Dental Fillings: Types, What to Expect, and When to Replace Old Ones

After a cavity is cleaned out, the remaining hollow space in the tooth needs to be filled with something durable enough to withstand normal chewing and biting forces for years. Modern fillings are most commonly made from tooth-colored composite resin, though other materials remain in use depending on the location of the cavity and specific circumstances.

The most common cause is a cavity — decay caused by bacteria that produce acid, gradually breaking down the hard structure of the tooth. Fillings are also sometimes used to repair minor chips or cracks that don't require a full crown, restoring the tooth's shape without needing the more extensive procedure a crown involves.

### Composite Fillings

Made from a tooth-colored resin material, composite fillings blend in closely with your natural tooth color and are currently the most commonly used filling material for visible teeth, since they bond directly to the tooth structure and don't require removing as much healthy tooth as some older filling techniques did.

### Amalgam Fillings

A silver-colored mixture of metals, including mercury in a stable, bound form, amalgam fillings have been used for well over a century and remain a durable, well-studied option, particularly for back teeth where appearance matters less and where the material's strength under heavy chewing force is valued.

### Glass Ionomer Fillings

Made from a mixture of acrylic and a specific type of glass material, glass ionomer fillings release fluoride over time, which can offer some additional cavity protection to the surrounding tooth structure, though they're generally less durable than composite or amalgam and are more often used for smaller fillings or in specific situations, such as certain fillings in children's teeth.

### Are Amalgam Fillings Safe?

Amalgam fillings have been extensively studied and used for a very long time in dentistry, and major dental and health authorities have generally considered them safe for most people. Some patients choose composite instead for cosmetic reasons or personal preference regarding mercury content, and this is a reasonable conversation to have directly with your dentist if it's a concern for you specifically.

Local anesthesia is typically used to numb the area around the affected tooth. Decayed tissue is removed, and the resulting space is cleaned and prepared. The filling material is then placed, shaped to match your natural tooth contour, and for composite fillings, hardened using a curing light. The filling is checked against your bite and polished for a smooth, comfortable finish.

Fillings stop the progression of decay, restore the tooth's strength and function for normal biting and chewing, and, particularly with composite material, restore appearance in addition to function. Compared to more extensive procedures like crowns, fillings are generally quicker, less invasive, and less expensive, making them the appropriate first-line treatment for cavities caught before they've caused more extensive damage.

Some temporary sensitivity to hot, cold, or pressure is common in the days following a filling, generally resolving on its own. In rare cases, a filling can be placed too close to the tooth's nerve, resulting in ongoing sensitivity that may eventually require further treatment like a root canal if the nerve becomes irritated enough. Fillings can also occasionally crack, chip, or wear down over time, particularly with heavy grinding or biting on very hard foods.

Most people return to normal activities immediately after a filling appointment, with numbness from the local anesthesia wearing off within a couple of hours.

### Can I Eat After a Filling?

It's generally recommended to wait until numbness has fully worn off before eating, simply to avoid accidentally biting your cheek or tongue while still numb. Once feeling has returned, eating normally is typically fine, though being mindful of very hard or sticky foods for the first day, particularly with a large filling, is a reasonable precaution.

### Inlay vs. Filling

An inlay is a custom-made, lab-fabricated restoration used when a cavity or damaged area is too large for a standard filling to adequately restore but doesn't require the full coverage of a crown. Unlike a filling, which is placed directly in a single visit, an inlay typically requires two visits, since it's crafted in a lab to precisely fit the specific shape of the prepared tooth.

### Onlay vs. Crown

An onlay is similar to an inlay but covers a larger portion of the tooth, including one or more of the chewing cusps, offering more coverage than a filling or inlay while still preserving more natural tooth structure than a full crown would require.

Older fillings, particularly amalgam fillings that have been in place for many years, can develop small cracks, wear down, or the seal between the filling and tooth can weaken over time, allowing new decay to develop underneath. Signs it may be time to consider replacement include visible cracks in the filling, new sensitivity around an old filling, or your dentist identifying decay underneath during a routine checkup and X-ray.

Cost varies based on the material used, the size of the filling, and your geographic location, with composite fillings generally costing somewhat more than amalgam due to the material and technique involved, though the difference varies by provider. Most dental insurance plans provide at least partial coverage for fillings, since they're considered a standard, medically necessary restorative procedure rather than an elective one.

Reach out if you notice a filling has cracked or fallen out, if you develop new or worsening sensitivity around a filled tooth, or if you notice a rough edge on a filling that's catching on your tongue or cheek, which can sometimes indicate the filling needs to be smoothed or is starting to wear.

Do fillings hurt when they're placed? The procedure is performed under local anesthesia, so you shouldn't feel pain during the filling itself, though you may feel pressure or vibration from the dental instruments. Some soreness or sensitivity for a day or two afterward, particularly as the anesthesia wears off, is common and generally mild.

Does getting a filling remove all the decay? When properly performed, yes — the goal of the procedure is to remove all decayed tissue before placing the filling material, since sealing decay in would allow it to continue progressing beneath the restoration.

When is it too late to get a filling instead of a crown or extraction? Once decay has progressed to affect a large portion of the tooth's structure, or has reached the inner pulp and nerve, a filling alone is generally no longer sufficient, and a crown, root canal, or in more severe cases, extraction becomes the more appropriate treatment. Regular checkups help catch cavities while they're still small enough for a filling to be the right, more conservative option.

Can I switch from amalgam fillings to composite ones? Yes, this is a common request, and your dentist can remove existing amalgam fillings and replace them with composite material if you prefer the appearance or have other reasons for wanting to switch, though this isn't medically necessary if your existing amalgam fillings are otherwise intact and healthy.

How long do dental fillings typically last? This varies by material and by individual factors like grinding habits and oral hygiene, but many fillings last well over a decade, sometimes considerably longer, before showing signs of wear that warrant replacement. Regular dental checkups help monitor the condition of existing fillings over time.