Nothing lasts forever.
This saying is true for many things.
It is also true for fillings in your teeth.
Below you will see a picture of a broken metal filling.
This individual has wonderful oral hygiene.
The cause of the breakage is simply, time.
Over time most people's fillings will need replacing.
Since the days of those metal fillings they have come up with filling
material that looks much more like real tooth and is still very durable.
Even if you have excellent dental hygiene please make sure
that you are seeing your dentist on a regular basis.
This situation had nothing to do with not taking care of your teeth.
It simply was time to get the filling replaced that had deteriorated over time.