What causes pain when you have a cavity

Posted on May 7, 2026 in Healthy You

woman holding her jaw in pain

No one wants their dentist to tell them that they have a cavity. But cavities are a common condition that affects people of all ages.

Cavities may develop quietly with no symptoms at all, but they can be quite painful as they progress. If you’ve ever wondered why cavities hurt, it’s helpful to understand what’s happening inside your tooth as a cavity forms.

What is a cavity?

A cavity is a small hole in the tooth. Cavities form when bacteria in your mouth feed on sugars and starches from food and drinks. These bacteria produce acids that combine with food particles and saliva to create plaque, a sticky film that coats your teeth.

Over time, the acids in plaque wear away your tooth’s outer layer, called enamel. When this protective layer breaks down, a cavity begins to form.

Hitting a nerve: Why cavities can be painful

Not every cavity hurts right away. New cavities may only affect the enamel, which doesn’t contain nerves. That’s why small cavities may go unnoticed unless you see your dentist.

Pain usually begins when the decay spreads deeper into the tooth to the dentin, which lies beneath the enamel. At this stage, cavities can cause tooth sensitivity, especially when you eat hot or cold foods.

If the cavity continues to grow, it can reach the pulp, the center of the tooth where nerves and blood vessels are located. At this stage, the pain may become more severe or constant because the decay is close to the tooth’s nerves. When a cavity remains untreated, it can lead to a tooth infection.

How dentists treat cavities

Treatment depends on how far the cavity has progressed:

Fluoride treatments: In very early stages, fluoride can help strengthen enamel and may even reverse early decay.
Fillings: If the cavity reaches the dentin, the dentist removes the decayed portion and fills the space with a durable material.
Root canals: If the decay reaches the pulp, a root canal may be needed to remove infected tissue and save the tooth.
Crowns: When a large part of the tooth is damaged, a crown may be used to restore strength and protect the remaining tooth.

How to prevent cavities

Having good at-home dental hygiene can greatly lower your risk of cavities. Brush your teeth twice a day with fluoride toothpaste, and floss daily to remove plaque between your teeth. Drink fluoridated water and avoid snacking regularly throughout the day. Limiting sugary snacks and acidic drinks will also go a long way toward keeping your teeth healthy and cavity free.

Also, keep your dental checkups on your calendar for every 6 months. During these preventive appointments, your dentist not only deep cleans your teeth but also can detect cavities at their earliest stages, when their damage can possibly be reversed.

Your teeth shouldn’t hurt

It’s never normal for your mouth to be in pain. If your teeth or gums hurt, call your dentist to find relief. If you need a new dentist, check out Delta Dental of Iowa’s online Find a Provider tool to find an in-network dentist near you.

REFERENCE: