Look in the mirror and open wide.  See any dark metal fillings?  Those are silver amalgam fillings and while they work fine for a while, new materials are available that are much better.  One big difference between amalgam fillings and new materials, called composite, is in the way fillings are made.  Amalgam fillings stay in place because the tooth is drilled out to form a pear shape, narrow at the top but with a larger area carved out of the tooth below.  The filling material, which is soft when placed in the tooth, fills the hole.  The filling hardens, then stays in place because of its shape.  The problem arises as these fillings age.  Like other metals, the filling expands and contracts with heat and cold.  So when you eat hot food, the filling expands, then shrinks when you have something cold.  Eventually, a tiny gap forms between the filling and the tooth, bacteria enters the gap, and cavities develop.  Also, amalgam fillings can cause the tooth to crack from expanding.  Last but not least, amalgam fillings contain mercury.

Composite fillings work very differently as they contain adhesives, so they stick seamlessly to the tooth.  Drilling is greatly reduced, as only the decay need be removed.  They also look better, as they are tooth colored, so they are almost impossible to see.  They can contain fluoride, so that decay won’t return. 

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