One common misconception patients have when they get a cavity filled is that their filling will last a lifetime. While it would be nice if that were true, the resin composite material used in most fillings lasts about 20 years, give or take a few. But sometimes fillings break down much sooner than anticipated, with some lasting as few as five years. So, what’s going on with those fillings? Are they made of inferior materials? Were they placed incorrectly? Or maybe there’s something else going on that could be causing them to wear out early. Here are some common reasons fillings break down sooner than expected.