When you have a cavity, your 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 20 to 60 minutes depending on the size and location of the cavity, and you can usually go back to normal activities the same day.
But there’s more to it than just “drill and fill.” Here’s what actually happens at each stage, from the moment your dentist spots the problem to what you’ll feel in the days after.
How Your Dentist Finds the Cavity
Sometimes you’ll come in because a tooth hurts or feels sensitive. Other times, your dentist catches a cavity during a routine checkup before you notice anything at all. Detection starts with a visual exam: the dentist dries your teeth with air, shines a bright light on them, and looks for white spots, brown discoloration, or tiny holes in the enamel. They may use a magnifying loupe, which increases the ability to spot early decay by about 50%.
Next comes the tactile check. Using a small pointed instrument called an explorer, the dentist gently probes the grooves and surfaces of your teeth. Soft or sticky spots signal decay. If dental floss shreds when passed between two teeth, that can point to a cavity forming on the side surface where two teeth touch.
For cavities between teeth or beneath the surface, your dentist takes bitewing X-rays. These are especially good at revealing decay hidden in the inner layer of the tooth, with a detection rate of 50 to 70% for cavities that have reached that depth. By the time a cavity shows clearly on an X-ray, the decay has usually already spread to at least the middle third of the tooth’s inner layer, which is why dentists don’t rely on X-rays alone for early-stage cavities.
What Happens During a Filling
Once the dentist confirms you have a cavity that needs treatment, the process follows a predictable sequence. Most people find it less uncomfortable than they expected.
Numbing. Your dentist injects a local anesthetic near the tooth. The most commonly used option keeps the area numb for one to two hours, which is plenty of time for a standard filling. For deeper or more complex work, a longer-lasting option may be used that can keep you numb for three to five hours. You’ll feel pressure but no pain once the anesthetic kicks in.
Removing the decay. Using a high-speed drill (the part that makes the familiar whirring sound), your dentist removes all the damaged and decayed tooth structure. The goal is to get down to healthy, solid tooth material while preserving as much of the original tooth as possible. Traditional drills are the standard tool, but some offices now use lasers that reduce vibration and noise. Laser treatment also significantly reduces the need for anesthesia, cutting it by roughly 70% in clinical studies, though lasers aren’t available everywhere and work best on smaller cavities.
Filling the hole. Your dentist packs the cleaned-out space with filling material, building it up in layers if using a tooth-colored composite. Each layer is hardened with a special curing light before the next one goes on. For silver amalgam fillings, the material is packed in and left to harden on its own.
Shaping and polishing. The dentist trims away excess material, smooths the surface, and then asks you to bite down on a thin piece of paper to check whether the filling sits at the right height. If the filling is even slightly too high, it will feel “off” when you chew, so getting the bite right matters. They’ll adjust until it feels normal.
A straightforward composite filling takes about 20 minutes longer than an amalgam filling because of the layering process. Most single-tooth fillings are done in one visit.
Filling Materials and How Long They Last
You’ll typically choose between a few options, and your dentist will recommend one based on the cavity’s size, location, and how much chewing force the tooth handles.
- Composite resin (tooth-colored): The most popular choice today, especially for teeth that show when you smile. The shade is matched to your natural tooth color, making it nearly invisible. These fillings last about 5 to 7 years on average, though good oral care can extend that. They’re not as durable under heavy chewing pressure, so very large cavities on back teeth may call for a different material.
- Silver amalgam: A metal alloy that’s been used for over a century. It’s extremely durable, lasting 10 to 15 years or longer, and holds up well on back teeth that take a lot of force. The tradeoff is appearance: amalgam is silver-gray and can darken the surrounding tooth over time. Fewer dentists offer it now, but it remains a solid option for large cavities on molars.
- Porcelain (ceramic): The most durable and stain-resistant option, lasting more than 15 years. Porcelain fillings are custom-made in a dental lab to fit your tooth precisely, which means you’ll need two visits: one to prepare the tooth and take impressions, and a second to place the finished restoration. They cost more, roughly comparable to gold.
When Drilling Isn’t the Only Option
Not every cavity requires a drill. For very early-stage decay that hasn’t broken through the enamel, your dentist may recommend fluoride treatments or improved brushing to remineralize the weakened area before it becomes a full cavity.
For cavities that have progressed but where drilling isn’t practical, a liquid treatment called silver diamine fluoride (SDF) can arrest the decay. Painted directly onto the cavity, SDF stops the progression of the cavity and hardens the damaged tooth surface. It’s especially useful for young children who can’t sit through a full filling procedure, elderly patients with root cavities, and people with multiple cavities that can’t all be treated in one visit. Biannual applications are recommended for sustained benefit.
SDF is remarkably effective. For root cavities in adults, it prevents new decay at rates 72% higher than a placebo, and it’s been shown to be as effective at stopping cavity progression as traditional fillings while costing up to twenty times less. The catch: it permanently stains the treated area black, which makes it a poor cosmetic choice for visible teeth. It’s also used off-label for cavities in the U.S., since the FDA has only cleared it specifically for treating tooth sensitivity.
What to Expect After a Filling
Some sensitivity after a filling is completely normal. Most general discomfort fades within a day or two. Sensitivity to hot, cold, sweet foods, or chewing pressure can linger for a week or two before resolving on its own.
Composite fillings are more likely to cause post-procedure sensitivity than amalgam. The resin material shrinks slightly as it hardens, which can create a microscopic gap between the filling and the tooth that allows temperature changes to reach the nerve. This usually settles as the tooth adjusts.
If your bite feels uneven after the numbness wears off, that’s worth a quick follow-up call. A filling that sits even a fraction too high creates an uncomfortable sensation every time you close your mouth, and the fix is simple: a few seconds of polishing at the dentist’s office. Persistent or worsening pain beyond two weeks, or sharp pain when biting down, can signal a deeper issue like an inflamed nerve, which may need additional treatment.
Larger Cavities Need More Than a Filling
Standard fillings work well when enough healthy tooth structure remains to hold them in place. When a cavity is too large for a regular filling but doesn’t require a full crown, your dentist may recommend an inlay or onlay. These are custom-made restorations, often porcelain or composite, that fit into or over the damaged area of the tooth. An inlay sits within the bumps on the chewing surface. An onlay extends over one or more of those bumps. Both require two visits, with a temporary filling placed while the permanent piece is fabricated.
If the decay has reached the nerve inside the tooth, a filling alone won’t solve the problem. In that case, your dentist will likely recommend a root canal to remove the damaged nerve tissue, followed by a crown to protect the weakened tooth. When decay is so extensive that the tooth can’t be saved at all, extraction and replacement with an implant or bridge becomes the path forward.