6 Signs of Tooth Decay Under Your Crown or Filling

inflammation of the gums abscess closeup cavity under crowns

When you get a dental crown or filling, it isn’t a guarantee that your tooth is never going to get a cavity ever again. Since fillings and crowns only affect part of your tooth, you still have to worry about the area of your tooth next to the margin of your restoration. Especially if your filling/crown is already several years old. If you have recurrent decay (a new cavity under fillings you already have) then you’ll need to address it ASAP. 

Here are a few things to look for if you think you’re getting a cavity under a dental crown or filling and what to do about it. 

What Is Recurrent Decay?

Recurrent decay is the term that we use in dentistry when there is a new area of tooth decay around an existing dental crown, filling, or other restoration. Decay being a cavity. 

You could almost say that your cavity “came back”. Even though the tooth decay was completely removed during your restorative treatment, lifestyle factors and diet choices can allow new tooth decay to re-develop at those areas of your mouth. Especially if they were already cavity-prone to begin with.

The margins around your existing dental fillings and crowns are some of the most likely areas to experience recurrent decay. When that happens, you get a cavity under filling material that seeps deeper into the tooth than you might think. And if you have a cavity under a dental crown, it may prevent you from being able to re-do the crown altogether.

Most recurrent tooth decay is because circumstances (like not flossing or a high sugar intake) continued after the filling or crown was placed. You can also get a cavity under fillings/crowns when the restoration starts to get old and begins to leak around the margins.[1]

Signs I Have Tooth Decay Under a Crown or Filling

How can you tell if you have recurrent decay around your dental work? There are several red flags to watch for. But most importantly, always listen to your dentist. They may be able to see early warning signs during your dental exams that you won’t notice at home.

1. Toothache In Your Tooth With Filling or Crown

Pain and sensitivity are common when you have cavities, especially large ones or decay close to the nerve of your tooth. The pain might be random when you bite down and even range from dull to sharp.

2. Tooth Discoloration Around Your Filling or Crown

When you look at your tooth in the mirror, do you see dark discoloration around the edges of your filling or crown? If it’s an amalgam or silver filling, you might notice darkening in the tooth next to the margins as your restoration begins to “leak” and need to be replaced. Sometimes the color leaches into that area naturally. But other times—especially with dental crowns or white fillings—having dark staining around your restoration means something else. Not all cavities are brown or black, but gradual changes in certain areas of your enamel may indicate recurrent decay. At the very least, it’s a signal that it’s probably time to update your old dental work.

3. Filling or Crown Falling Out Of Your Tooth

A surefire way to know you have a cavity under dental crown or bridge work is if your restoration falls out. Normally dental crowns and fillings don’t fall out of your tooth unless there’s something majorly wrong. The exception would be if you’re wearing a temporary crown or the bonding agent on your permanent crown didn’t have time to cure (set) completely. By the time your filling or crown breaks off or falls out, you can almost guess without a doubt that there was recurrent decay underneath it.

4. Filling or Crown Is Sensitive

Does your tooth seem to be sensitive for no reason? Perhaps brushing that tooth or tapping on it with a toothbrush sends a jolt through your mouth? Or maybe you just notice that it’s a little more tender than its neighboring teeth? Your mouth is extremely sensitive, so be sure to let your dentist know when something seems “off”. Especially if you notice any tiny movements, indicating that your restoration could be loose.[2]

5. Pain When Eating

Does it hurt or feel tender whenever you bite down on your tooth? Are certain types of foods or drinks causing toothaches whenever you eat them? Check to see if you have a dental crown or filling in that part of your mouth. There might be bacteria seeping in around the edges, irritating the more sensitive dentin underneath (or even reaching into the nerve of your tooth.) 

6. Floss or Food Getting Caught Around That Tooth

A “good” dental crown or filling will have a tight seal against your tooth enamel. But as new cavities form or the restoration ages, an open margin is created between the tooth and filling/crown. These open spaces can trap food whenever you eat. And when you go to floss them each day, you may notice the floss either getting caught in that space or shredding/breaking in that area.

What Should You Do?

If you even remotely think you have a cavity under dental crowns/fillings/bridges, etc., get to your dentist ASAP. You’ll need to make a game plan to treat the tooth decay before it can spread deeper into your tooth or adjacent teeth.

If you just have decay under a filling, all you may need is a new filling. But extremely large cavities will need a crown instead. If you have a cavity under a crown or filling that already reaches into the nerve of your tooth structure, root canal therapy will be unavoidable.[3]

The earlier you treat your recurrent decay, the better chance you have of saving your tooth and avoiding a root canal. But untreated, active tooth decay under a crown or filling will just continue to spread and cause further complications throughout your mouth.

Don’t let pain be the determining factor. Intercept the cavity as early as possible. Your dentist will take an x-ray but may need to remove the old filling or crown to truly know how “bad” the situation has gotten.

Recurrent Decay Prevention 

Since it’s physically possible to get a new cavity around your dental crown or filling, excellent oral hygiene and home care are a must.

  1. Always brush your teeth twice a day for a minimum of two minutes, focusing particularly along the gumlines and margins of your current dental work. Electric toothbrushes are great for cavity prevention!
  2. Floss daily. Flossing will NOT “pull off” your dental work unless it’s already loose or has a cavity around it.
  3. Use fluoride daily. Either in the form of a toothpaste, rinse, or gel. Fluoride helps remineralize areas to stop the tooth decay process before physical cavities form.
  4. See your dentist every six months for an exam and cleaning.  X-rays can bring areas to your attention before recurrent decay ruins your smile. Also, it's vital to maintain proper oral hygiene habits in-between visits as well!

When to See a Dentist

Over time, anyone can develop a new cavity under dental crowns or fillings. Especially if you have a history of recurrent decay, not flossing, or a high sugar intake. If you notice pain, tenderness, sensitivity, or floss/food getting stuck around dental work, you might have active tooth decay under a crown, filling, or other restorations. The best thing to do is see your dentist for regular checkups and replace your old dental work ASAP before you run the risk of a root canal or the cavity spreading into the adjacent teeth.

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