When you have a cavity, the dentist removes the decayed part of your tooth and fills the hole with a durable material that restores its shape and function. The whole process typically takes 20 to 60 minutes per tooth, depending on the size and location of the cavity. But not every cavity gets the same treatment. What your dentist does depends on how far the decay has spread, which tooth is affected, and whether the nerve inside is still healthy.
How the Dentist Decides What You Need
Your dentist uses X-rays and a visual exam to figure out how deep the decay goes and how much tooth structure is still intact. That assessment determines which of several paths your treatment takes.
Small cavities that haven’t damaged much of the tooth get a standard filling. This is the most common scenario. If the decay is larger and has weakened a significant portion of the tooth, a filling alone won’t hold up, so the dentist may recommend a crown, which is a cap that covers the entire visible part of the tooth and provides structural support. Crowns are also the go-to option after a root canal or when a tooth is cracked.
If decay has reached the pulp (the soft tissue deep inside your tooth that contains the nerve), you’re looking at a root canal rather than a simple filling. The telltale sign is lingering sensitivity to hot, cold, or sweet foods that lasts more than a few seconds, or a throbbing, aching pain. Pain when the dentist taps the tooth is another indicator. Once the nerve tissue is too inflamed to recover, the only options are a root canal or extraction.
The Filling Procedure, Step by Step
A standard filling follows a predictable sequence. First, the dentist numbs the area around the tooth with a local anesthetic, usually injected into the gum near the affected tooth. You’ll feel pressure but no pain once it kicks in, which takes a couple of minutes.
Next, the dentist uses a small drill or similar instrument to remove all the decayed tissue from inside the tooth. This is the part most people dread, but with the numbing in place you’ll mostly hear noise and feel vibration. Once the decay is gone, the dentist cleans the cavity to remove bacteria and debris, then fills the hole with the chosen material. For tooth-colored composite fillings, each layer gets hardened with a special curing light. The dentist then shapes and polishes the filling to match your tooth’s natural contours, and finally checks your bite to make sure your teeth come together normally.
Filling Materials and How Long They Last
The two most common filling materials are composite resin and amalgam, and each has trade-offs.
- Composite resin is tooth-colored and blends in with your natural teeth, making it the popular choice for visible areas. It works best for small to medium cavities, especially in spots that don’t take heavy chewing force. On average, composite fillings last about 5 to 7 years, though good oral care can extend that.
- Amalgam is the silver-colored filling material that’s been used for over a century. It’s more durable than composite and typically lasts 10 to 15 years, sometimes longer. That makes it a strong option for molars and other teeth that endure a lot of chewing pressure. The downside is its dark, metallic appearance.
Your dentist may recommend one over the other based on which tooth is involved, how large the cavity is, and your preference for appearance versus longevity.
Drill-Free Options for Small Cavities
Not every cavity requires drilling. For very early or small cavities, particularly in children, dentists can apply a liquid solution called silver diamine fluoride (SDF) directly to the decay. The liquid absorbs into the cavity and stops it from progressing further. A single drop can treat up to five small cavities. There’s no drilling, no injection, and no numbing needed.
The catch: SDF permanently stains the treated area black, so it’s mostly used on baby teeth or surfaces that aren’t visible when you smile. It also doesn’t restore the tooth’s shape the way a filling does. It’s a tool for buying time or managing cavities in patients who can’t tolerate traditional treatment.
Laser dentistry is another alternative for smaller cavities. Instead of a mechanical drill, the dentist uses focused light energy to remove decayed tissue. The laser targets only the damaged area, leaving more healthy tooth intact, and it kills bacteria in the process. Some small cavities treated with a laser require little or no numbing, which means less time with a numb mouth afterward. Lasers work best for early decay and small cavities. Deep decay, fractured teeth, or large failing fillings still need a traditional drill for thorough removal.
What to Expect After a Filling
The numbness from the anesthetic can last anywhere from a couple of hours up to seven hours, depending on the type used and where the injection was placed. During that time, be careful eating or drinking so you don’t accidentally bite your cheek or tongue.
Some sensitivity in the days following a filling is normal. You may notice discomfort when eating hot, cold, or sweet foods, or when biting down. Composite resin fillings in particular can cause temporary sensitivity because the material shrinks slightly as it hardens, creating a tiny gap that exposes the tooth underneath. This usually resolves on its own within a week or two.
If the filling sits even slightly too high, your bite will feel off and the tooth may hurt when you chew. This is one of the most common post-filling complaints, and it’s an easy fix: the dentist shaves down the high spot in a quick follow-up visit. If your pain persists beyond two weeks, gets worse, or you develop a throbbing ache, contact your dentist. Persistent pain can signal that the decay was close to the nerve, and you may need further treatment.
When a Cavity Needs More Than a Filling
A filling repairs the tooth by replacing lost structure. But when too much of the tooth is compromised, the remaining walls become fragile and a filling won’t protect them from cracking under normal chewing forces. In these cases, a crown covers the entire tooth like a helmet, distributing pressure evenly and preventing fractures.
If the decay has reached the nerve and caused irreversible damage, the dentist performs a root canal before placing a crown. During a root canal, the infected pulp tissue is removed from the inside of the tooth, the internal channels are cleaned and sealed, and a crown is placed on top to protect what’s left. The tooth stays in your mouth and functions normally, but without a living nerve inside. In cases where the tooth is too far gone even for a root canal, extraction and replacement with an implant or bridge becomes the final option.