When you have a cavity, your dentist numbs the tooth, removes the decayed portion, and fills the hole with a durable material to restore its shape and function. The whole process typically takes 20 to 60 minutes per tooth. But the specifics depend on how far the decay has progressed, so the appointment actually starts with figuring out exactly what they’re dealing with.
How Dentists Find and Assess Cavities
Your dentist’s first tool is their own eyes. A visual exam on a dry tooth surface, sometimes enhanced with magnifying loupes, can reveal discoloration, rough spots, or visible holes. Dentists classify what they see using a standardized scale that ranges from 0 (healthy) to 6 (extensive decay), which helps them track changes over time and decide on treatment.
For cavities hiding between teeth, where visual inspection can’t reach, bitewing X-rays are the standard. These capture the upper and lower back teeth biting together and are especially good at catching decay in the tight spaces between molars and premolars. Periapical X-rays, which show the entire tooth from crown to root tip, help when the dentist suspects the decay has gone deeper.
Some offices also use newer detection tools. Fiber-optic transillumination shines a bright light through the tooth, making cavities appear as shadows since decayed areas transmit less light than healthy enamel. Laser fluorescence devices scan each tooth and compare the light reflected by healthy structure versus areas affected by bacteria, producing a numerical score that indicates whether the tooth is healthy, decaying, or in advanced decay. Neither method uses radiation, making them useful supplements to X-rays.
The Filling Procedure, Step by Step
Once your dentist confirms a cavity needs treatment, the process follows a predictable sequence. First, they numb the area around the tooth with a local anesthetic, most commonly lidocaine, which is considered the gold standard in dentistry for its safety and reliability. You’ll feel a brief pinch from the injection, then the area goes numb within a few minutes.
With the tooth fully numbed, the dentist uses a small drill or similar instrument to remove all the decayed tissue. This is the part most people associate with the classic dental sound. Once the decay is completely cleared out and only healthy tooth structure remains, the dentist cleans the prepared space and fills it with the chosen material. For tooth-colored composite resin fillings, a special curing light is used to harden the material in layers. The final steps involve polishing any rough edges and checking your bite to make sure the filling sits at the right height. A filling that’s even slightly too high can cause discomfort when you chew.
Laser Removal as an Alternative
Some dental offices now use erbium lasers instead of traditional drills to remove decay. A systematic review with meta-analysis found that laser treatment significantly reduced the need for local anesthesia, meaning many patients didn’t need a numbing injection at all. The trade-off is time: laser cavity preparation takes noticeably longer than drilling. The long-term results, including how well the filling holds up and how the tooth’s nerve responds afterward, showed no significant difference between the two approaches.
Types of Filling Materials
The two most common filling materials are composite resin and amalgam, and they differ in appearance, composition, and how long they last.
- Composite resin is made of plastic and glass compounds. It’s matched to your natural tooth color, making it the popular choice for visible teeth. With good care, composite fillings typically last 5 to 10 years.
- Amalgam is a mixture of metals including silver, tin, copper, and about 50% mercury. It’s silver-colored, so it’s more noticeable, but it’s exceptionally durable. Amalgam fillings often last 10 to 15 years or longer.
Your dentist may recommend one over the other based on the cavity’s location and size. Back teeth that absorb heavy chewing forces sometimes benefit from amalgam’s durability, while front teeth or visible surfaces are better served by composite’s natural appearance.
What Happens With Deeper Decay
A standard filling works well when the cavity is caught early and the remaining tooth structure is still strong. But decay doesn’t stay small forever, and the treatment changes as it progresses.
Tooth decay moves through distinct stages. It starts as demineralization, where acids from bacteria weaken the enamel’s surface. At this earliest point, the damage can actually be reversed with fluoride treatment, and no filling is needed at all. Once the enamel breaks through into an actual hole, that’s a true cavity requiring a filling. If the decay reaches the dentin, the softer layer beneath the enamel, it speeds up considerably. Dentin contains tiny tubes that connect to the tooth’s nerve, which is why you may start feeling sensitivity or pain at this stage.
When decay penetrates all the way to the pulp (the innermost part containing nerves and blood vessels), a filling alone won’t solve the problem. At this point, a root canal is typically needed to remove the infected tissue inside the tooth before it’s sealed. If the decay has progressed even further and an abscess (a pocket of infection) has formed at the root, the dentist will need to address the infection, sometimes with a root canal and sometimes by extracting the tooth entirely in severe cases.
Even without reaching the pulp, a cavity that destroys a large portion of the tooth’s structure may be too big for a filling to handle. When too much of the tooth is compromised, a filling won’t provide enough structural support, and a crown becomes necessary. A crown covers the entire visible portion of the tooth, essentially acting as a protective cap that holds everything together.
What to Expect After a Filling
The numbness from the anesthetic wears off within a few hours, though the exact timing depends on which agent was used. Standard options last a couple of hours, while longer-acting anesthetics can keep the area numb for up to eight hours. Your dentist will likely remind you not to chew on the numb side until sensation returns, since you can accidentally bite your cheek or tongue without realizing it.
Some sensitivity after a filling is normal. You may notice a brief zing when eating hot, cold, or sweet foods for a few days to a couple of weeks. This happens because the drilling process can irritate or inflame the nerve inside the tooth. The tooth’s outer layers normally protect that nerve from exposure, but fillings, especially deep ones, can get close to the nerve endings and cause temporary discomfort. This sensitivity typically fades on its own as the inflammation settles.
If your bite feels uneven after the numbness wears off, or if sensitivity lasts beyond two weeks, contact your dentist. An uneven bite is a quick fix: the dentist simply reshapes the filling slightly so it sits flush with your other teeth. Persistent sensitivity could indicate the filling is very close to the nerve and may need further evaluation.