How long will it take for a cavity to kill you?

Depends: In this day and age, a person is unlikely to die from a cavity in their tooth. It depends on their oral hygiene habits. If a person has a cavity and never brushes/flosses their teeth they are likely to get more cavities which can result in periodontal infections. Untreated periodontal infections can be fatal if they spread to the blood stream. However, this would be very unlikely to happen.

I think the better: question is, what is the likelihood that a cavity will kill you? A cavity alone, unless it's produced by a bullet that pierced your brain, will NOT kill you ever. If left alone, decay can continue, the surrounding gum and root of the tooth can become infected, the infection can spread to the bloodstream. Blood stream infections,i f not treated promptly, can lead to death. Wow!