Filling Materials
Every filling material, explained honestly.
Composite, amalgam, glass ionomer, and gold — what each material is, where it's used, how long it lasts, and what questions to bring to your dentist.
The short answer: Most cavities today are filled with composite resin (tooth-colored) or amalgam (silver). Composite is more aesthetic and mercury-free; amalgam is more durable in back teeth and less expensive. Glass ionomer releases fluoride and is gentle on teeth. Gold lasts the longest of any material but is visible and costly.
Composite Resin
Composite resin is the most common tooth-colored filling material. It bonds directly to tooth structure, requires less removal of healthy tooth than amalgam, and matches natural tooth color — making it suitable for both front and back teeth.
Advantages
✓Tooth-colored and aesthetically natural
✓Bonds to tooth structure — less drilling needed
✓Repairs chips and cracks as well as cavities
✓Free of mercury and metal
Trade-offs
—Less durable than amalgam in high-stress biting areas
—More technique-sensitive to place correctly
—May stain over time with coffee, tea, or wine
—Typically costs more than amalgam
Typical lifespan
7–12 years on average in posterior teeth; longer in lower-stress areas with good oral hygiene
Cost range
$150–$300 per surface
What research shows
Composite resins have improved substantially since the 1990s. Modern formulations show durability rates approaching amalgam in many clinical studies, though long-term (15+ year) data still favors amalgam for posterior high-stress restorations.
Alternatives to consider
Questions to ask your dentist
Q: Is composite resin safe?
Composite resins are considered safe for the general population. They contain bis-GMA, a BPA derivative, but the amounts released post-curing are extremely small. Patients with specific sensitivities should discuss this with their dentist.
Q: How long does composite last on a back tooth?
On average, 7–12 years in posterior teeth, though this varies significantly based on bite force, oral hygiene, and the skill of placement. Some last 15+ years; others may need replacement sooner.
Dental Amalgam
Dental amalgam is an alloy containing mercury, silver, tin, and copper. It has been used for over 150 years and has an extensive safety and durability record. Most dental and health regulatory agencies consider it safe for the general population, though it contains mercury and its use is declining in many countries.
Advantages
✓Exceptional durability — often lasting 15–20+ years
✓More forgiving in wet conditions during placement
✓Less technique-sensitive than composite
✓Lower cost than most alternatives
Trade-offs
—Silver-gray color is not tooth-colored
—Requires more tooth removal to place
—Contains mercury — a concern for some patients and environmental reasons
—Being phased out in some countries under Minamata Convention
Typical lifespan
15–20+ years, often longer
Cost range
$75–$200 per surface
What research shows
Decades of research have found amalgam safe for most patients. The mercury in amalgam is in a stable alloy form (methylmercury), different from the organic mercury that causes neurological harm. However, regulatory restrictions are increasing due to environmental concerns, and some patients prefer alternatives.
Alternatives to consider
Questions to ask your dentist
Q: Is amalgam mercury dangerous?
The mercury in amalgam is bound in a stable alloy and behaves differently from the organic mercury associated with fish contamination. Major health bodies including the WHO and FDA consider it safe for most people. Patients with mercury sensitivity, kidney problems, or who are pregnant may wish to discuss alternatives.
Q: Should I have my old amalgam fillings removed?
Removing intact amalgam fillings can release more mercury vapor than leaving them in place. Most dentists recommend replacing them only when they fail or need repair, not prophylactically. See MercuryFreeDental.com for guidance on safe amalgam removal if you choose to proceed.
Glass Ionomer
Glass ionomer cement is a tooth-colored material that releases fluoride continuously over time. It bonds chemically to tooth structure and is gentler on the tooth than many alternatives, making it particularly useful in specific clinical situations.
Advantages
✓Releases fluoride — helps prevent secondary decay
✓Chemical bond to tooth — no etching required
✓Biocompatible and gentle on pulp
✓Good choice for root-surface cavities
Trade-offs
—Less durable than amalgam or composite under biting force
—More susceptible to wear and fracture
—Aesthetic quality less refined than composite
—Not suitable for high-stress posterior areas
Typical lifespan
5–7 years in appropriate applications
Cost range
$100–$250 per surface
What research shows
Glass ionomer is well-established in pediatric dentistry and root-caries treatment. Resin-modified glass ionomers (RMGIs) combine fluoride release with improved strength and are increasingly used in liner and base applications.
Alternatives to consider
Questions to ask your dentist
Q: Does glass ionomer release enough fluoride to matter?
Yes — glass ionomer releases fluoride at clinically meaningful levels for months to years, particularly benefiting patients at high caries risk. The release reduces over time but can be recharged by fluoride toothpaste.
Gold
Gold restorations — including inlays, onlays, and crowns — represent one of the most durable and long-lasting options in dentistry. Gold is biocompatible, gentle on opposing teeth, and has a 50+ year track record. The primary limitation is aesthetics and cost.
Advantages
✓Exceptional longevity — 20–40 years or more
✓Gentle on opposing teeth
✓Very high biocompatibility
✓Less tooth removal required than full ceramic crowns in some cases
Trade-offs
—Highly visible — obvious metallic appearance
—Highest upfront cost of any filling material
—Requires at least two appointments
—Less popular as a cosmetic concern — some patients prefer invisible restorations
Typical lifespan
20–40 years, sometimes lifetime with good care
Cost range
$800–$2,500 for inlays/onlays
What research shows
Gold is sometimes described as the 'gold standard' in dentistry for a reason — its clinical track record surpasses most modern alternatives for durability. Several long-term studies show survival rates of 80–90% at 20 years.
Alternatives to consider
Questions to ask your dentist
Q: Why do dentists still recommend gold when newer materials exist?
Gold's unmatched longevity, gentle wear properties, and exceptional biocompatibility make it a clinically sound choice for many patients. Some dentists prefer it specifically for back teeth where cosmetics are less important and durability is paramount.
Not sure which to choose?
Compare them side by side
Our comparison pages put composite, amalgam, and other materials side by side so you can see the trade-offs clearly before your appointment.
Related resource — sister site
Specific guidance on amalgam removal, the SMART protocol, and finding mercury-safe dental providers.