Tooth decay is caused by bacteria in the mouth that eats away at tooth enamel. This can lead to a cavity  (a hole in the tooth). A cavity in your tooth doesn't always have symptoms at first, but as it grows into the deeper layers of your tooth, you may feel it.

Common cavity symptoms include tooth pain or sensitivity and visible changes in the tooth, like holes or pits.

Here we explain how cavities look and feel, what happens if they go untreated, and how we diagnose them.

Visible Small Cavity Signs

You may not notice a cavity right away since the changes are visually small. Also, it's possible to have a cavity and not feel anything.

However, even though small cavities may have visible changes, most people don't examine their teeth routinely, especially those that are more difficult to see in the back of your mouth.

Teeth in the back of the mouth are where cavities often occur. Cavities most commonly pop up on chewing surfaces and between teeth.¹ Both of these areas are difficult to see yourself.

Warning signs of a cavity include:

• White spots on the teeth
• Spots that turn darker shades of grey, brown or black
• Continually getting food trapped between your teeth

Invisible Cavities

An invisible cavity (also called a hidden cavity) is one you can't see with the naked eye. Usually, that's because the cavity is between teeth. 

Dental X-rays can catch early cavities between teeth and those not yet visible on the tooth's surface. Researchers have found that X-rays increase the diagnosis of hidden cavities by nearly 10 times.

How Cavity Symptoms Feel (or Don't Feel)

It can help to understand what a cavity feels like.

Cavity symptoms include:

• Tooth pain that can be sharp or dull
• Tooth pain that occurs when you bite down 
• Tooth sensitivity (to hot, cold, or sweet things)
• Feeling pits or holes in your tooth

Researchers call cavities one of the most prevalent diseases among children globally.

Untreated, Worsening Symptoms

Before a cavity begins, there are things you can do to prevent it. Some steps for reducing your risk of a cavity include:

• Using fluoride toothpaste, mouth rinse and dental applications
• Minimising sugar and starches
• Limiting fruit juice
• Brushing two times a day

That said, once you have a cavity, it will likely continue to get worse if left untreated. A cavity spreading beyond the enamel could lead to an abscessed tooth  (a severe infection).

An abscess might occur if the pulp (the soft tissue in the root) dies and swells. When bacteria enter the pulp, it causes an infection, leading to a pocket of pus that forms around the root. This infection can spread throughout the body and can sometimes be fatal.

Symptoms of a tooth abscess include:

• Pain
• Swelling
• Redness in the gums
• Bad taste in the mouth
• Fever

In the early stages, when there is a white spot in the tooth's enamel, for instance, the enamel could repair itself with minerals from saliva and fluoride.  However, as a cavity develops and becomes worse, the enamel becomes too weak and destroyed to repair itself.

Seeing a Dentist: How to Tell for Sure

While cavities offer some visual signs, they are not always on visible parts of your teeth. Cavities are sometimes in between teeth and in the back of your mouth. To be sure, you'll need to see a dentist, who will visually examine your teeth and, if necessary, do an X-ray.

Inspection

Dentists use a visual inspection to determine if a cavity is present on a tooth. The International Caries Detection and Assessment System (ICDAS) is a clinical scoring system that measures surface changes and the depth of cavities. Cavities are coded between 0 and 6, with the lower score indicating a healthy tooth and the higher score showing extensive tooth damage.

Cavity on X-Ray

An X-ray is the most definitive way to diagnose a cavity. X-rays allow dentists to see through layers of teeth to determine how severe a cavity is. This can inform their treatment plan. However, X-rays are not fool proof, and they sometimes underestimate the depth of a cavity.

Summary

There are numerous ways to tell if you have a cavity. When a cavity is small, you may not feel anything, but you might notice some discolouration, like white, grey, or brown spots. As the cavity progresses, pain and sensitivity are common symptoms.

If you suspect a cavity, the best thing to do is make an appointment with a dentist. They can determine how advanced the cavity is and develop a treatment plan.