Teeth that have already been treated for a dental problem can start to hurt again, regardless of the problems they were treated for. This is because the toothaches you feel aren’t from nerves inside the teeth, they are from the dental nerve that is in the gums. This means that if you have a dental crown that is on top of a tooth stub, and the tooth is still alive (meaning that it is connected to the dental nerve), then it can start to hurt if it is bombarded by bacteria.
Dental crowns frequently go on top of teeth that have once been root canaled, filled, or have parts of them missing for some reason. The reason could be a trauma to the mouth that leaves a tooth broken, or it can be advanced tooth decay as well. These teeth are usually filled up, any sharp or pointy bits filed down, and then the tooth stub is shaped so that the dental crown can go on top of them. By getting a dental crown they regain their function, and the tooth can now take part in biting, chewing and speech again, but the dental crown also insulates the dental nerve against forces of the outside world, to which the dental nerve reacts to with pain. The crown covers the nerve and prevents toothaches, but dental crowns, and the tooth stubs under them, are subject to change, as everything inside the mouth is.
If the dental crown has shifted and leaves the tooth stub exposed, or even worse, is pushing down on the dental nerve, then the slightest amount of pressure or change in temperature can send intense pain signals. The tooth stubs are also subject to all of the problems that regular teeth are subject to, meaning they can get infected, be broken, and become sensitive if the enamel is worn off. So if the tooth stub is alive and connected to the dental nerve, it can start hurting underneath the dental crown, and if it does, that is some seriously bad news.
Tooth decay underneath a dental crown is bad news for several reasons. First of all, this is a region that you cannot clean using your at-home oral hygiene routine. This means that there can be a very intense accumulation of bacteria underneath the dental crown. The crown will definitely have to be removed, which may in and of itself end up damaging your teeth, but there are other problems as well. Because the treatment that you will get will change how the tooth looks, you will need to get a new dental crown. If you are lucky, then you will only need to have the filling changed, but more often than not, these kinds of procedures end in a root canal treatment. If the tooth is too far gone, then an extraction will become necessary, and you will need to get a different kind of dental crown, one that connects to the adjacent teeth. This is also not an infrequent occurrence with these kinds of tooth stubs.
As with all dental treatments, the easiest, most affordable thing to do is to prevent the problem from occurring in the first place. If you have dental crowns, you need to show up to your half-year check-ups, because this is a prerequisite to making sure you keep any guarantees that may be on the dental crowns or bridges. During these consultation and hygiene sessions, the dentist will take extra care to clean the teeth under the dental crowns, as these are at risk by their very nature. Cleaning the bacterial residue and possible food detritus away from beneath the dental crown will stop bacterial infections and tooth decay from forming in the first place, and together with a healthy at-home oral health care routine, including the use of dental floss and mouthwash, it should be enough to make sure that more serious problems never develop on the vulnerable tooth stubs covered by a dental crown.