Most dental fillings today are made from one of two materials: tooth-colored composite resin or traditional silver amalgam. Both materials have decades of clinical evidence, both are accepted by the American Dental Association, and both have legitimate roles in modern dentistry. Choosing between them is rarely a black-and-white decision — it depends on the location of the cavity, your priorities, your budget, and how the tooth needs to perform over time.
This guide compares composite and amalgam across the factors that genuinely matter at the chair, walks through what each is made of, and explains why most modern offices, including ours, have shifted toward composite as the default. Use it to walk into your next conversation about a filling already informed and ready to ask better questions.
The Two Materials at a Glance
Before diving into the details, a side-by-side comparison helps frame the rest of the conversation. Cost figures are deliberately framed in ranges; exact pricing depends on the size of the filling, the tooth involved, your insurance, and your office.
| Factor | Composite (Tooth-Colored) | Amalgam (Silver) |
|---|---|---|
| Appearance | Matches natural tooth color | Visible silver/grey |
| Bonded to tooth | Yes — bonds chemically to enamel and dentin | No — held by mechanical undercuts |
| Tooth structure removed | Less — more conservative preparation | More — needs undercuts to retain |
| Typical longevity | About 5 to 10 years | About 10 to 15+ years |
| Placement technique | Layered and light-cured; technique-sensitive | Packed and self-hardening; faster |
| Mercury content | None | Yes — bound in alloy |
| Sensitivity to moisture during placement | High — requires excellent isolation | Lower |
| Upfront cost | Higher | Lower |
| Insurance coverage | Often fully covered, sometimes downgraded to amalgam fee | Typically fully covered when used |
What Composite Fillings Are Made Of
Composite resin is a mixture of plastic resin and finely ground glass or ceramic particles. The resin acts as a binder, the particles add strength and wear resistance, and a small amount of light-activated chemistry lets the dentist harden the material instantly with a curing light. The mixture is layered into the prepared tooth in small increments, each layer cured before the next is placed, until the natural shape is rebuilt.
Modern composites are dramatically improved from earlier generations. The wear resistance, polish-ability, and color stability of today's materials are excellent for small and moderate fillings on any tooth, and the bond to the underlying tooth is meaningfully strong when the technique is done well.
What Amalgam Fillings Are Made Of
Dental amalgam is an alloy that combines silver, tin, copper, and a small amount of zinc with elemental mercury. The mercury serves as a binder that allows the metal powder to be packed firmly into the prepared tooth, where it then hardens over the next several hours. Once set, the mercury is bound within the alloy structure.
Amalgam has been used in dentistry for over 150 years, with continuous refinement and a substantial body of safety research. The ADA's overview of dental amalgam summarizes the current consensus: amalgam remains a safe, durable restorative material for most patients, while alternatives are reasonable for those who prefer them or fall into specific higher-risk groups.
Where Each Material Shines
Composite Excels When...
- The tooth is visible when you smile, talk, or laugh
- The cavity is small to moderate and well-contained
- The patient prefers a metal-free restoration
- Conserving healthy tooth structure is a priority — composite needs less aggressive preparation
- The dentist can keep the tooth completely dry during placement
Amalgam Excels When...
- The cavity is large, on a back molar, and especially difficult to keep dry
- The patient grinds heavily and the bite forces would stress a composite
- Cost is a significant consideration and aesthetics are not
- The patient already has amalgams that are working well — no reason to replace them
In most modern practices, including ours, composite is the default first choice for visible teeth and for most small to moderate fillings everywhere. Amalgam still has a place in selected back-tooth situations where moisture control is genuinely difficult or budget is a primary factor.
The Mercury Question, Honestly Addressed
Patients commonly ask whether the mercury in amalgam is safe. The U.S. FDA and the American Dental Association both consider amalgam safe for the general adult population. The agencies do recommend that pregnant or nursing women, young children, individuals with neurological diseases, individuals with kidney disease, and individuals with mercury allergy or sensitivity discuss alternatives with their dentist.
For patients who want a metal-free restoration for personal preference or any of the above reasons, composite is a reasonable, well-supported choice. Removing existing intact amalgams purely for general health reasons is not generally recommended, since the removal process itself causes some exposure and removes a small amount of additional tooth structure.
"The decision is not whether amalgam is dangerous — current evidence does not support that — but whether composite better fits your priorities, your tooth, and your specific situation."
Cost and Insurance Realities
Amalgam is typically the lower-cost option upfront. Composite fillings tend to cost more, sometimes notably more for larger restorations on back teeth where the layering technique takes longer. Many dental insurance plans cover composite at the amalgam fee, with the patient paying the difference. Others cover both fully. Plans vary widely.
Our front desk in Folsom, CA can verify benefits before treatment so there are no surprises — see our insurance information or membership plans for patients without coverage. For payment options, our financing page walks through the available programs.
Longevity in Real Life
Average lifespans you will see in textbooks are useful starting points, but real-world longevity depends heavily on the specific situation:
- Filling size matters more than material — very large fillings of any material tend to fail sooner
- Heavy grinders shorten the life of every restoration; a custom nightguard can dramatically extend it
- Recurrent decay around the margins is the leading cause of replacement, regardless of material
- Excellent home care and regular cleanings extend the life of every filling
For more on what affects how long any filling lasts, see our companion guide on how long dental fillings last.
What the Procedure Looks Like
The patient experience differs slightly between materials. Both visits start with numbing, decay removal, and tooth preparation. The differences:
For composite: the dentist places a bonding agent and layers the composite in small increments, curing each layer with a blue light. The technique is more time-intensive and requires excellent moisture control. After the final cure, the bite is checked and the surface is polished.
For amalgam: the prepared cavity is shaped with small undercuts that hold the material in place mechanically. The amalgam is mixed, packed firmly into the prep, and carved to match the natural tooth contour. The bite is checked, and the patient is asked to avoid hard chewing for the first few hours while the material reaches full hardness.
For the full visit walk-through, see our resource on what to expect when getting a filling.
Making the Choice
The right material is the one that fits your tooth, your priorities, and your situation. For most patients today, that means composite. For some patients in some situations, amalgam still earns its place. The most important conversation is the one you have with your dentist looking at the actual tooth on a screen and discussing the trade-offs as they apply to your case.
To talk through your options or schedule an evaluation, book an appointment or learn more on our fillings page. For broader preventive care that helps every filling last longer, see our cleanings overview.
Frequently Asked Questions
Are silver amalgam fillings safe?
According to the U.S. Food and Drug Administration and the American Dental Association, dental amalgam is considered a safe and effective restorative material for most patients. The FDA does recommend that certain higher-risk groups — such as pregnant or nursing women, young children, and individuals with specific medical conditions — discuss alternatives with their dentist when possible.
Why do most modern dentists prefer composite?
Composite fillings bond directly to the tooth, allow the dentist to remove less healthy tooth structure, match the natural tooth color, and serve patients who prefer a metal-free option. Many practices, including ours, have moved toward composite as the default while still respecting patients who prefer or already have amalgam.
Should I replace my existing amalgam fillings?
Not unless there is a specific reason. Replacing a sound, intact amalgam filling for cosmetic or general health reasons is a personal choice, but the procedure itself removes some additional tooth structure. Most dentists recommend replacing amalgams only when they are leaking, fractured, decayed underneath, or causing other problems.
Which type lasts longer?
Amalgam fillings have a longer track record and historically average 10 to 15 years or more in many studies, while composite averages 5 to 10 years. Modern composite materials and techniques have closed much of that gap, especially for small to moderate fillings, and the gap depends heavily on the size of the filling and the patient's habits.
Can I see the difference between composite and amalgam in photos?
Easily. Amalgam appears as a dark, silver-grey area in the tooth, often with a subtle dark halo around the edge over time. Composite is tooth-colored and, when placed well, blends in so closely that most people cannot tell where the natural tooth ends and the filling begins.