The Trouble With Mercury
Mercury from fillings contributes 3 to 4 times more
mercury to our bodies than all the environmental sources combined.
Many people still don't realize that the majority of the new cavities we
see in children today occur just in the center of the molar teeth. The
tiny groves there are flaws which invite early decay. By the age of 6 a
child has 4 permanent first molars.
Mercury fillings require the removal of the middle third of the tooth. The
material itself is weak and cannot be used in a thin layer. The dentist
must drill deeply into the softer dentin area of the tooth and drill
undercuts into the healthy tooth even where there is no disease. This
approach was developed in 1908 by G.V. Black. As a result of this kind of
filling, the tooth is now weakened by 75%.
Mercury fillings also expand after being placed in the tooth. The bigger
the filling the more they expand. If any moisture gets into the filling
they expand rapidly. Temperature can also cause expansion. All this
expansion within the tooth eventually results in fracture.
Once broken the tooth may require a root canal or crown or extraction.
Often the fracture is so severe that in spite of all efforts the tooth is
lost.
The Best Choice:
Composite Filling Materials
If you are restoring a
tooth for the first time then composite filling materials will not only
strengthen the tooth as well as provide greater longevity and beauty than
the mercury/silver ones but, more importantly it is far less damaging to
the healthy tooth.
The
majority of initial composite fillings require only minimal natural tooth
removal and not only restore decayed areas but also seal up weak spots so
decay will not penetrate the other surface groves.
Sealed surfaces ARE protected
as long as the sealant lasts. When it wears
out it can easily be reapplied until the child grows out of this cavity
prone period. However, the composite sealant must be placed before decay begins.
On the average 36% of the children today are cavity free. However, those
children raised in the southwest are much more likely to be cavity free
than those from the northeast. No single cause can be found for these
differences.
Earlier Composites
When I quit using mercury/silver fillings my immediate choice for
replacement was a posterior composite. These white plastic fillings looked
great and were much less toxic than the mercury/silver fillings.
Unfortunately, they simply were not strong enough for replacing big mercury/silver fillings in the
hard-biting back teeth. As a result, stronger and better light cured
materials have been developed,yet technical problems still exists in
placing these restorations. They shrink 1% to 3% upon setting and lack the
crushing strength to withstand the enormous biting forces some people can
generate. Sensitivity and recurrent decay results from the shrinkage and
excessive wear is the result of low strength.
Progress for the 1990's: Indirect Composites
Since the mid-80's a new system, called indirect composites combines the best of the
composite and the strength of a natural tooth. This inlay process is much
easier on the patient (and dentist) and has virtually eliminated the two
major drawbacks to the composite restoration.
 [Go to IAOMT protocol.]
The IAOMT recommended patient protection procedure for mercury/silver
replacement is to:
First: Protect the patient's breathing zone. Drilling out old fillings can
release enormous amounts of mercury into the air. If the patient is given
a nasal hood this exposure can be prevented. Many dentists recommend a
rubber dam. I find this helpful as well.
Second: The dentist should cut the fillings in half or quarters with a
small burr and lots of water then remove the pieces. This avoids excessive
drilling of tooth or grinding on the old fillings.
Third: The tooth is cleaned and shaped with a diamond burr, some undercuts may be
removed, and an accurate impression is made. Here technique
may differ from office to office. I prefer to temporize the tooth with a
light cured temporary composite and send the patient home.
We then make a model of the tooth preparation in out lab and fill the
preparation with a good quality posterior composite. This filing is first
set with light and then heated or baked at 270o F for 14 minutes. Special
ovens are available but not required. Even a simple toaster oven can be
utilized. Once baked the filling is then etched with acid and sand blasted
so it can be bonded to the tooth.
Last: The patient returns usually in a day or two and the temporary is
removed. The tooth is cleaned and prepared for bonding. The Bowen system
is currently the strongest in attaching the new filling to enamel and dentin. With
the newest generation of dentin bonding the filling can be essentially
welded to the remaining tooth structure. Once completed the bite is
adjusted and margins polished. This restoration can be virtually invisible
to the naked eye and feels wonderful. I have used this technique in all
areas of the mouth and it holds up very well. Some situations will still
require a full (or partial) crown but almost any tooth that can hold a filling now can
be restored with this procedure.
The baking process more completely cures the filling and greatly increases
the crushing strength. Minimal uncured chemical resin is left and the
result is a much stronger wear resistant and far less toxic filling. In
addition the shrinkage takes place outside of the mouth and the small gap
that results will be filled with a thin layer of composite resin cement.
The welding of the filling to the tooth makes the tooth stronger and more
resistant to fracture. The appearance of the smile is enhanced greatly. If
you are considering having your fillings replaced or just have a old
filling break, I strongly urge you to discuss this procedure with your
dentist. The cost can be quite reasonable for the benefit that will result.
Conclusion
Children born today need never have the enormous amount of mercury packed
into their teeth that the post war baby boomers did.
Those of us who
already have the large mercury/silver fillings must consider how best to
restore our teeth.
The larger the cavity the worse a composite filling
will hold up. Excessive wear especially becomes a problem for some brands
when used in molar teeth. If the decay has penetrated deeply in between
the teeth composites can leak and are more difficult to place. Lab
processed composites and porcelain fillings appear to have solved both the
wear and placement problems.
As to expense.the initial cost of a filling must be weighed against the long term
expense. Fillings which require the dentist to remove excessive amounts of
good tooth structure are not cheap. Which is best? My first
recommendation is to prevent the cavity if at all possible. Seal out
decay. If the damage is already done then repair it with the most durable
material available and try harder to prevent the next cavity. As
Hippocrates said, "First and foremost do no harm". I don't think he would
have approved either toxic fillings or drilling away the good tooth.
Non-metal, non-toxic dentistry is truly a
reality of today.
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