The tooth is three dimensional. When decay extends through the top of the tooth and all the way into an area that’s either inaccessible, or it’s just an area where it’s going to make the tooth so fragile where it just doesn’t make sense to restore it, in those instances the tooth would need to be extracted versus placing a filling.
A filling is really just indicated when you’ve got a cavity that is not that extensive and doesn’t involve the tooth so much so that it is going to deem the tooth non-restorable or give it a poor or hopeless prognosis. To extract a tooth, in some cases, it might sound like it’s not necessarily the tooth is bad and rotten so it’s extracted.
In some cases, I have orthodontists send patients where they need their first bicuspid extracted to provide space to reposition the teeth and place braces on the teeth. That sort of thing is actually quite common. And in other cases you need to extract teeth because, your wisdom teeth for instance, there’s just not enough space for them.
Or they come into a poor position and they’re not going to reposition themselves so that the patient can be hygienic and cleaned effectively, so in those cases I would recommend having the wisdom teeth out as well. But as far as having decay or possibly a fracture or a crack through the tooth, that will often deem the tooth not restorable as well. So if a crack has propagated completely through the tooth, there is no sense in restoring it because it will fail.