When you have a cavity, your dentist removes the decayed portion of your tooth and fills the space with a durable material to restore its shape and function. That’s the standard treatment for most cavities, and the whole process typically takes 30 to 60 minutes. But the exact approach depends on how deep the decay has spread, and larger cavities may need more involved treatment like a crown or root canal.
How Your Dentist Finds the Cavity
Some cavities are visible as dark spots or holes on the tooth surface, but many aren’t obvious to the naked eye. Cavities that form between teeth or below the gumline are especially hard to spot during a visual exam alone. That’s why dental X-rays are a routine part of checkups. Bitewing X-rays, the most common type, reveal decay hiding between teeth and below the gumline. Periapical X-rays show cavities near the tooth roots and can detect bone loss or infection.
Your dentist may also use a small pointed instrument called an explorer to probe soft spots on the tooth surface. Healthy enamel feels hard and smooth, while decayed areas feel soft or sticky.
What Happens During a Filling
A standard filling follows five basic steps. First, the dentist numbs the area by applying a topical gel to your gum, then injecting a local anesthetic into the surrounding tissue. You’ll feel a brief pinch from the injection, but within a few minutes the entire area goes numb.
Once you can’t feel anything, the dentist uses a high-speed drill to remove the decayed enamel. When the drill reaches the softer layer underneath (called dentin), the dentist switches to a slower, more precise drill to avoid removing more tooth structure than necessary. After all the decay is cleared out, the dentist shapes the remaining cavity so it can hold a filling securely.
Before placing the filling material, the dentist applies an acid gel to the prepared surface. This roughens the tooth slightly and strengthens the bond between your tooth and the filling. The filling material is then packed into the cavity and shaped to match the natural contour of your tooth. Finally, the dentist places a thin piece of carbon paper between your teeth and asks you to bite down. The paper marks any high spots where the filling sits too tall, and the dentist shaves those down so your bite feels normal.
Filling Materials
The two most common options are composite resin (tooth-colored) and amalgam (silver-colored). Composite fillings blend in with your natural teeth, making them the go-to choice for visible areas. They harden instantly under a UV light during the appointment, so you can chew on them right away. The tradeoff is durability: composite fillings last about 5 to 7 years on average, though they can go longer with good care.
Amalgam fillings are a mix of metals and have been used for over a century. They’re stronger and typically last 10 to 15 years, sometimes longer. But they’re silver in color, which makes them more noticeable. Amalgam also takes about 24 hours to fully harden, so you’ll need to avoid chewing on that side for a day after your appointment.
Alternatives to the Traditional Drill
If the sound or sensation of a drill makes you anxious, some dentists offer air abrasion. Instead of a rotating drill bit, this tool shoots a fine stream of particles at the tooth to blast away decay. It produces no heat, pressure, or vibration, and for shallow cavities, it can sometimes eliminate the need for anesthesia entirely. Air abrasion also preserves more healthy tooth structure and reduces the risk of tiny fractures that can shorten a filling’s lifespan.
Air abrasion has limits, though. It can’t cut through hard enamel effectively, so if the dentist needs to drill through the outer surface to reach decay underneath, a traditional drill is still required. It also isn’t suitable for deep cavities, cavities between teeth, or any procedure that involves placing a crown.
For certain patients, there’s also a no-drill option. A liquid treatment containing silver and fluoride can be painted directly onto a cavity to stop decay from progressing. The American Dental Association recognizes this approach for both baby teeth and permanent teeth. It’s most commonly used for young children who can’t sit through a drilling procedure, people with special needs, elderly patients with root cavities, or anyone who can’t safely undergo general anesthesia. The liquid is typically reapplied every six months. The main downside: it permanently stains the decayed area black, so it’s generally reserved for less visible teeth or situations where drilling isn’t practical.
When a Filling Isn’t Enough
A filling works well when the cavity is relatively small and the remaining tooth structure is strong enough to hold it. When too much of the tooth has been destroyed by decay, a filling won’t provide enough support. In these cases, your dentist will likely recommend a crown, which is a cap that fits over the entire visible portion of the tooth. Crowns are also used for teeth that are cracked, broken, or already so heavily filled that another filling would compromise their strength.
If decay has reached the innermost part of the tooth, where the nerve and blood vessels live, the situation is more serious. Signs that this has happened include lingering pain when you chew or bite down, sensitivity to hot or cold that doesn’t fade quickly, swollen or tender gums near the tooth, a tooth that’s turned noticeably darker, or a small bump on the gum that looks like a pimple. These symptoms point toward a root canal, where the dentist removes the infected tissue from inside the tooth, cleans and seals the internal chambers, and then places a crown over the top. The crown is almost always necessary after a root canal because removing the inner tissue makes the tooth more brittle and prone to cracking.
Recovery and What to Expect After
The numbness from local anesthesia typically wears off within 1 to 3 hours, though it can last longer depending on how much was used. Until the feeling returns, be careful not to bite your cheek, tongue, or lip, since you won’t feel it if you do.
With a composite filling, you can eat as soon as the numbness fades. With amalgam, wait a full 24 hours before chewing on that side to let the material reach its full strength. Regardless of the type, some sensitivity to hot, cold, or pressure around the filled tooth is normal for a few days to a couple of weeks.
If your bite feels off after the numbness wears off, or if sensitivity gets worse instead of better over the following week, call your dentist. The filling may be sitting slightly too high and need a quick adjustment, which takes just a few minutes and usually doesn’t require another round of numbing.