Dentists treat cavities by removing decayed tooth material and replacing it with a filling, but the specific approach depends on how far the decay has progressed. A small cavity caught early might not need drilling at all, while one that has reached the nerve may require a root canal. Here’s what actually happens at each stage.
How Dentists Assess the Damage First
Before any treatment begins, your dentist evaluates how deep the decay goes. They use a standardized scoring system that rates cavities on a scale from 0 to 6. At the low end (codes 1 and 2), the decay is still confined to the enamel surface and shows up as a white or brown spot that hasn’t broken through. These early-stage cavities often don’t require drilling.
At code 3, there’s a small physical breakdown in the enamel but the deeper layer of the tooth (dentin) isn’t exposed yet. By codes 4 and 5, decay has reached the dentin, and you can see a dark shadow or an actual hole in the tooth. Code 6 means the cavity covers at least half the tooth surface. Your dentist combines this visual assessment with X-rays to determine whether the cavity can be monitored, treated conservatively, or needs a full restoration.
When a Cavity Doesn’t Need Drilling
If decay is caught at the earliest stages, before it breaks through the enamel surface, your dentist has several options that skip the drill entirely.
Fluoride treatments can remineralize weakened enamel, essentially reversing the very beginnings of a cavity. For slightly more advanced early decay, a technique called resin infiltration seals the tiny pores that acid has created in the tooth. The dentist etches the surface with a mild acid, dries it, then applies a liquid resin that soaks into the damaged enamel and hardens. This blocks further acid penetration and can also mask the chalky white spots that early decay leaves behind. It’s particularly useful for spots that develop around orthodontic brackets.
Silver diamine fluoride (SDF) is another no-drill option that can actually arrest cavities that have already formed visible holes. The American Dental Association recommends twice-yearly applications for stopping decay in both baby teeth and adult teeth. For root cavities in adults, SDF prevented new decay at rates 72% higher than a placebo. The tradeoff: it permanently stains the treated area black, which makes it less popular for visible front teeth but a practical choice for back teeth or children’s baby teeth.
The Standard Filling Procedure
For most cavities that have progressed beyond the earliest stage, the standard treatment is removing the decay and placing a filling. The whole process typically takes 20 to 60 minutes per tooth.
Your dentist starts by numbing the area with a local anesthetic injected into the gum near the affected tooth. The numbness typically sets in within a few minutes, though your mouth may stay numb for several hours afterward. Once you’re comfortable, the dentist uses a high-speed drill to remove the decayed portion of the tooth, then cleans and dries the resulting space.
For tooth-colored composite fillings, which are now the most common type, the next steps are precise. The dentist applies an etching solution to roughen the tooth surface microscopically, then paints on a bonding agent that helps the filling material grip the tooth. The composite resin is applied in thin layers, with each layer hardened using a special curing light before the next one goes on. Once the cavity is filled, the dentist shapes and contours the material to match your bite, then polishes it smooth.
Composite vs. Amalgam Fillings
Most fillings today are composite resin, a tooth-colored material that blends in with your natural teeth. Composite fillings typically last 7 to 10 years. Silver amalgam fillings, the traditional “metal” fillings, last longer at 10 to 15 years or more, but they’re increasingly less common because of their appearance and the need to remove more healthy tooth structure to place them.
Both materials perform similarly in terms of protecting the tooth. The choice often comes down to location (amalgam holds up better under heavy chewing forces on back teeth), cavity size, and cosmetic preference. Your dentist may recommend one over the other based on where the cavity is and how much tooth structure remains.
Laser Treatment as an Alternative to Drilling
Some dental offices offer laser cavity preparation as an alternative to the traditional drill. These lasers work by vaporizing the water inside decayed tooth tissue, removing it in tiny microexplosions without the vibration and noise of a drill.
The biggest advantage is comfort. A systematic review found that laser treatment reduced the need for local anesthesia by 72% compared to drilling, meaning many patients can have a cavity treated without a numbing injection at all. The outcomes are equivalent: restoration longevity, nerve health, and post-procedure sensitivity are no different between laser and drill. The downside is speed. Laser preparation takes noticeably longer than drilling, on average several additional minutes per tooth. Not all cavities are candidates for laser treatment, and not all offices have the equipment.
When a Filling Isn’t Enough
If decay has reached the pulp, the soft tissue inside the tooth that contains nerves and blood vessels, a simple filling won’t solve the problem. Signs that decay has gone this deep include a persistent toothache, lingering sensitivity to hot and cold that doesn’t fade, and swollen or tender gums around the tooth. At this point, a root canal is typically necessary.
During a root canal, the dentist or endodontist removes the infected pulp tissue, cleans and disinfects the interior channels of the tooth, then fills and seals them. The tooth itself stays in place, but because a root canal removes the nerve and blood supply, the tooth becomes more brittle over time. That’s why most teeth that undergo root canal therapy also need a crown, a custom-made cap that fits over the entire visible portion of the tooth to protect it from cracking.
Crowns are also used without root canals when a cavity has destroyed so much tooth structure that a filling alone can’t restore strength. If more than about half the tooth’s biting surface is compromised, a crown provides the structural support a filling can’t.
What to Expect After a Filling
Some sensitivity after a filling is normal and almost expected. It typically peaks within the first 24 to 48 hours and gradually fades over one to two weeks. For shallow to moderate fillings, most people feel back to normal within 7 to 10 days. Deep fillings placed close to the nerve can cause sensitivity for 3 to 4 weeks or longer, but you should notice steady improvement throughout that period, with more good days than bad.
During recovery, stick with lukewarm foods and drinks rather than anything very hot or cold. Cut back on sugary and acidic items like soda, citrus, and candy, which can aggravate the sensitive tooth. Brush gently around the area with a soft-bristled toothbrush. Desensitizing toothpaste containing potassium nitrate or stannous fluoride can help, and for best results, dab a small amount directly on the sensitive tooth before bed and leave it without rinsing. Over-the-counter anti-inflammatory pain relievers like ibuprofen, taken with food, address both pain and inflammation.
If you’re still experiencing significant sensitivity six weeks after a filling, that warrants a follow-up visit. It could indicate the filling needs adjustment, the bite is slightly off, or the decay was closer to the nerve than initially assessed.