It is possible for a dead pulp tooth to last up to 20 years. A well-treated dead pulp tooth lasts a long time, while an untreated dead pulp tooth lasts a relatively short time, as follows. 1. Perfectly treated pulp: The necrotic pulp is completely removed to prevent secondary infection. When the tooth loses the nutrients from the pulp, it will become fragile, so you need to pay attention to the daily cleaning and maintenance as well as do not use the tooth to chew hard objects, how to prolong the usage time of the pulpless tooth. 2. Untreated dead pulp teeth: necrotic pulp will breed bacteria, if the bacteria enter the periapical tissue through the apical foramen, it will cause periapical periodontitis, which will lead to periapical alveolar bone resorption in severe cases, and the tooth will become loose until it falls off, and the use of time is shorter. If the above symptoms occur, it is recommended to go to the hospital in time.