Dental updates from Dr. Mckeever.

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METAL MOUTHS

The so-called "silver amalgam fillings" that are used to fill teeth are made up of a combination of metals (silver, tin, zinc, copper, mercury). A lot of fuss has been made over the use of amalgam alloys by those alleging that such restorations have the potential to cause systemic illnesses such as MS, autism, Alzheimer's disease and immune system dysfunction. Critics of amalgam use say that, over time, the mercury contained in the amalgam (which by the way means "mixture") is slowly released into the body eventually accumulating to a level that is sufficient to initiate various pathological responses. These fears have been fueled by anecdotal reports in the professional literature, media and by politicians pandering to the fears of their constituents.
Reported adverse health effects from amalgam restorations do not stand up to scrutiny by the technique of an evidence-based care approach to scientific analysis when this tried and true method of investigation is applied to all of the studies trying to make that case. Repeated findings reaffirm that the continued use of amalgam for fillings is, indeed, safe. The National Institute of Health and the Food and Drug Administration have presented a summary of the literature associated with the debate and have found no evidence to support toxicity of amalgam used in the oral environment. Studies conducted on old amalgam fillings that have been removed and analyzed have shown that the mercury level in these fillings to be at the same levels as when they were originally placed.
That having been said, there are still dentists out there that are trying to "scare" patients into believing that amalgam filings are toxic to the body and need to be replaced by another material. The evidence of any toxicity is so underwhelming that it is actually unethical for any dentist to do this and, in fact, his or her dental license can be suspended for doing so. The materials that are available for direct placement into a tooth other than amalgam are quite a bit more costly (because they take much longer to put into the tooth) and not that free from controversy. By far the most commonly used replacement material is composite resin which is bonded into place but requires much more skill and patience than amalgam. The upside to composite resin is that it is much more esthetically appealing than amalgam (let's face it, amalgam fillings are flat ugly!). And, that's about it. The downside is as follows:

1. Composite resin is not as durable as amalgam fillings (controlled studies
have shown a failure rate of up to 46% over and eight-ten year period).
This failure reate is not necessarity a materials failure but probably more
of a technique failure. Dr. Karl Leinfelder, one of dentisry's main "guru's"
and a leading dental materials consultant, states that, "The problem
(with bonded composite fillings) is that the success of these materials
depends upon the clinician even more than it does on the material. The
patient doesn't have this information, however. In fact, even dentists
don't know who is a good clinician and who isn't when it comes to using
posterior composite resins (posterior means the molar and premolar
teeth). And the greatest influence on the success of the composite
is the clinician's skill". He goes on the state that the longevity of any
posterior composite restoration is approximatelly 50% that of silver
amalgam fillings and that over half of the dentists place composites
using the same rules as when placing amalgams i.e. they pretty much
"stuff" them into the hole in bulk which leads to tooth sensitivity, leak-
age (see below) excessive wear or breakage and staining around the
edges.

2. Composite fillings leak more than amalgam fillings especially when
placed near or under the gum line. That is because composite shrinks
from 2% to 9% when it is cured (hardened). That leaves a gap at the
tooth-composite interface which allows leakage and the entry of decay-
producing bacteria that can cause a renewal of the decay process. Dr.
Leinfelder states that composite resins have a basic componant (which
is a chemical related to plastic) that actually stimulates cavity formation
making this new decay proceed at a "substantially faster rate than it
with amalgam". (Amalgam is one of the few materials that can actually
discourage the growth of cavity-causing bacteria).

3. Composite resins are also linked to long-term toxicity. Recent scientific
findings have reised questions about resin-based materials and have
associated their use with systemic medical conditions similar to those
alleged to result from the use of dental amalgam. I think we will find
that, when all of the evidence is examined scientifically, this indictment
will also prove to be much ado about nothing.

4. When a composite resin comes in contact with an opposing tooth, small
cracks begin to form in the restoration. Over a period of months and
years these cracks grow and begin to join together. Eventually, pieces
of the composite break off. Amalgam, on the other hand, flows away
from any contact point created by opposing teeth leaving it pretty well
in tact.

Patients have to realize a tooth can be broken down past the point at which any type of filling material can last and that requires full or partial coverage of the tooth with a laboratory-fabricated restoration. Do I place composite resin fillings? Certainly I do but only in teeth that don't take much of a beating from the oppos-ing teeth or teeth with only small cavities. There are some areas of the mouth where esthetic considerations are actually more important than some of composite's negative properties. Both amalgam and composite work well in the right circumstances and both can and will fail if used in the wrong places. However, patients should not expect miracles resulting from amalgam replacement and should balk at any dentist who tries to "scam" them.

The next topic will tackle the toxicity of cast metal restoration in the mouth which is really interesting and something nobody wants to talk about! Stay tuned. (Also, web site processing (called a "Blogger") doesn't have a spell checker nor does it allow anything even bordering on fancy such as italics, underlining or indentations; please ignore misspelled words and bad punctuation - thank you!)
posted by Steve at 8:20 PM