Getting a cavity filled is one of the most common dental procedures, and the whole process typically takes 20 to 60 minutes depending on the size and location of the cavity. Most of the appointment involves numbing, removing decay, and placing the filling material. Here’s what to expect at each stage.
Numbing the Area
Your dentist starts by applying a numbing gel to the gum tissue near the affected tooth. This gel dulls the surface so you barely feel what comes next: an injection of local anesthetic into the gum. The most commonly used anesthetic is lidocaine, which keeps the area numb for roughly 30 to 120 minutes. When paired with a vasoconstrictor (a substance that narrows blood vessels to keep the anesthetic concentrated in one spot), that window can stretch even longer.
You’ll typically wait a few minutes after the injection for full numbness to set in. Your lip, cheek, and part of your tongue on that side of your mouth will feel thick and tingly. This is normal and temporary.
Removing the Decay
Once you’re numb, your dentist uses a high-speed drill to remove the decayed portion of your tooth. This is the part most people dread, but with the anesthetic working, you won’t feel pain. What you will feel is pressure and vibration, along with the sound of the drill and a spray of water used to keep the tooth cool.
Some dental offices now offer laser cavity preparation as an alternative to the traditional drill. A specific type of laser can remove decay and shape the cavity with no microfracturing of the surrounding tooth structure, and studies have shown patients can sometimes be treated without anesthesia at all. Laser preparation isn’t available everywhere and works best on smaller cavities, but it’s worth asking about if drill anxiety is a concern for you.
After the decay is cleared, your dentist shapes the remaining space so the filling material will bond securely. They may also apply a mild acid solution to etch the tooth surface, which helps the filling grip to it.
Placing the Filling
The two most common filling materials are composite resin (tooth-colored) and amalgam (silver-colored). The placement process differs slightly for each.
With composite resin, your dentist layers the material into the cavity in small increments. After each layer, they shine a special blue light on it. This light, typically at a wavelength around 450 to 490 nanometers, triggers a chemical reaction that hardens the resin in seconds. A light-sensitive compound inside the resin absorbs the blue light and causes the material to polymerize, turning it from a pliable paste into a solid. Because each layer hardens almost instantly, the filling is fully set by the time you leave the chair.
Amalgam fillings are mixed from a combination of metals and packed into the cavity as a soft mass. Unlike composite, amalgam doesn’t harden immediately. It sets gradually over the next 24 hours, which changes what you can do right after the appointment.
Shaping and Polishing
Once the filling is placed, your dentist trims away any excess material and shapes it to match the natural contour of your tooth. They’ll ask you to bite down on a thin piece of colored paper (called articulating paper) that marks where your upper and lower teeth make contact. If the filling sits even slightly too high, it can cause pain every time you bite. Your dentist files it down until your bite feels even.
A final polish smooths the surface, which helps prevent staining on composite fillings and makes the whole tooth easier to keep clean.
What You Can Eat and When
If you got a composite filling, the material is already fully hardened, so you can technically eat right away. However, most dentists recommend waiting at least two hours before eating simply because your mouth is still numb. Chewing while numb puts you at risk of accidentally biting your cheek, lip, or tongue without realizing it.
If you got an amalgam filling, you’ll need to wait a full 24 hours before chewing on that side. The metal needs time to reach its maximum strength, and biting down too early can deform or crack the filling.
Regardless of the filling type, it’s smart to avoid very hard, sticky, or crunchy foods for up to a week. Think: ice, caramel, hard candy, and nuts. These can dislodge or damage a new filling before it fully bonds to the surrounding tooth.
Sensitivity After the Procedure
Some degree of tooth sensitivity after a filling is common and usually not a sign of a problem. You may notice sharp, brief pain when the tooth contacts something hot, cold, sweet, or even cold air. This sensitivity typically fades within a few days to a couple of weeks as the tooth adjusts.
There are a few types of post-filling discomfort worth paying attention to, though. Pain when you bite down that starts as soon as the anesthesia wears off usually means the filling is slightly too high and is hitting before the rest of your teeth. This is an easy fix: your dentist reshapes the filling at a quick follow-up visit. A constant, throbbing toothache after a filling can mean the decay was deep enough to irritate the nerve inside the tooth (the pulp). If the pulp becomes inflamed and doesn’t settle down on its own, further treatment may be needed.
The key distinction is duration. Sharp sensitivity that lasts a few seconds and goes away when the trigger is removed is normal healing. Pain that lingers for minutes after the hot or cold source is gone, or a dull ache that doesn’t let up, signals something that needs attention.
How Long Fillings Last
Composite resin fillings last up to about 7 years, while amalgam fillings can last up to 15 years. These are averages, and your actual mileage depends on factors like the size of the filling, where it is in your mouth (back teeth take more chewing force), your oral hygiene, and habits like grinding your teeth.
Composite fillings trade some durability for aesthetics since they match your natural tooth color and bond directly to the tooth structure. Amalgam fillings are stronger under heavy chewing pressure but are visibly metallic. Most fillings placed today, especially on front teeth and smaller cavities, are composite. Your dentist will typically recommend the material that makes the most sense for the specific tooth and cavity involved.
Over time, any filling can chip, crack, or develop a gap between its edge and the tooth. When that seal breaks, bacteria can work their way underneath and cause new decay. This is why your dentist checks existing fillings at regular visits, even if nothing hurts. A filling that’s starting to fail can usually be replaced before it becomes a bigger problem.