Is it common to lose a dental filling?

It could happen: You may lose a dental filling due to fracture caused by trauma and or recurrent decay. Usually sound dental fillings do not just fall out on their own.

Yes, but fix it!: Dental fillings do not last forever. The most common way for them to fall out is new decay, and so i strongly recommend seeing a dentist quickly.

Lost dental filling: A good, functioning and well placed dental filling should not be lost. Loss of a dental filling is an indication of a problem with the filling or the tooth. So if a filling is lost it's best to see dentist asap to evaluate the condition and and take corrective measures. If not addressed in timely fashion it can lead to further problems like root canal or tooth loss.

Yes: Fillings don't last for entire human lifespan and many things influence if they will fall out. Poor oral hygiene would lend itself to new decay, eating hard candy, chewing ice, grinding at night, etc..all can loosen a filling or cause it to fail sooner than under ideal conditions.

Yes: especially as they age.

Dental restorations: They don't last forever, so I guess it's common.

It happens: Fillings do not last forever. They can come out when there is a problem with the tooth. Tooth breaks, or there is decay. See a dentist and get the tooth fixed. The problem will get bogger, more complex and more costly the longer you wait

Fillings: Fillings can chip, wear down, break, or fall out if undermined by recurrent caries. Car keys and important papers get lost. Forgive for my sense of humor this early in the morning.