Usually necrotic pulps are the end results of the process of pulp tissue degeneration. Necrotic pulp is actually a non vital tooth that has sustained the conditions from which it cannot recover. These conditions may include various types of tooth problems which finally results in the pulp tissue necrosis causing the non-vital or dead tooth.
Some conditions causing necrotic pulp include:
Traumatic injury
Extensive tooth decay
Rapid orthodontic tooth movement
Periodontal disease
Non vital tooth