Dental fillings are made from one of several materials, with the most common being composite resin (a tooth-colored plastic mixed with glass particles) and dental amalgam (a metal alloy containing roughly 50% mercury combined with silver, tin, and copper). Less common options include glass ionomer cement, porcelain ceramics, and gold alloys. Each material has a different composition, lifespan, and price point, and the best choice depends on where the filling goes in your mouth and what you prioritize.
Composite Resin (Tooth-Colored Fillings)
Composite resin is the most popular filling material today, largely because it blends in with your natural teeth. It’s a combination of finely ground glass or quartz particles coated in silane and embedded in a plastic resin. The resin portion is typically built from a molecule called Bis-GMA or urethane dimethacrylate, both of which are thick, paste-like plastics that harden when exposed to light. The glass filler particles are usually barium silicate glass, quartz, or zirconium silicate, often mixed with a small amount of colloidal silica (about 5 to 10% by weight). Some formulas also include a radiopaque glass, like barium aluminosilicate, so the filling shows up clearly on X-rays.
Your dentist places composite as a soft paste and then hardens it with a blue LED light held against the tooth for several seconds. The light activates a chemical in the resin called camphorquinone, which generates free radicals that link the resin molecules into a solid polymer chain. This reaction happens fast. The half-life of the activated state is only about 0.05 seconds, which is why the light source needs to match the right wavelength precisely.
One concern that comes up with composite fillings is BPA, a chemical linked to hormonal disruption. Pure BPA is not actually an ingredient in dental composites. However, about 86% of composite resins on the market are based on BPA derivatives, most commonly Bis-GMA. The distinction matters: Bis-GMA is a modified, much larger molecule than BPA itself, and the amount of any BPA that could leach from it is extremely small.
Composite fillings cost between $150 and $400 per tooth, more than amalgam because the placement technique takes longer and requires more precision. In terms of durability, studies report median survival times ranging from about 8 to 17 years, with one long-term study in a general dental practice finding a median lifespan of 16 years for composites in back teeth.
Dental Amalgam (Silver Fillings)
Amalgam has been used for over 150 years. It’s made by mixing a fine metallic powder with liquid mercury, which makes up 40 to 50% of the final filling by weight. The powder itself is mostly silver, tin, and copper, with small amounts of zinc and occasionally traces of palladium or indium. Modern “high-copper” amalgam uses 40 to 60% silver, 12 to 30% tin, and 8.5 to 33% copper in the powder portion. Older “low-copper” formulas contained more silver (55 to 60%) and less copper (6 to 8%).
When the powder and mercury are mixed together, they form a soft, workable material that your dentist packs into the cavity. Over the next several hours, the mercury reacts with the silver and tin to form a hard, stable alloy. Amalgam is strong, fast to place, and cheap, typically running $100 to $250 per tooth.
The mercury content is the obvious concern. The FDA considers amalgam safe for most adults and children over six but recommends that certain groups avoid it if possible: pregnant women, nursing mothers, children under six, and people with neurological conditions or kidney problems. If you already have amalgam fillings in good condition with no decay underneath, the FDA recommends leaving them in place rather than removing them, since the removal process itself releases more mercury vapor than leaving the filling alone.
Amalgam fillings are among the longest-lasting options. Studies report median survival times ranging widely, from about 6 to 15 years in typical dental practices up to much longer under ideal conditions. A systematic review placed the median at 5 to 23 years.
Glass Ionomer Cement
Glass ionomer fillings are made from a special glass powder (containing silica, alumina, and fluoride compounds like calcium fluoride or cryolite) mixed with an acidic liquid, typically a solution of polyacrylic acid. When the powder and acid combine, the acid attacks the glass surface and releases ions that cross-link into a hardened cement. This chemical bond forms directly with the calcium in your tooth structure, giving glass ionomers a natural adhesion that other filling materials don’t have without extra bonding agents.
The standout feature of glass ionomer is that it releases fluoride over time. The fluoride is built into the glass itself, originally added to lower the temperature needed to manufacture the glass. Once the filling is placed, fluoride slowly leaches out into the surrounding tooth, which helps protect against further decay. A newer version called resin-modified glass ionomer adds a light-cured resin component, giving it two hardening mechanisms and better strength.
Glass ionomer is weaker than composite or amalgam, so it’s mostly used in low-stress areas: small fillings near the gum line, baby teeth, or as a temporary filling. Its fluoride release makes it especially useful for patients at high risk of cavities.
Porcelain and Ceramic Fillings
Ceramic fillings, often called inlays or onlays, are custom-made in a dental lab rather than shaped inside your mouth. The two most common ceramic types are lithium disilicate and leucite-reinforced glass ceramic. Both are rigid materials that mimic the stiffness and light-reflecting properties of natural tooth enamel, producing a very natural appearance.
Because ceramics are stiff, they distribute chewing forces in a way that’s similar to an intact tooth. Lithium disilicate in particular is used for structurally weakened or cracked teeth, where its rigidity helps hold everything together. Composite resin onlays are more flexible and may be a better fit for people who grind their teeth, since the material absorbs impact rather than transferring it to the tooth walls.
Ceramic fillings are at the high end of the price range, anywhere from $500 to $4,500 per tooth depending on the size and complexity. The higher cost reflects both the material and the lab work involved in fabricating a custom piece.
Gold Alloy Fillings
Gold fillings are alloys, not pure gold. The typical dental gold alloy contains gold mixed with copper, silver, platinum, palladium, and zinc. These metals are added to make the gold harder and more durable, since pure gold would be too soft to withstand chewing forces. Gold inlays and onlays, like ceramic ones, are fabricated in a lab and cemented into the prepared tooth.
Gold is the most durable filling material available and causes very little wear on opposing teeth. It’s also the most expensive option, often comparable to or exceeding porcelain in cost ($500 to $4,500 per tooth). The obvious drawback is appearance: a gold filling is immediately visible. For that reason, gold fillings are mostly placed on back teeth where aesthetics are less of a concern, and they’ve become less popular as tooth-colored materials have improved.
How the Materials Compare
- Cost: Amalgam is cheapest ($100 to $250), composite is mid-range ($150 to $400), and gold or porcelain are the most expensive ($500 to $4,500).
- Appearance: Composite, porcelain, and glass ionomer can all be matched to your tooth color. Amalgam is silver-gray. Gold is gold.
- Durability: Gold and porcelain generally last the longest. Amalgam and composite have overlapping lifespans in studies, with medians typically falling between 7 and 17 years depending on placement quality and location in the mouth.
- Best use: Composite works well for small to mid-sized fillings anywhere in the mouth. Amalgam is strong and affordable for back teeth. Glass ionomer suits low-stress areas and patients prone to decay. Ceramic and gold are best for larger restorations where strength and longevity are priorities.