When you have a cavity, the dentist removes the decayed portion of your tooth and fills the hole with a durable material that restores the tooth’s shape and function. The whole process typically takes an hour or less, and for a small cavity, it can be done in as few as 20 minutes. But the exact approach depends on how deep the decay has spread, so the appointment starts with figuring out what they’re dealing with.
How the Dentist Finds and Assesses a Cavity
Most cavities are spotted through a combination of visual examination and X-rays. Your dentist looks at your teeth directly, checking for visible holes, dark spots, or soft areas. X-rays reveal what the naked eye can’t: decay hidden between teeth or beneath the surface of the enamel. As a cavity progresses, the tooth loses mineral content in that area, and this shows up on an X-ray as a darker spot because the weakened tooth absorbs less radiation.
Some offices also use a laser fluorescence device, which shines a laser on the tooth and measures how much light bounces back. Decayed areas fluoresce differently than healthy enamel. This tool can help catch early-stage decay, though visual exams and X-rays remain the standard for most diagnoses.
What the dentist finds during this assessment determines the treatment plan. A cavity caught very early, at the “white spot” stage where minerals are just starting to break down, may not need drilling at all. Once decay has penetrated through the enamel into the softer layer underneath (called dentin), a filling becomes necessary. And if the damage is extensive enough that a large portion of the tooth is compromised, you may need something more substantial than a standard filling.
What Happens During a Filling
The procedure follows a predictable sequence. First, the dentist numbs the area around the affected tooth with a local anesthetic, injected into the gum tissue near the tooth. Your mouth will feel numb for several hours afterward, but the injection itself is brief, and many dentists apply a topical numbing gel first to reduce the sting of the needle.
Once you’re numb, the dentist uses a drill or other specialized instruments to remove all the decayed tissue from inside the tooth. This is the part most people dread, but you shouldn’t feel pain, only pressure and vibration. The goal is to clear out every bit of softened, damaged tooth structure while preserving as much healthy tooth as possible. After the decay is removed, the dentist cleans the cavity to eliminate bacteria and debris.
Next comes the filling material itself. The two most common types are composite resin (tooth-colored) and amalgam (silver-colored). Your dentist packs the material into the cleaned-out space, building up the tooth’s shape layer by layer. If you’re getting a composite filling, each layer is hardened with a blue UV curing light before the next one is applied. The dentist then shapes and polishes the filling, smoothing any rough edges. The last step is checking your bite: you’ll be asked to bite down on a thin piece of paper so the dentist can identify and adjust any high spots that would feel uncomfortable when you chew.
How Long It Takes and What It Feels Like After
A simple, single-surface filling can take as few as 20 minutes from start to finish. Larger fillings or multiple fillings in one visit take longer, but most appointments wrap up within an hour. Some dental offices now have the technology to fabricate larger restorations like onlays in a single visit, which used to require two separate appointments.
When you can eat afterward depends on the filling material. Composite resin hardens immediately under the curing light, so you can technically chew on it right away, though most dentists recommend waiting one to three hours until the numbness wears off. You don’t want to accidentally bite your cheek or tongue while you can’t feel them. Amalgam fillings take about 24 hours to fully harden, so you should avoid chewing on that side for a full day.
Some sensitivity to hot and cold is normal after a filling and typically lasts one to three days. If sensitivity persists beyond a week or you feel a sharp pain when biting down, the filling may need a minor adjustment.
When a Filling Isn’t Enough
Not every cavity is treated with a simple filling. The approach scales with the severity of the damage.
- Crowns: When decay has weakened a cusp (one of the raised points on a molar), the remaining tooth structure needs protection. A crown covers the entire visible portion of the tooth, acting like a cap. This is common when so much tooth has been lost that a filling alone wouldn’t hold up under chewing forces.
- Root canals: If decay has reached the pulp, the soft tissue inside the tooth containing nerves and blood vessels, simply removing the decay and filling the hole won’t solve the problem. The infected pulp has to be removed from the inside of the tooth, the canals cleaned and sealed, and a crown placed on top. This sounds intense, but it saves the tooth from extraction.
- Extraction: In cases of extreme damage where the tooth structure is too far gone to restore, the dentist may need to remove the tooth entirely and discuss replacement options like an implant or bridge.
Alternatives to the Drill
For very early cavities that haven’t broken through the enamel surface, your dentist may recommend remineralization instead of drilling. This involves fluoride treatments, improved oral hygiene, and sometimes prescription-strength fluoride toothpaste to help the tooth repair itself. At this stage, the damage is reversible.
Silver diamine fluoride (SDF) is another option that doesn’t involve drilling. It’s a liquid painted directly onto a cavity to stop decay from progressing. The American Dental Association notes it’s particularly useful for patients who can’t tolerate traditional treatment, including young children, people with special needs, or those without easy access to dental care. Applied twice a year, SDF prevented root cavities at rates 72% higher than placebo in a large review of studies. The major drawback: it permanently stains the decayed area black, which makes it a less popular choice for visible front teeth.
Laser dentistry is a newer option available at some practices. Instead of a traditional drill, the dentist uses a focused beam of light energy to remove decay. The experience is quieter, with clicking or popping sounds instead of the high-pitched whir of a drill, and there’s no vibration. Because the laser is more precise and causes less trauma to surrounding tissue, many patients need little or no anesthesia. It’s not available everywhere and doesn’t work for every type of cavity, but for people with significant dental anxiety, it can make the experience far more manageable.