelihood of your having periodontitis by as many as 20 times.

But you can avoid such predictability by proactively taking care of your mouth. Do the following:

  • Maintain good oral health.
  • Eat a balanced diet.
  • See your dentist at least every six months.

How to treat tooth decay under crowns?

  • Filling. If the cavity is visible and not very deep, it can be filled with a composite filling.
  • Removing the crown. In some cases, the crown has to be removed to treat the tooth, and a new crown has to be placed on the tooth.
  • Root canal. This situation occurs if a root canal treatment fails.
  • New root canal. Some teeth have more than one canal. After root canal therapy, the same tooth may require another root canal, provided it has an infection in a different pulpal chamber.
  • Dental implant. If the tooth is so decayed that it is considered unsuitable for a crown, your dentist may require it to be extracted. You can have a dental implant in its place and get a new crown on the implant.

Also read: Cost of root canal in major US cities and abroad

What happens when tooth decay under crowns is left untreated?

If you do not treat your tooth decay at all or on time, you may find yourself in a more complicated situation dental health-wise. Any minor decay can turn into something serious, given the opportunity. The following can happen:

  • Decay may intensify and go beyond correction.
  • The problem may kill the tooth requiring it to be extracted.
  • Your tooth may become loose.
  • The problem may spread to your other teeth and infect them.
  • Tooth misalignment is a possibility. A misaligned tooth can damage the tooth on the opposite arch.
  • The infection may reach your jawbone and cause bone erosion.
  • Small decay can let bacteria into the pulp chamber, thus causing infection at the tooth’s root. The tooth has to be drilled for a new root canal.
  • A pulp infection cannot be treated with antibiotics. You will require surgery.
  • Quality of life will fall.

How to prevent tooth decay and gum infections?

  • Brush your teeth at least twice daily with a soft-bristled toothbrush and fluoride-rich toothpaste.
  • Floss your teeth at least once a day.
  • Stay hydrated. Your mouth needs to stay moist at all times.
  • Wear mouthguards if you grind your teeth.
  • Repair your crown as quickly as possible.
  • Eat a balanced diet. Eat calcium-rich foods such as milk, yogurt, and cheese to stay healthy.
  • Quit smoking.
  • Quit eating sugary food.
  • Avoid eating crunchy and sticky food with your crown. Avoid chewing sugary gums.
  • If you allow plaque build-up, you need to see your dentist. The plaque will soon turn into tartar, which you cannot remove from your teeth at home.

Final word

Early detection of decay is vital for saving your tooth. Talk to your dentist if you notice any symptoms of decay in your crowned tooth. Detecting the breadth and depth of decay requires professional experience. Do not miss your appointments with your dentist.


  • American Dental Association. Gum Disease.
  • The Well Project. HIV and Your Mouth.
  • National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Diabetes, Gum Disease, & Other Dental Problems.
  • Colgate. Family History Affects Your Risk For Gum Disease.
  • Diabetes Canada. Diabetes and your teeth.