A tooth filling typically takes 20 to 60 minutes from start to finish, depending on the size and location of the cavity. The process follows a predictable sequence: numbing the area, removing decay, preparing the tooth surface, placing the filling material, and shaping it to match your bite. Here’s what each step actually looks and feels like.
Numbing the Area
Your dentist starts by applying a topical numbing gel to the gum tissue near the affected tooth. This takes the sting out of what comes next: an injection of local anesthetic into the gum. You’ll feel pressure and possibly a brief pinch, but the topical gel dulls most of it. Within a few minutes, the entire area around the tooth goes numb, including your lip, cheek, and sometimes part of your tongue on that side.
The numbness typically lasts one to three hours after the procedure, depending on how much anesthetic was used and where it was injected. Lower teeth generally require a deeper nerve block that takes longer to wear off than upper teeth, which can be numbed with a more localized injection.
Removing the Decay
Once you’re fully numb, your dentist uses a high-speed handpiece (the drill) to cut through the hard outer enamel and reach the decayed area underneath. This tool spins at extremely high speeds and uses a constant stream of water to keep the tooth cool. You’ll hear the familiar whirring sound and feel vibration, but no pain. The high-speed drill is precise enough to remove damaged enamel quickly while preserving as much healthy tooth as possible.
After breaking through to the cavity, your dentist often switches to a low-speed handpiece, which operates at 5,000 to 50,000 RPM. This slower tool is better suited for carefully scooping out softer decayed material closer to the inner layers of your tooth without removing healthy structure. Your dentist checks the cavity periodically to make sure all the decay is gone before moving on. Throughout this process, a small suction tube sits in your mouth to remove water and debris.
Protecting the Deeper Layers
If the cavity was deep enough to get close to the pulp (the living tissue inside your tooth that contains nerves and blood vessels), your dentist may place a protective liner at the bottom of the cavity before filling it. These liners, typically made from calcium hydroxide or glass ionomer cement, serve as an insulating barrier between the filling material and the sensitive inner tooth.
Calcium hydroxide liners are used most often in the deepest cavities. They have a high pH that encourages the tooth to produce reparative dentin, essentially helping the tooth build a natural protective wall over its own nerve. For shallow or moderate cavities, a liner usually isn’t necessary. About half of dentists use one for moderate-depth cavities, while the majority place one when the preparation is deep.
Etching and Bonding
For tooth-colored composite fillings, the next steps are what make the material actually stick. Your dentist applies an acid etching gel, which contains roughly 37% phosphoric acid, directly onto the prepared tooth surface. This sits for about 30 seconds, then gets rinsed off. The acid creates thousands of microscopic pores in the enamel and dentin, giving the filling material something to grip onto at a structural level.
After rinsing and drying, your dentist paints a thin layer of liquid bonding agent over the etched surface using a tiny brush. A gentle puff of air spreads it evenly into all the micro-pores. Then a bright blue curing light is held over the tooth for 10 to 20 seconds. This light, which peaks at around 469 nanometers in wavelength, triggers a chemical reaction in the bonding agent that hardens it almost instantly. The result is a resin-impregnated “hybrid layer” that mechanically locks the filling to your tooth.
Placing the Filling Material
With the bonding layer set, your dentist begins packing the composite resin into the cavity. Composite is a putty-like material that can be color-matched to your natural teeth. It’s placed in layers rather than all at once, because each layer needs to be hardened individually with the curing light. This layering technique reduces shrinkage as the material sets, which helps prevent gaps between the filling and the tooth wall.
Each layer gets about 10 to 20 seconds of blue light exposure. For a small cavity, this might only take two or three layers. A larger cavity can require more, which is one reason bigger fillings take longer. If you’re getting an amalgam (silver) filling instead of composite, the process is simpler: there’s no etching or bonding step. The amalgam is packed directly into the cavity, where it’s held in place by the shape of the preparation rather than chemical adhesion.
Shaping and Checking Your Bite
Once the cavity is filled and fully cured, your dentist shapes the filling to match the natural contours of your tooth. This involves trimming away excess material and carving grooves into the biting surface so it mirrors the original anatomy. A piece of thin colored paper (articulating paper) is placed between your upper and lower teeth, and you’re asked to bite down and slide your teeth side to side. The paper leaves marks showing where the filling hits first, and your dentist shaves down any high spots.
Getting the bite right matters. A filling that sits even slightly too high will hit before the surrounding teeth do, concentrating pressure on that one spot. This can cause soreness, sensitivity, or even cracking over time. Finally, the filling is polished smooth, which helps it resist staining and makes it feel natural against your tongue.
Composite vs. Amalgam Lifespan
Composite resin fillings last a median of about 11 years, while amalgam fillings tend to last longer, with median survival times exceeding 16 years. That longevity gap is one reason amalgam is still used, particularly on back teeth that bear heavy chewing forces. However, composite technology continues to improve, and the aesthetic advantage of a tooth-colored filling makes it the more popular choice for most patients today.
The FDA issued recommendations in 2020 suggesting that certain groups consider alternatives to amalgam when possible, including pregnant women, people with kidney disease, and those with neurological conditions. This is due to low-level mercury vapor that amalgam releases over time. For the general population, both options remain considered safe.
What Sensitivity Feels Like Afterward
Some sensitivity after a filling is normal, particularly with composite restorations that use an etch-and-rinse bonding approach. In clinical studies, nearly half of patients with this type of filling reported some sensitivity at 24 hours. By one week, that dropped to about a quarter. By one month, only about 13% still noticed anything. Most people find the sensitivity is triggered by hot or cold foods and drinks rather than being a constant ache.
Several factors influence how much post-filling sensitivity you experience. Deeper cavities tend to produce more sensitivity because the filling sits closer to the nerve. The bonding technique matters too: etch-and-rinse adhesives create stronger bonds but are associated with more short-term sensitivity than self-etching systems, which are gentler on the tooth’s inner layer. The type of composite and how it was layered also play a role. If sensitivity persists beyond a few weeks or gets worse instead of better, the bite may need adjusting, or the cavity may have been deeper than expected.
You can eat on the filled side as soon as the numbness wears off with composite fillings, since the curing light hardens them completely during the procedure. Amalgam fillings take longer to fully set, so your dentist may recommend chewing on the opposite side for 24 hours.