Thirty patients with necrotic immature permanent teeth showing periapical lesions will be randomly divided in two groups: group (1) single visit regeneration and group (2) multiple visits regeneration protocol, in which calcium hydroxide will be applied for one week or more according to resolution of signs and symptoms. Dentin debris collected on a file will be taken as microbiologic sample to be cultured and examined by MALDI-TOF MS. This will be performed after the access cavity preparation and after irrigation in both groups, these samples will be labelled A and B, respectively. In group (2) there will be a third sample labeled C which will be taken after the removal of the intra canal calcium hydroxide.
Aim of the study is to assess canal disinfection using matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) in single visit and multiple visit regeneration protocols, and to assess clinical and radiographic outcomes of single visit and multiple visit regeneration protocols.