Which factor is NOT necessary for successful healing of a retained root tip?

For successful healing of a retained root tip, the presence of dental infection is not necessary; in fact, an infection can hinder the healing process. Successful healing typically requires the pulp vitality of the fractured tip, as healthy pulp tissue promotes healing and regeneration. Additionally, minimizing the movement of the fractured root is important, because excessive mobility can disrupt the healing process and impede recovery. Complete wound closure is also a critical factor since it helps prevent secondary infection and allows for proper healing. Therefore, the absence of dental infection is advantageous for healing, making the presence of infection an unnecessary factor.