People get fillings because bacteria in the mouth produce acid that eats through tooth enamel, creating holes called cavities. Once a cavity forms, the damaged tooth structure can’t repair itself, so a dentist removes the decayed material and fills the space with a durable material to restore the tooth’s shape and function. Fillings are also used to repair minor chips and cracks that could worsen over time.
How Cavities Actually Form
Your mouth is home to hundreds of species of bacteria, many of which live in a sticky film called plaque that coats your teeth. When you eat or drink something containing sugar, those bacteria feed on it and produce acid as a byproduct. That acid attacks the minerals in your tooth enamel, the hard outer shell of each tooth, in a process called demineralization. Each time you consume sugar, this acid assault lasts 20 to 40 minutes before your saliva can neutralize it.
If these acid attacks happen frequently enough, your enamel loses minerals faster than it can rebuild them. Over time, a weak spot forms, then a tiny hole. Left alone, the hole deepens through the enamel and into the softer layer underneath called dentin, where decay can spread more quickly. At that point, a filling is the standard fix. Your body can remineralize very early enamel damage on its own with the help of fluoride and saliva, but once an actual hole has formed, the tooth needs professional repair.
Signs You May Need a Filling
Cavities don’t always announce themselves right away. Small ones can develop without any symptoms at all, which is one reason routine dental exams matter. But as decay progresses, your body starts sending signals:
- Sensitivity to temperature or sweetness. A sharp zing when you sip hot coffee, bite into ice cream, or eat something sugary often means decay has reached the layer beneath your enamel.
- A nagging toothache. Pain that comes and goes, or that flares when you bite down, points to a cavity or crack.
- Visible holes, pits, or dark spots. Brown, yellow, or black discoloration on a tooth surface can indicate decay.
- Food constantly getting stuck. If debris keeps collecting in the same spot, a cavity or broken filling may have created a pocket.
- A rough or jagged surface. Running your tongue over your teeth and feeling an uneven edge can signal early decay or a chipped filling that needs replacing.
- Persistent bad breath or an unpleasant taste. Bacteria trapped in a cavity can produce odor even when you’re brushing regularly.
It’s Not Just Cavities
Tooth decay is by far the most common reason for fillings, but it’s not the only one. Dentists also place fillings to repair teeth that have been chipped by an impact or cracked from biting down on something hard. Small fractures can expose sensitive inner layers of the tooth and create entry points for bacteria, so filling them early prevents bigger problems later.
What Happens During the Procedure
Getting a filling is one of the most routine procedures in dentistry. Your dentist numbs the area around the tooth with a local anesthetic so you won’t feel pain during the work. Then they use a small drill or laser to remove the decayed portion of the tooth, clean the cavity to eliminate bacteria, and fill it with the chosen material. For composite (tooth-colored) fillings, the material is applied in layers and hardened with a special curing light. The whole process typically takes 20 to 60 minutes depending on the size and location of the cavity.
Most people feel normal within a couple of hours once the numbness wears off. Some mild sensitivity to hot or cold is common for a few days afterward but usually resolves on its own.
Types of Filling Materials
The two most widely used filling materials are amalgam (silver-colored) and composite resin (tooth-colored), and each has trade-offs worth understanding.
Amalgam fillings are extremely durable, lasting about 15 years on average, and they hold up well under heavy chewing forces. That makes them a practical choice for molars in the back of the mouth. The downside is appearance: they’re visibly metallic and can darken over time.
Composite fillings are matched to the color of your natural teeth, making them nearly invisible. They work well for small to medium cavities and require less drilling, which preserves more of your natural tooth structure. They’re suitable for both front and back teeth. The trade-off is longevity: composites last about 7 years on average, though smaller fillings in people with good oral health can last 10 years or more.
Ceramic fillings, made from porcelain, combine aesthetics with durability. They resist staining better than composite and can last 15 years or longer, but they tend to cost more.
Can Early Decay Be Treated Without Drilling?
Not every spot of decay requires a traditional filling. When a cavity is caught very early, before it has broken through the enamel into a full hole, fluoride treatments can help the tooth rebuild lost minerals and halt the process. This is why regular checkups catch problems at a stage where the fix is simpler.
Another option gaining traction, especially for children, is silver diamine fluoride (SDF). It’s a liquid painted directly onto the affected tooth with no drilling and no anesthesia. The silver component kills bacteria, while the fluoride strengthens enamel, effectively stopping decay from progressing. It won’t restore tooth structure that’s already been lost, and it does leave a dark stain on the treated area, so it’s more commonly used on baby teeth or in situations where traditional treatment isn’t practical. But for halting early decay painlessly, it’s a useful tool.
How Long Fillings Last
No filling lasts forever. Over years of chewing, grinding, and exposure to temperature changes, filling materials gradually wear down, crack at the edges, or pull away from the tooth. When that happens, bacteria can seep into the gap and cause new decay underneath the old filling. That’s why fillings sometimes need to be replaced even when you’re taking good care of your teeth.
As a general guide: amalgam fillings last roughly 15 years, ceramic fillings around 15 years, and composite fillings about 7 to 10 years. These numbers vary based on the size of the filling, where it is in your mouth, how hard you clench or grind, and how well you maintain your oral hygiene. Smaller fillings tend to outlast larger ones because there’s more natural tooth structure supporting them.
You can extend the life of any filling by brushing twice a day with fluoride toothpaste, flossing daily, and limiting sugary snacks and drinks. The same acid attacks that caused the original cavity will keep working on the margins of a filling if plaque is left to accumulate there.