Dentists fill cavities with one of five main materials: composite resin, silver amalgam, glass ionomer, porcelain, or gold. Composite resin is by far the most common choice today because it matches the color of your natural teeth. The material your dentist recommends depends on where the cavity is, how large it is, and how much chewing force that tooth handles.
Composite Resin
Composite resin is the standard filling material for most cavities. It’s a tooth-colored mixture of a plastic resin base with powdered quartz, silica, or glass particles, and it bonds directly to the tooth structure. Because it blends in visually, composite works well for both front and back teeth.
Durability is solid. A large meta-analysis of clinical studies found that composite fillings placed on back teeth had an annual failure rate of just 1.8% over five years and 2.4% over ten years. That means the vast majority of composite fillings last well beyond a decade. The main reasons they eventually fail are new decay forming around the edges or the filling chipping under heavy bite forces.
Your dentist places composite in layers, hardening each layer with a special UV light before adding the next. The whole process usually takes one visit. Cost typically runs $90 to $250 for one to two teeth before insurance.
Silver Amalgam
Amalgam is the silver-colored filling material that’s been used for over 150 years. It’s a mixture of liquid mercury (about 50% by weight) combined with a powdered alloy of silver, tin, and copper. The mercury binds the metal particles together into a hard, durable mass once it sets.
Amalgam’s main advantage is strength. It holds up extremely well under the heavy chewing forces on back molars, and it’s the least expensive option at $50 to $150 for one to two teeth. Its main drawback is appearance. The dark silver color is visible when you talk or laugh, so it’s rarely used on front teeth.
The mercury content is the most common concern patients have. The FDA says available evidence does not show that amalgam fillings cause adverse health effects in the general population, but the agency strongly encourages certain groups to choose non-mercury alternatives. Those groups include pregnant or nursing women, children under six, people with kidney disease, people with neurological conditions, and anyone with a known sensitivity to mercury or the other metals in amalgam. If you fall into one of these categories, composite resin and glass ionomer are the recommended alternatives.
Glass Ionomer
Glass ionomer is a tooth-colored material made from silica glass powder. What makes it unique is that it continuously releases small amounts of fluoride into the surrounding tooth structure. This happens through an ion exchange process: fluoride ions leach out of the cement and are replaced by other ions from your saliva. The fluoride release is highest in the first days after placement and then settles into a slow, steady release over time.
Research shows that enamel right next to a glass ionomer filling is harder and more resistant to acid attacks than enamel farther away. That protective effect makes glass ionomer a popular choice for fillings on root surfaces, for small cavities in baby teeth, and as sealants on the chewing surfaces of teeth prone to decay.
The trade-off is durability. Glass ionomer isn’t as strong as composite resin or amalgam, so it’s not ideal for large cavities on molars that take heavy biting pressure. Cost falls in the same range as composite, roughly $90 to $250 for one to two teeth.
Gold
Gold fillings (technically gold alloy mixed with silver, tin, copper, or palladium) are the longest-lasting option available. Gold’s metallic structure can flex slightly under pressure without cracking, which means fracture is essentially never a concern. In a long-term clinical study, gold restorations had a cumulative survival rate of about 92% after nearly 15 years and still held at roughly 92% past 23 years.
The main complications with gold fillings are new decay forming at the margins and, less commonly, issues with the tooth’s nerve. Gold fillings are indirect restorations, meaning your dentist takes an impression of the prepared cavity, a lab crafts the filling, and you return for a second visit to have it cemented in place.
Cost is the major barrier. Gold fillings range from $250 to $4,500 for one to two teeth, depending on the size and location. They’re also visibly gold-colored, which some people prefer as an aesthetic choice and others want to avoid.
Porcelain
Porcelain (ceramic) fillings are made from a blend of minerals like feldspar, quartz, and kaolin. They’re tooth-colored, stain-resistant, and can be closely matched to your natural shade. Like gold, porcelain fillings are typically indirect restorations that require an impression and a lab fabrication step, though some dental offices now use same-day milling technology to make them in one visit.
A long-term study tracking ceramic fillings over more than two decades found cumulative survival rates of about 94% at 15 years and 92% at 23.5 years. The most common reason ceramic fillings fail is fracture, since ceramic is a brittle material with low toughness compared to metals. About 6.7% of ceramic fillings in that study fractured over the full follow-up period. Still, the overall annual failure rate was just 0.5%, slightly better than gold’s 0.7% in the same study.
How Your Dentist Chooses
The location of the cavity matters most. Front teeth and other visible areas almost always get tooth-colored materials like composite resin or porcelain, since appearance is a priority. Back molars need materials that can handle constant chewing force, which is where amalgam, gold, and porcelain have traditionally been favored, though composite has become strong enough for most back teeth as well.
Cavity size plays a role too. Small to medium cavities are usually filled directly in the chair with composite, amalgam, or glass ionomer. Larger cavities, especially those that involve the cusps (the raised points on a molar), often call for an indirect restoration like a porcelain or gold inlay or onlay, which is custom-made to fit precisely.
Your overall oral health also factors in. If you’re at high risk for new cavities, glass ionomer’s fluoride release offers a protective advantage. If you grind your teeth, your dentist may steer toward a tougher material. And budget matters: amalgam and composite are the most affordable, while gold and porcelain cost significantly more but can last decades with proper care.