How can you tell if a recent dental filling is not in right?

Not simple: In simplest cases, filling may actually be loose (not adhering to tooth) and mobile. More likely are concerns due to possible post-op symptoms. Sensitivity to cold or hot stimuli are common with silver fillings and usually fade. Sensitivity to biting, especially with tooth-colored fillings may be due to bite (simple fix) or unseen problems w/ bonding (harder to detect, and may require new fill.

Get it checked: Even though it sometimes seems easy, people forget that getting a filling is actually a surgical procedure where the dentist "cuts out" the rotten part and re-seals the tooth. It can sometimes take a while for a tooth to feel good again. Get a quick check to make sure the bite is ok - you may be biting different when you are not numb - and that nothing is broken. If it's good, give it some time.

Couple of ways: Most commonly, you will feel that you cannot close your teeth together the same as before the treatment. The filling will need to be adjusted to return you to the pre-treatment bite. See your dentist. You may also have sensitivity. If this persists, see your dentist. Don't be shy about calling for an appointment to recheck the filling. You should not be charged for this. Good luck.