I understand that dentist give fillings after removing or cleaning a cavity, but are you able to then get a cavity underneath that filling, and if so, how?
Thanks for asking the question, Aaron. the most common reason this can happen is that over time the filling can begin to leak, this happens in amalgam fillings (the old silver style filling) if they are particularly big. The tooth around the filling can flex and overtime this flexing can open up a gap into which bacteria can reach.
Another possibility could be that the filling is made in a white composite material, this can erode over time, this gentle erosion can then begin to let in bacteria after a few years.
This is why it’s incredibly important to look after your teeth as much as possible from an early age to prevent having cavities and fillings in the 1st place, it’s also a reason why one should visit the dentist regularly, they can then watch any fillings to ensure they are not showing signs of leaking, if they are, they can be repaired prior to the cavity developing more decay underneath.