They are restorative materials your dentist places inside a tooth after removing decay, drawn from one of five main families: dental amalgam (about 50% mercury bound to silver, tin, and copper), composite resin (a plastic-and-glass blend), glass ionomer (a fluoride-releasing acrylic-glass hybrid), ceramic (usually porcelain), and gold alloys. Each one hardens differently inside your tooth, wears at a different rate, costs a different amount, and raises different safety questions.
This article explains how dentists choose filling materials, weighing longevity against appearance, cost, and safety concerns, so anyone weighing their options can make a confident call.
The Core Materials Dentists Use to Restore Teeth
The filling on the menu at your dentist’s office is less about color and more about chemistry. Two “white” fillings can contain completely different ingredients, and a “silver” filling contains no silver at all in the elemental sense. Knowing what actually goes into each material changes how you compare them.
The five material families dentists place most often
- Amalgam: A metallic alloy of about 50% elemental mercury bound to silver, tin, copper, and small amounts of zinc or indium.
- Composite resin: A blend of plastic (typically Bis-GMA or UDMA) reinforced with fine silica or glass particles.
- Glass ionomer: An acrylic-acid polymer plus a reactive glass powder that releases fluoride over time.
- Ceramic: Usually a porcelain (feldspathic or lithium disilicate) shaped in a dental lab and cemented into place.
- Gold alloy: A mix of gold, copper, silver, palladium, and other metals cast as a single piece in a lab.
Amalgam has been placed for more than 150 years and remains in use for its durability and low cost. Composite resin overtook amalgam in front-tooth work decades ago because it bonds directly to enamel and can be shaded to match. Glass ionomer stays popular for small cavities near the gumline and pediatric work because of its steady fluoride release. Ceramic and gold are the lab-made options, usually reserved for larger restorations like inlays, onlays, and crowns.
How each material is actually formulated
Amalgam starts as a powder of silver, tin, and copper that the dentist mixes with liquid mercury just before placing it. The mixture reacts to form a hard, stable metallic compound inside the cavity. Composite resin comes pre-mixed as a paste. A blue LED curing lamp hardens it in layers inside the prep. Glass ionomer sets on its own through an acid-base reaction between the polymer and the glass powder, with no curing light required. Ceramic and gold are not made chairside; you wait for a lab-made piece that the dentist cements in at a second visit.
“Tooth-colored” is a marketing umbrella, not an ingredient label. Composite resin, glass ionomer, and porcelain can all be matched to enamel shade, but they behave very differently once placed in the mouth.
Amalgam, Composite, Glass Ionomer, Gold, and Ceramic Compared
Comparing the five material families side by side makes the trade-offs concrete. Strength, lifespan, appearance, and cost diverge sharply, and the “best” material depends on which tooth and which patient.
| Material | Core Composition | Typical Lifespan | Best For | Relative Cost |
|---|---|---|---|---|
| Amalgam | ~50% mercury + silver/tin/copper | 10–15+ years | Large back-tooth cavities | Lowest |
| Composite resin | Plastic matrix + silica/glass filler | 5–10 years | Front teeth and visible zones | Moderate |
| Glass ionomer | Acrylic polymer + reactive glass | 5 years or less | Gumline cavities and pediatric work | Moderate |
| Ceramic (porcelain) | Lithium disilicate or feldspathic porcelain | 10–15+ years | Larger restorations and cosmetic zones | High |
| Gold alloy | Gold + copper/silver/palladium | 20+ years | Durability-focused back-tooth work | Highest |
Where amalgam still wins on durability
For a large cavity on a molar that takes the brunt of chewing force, amalgam remains one of the most durable options dentists place. It handles heavy bite loads, tolerates moisture during placement better than composite (which is fussy about a dry field), and rarely chips at the edges. The trade-off is its metallic gray color and the mercury question, which the next section covers directly.
Why composite resin dominates front-tooth work
Composite bonds micromechanically to enamel, so the dentist can preserve more healthy tooth structure by bonding the filling directly to the tooth rather than cutting undercuts for mechanical retention. That bond also seals the margin (the edge where filling meets tooth) against leakage. For visible teeth, composite’s shade-matching ability is unmatched among chairside materials. The cost is faster wear and a higher chance of needing replacement within a decade, especially on back teeth under heavy chewing loads.
The fluoride advantage of glass ionomer
Small amounts of fluoride leach steadily from glass ionomer fillings, shielding the adjacent tooth from recurrent decay for years after placement. That makes it a smart pick for cavities along the gumline, baby teeth, or patients with high decay risk. The material is softer than composite and wears faster, so it isn’t used on biting surfaces of permanent molars.
What gold and porcelain actually buy you
Gold is the longevity benchmark in dentistry, and the cliché holds up: cast gold inlays regularly last 20 years or more because the metal flexes slightly under bite force instead of cracking. Porcelain offers similar longevity with a natural look, especially newer lithium disilicate ceramics, at the cost of higher lab fees and slightly more brittle behavior under very heavy loads. Both require two visits, lab work, and cementation.
With lab-fabricated options now priced against same-day alternatives, patients increasingly weigh cost against biocompatibility concerns.
Mercury, BPA, and the Safety Questions Patients Actually Ask
Material safety is the question most patients ask but few articles answer without leaning toward alarm or dismissal. Both extremes miss the actual picture, which is closer to the middle than either side admits.
Amalgam’s mercury content and the official position
Dental amalgam contains roughly 50% elemental mercury by weight. The FDA classifies it as a medical device and has reviewed its safety repeatedly; the current position is that amalgam is safe for most adults and children over six, though a small number of devices have been flagged for closer review. The American Dental Association maintains that amalgam is a safe and effective material. Multiple large-scale studies have not found a causal link between amalgam fillings and general health problems in the broader population, and that body of evidence aligns with reviews referenced on NIH and CDC pages.
What the mercury controversy actually hinges on is mercury vapor release. A small amount of vapor is released during placement and removal, and very low levels during chewing. For most adults, daily mercury exposure from amalgam falls below the EPA reference dose. The concern is concentrated in specific groups.
Who should genuinely consider avoiding amalgam
- Pregnant people: Out of precaution rather than documented harm, most guidelines recommend deferring elective amalgam placement or removal during pregnancy.
- Children under six: Developing nervous systems are more sensitive to mercury exposure, so alternatives are recommended.
- People with known mercury hypersensitivity: Rare but real; another material is the safer pick.
- Patients with kidney impairment: Reduced mercury excretion can shift the risk balance.
Tip: never insist your dentist remove a sound amalgam filling for “detox” reasons. Removal drills out mercury-containing material and briefly elevates vapor exposure, with no proven health upside.
Composite, BPA, and what the evidence actually shows
Some composite resins use monomers derived from bisphenol A (BPA), and trace BPA can be detected in saliva for hours after placement. The exposure is transient and small, and major reviews have not found a clinical link between composite fillings and adverse health effects. Newer composite formulations are BPA-free or use BPA-analog monomers that don’t break down the same way. If you want to skip the question entirely, ask for a BPA-free composite, which most manufacturers now offer as a standard option.
Once the safety picture clears, the practical question shifts to which material actually fits the tooth in front of you.
Matching the Right Material to the Right Tooth and Patient
The best material depends on which tooth is being filled, how large the cavity is, and what kind of bite force the tooth absorbs. A material that excels in one spot can fail in another.
Front teeth, molars, and gumline cavities call for different choices
Front teeth (incisors and canines) are visible, take light bite force, and are usually restored with composite resin for aesthetics. Molars take the heaviest chewing loads, are hidden from view, and can take amalgam, composite, gold, or ceramic depending on cavity size and priorities. Gumline cavities, called Class V lesions, sit at the cementoenamel junction and often show up in patients with gum recession. Glass ionomer is the frequent pick here because it bonds well to dentin and releases fluoride along a margin that is prone to recurrent decay.
Small fillings versus large restorations
A small filling (under about a third of the tooth’s biting surface) can be handled by any of the five materials. A large restoration, where more than half the tooth is missing, usually needs a lab-made inlay, onlay, or crown in ceramic or gold rather than a direct filling. Composite can fill larger spaces, but the bulk of plastic shrinks slightly during curing, and that microscopic shrinkage can stress the remaining tooth over time.
The grinder and clencher factor
Bruxism (grinding or clenching, especially at night) puts 4 to 6 times normal bite force on back teeth. Amalgam tolerates this well. Composite wears and can chip under bruxism, but a night guard mitigates that. Gold handles bruxism best because the alloy is tough and slightly forgiving. Ceramic is hard but can fracture under extreme force, especially older formulations; modern lithium disilicate performs better but isn’t immune.
Quick “best for / avoid if” guide for each material
- Amalgam: Best for large molar cavities, budget-conscious patients, and situations where moisture control is tough. Avoid if appearance matters, during pregnancy, or for children under six.
- Composite resin: Best for front teeth, visible molars, and small to moderate cavities. Avoid in very large restorations on heavy biters without a night guard.
- Glass ionomer: Best for gumline cavities, baby teeth, and high-decay-risk patients. Avoid on biting surfaces of permanent molars under heavy load.
- Ceramic: Best for larger inlays/onlays, cosmetic zones, and patients wanting a metal-free option. Avoid in heavy bruxism without a protective splint.
- Gold: Best for durability-first back-tooth work and patients who want a set-it-and-forget-it restoration. Avoid if appearance is a priority or budget is tight.
Questions worth asking before committing
Ask why this material over the alternatives, what the expected lifespan is for your specific cavity, whether a night guard would extend the filling’s life, and what the cost difference is between options. A confident dentist welcomes these questions; a defensive answer is its own signal.
Knowing why a dentist recommends a specific material makes it far easier to evaluate the price tag that follows.
Lifespan, Cost, and the Real Economics Behind Each Filling
The sticker price of a filling is one number; the lifetime cost is another. A $150 amalgam that lasts 15 years costs less per year than a $250 composite that needs replacement in seven.
Realistic longevity by material
Amalgam averages 10 to 15 years and often longer. Composite resin averages 5 to 10 years, with smaller fillings lasting longer. Glass ionomer typically lasts 5 years or less in adult bite surfaces. Ceramic inlays and onlays track with amalgam, often 10 to 15+ years. Gold is the outlier, with 20+ year survival rates well documented in the dental literature. Bite force, hygiene, and cavity size all shift these averages.
Typical out-of-pocket cost ranges
Costs vary by region and dentist, but rough national ranges per filling (without insurance) put amalgam around $90 to $200, composite around $150 to $300, glass ionomer around $140 to $250, ceramic inlays and onlays around $500 to $1,500, and gold restorations from $800 up to $2,500 depending on size and gold price. Lab-made options cost more because they require a second visit and a dental technician’s work.
What dental insurance usually covers
Most US dental plans cover amalgam and composite at the same rate, classifying both as basic restorative services with 80% coverage after deductible. Plans often downgrade ceramic and gold coverage to the amalgam rate, which means you pay the lab-fee difference out of pocket. Pre-treatment estimates from your insurer can prevent surprises on larger restorations.
When replacing an old filling is medically warranted
Replacement is warranted when there’s recurrent decay around the filling’s margin, a visible crack in the filling, breakdown of the filling material, or pain or sensitivity that points to the filling. Replacement for “looks old” or “I want white instead of silver” without a clinical reason is a cosmetic choice, and one worth pricing as such when you sit down to weigh the trade-offs.
Choosing With Confidence at Your Next Dental Visit
A few minutes of preparation turns a default “whatever you recommend, doc” into a deliberate choice. You’re not picking a car, but the same logic applies: know what you want, know what you’re paying for, and know what trade-offs you’re accepting.
Short checklist before agreeing to a material
- Confirm the diagnosis: Ask to see the cavity on the X-ray or intraoral photo.
- Ask the alternatives: “What would you pick if cost weren’t a factor?” is a useful framing.
- Confirm the longevity estimate: A dentist should be able to give a range.
- Check the insurance math: Ask for the billing code and your plan’s coverage.
- Ask about a night guard: If you grind, this can double a composite’s life.
Red flags that suggest a margin-driven recommendation
Pressure to upgrade from composite to ceramic for a small, non-visible filling, claims that amalgam is dangerous for any adult patient, or refusal to discuss cost differences all warrant a second opinion. None of those is proof of anything, but each is worth pausing on when you’re evaluating your options.
The single most useful question to ask
“If this were your tooth, which material would you use, and why?” is the question that cuts through the sales pitch and into the dentist’s actual clinical judgment. Most experienced dentists have an honest, opinionated answer, and that answer is the single best input you can leave the visit with.
The Bottom Line
The five filling materials dentists place today cover a real spread of chemistry, durability, aesthetics, and cost, and the right pick depends on which tooth, how large the cavity, and what trade-off fits your situation. Amalgam still works well in tough, hidden spots; composite dominates visible work; glass ionomer protects high-risk margins; ceramic and gold handle larger restorations with longer life. Knowing the ingredients behind each option turns the dental chair from a place where decisions happen to you into one where they happen with you.
FAQ
Which filling material is safest for teeth?
All five materials placed by licensed dentists in the US are considered safe for the general population by the FDA and the American Dental Association. Specific groups (pregnant people, children under six, and patients with known mercury sensitivity) should avoid amalgam and use composites, glass ionomers, or ceramics instead. Ask for BPA-free composite if you want to minimize that exposure category entirely.
Do composite fillings contain BPA?
Trace BPA-derived monomers present in some older composite resins can leach into saliva for several hours following placement. Major reviews have not linked this exposure to clinical health problems, and most manufacturers now offer BPA-free formulations. Ask your dentist which line they use if this matters to you.
Why is amalgam still used if it has mercury?
Amalgam is still used because it is durable, affordable, and tolerant of difficult placement conditions, especially in large back-tooth cavities. Decades of evidence have not shown health harm in the general adult population, and the FDA’s current position confirms its safety for most patients. Mercury is bound in the hardened alloy rather than free.
What is the most durable filling material?
Cast gold restorations are the most durable, with documented survival rates exceeding 20 years in many studies. Amalgam and modern ceramic inlays tie for second, often lasting 10 to 15 years. Composite resin averages 5 to 10 years and glass ionomer shorter, depending on location and load.
How do dentists choose a filling material?
Your dentist weighs the cavity’s size and location, the bite force on the tooth, your aesthetics preference, your decay-risk profile, your insurance coverage, and any medical conditions or sensitivities. The right answer is rarely universal; it’s the one that fits your tooth and priorities.
Can fillings be made of ceramic or gold?
Yes. Ceramic fillings (often porcelain inlays or onlays) are lab-made from materials like lithium disilicate and cemented in place. Gold fillings are cast from gold alloy in a dental lab. Both cost more and require two visits, but both can outlast direct composite or amalgam restorations when placed well.
