Dental fillings are made from one of several materials: composite resin (a tooth-colored plastic and glass mixture), dental amalgam (a metal blend containing mercury, silver, tin, and copper), glass ionomer cement, ceramic, or gold alloy. The most common choice today is composite resin, though the best material for a given filling depends on the tooth’s location, the size of the cavity, and your budget.
Composite Resin: The Tooth-Colored Standard
Composite resin is the most widely used filling material in modern dentistry. It matches your natural tooth color, which makes it the default choice for front teeth and increasingly popular for back teeth too. A composite filling typically costs $90 to $250 for one or two surfaces.
The material itself has two main ingredients. The first is an organic resin matrix, a type of plastic polymer. The second is a load of tiny inorganic filler particles, usually made from glass or silica. A chemical coupling agent bonds the filler to the resin so the material holds together under the pressure of chewing. Pigments are mixed in to match various tooth shades.
The size of those filler particles matters. Some composites use very fine “microfil” particles for a smoother, more polished look. Others use larger “macrofil” particles for added strength. Most modern composites are hybrids that blend both sizes, and newer “nanofilled” versions use extremely small particles clustered together for a combination of strength and polish. The higher the ratio of filler to resin, the better the filling resists wear.
Once your dentist places the composite, it’s hardened with a blue LED curing light held against the tooth for several seconds. The light triggers a chemical reaction that causes the resin to polymerize, essentially linking its molecules into a rigid chain. One downside: composite resin shrinks slightly as it hardens, typically 2% to 3%. Your dentist compensates by placing it in thin layers and curing each one individually.
In terms of durability, composite fillings in back teeth last a median of about 8 to 17 years depending on the study and setting, with roughly 82% still functional after ten years in some clinical data. In general dental practices, surveys put the typical lifespan at four to eight years before a replacement is needed, though well-placed fillings in patients with good oral hygiene can last much longer.
Dental Amalgam: The Silver Filling
Amalgam is the metallic “silver filling” that has been used for over 150 years. It’s made by mixing a fine powder of metals with liquid mercury, which makes up about 40% to 50% of the final filling by weight. The rest of the powder in a modern high-copper amalgam is roughly 40% to 60% silver, 12% to 30% tin, 8.5% to 33% copper, and small amounts of zinc, indium, and occasionally a trace of palladium.
When the metal powder and mercury are combined, they react to form a solid, rigid mass. This chemical setting process happens inside the tooth, giving the dentist a few minutes of working time before the material hardens. Amalgam is exceptionally durable. Clinical studies report median survival times ranging from about 12 to 22 years, and some fillings placed under ideal conditions have lasted far longer. After ten years, around 72% to 80% of amalgam fillings are still intact. It’s also the least expensive option, typically $50 to $150 for one or two tooth surfaces.
The obvious drawback is appearance. Amalgam is silver-gray and darkens over time, making it conspicuous in any visible tooth. The bigger concern for many people is the mercury content. Mercury in amalgam is chemically bound and behaves differently from the liquid mercury you’d find in an old thermometer, but small amounts of mercury vapor are released during chewing and grinding.
The FDA has stated that amalgam is generally safe for most adults and children over six but recommends that certain groups avoid it whenever possible. Those groups include pregnant or nursing women, children under six, and people with neurological conditions like multiple sclerosis, Alzheimer’s, or Parkinson’s disease, as well as anyone with impaired kidney function or a known sensitivity to mercury. The FDA does not recommend removing existing amalgam fillings that are in good condition, because the removal process itself temporarily increases mercury vapor exposure and can damage healthy tooth structure.
Glass Ionomer Cement
Glass ionomer is a less common filling material made from a powder of fluoride-containing glass (technically called fluoro-aluminosilicate glass) mixed with a liquid solution of polyacrylic acid. When the two are combined, an acid-base reaction sets the cement into a hard mass that chemically bonds directly to tooth structure, unlike composite resin, which needs an adhesive layer.
The standout feature of glass ionomer is its ability to release fluoride over time. Fluoride ions sit in the set cement in an unbound form, and they slowly diffuse out into the surrounding saliva through two phases: a quick initial burst from the surface, followed by a gradual, sustained release that can continue for months or years. This ongoing fluoride exposure helps protect the tooth against further decay around the edges of the filling.
Glass ionomer is weaker than composite resin and significantly weaker than amalgam, so it’s typically reserved for small fillings in low-stress areas, baby teeth, or as a temporary filling. It falls in the same general price range as composite, roughly $90 to $250. Hybrid versions exist that blend glass ionomer with resin composite to improve strength while retaining some fluoride release.
Ceramic and Porcelain Fillings
Ceramic fillings are usually fabricated outside the mouth as custom-made inlays or onlays, then bonded into the prepared tooth. They’re made from various types of dental ceramics, and the options differ mainly in strength and appearance.
Feldspathic ceramic is the most natural-looking but also the weakest, with a flexural strength of about 60 to 70 megapascals. Leucite-reinforced ceramic roughly doubles that strength. Lithium disilicate is the most popular choice for ceramic inlays today, offering around 407 MPa of flexural strength while still looking very close to natural enamel. Zirconia is the strongest ceramic option by a wide margin, reaching 900 to 1,400 MPa, but older versions looked more opaque and less lifelike than glass-based ceramics. Newer formulations have improved its appearance considerably.
Because ceramic fillings are milled or pressed to fit precisely and then cemented in place, they require at least two appointments or an in-office milling machine. They resist staining better than composite, hold up well over time, and are highly biocompatible. The tradeoff is cost: ceramic inlays and onlays are significantly more expensive than direct fillings, though exact pricing varies by lab and location.
Gold Alloy Fillings
Gold fillings are the most durable and most expensive option, costing anywhere from $250 to $4,500 depending on the size and number of tooth surfaces involved. They aren’t pure gold. The International Organization for Standardization classifies dental gold alloys into four types, all containing gold, silver, and copper in varying proportions. Type 1 alloys have the highest gold content at around 85%, while Type 4 alloys drop to about 65% gold and add more copper (up to 15%) plus platinum or palladium (up to 10%) for extra hardness.
Gold is gentle on opposing teeth, resists corrosion, and can last 20 years or more. Like ceramic fillings, gold inlays are fabricated in a lab and cemented in place over two visits. Their metallic color makes them a purely functional choice, and most people who opt for gold do so for back teeth where appearance is less of a concern.
How Materials Compare on Longevity
Direct comparisons are tricky because filling lifespan depends heavily on the size of the restoration, which tooth it’s in, and the patient’s habits. Still, clinical data offers useful benchmarks. One large analysis calculated a median survival time of 22.5 years for amalgam and 16.7 years for composite in the same study conditions. In everyday dental practice settings, surveys put amalgam at 6 to 15 years and composite at 4 to 8 years, with the gap narrowing as composite materials continue to improve.
Gold and well-made ceramic restorations routinely last 15 to 30 years, though head-to-head clinical trials comparing all four materials over identical time periods are limited. The biggest predictor of any filling’s lifespan isn’t the material itself but the size of the cavity, oral hygiene, grinding habits, and the quality of the placement.