“How long can a dead tooth stay in your mouth?”

A dead tooth can always become infected and can cause serious issues. Sometimes after a root canal and a crown on them, they can stay for a long time.

Until it gets so infected it comes out while you eating unless you have it removed

If this tooth has had a root canal it can stay in your mouth for a lifetime. If it has not had treatment then this could lead to other problems up to and including loosing the tooth.

There are lots of variables to how long a "dead tooth" can stay in your mouth. Technically, a tooth that has received root canal therapy is dead and it can stay many years. The big question is more a matter of if there is an infection associated with the "dead tooth" and if the infection is active (destroying bone) or not. If there is an active infection the tooth can stay there until the infection causes enough destruction to either allow the tooth to become loose and fall out or gets severe enough to cause the person to get sick enough to need it removed. Having an active tooth related infection is never a good thing and will almost always result in more costly and damaging problems.

Dead teeth are infected and that infection goes from your mouth throughout your body so there is no safe time to not treat the dead tooth as the bacteria login you heart and brain causing damage.

A tooth may have become necrotic and it can remain in your mouth indefinitely. But if the tooth needs a root canal, it needs to be treated.