What a cavity is and how it is found

A cavity is tooth decay: bacteria in plaque feed on sugars and produce acid, and over time that acid dissolves the hard outer enamel and forms a hole. Left alone, decay works its way deeper toward the softer inside of the tooth. Early on, a cavity often causes no symptoms at all, which is exactly why regular checkups matter. Dentists find cavities by looking, by gently probing the tooth, and with x-rays that reveal decay hiding between teeth or under the surface. Catching one early usually means a smaller, simpler filling.

Why fillings are done

A filling does two jobs: it removes the decayed material so the damage stops spreading, and it rebuilds the tooth so you can chew normally and keep bacteria out of the hole. Without a filling, a cavity tends to grow until it reaches the nerve, at which point a simple fix can turn into a root canal or an extraction. In other words, a filling is the small, inexpensive step that prevents the big, expensive one.

The filling materials

There is no single best material — the right one depends on where the tooth is, how much bite force it takes, how it will look, and your budget. Here are the common options:

• Amalgam (silver): A durable, long-proven metal blend. It stands up well to heavy chewing and is typically among the least expensive, but it is silver-colored and more visible on back teeth.
• Composite (tooth-colored): A resin matched to your tooth shade, so it blends in. Very popular for visible teeth; it bonds to the tooth and usually costs more than amalgam.
• Glass ionomer: A tooth-colored material that can release fluoride, often used for smaller fillings, along the gumline, or for children. Generally less wear-resistant on chewing surfaces.
• Gold: Extremely durable and long-lasting, and gentle on opposing teeth, but among the most expensive and clearly visible.
• Ceramic (porcelain): Tooth-colored, stain-resistant, and strong; often used for larger restorations. Typically at the higher end of the cost range.

What the procedure is like

A routine filling usually takes one visit and follows the same basic steps. First, the dentist numbs the area with a local anesthetic so you should not feel pain, only some pressure. Next, they remove the decayed part of the tooth, clean the space, and shape it to hold the filling. Then the filling material goes in; a composite is placed in layers and hardened with a curing light, while other materials are packed and shaped. Finally, the dentist checks your bite and polishes the surface. Most people drive themselves home and return to normal activities the same day.

Typical costs and how insurance usually works

Cost depends mostly on the material and on how many surfaces of the tooth need filling — a small one-surface filling costs less than a large filling that wraps around several surfaces. Your location and your dentist’s fees also matter. The ranges below are broad, typical figures for a single filling without insurance, and your actual price may fall outside them.

Many dental plans treat basic fillings as a covered restorative service and pay a set percentage after any deductible. One detail worth knowing: some plans reimburse tooth-colored fillings on back teeth only up to what a silver filling would have cost, leaving you to pay the difference if you choose composite. Because plans differ so much, confirm your coverage and get a written estimate before treatment.

When a filling is not enough

Sometimes decay has gone too far for a simple filling. If a large part of the tooth is missing, a crown may be needed to cap and protect what remains. If the decay has reached the nerve and caused infection, a root canal may be required before restoring the tooth. Your dentist can explain why a filling alone will not hold and what the alternatives cost. As always, the earlier a cavity is caught, the more likely a straightforward filling will do the job.

General educational information only — NOT medical or dental advice. Always consult a licensed dentist about your care. Procedures, costs, and insurance coverage vary by provider and location.