How much time does it take for a nerve to die in a tooth?

Varies: Pulp (nerve and vessels) can die soon after tooth injury or slowly over several years due to an advancing cavity or crack. A dead nerve is not a good thing since pain may only temporarily subside but now there is risk of infection and loss of bone and possibly the tooth if the "dead" nerve is not treated

Nerve: The nerve in the tooth can die quickly due to trauma or very slowly due to decay, cracks, or fracture. If you are concern about a tooth the best thing to do is have a dentist evaluate your tooth

Nerve vitality: The nerve and blood supply to a tooth commonly referred to as the "nerve" may go non-vital (die) within days from a traumatic fracture of the tooth or take years to eventually show up on x-rays or with symptoms such as pain and swelling.