What type of nonavulsive tooth displacement has the worst prognosis?

Intrusion represents a type of nonavulsive tooth displacement where the tooth is driven into the alveolar bone. This can lead to a severe prognosis for several reasons. First, the apical blood supply may be compromised as the tooth is dislodged and pushed into the socket, reducing the chance for pulp vitality. The damage to the periodontal ligament can be extensive, making it difficult for the tooth to re-establish proper support and function. Additionally, the potential for nerve damage increases in cases of intrusion, further complicating the situation. The healing process may lead to complications such as pulp necrosis, ankylosis, or even tooth loss.

In contrast, other types of nonavulsive tooth displacements, such as extrusion, subluxation, and lateral luxation, generally maintain a better blood supply and periodontal support, allowing for improved healing and prognosis. These conditions typically allow for the possibility of re-establishment of the tooth's vitality, leading to a more favorable outcome compared to intrusion.