Composite vs. amalgam fillings

Modern composites perform well on load-bearing surfaces, and the more meaningful variables are the size of the restoration, how much sound tooth surrounds it, and whether the field could be kept dry during placement. A well-placed composite in a moderate cavity behaves very differently from one in a huge cavity with thin walls. Where the cavity is very large, the more useful comparison is direct filling versus onlay instead of composite versus amalgam.

Not simply because they are amalgam. Replacing sound, serviceable restorations removes tooth structure and starts a new cycle without an established benefit, and the claim that removal improves general health is not supported. Replacement is indicated where there is decay at the margin, a fracture, a failing margin, or where the tooth needs cuspal coverage anyway. Appearance is a legitimate personal reason, provided you understand the trade-off in tooth structure.

Dental amalgam contains mercury in a bound alloy and has been reviewed by regulators including the FDA, which publishes guidance covering considerations for certain groups. Instead of paraphrase a position that has been revised over time, the sensible step is to read the FDA's own page, which is cited on this site. If you have specific concerns or fall into one of the groups discussed there, raise it with your dentist before treatment instead of after.

Because of an alternate benefit provision. Many plans calculate payment for a posterior tooth based on what an amalgam restoration would have cost, treating composite on back teeth as an aesthetic upgrade. You can still have the composite; the plan pays the amalgam-equivalent fee and you cover the difference. A pretreatment estimate shows this before treatment, which is worth doing if the difference would affect your decision.

There is no honest single answer, because longevity depends far more on how much sound tooth remains, the size and position of the restoration, the bite, grinding and oral hygiene than on the material. Both fail in the same way: decay at the margin, or fracture of the remaining tooth. A small restoration in a low-risk mouth outlasts a large one in a high-risk mouth regardless of which material was used.

Yes: you can have whichever material is clinically appropriate for your tooth regardless of what the plan pays toward. The downgrade only affects what the plan contributes; the choice of material for your own tooth is yours and your dentist's to make.

Not necessarily, though composite margins can stain and wear over time in ways that sometimes prompt earlier replacement for appearance reasons even when the restoration is still functionally sound. A restoration that is failing structurally, versus one that simply looks worn, are different reasons for replacement worth distinguishing.

Environmental concerns about mercury disposal, along with a broader regulatory trend toward phasing down amalgam, have led some jurisdictions to restrict or phase it out for certain uses, particularly in children and pregnant patients. This is distinct from a finding that placed amalgam is unsafe in the mouth, which is a separate question addressed by health regulators like the FDA.

Yes, once the old amalgam is removed and the cavity reprepared appropriately for bonding. The tooth is treated as a new restoration at that point, following the same considerations, remaining sound structure, moisture control and bite forces, as any composite placement.

Removal does release some mercury vapor, which is why standard precautions, a rubber dam, high-speed suction and adequate ventilation, are used during removal, particularly recommended by some guidance for pregnant patients considering elective removal. Discuss precautions with your dentist, not assuming a routine replacement carries no procedure of its own.

Yes, commonly: visible silver fillings on back teeth that show when smiling widely, or a general preference for tooth-colored restorations, are legitimate personal reasons some people choose to replace sound amalgam. This is a personal choice about appearance instead of a response to any established health concern with the existing filling.

Yes: removing an old amalgam often reveals more missing tooth structure than a fresh cavity would have, since amalgam preparations require more removal for mechanical retention. The replacement composite is planned around what actually remains once the old material is out, which sometimes changes the plan on the day.