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Can my fillings be making my teeth crack?

added on: March 15, 2015

Sadly, yes, that can sometimes be the case.  I’m referring here, of course, to mercury — also known as amalgam — fillings, which have been used to restore teeth in the United States for over 200 years.  Amalgam has been used because it is not only strong, but most importantly inexpensive (a fact dental insurance companies love).

Cracked Tooth Soft

But wait, before you get too upset with your dentist for “fixing” your teeth with amalgam, remember that, for many years, it was the only material available and, if it weren’t for that filling, the tooth may have been extracted!

The reason teeth may crack due to these metal fillings is pretty easy to understand.  The enamel on our teeth is very strong, but it is also very brittle and not very flexible.  Generally these fillings were placed when a patient had a cavity or hole in a tooth.  The decay was cleaned out and the mercury was put in.  One of the challenges faced is that amalgam isn’t very sticky, so it is difficult to get it to stay inside a tooth.  This can be overcome, however, by shaping the new hole in the tooth so it is wider at the bottom than at the top.  (Imagine trying to get your hand out of the cookie jar after it’s full of cookies)

Prep Design 2

And here lies the problem, right before our eyes.

Prep Design 3

We all know from high school science class that metal expands when it is heated and contracts when it is cooled; so why would we expect metal fillings to be any different?  When the temperatures of our diets range from steaming hot coffee to freezing cold ice cream, multiplied by the daily pounding of those metal fillings from the tremendous strength of our biting force, we should already know what to expect, and sure enough…

Cracked Tooth 2-2


Of course, some fillings last a long time before they do any damage to the teeth they were meant to protect.  These are generally the smallest fillings which aren’t as destructive as a larger piece of metal in a tooth.

Soon we will talk about how to fix these cracks both before and after they’ve broken.

Dr. Crosby