A cavity filling typically takes 20 to 60 minutes and follows a predictable sequence: numbing, decay removal, cleaning, bonding, filling, and polishing. The process is straightforward, and knowing each step can make the experience far less stressful.
Numbing the Area
The first thing your dentist does is numb the tooth and surrounding tissue with a local anesthetic, usually delivered by injection into the gum near the affected tooth. The anesthetic works by blocking sodium channels in your nerve cells, which stops pain signals from traveling to your brain. You’ll feel pressure during the procedure but not sharp pain.
Before the injection itself, most dentists apply a topical numbing gel (often benzocaine-based) to the gum so you barely feel the needle. The injection takes effect within a few minutes. Your lip, cheek, and part of your tongue on that side will feel heavy and tingly. This numbness lasts 1 to 3 hours after the procedure, depending on the amount used and your individual response.
Removing the Decay
Once you’re numb, the dentist removes the decayed portion of your tooth using a dental handpiece, commonly called “the drill.” Most offices use two types. A high-speed handpiece spinning at 200,000 to 400,000 rpm cuts through the hard outer layers of your tooth (enamel and the dentin beneath it) quickly and efficiently. You’ll hear a high-pitched whine and feel vibration, but not pain. A fine mist of water keeps the tooth cool.
For the softer, decayed material closer to the interior of the tooth, your dentist may switch to a low-speed handpiece running at 5,000 to 40,000 rpm. This slower speed gives much finer control, which matters when the decay sits close to the nerve inside your tooth. The goal is to remove all the damaged tissue while preserving as much healthy tooth structure as possible.
When Decay Runs Deep
If the cavity extends close to the pulp (the soft tissue containing the tooth’s nerve and blood supply), your dentist may place a protective liner over the floor of the cavity before filling it. This liner, typically made from calcium hydroxide, acts as a buffer between the filling material and the nerve, reducing the chance of irritation or inflammation. In some cases where removing every last bit of decay would risk exposing the nerve, a dentist may intentionally leave a thin layer of firm, discolored dentin in place, cover it with a liner, and place a temporary restoration. This “stepwise” approach gives the tooth time to lay down a protective layer of new dentin before the final filling is placed at a follow-up visit.
Cleaning and Preparing the Tooth
After the decay is gone, the cavity is cleaned with an acid gel, typically phosphoric acid. This does two things: it removes any remaining bacteria and debris, and it etches microscopic grooves into the enamel surface. Those tiny grooves are essential because they create a rough texture that the filling material can grip onto, forming a strong mechanical bond. The acid is rinsed away after a few seconds, taking dissolved mineral residue with it, and the tooth is dried.
If you’re getting a tooth-colored composite filling (the most common type today), the dentist then paints a liquid bonding adhesive into the etched surface. This adhesive seeps into all those microscopic grooves and acts as a glue layer between your natural tooth and the filling. The tooth needs to stay completely dry during this step because moisture interferes with the bond, so your dentist may use cotton rolls, a small suction device, or a rubber dam to isolate the area.
Placing the Filling
With the bonding agent in place, the dentist applies the composite resin in layers. Composite is a paste-like material made of a blend of plastic resin and fine glass or ceramic particles. It starts soft and moldable, which lets the dentist shape it precisely to match the contours of your tooth.
Each layer is hardened with a special curing light that emits blue light at a wavelength around 470 nanometers. This light activates a chemical in the resin that triggers it to harden within seconds. You’ll see the dentist hold a small wand-like device right up against the tooth for several seconds per layer. The light is bright but harmless. Building the filling in layers rather than all at once ensures each section cures completely and bonds firmly to the one below it.
Shaping and Polishing
Once the final layer is cured, the dentist trims and shapes the filling so it matches your bite. You’ll be asked to bite down on a thin piece of colored paper (articulating paper) that marks any high spots where the filling contacts the opposing tooth too early. The dentist shaves those spots down with a fine bur until your bite feels natural. Even a fraction of a millimeter too high can cause discomfort when chewing, so this step is worth getting right. Finally, the filling is polished smooth. A well-polished surface resists staining, feels comfortable against your tongue, and is less likely to accumulate plaque.
Types of Filling Materials
Composite resin is the most widely used filling material today because it matches natural tooth color and bonds directly to tooth structure. The American Dental Association recognizes four main categories of direct filling materials: amalgam, resin-based composites, glass ionomer, and resin-modified glass ionomer. Your dentist will recommend a material based on the size and location of the cavity, how much biting force the tooth handles, and cosmetic considerations.
Amalgam (silver) fillings have a long track record of durability. Studies show amalgam fillings last a median of roughly 12 to 23 years depending on the setting, while composite fillings last around 7 to 17 years. One well-known longitudinal study following patients for over 12 years found a median survival of 22.5 years for amalgam and 16.7 years for composite. That said, composites have improved significantly in recent decades, and many dentists now use them almost exclusively because of their bonding ability and natural appearance. Amalgam is increasingly uncommon in many practices.
Glass ionomer fillings release fluoride, which can help protect against future decay, but they’re less durable than composite or amalgam. They’re most often used in low-bite-pressure areas or for children’s teeth.
What to Expect Afterward
Composite fillings harden completely under the curing light during your appointment, so they’re at full strength the moment you leave the chair. You can technically eat right away, though most dentists suggest waiting at least 2 hours so the numbness wears off first. Chewing while numb puts you at real risk of biting your tongue, cheek, or lip without realizing it. If you received an amalgam filling, it takes about 24 hours to fully harden, so you should avoid chewing on that side for a full day.
Mild sensitivity to hot, cold, or pressure around the filled tooth is normal for a few days to a couple of weeks. This is especially common with deeper fillings where the work came closer to the nerve. The sensitivity typically fades on its own. If your bite feels uneven or if sensitivity worsens rather than improves after a week or two, a quick follow-up visit to adjust the filling’s height usually solves the problem.