Quick answer: Yes. A crown cannot get a cavity, but the natural tooth underneath it still can. Decay usually starts where the crown meets the tooth, especially if plaque collects there or the edge no longer seals well. You may notice sensitivity, pain, a bad taste, or a loose crown, but some cavities cause no obvious symptoms. A dental exam and X-ray, when needed, are the safest way to check.
I sometimes hear, “I thought the crown covered the whole tooth, so how could I get another cavity?” It is a fair question. A crown protects and restores the part of the tooth above the gumline, but it does not make the tooth immune to decay. The edge of the crown still meets natural tooth structure.
In our Peculiar office, I look closely at that meeting point, called the crown margin. If bacteria and plaque stay along the margin, acid can damage the tooth. A small gap can also develop if the cement washes out, the crown loosens, or the tooth changes around an older restoration.
Why a crowned tooth can still decay
The American Dental Association’s guide to crowns explains that a crown covers a tooth to restore its shape, size, strength, or appearance. Under that covering, however, living or previously treated tooth structure remains.
Decay tends to begin at an exposed edge rather than somehow passing through the crown material. Risk can be higher when plaque is hard to remove, the mouth is dry, sugary drinks or snacks are frequent, or the crown margin is rough or open. Gum recession can uncover part of the root near the crown, and root surfaces are less resistant to decay than enamel.
A crown may also have been placed because the tooth already had a large filling, fracture, or root canal. That history does not mean another cavity is inevitable. It does mean I want to protect the remaining tooth and catch changes before they become larger.
Signs that deserve a dental check
None of these signs proves there is decay under a crown, but each one is worth checking:
- new sensitivity to cold, sweets, or pressure;
- pain when you bite or release your bite;
- food repeatedly catching near the crown;
- floss snagging, shredding, or sliding under an edge;
- a bad taste or odor from one area;
- redness, swelling, or drainage near the tooth; or
- a crown that feels loose or different.
Decay can also be quiet. That is one reason routine exams matter even when a crown feels fine. If a crowned tooth starts hurting, do not assume the crown itself is the only possible cause. Bite pressure, gum inflammation, a crack, or a problem with the nerve can feel similar.
How I check a crown
I start by asking when the symptoms began and what triggers them. Then I check the crown edge, surrounding gum, contact with nearby teeth, and bite. Dental X-rays may show decay or changes that cannot be seen directly, although some areas remain difficult to judge through crown material.
Sometimes the only way to know how much healthy tooth remains is to remove the crown. I do not recommend that based on age alone. A crown that is many years old can still be sound, while a newer crown may need attention if it is loose, damaged, or difficult to clean around.
If a crown comes off, keep it in a clean container and call the office. Do not use household glue or force it back into place. The tooth may be sensitive, and the fit needs to be checked before the crown is recemented or replaced.
What treatment may involve
The plan depends on where the decay is and how much tooth is left. A small, accessible area may sometimes be repaired. More often, decay at or under a crown means the old crown must come off so the damaged tooth can be cleaned and rebuilt. A new crown may then be made.
If decay reaches the pulp, root canal treatment may be considered when the tooth can still be restored. If a fracture or decay extends too far below the gum or leaves too little dependable tooth structure, extraction may be the safer option. I explain what I see and compare the realistic choices before treatment begins. Our general dentistry page covers restorative care available at Peculiar Family Dental.
How to protect a crowned tooth
The ADA’s cavity guidance recommends brushing twice a day with fluoride toothpaste, cleaning between teeth daily, limiting frequent snacking, and keeping regular dental visits. Those habits still apply after a crown is placed.
- Brush gently along the gumline rather than scrubbing hard.
- Clean between the crowned tooth and its neighbors every day.
- Tell us if floss catches or tears in the same place.
- Avoid chewing ice or using the crowned tooth to open packages.
- Wear a night guard if I have recommended one for clenching or grinding.
Call promptly for increasing pain, swelling, fever, drainage, or a loose crown. Rapidly spreading facial swelling or trouble breathing or swallowing calls for emergency medical care. Our emergency dental page has more guidance for urgent symptoms.
Frequently asked questions
Can a cavity under a crown be filled?
Sometimes a small, reachable area can be repaired, but decay under a crown often requires removing the crown first. The right option depends on the location of the decay, the crown’s fit, and how much healthy tooth remains.
Does pain mean there is decay under my crown?
Not necessarily. Pain can also come from bite pressure, gum inflammation, a crack, or a problem inside the tooth. An exam helps identify the cause instead of treating the symptom by guesswork.
Will decay under a crown show on an X-ray?
Dental X-rays can reveal some decay around or beneath a crown, but crown materials and the location of the problem can limit what is visible. The X-ray is considered with the exam and your symptoms.
How often should a dental crown be replaced?
There is no automatic replacement date. A crown should be checked for fit, damage, decay, bite changes, and the health of the tooth and gum. If it remains sound and cleanable, age alone does not require replacement.
Concerned about a crowned tooth?
I can check the crown, the tooth underneath it, and your bite, then explain what I find. Read more about my background and approach, or schedule an appointment online.