Putting a Composite Filling Over an Amalgam Filling

Dear Doctor,

My dentist has proposed that he can put a composite sealant filling on each of my amalgam fillings so that they won’t leak out mercury gas. This way, he says, I don’t have to have the entire amalgam filling removed and replaced with an more expensive composite if I’m worried about the mercury dangers of amalgam fillings. What do you think of this idea? Won’t the mercury still leak into the bloodstream from inside the left over amalgam filling through the tooth’s root tissue that is in contact with my bloodstream? My dentist says no. Please advise.
-Mike in Texas


Sealing in the amalgam with a composite filling?

The main problem with this approach is that it’s hard to get a good bond between the amalgam and the sealant. Yes, you can do a bond, but it’s a weak bond, and because the amalgam tends to “flow” a little in response to occlusal pressures, the bond would break, and I’m guessing that will happen rather soon under the heavy occlusal stresses it will experience.

Another problem is that, if you have an older filling, it’s always wisest to remove it, because you never know what you’ll find under it. Especially with silver fillings, that block x-rays and are opaque to visual examination. They can have some nasty surprises under them.

I had a patient once that had this done, if I understand what you’re saying. The dentist had removed part of the amalgam filling and just put a composite filling over the amalgam. This dentist was the old-fashioned sort who was very uncomfortable with new technology or with things that he may not have been taught in dental school. For the sake of the her safety, the patient elected to have me remove the entire fillings and re-do them correctly. I believe we did find some tooth decay under one or two of them.

Additionally, it really isn’t that much more work to take out the entire filling. My guess is that it would take maybe a minute or two more to do the whole thing, possibly more for a large filling.

When dentists come up with these strange objections to putting in composite fillings on back teeth, it’s a red flag that the dentist simply isn’t comfortable with doing composite fillings on back teeth. Do you realize that most dental schools don’t teach dentists how to do these composite fillings on back teeth? Your dentist may have done one of these composite fillings on a back tooth once and the tooth became very sensitive afterwards because he didn’t do it right. Leaving amalgam in the bottom of the filling means that, whatever else goes wrong down the road, at least the tooth won’t be sensitive in the short term. Dentists, however, are trained not to reveal their lack of confidence with any dental procedure because it makes patients nervous. That’s understandable, because it really does make the patient nervous and can create a bad situation. But sometimes as a patient you need brutal honesty, and I don’t think you’re getting it. Fortunately, you’re astute enough to pick up that something doesn’t sound quite right about his objection to just putting in the composite fillings.

Your area code suggests to me that you’re from the Austin area. Go to Dr. Mark Sweeney there (512-452-9296). He knows what he’s doing with these white fillings on back teeth. I really doubt that your dentist does.

Dr. Hall

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