Question: how do you know if you need to replace a filling?
Answer: The filling is cracked. Wear and tear can eventually cause fillings to crack. ... 
Your tooth hurts. If you have a crack in your tooth, you may develop a cavity under the filling. ... 
You feel pain when you drink cold beverages. ... 
Your old filling has changed color. ... 
Your filling has fallen out. ... 
Your filling is old.