Many people, at one point or another during their lives, will need to get a filling to cover up the spots in the tooth that have been eroded by tooth decay. While most fillings last a long time - generally around 5 to 10 years, if they are placed correctly and taken care of - they will on occasion fall out.

There are a number of reasons why old fillings fall out. In some cases, a filling will fall out because of an error on the dentist's part. The filling may not have been placed properly, meaning it wasn't fit tightly enough into the tooth. Other times, the cavity being filled is contaminated with saliva when the filling is placed. This weakens the bond used to hold the filling in place, and if the bond is not strong enough, the filling can fall out.

Old fillings also begin to leak and crack over time. Cracks can occur soon if the filling has not been shaped properly. So, for example, if the filling is higher than the rest of the surface of the tooth, the force of biting and chewing is placed directly on the filling. This can cause the filling to crack.

Leaking fillings occur when the side of the filling doesn't fit tightly enough against the tooth. This can allow debris and saliva to leak in between the filling and the tooth, which can lead to even more decay.

Fillings aren't designed to last forever, and in some cases, fillings just wear out. As fillings wear, food and debris can seep under them, causing decay and pain and more expensive problems. Regular visits to the dentist to have your fillings checked will help you to know when your fillings need to be replaced.

What if my filling falls out?
If you have an old filling that falls out, the following steps should be taken:
    First of all, call and make an appointment with the dentist and ask to be seen as soon as possible. Even if you are not experiencing pain, the filling needs to be fixed. Neglecting to see the dentist can result in the growth and spread of infection, which can result in more painful, expensive procedures than fillings, like a root canal.
    If possible, save the piece of filling that has fallen out. In some cases, the dentist can re-cement the filling instead of having to drill more teeth away for the new filling.
    Rinse your mouth with warm water, and then gently brush and floss the teeth to remove any debris from the filling. Do not brush or floss too hard around the tooth that lost the filling, as the tooth will probably be cracked and hard brushing and flossing could be painful.
    If you have any, take a piece of dental wax and soften it by rubbing it between your fingers. Place a small piece of the wax over the exposed tooth to prevent it from exposure to air and debris until you can see the dentist. This will also help to alleviate any pain while protecting the tooth from further damage.
    If the tooth is painful, take an over-the-counter pain reliever such as Tylenol, Advil, or ibuprofen.