When a tooth has a cavity, the dentist patches it up with filling and solves the problem, right? Not quite right. The tooth filling can fail. When it fails, it will ultimately lead to decay or cavity under the filling.
A tooth filling used to fill up the tooth cavity is just an artificial substance. It can eventually fail because it has a limited lifespan. The composite resin (the most commonly used tooth-colored filling material nowadays) has a median survival time of around 4 years.
It was calculated that after 5 years of placing the composite resin fillings, 84% of the fillings remained well [6].
A failed filling can cause a cavity under it without your notice. Fortunately, there are few signs that you can recognize for yourself if a filling has failed. If you can identify them, you can be a step earlier to prevent the cavity from forming.
Signs of Cavity Under Filling
Below are the important signs of the cavity under filling. However, you must understand that the signs below do not necessarily mean that there is definitely a cavity under the filling, or that the filling is going bad. They can also mean other conditions not discussed here.
The signs below will help you to recognize if the filling is failing and causing a cavity under it.
Sign #1: Toothache
Toothache can mean a few things. It is an indicator of tooth injury. Some of the reasons for toothache are decay, cracked tooth, injured tooth, and dead tooth.
A tooth with an old filling can cause toothache. If you feel that the pain is coming from the tooth that has a filling on it, there may be decay or cavity under the tooth which is causing the pain.
A toothache typically feels like a sharp pain or a dull aching pain that is triggered by having a hot or cold drink or food. Sometimes, it can be more severe and cause a headache as well as disturb your sleep. Most of the time, it is hard to point to which tooth is the culprit of toothache. Click on this to read on the Truth About Tooth Cavity: Can I Leave It Untreated?
Sign #2: Sensitive teeth
If you have sensitive teeth, you will feel a sharp pain when you have a hot or cold drink or food. Sometimes, a strong sweetness or sourness can also trigger sensitive teeth.
Sensitivity can happen to a tooth that has a “leaky” filling. The filling leakage means that there is space between the filling and the tooth wall. Fluid can go in and out freely through this space and this causes teeth sensitivity. If the space is large and food starts to accumulate, decay can happen under the filling. (Read more about the reasons for the cavity under the filling here.)
Besides that, sensitivity can also happen to teeth that have gum recession. The exposed root has no protective layer. Whenever there is a temperature change, the tooth will give a sharp pain.
Therefore if you notice that the sensitive tooth has a filling but no gum recession, it is possible that the filling is failing.
Sign #3: Food accumulation with bad smell
When you notice food debris is accumulating around the filling, it is a dangerous sign.
It means that bacteria and food are getting into the groove between the filling and the tooth wall. The groove is a good shelter for them to grow and produce acids that destroy your teeth and form a cavity.
This usually happens to the filling that is in between two teeth. Whenever you try to remove the food debris once in a while, you may notice a bad smell. This usually means the cavity underneath has active decay.
This is also a common sign for a failing dental prosthesis such as the dental crown or bridge. The decay can happen under the crown or bridge and this can cause a bad smell. If you are interested, click here to find out the 3 reasons for bad smell coming from the crowns and bridges.
Sign #4: Fractured filling
It is reasonable to expect a filling to fracture given the fact that any tooth could also fracture (read about cracked tooth here).
When a filling has fracture, you may notice it with your eyes or your tongue. There might be a hole on the tooth or a sharp edge when feeling it using your tongue.
If you notice that, you should get it changed or repaired. This is because the fractured area will leave behind a hole or cavity for bacteria and food to accumulate. Over time, decay will form around the filling and this will lead to a cavity under the filling.
Sign #5: Dark spot around the filling
When a filling is failing, there may be a small space between the filling and the tooth wall. Bacteria can seep through this tiny space and this is called leakage.
Those bacteria will start to grow and destroy the tooth from inside. This will form decay or cavity under the filling.
When it happens, you may notice the area surrounding the filling become dark in color. This dark shadow reflects the decay or cavity under the filling.
Sign #6: Loose filling
A loose filling means that the filling has lost its bond on the tooth wall.
When this happens, there will be empty spaces between the loose filling and the tooth wall. This is similar to the leakage as mentioned above.
The food and bacteria can start going into the spaces and destroy the tooth. This can form a cavity under the filling.
How do dentists detect cavity under the fillings?
When you notice the signs mentioned above, you should suspect that the filling is failing. There may be a chance that there is a cavity under the filling too. You should go to your dentist soon.
The dentist will investigate further to confirm that there is decay or cavity under the filling. Below are the common methods used by the dentist [4]:
- Visual detection: discoloration, staining, decay around the filling
- Tactile detection: feel for any catch or hole using a fine instrument
- Laser fluorescence: a digital device that gives reading which indicates decay
- X-ray: widely used to detect decay under the filling
- Transillumination: detect decay by passing light through the tooth
Commonly, your dentist can tell whether there is a cavity under the filling by visual (seeing) and tactile (feeling). An additional X-ray could almost confirm the presence of a cavity.
After it is confirmed, the filling should be either repaired or replaced with a new filling.
Summary
Now you know that a tooth filling can fail and cause a cavity under the filling. When it just happens, it is important to recognize those signs as mentioned above. If any of these signs are seen, go to your dentist soon to get it checked. The dentist is the best person to tell if the filling needs to be changed or repaired. If you ignore these signs, the decay may progress deeper and involve the inner part of the tooth – the pulp. At that time, the tooth may need root canal treatment to be saved.
