This study aims to assess the hypothesis that revitalization of teeth without (a)symptomatic apical periodontitis have a more favourable outcome in terms of further root development, periapical bone healing, maintaining/regaining pulp sensitivity and survival, than teeth with (a)symptomatic apical periodontitis.

1. Trial objectives

   This study aims to investigate the effectiveness of revitalization procedures, in terms of maintaining or restoring periapical health, further root development and regaining of pulp sensitivity, in immature permanent teeth with (group 1) or without (group 2) (a)symptomatic apical periodontitis .

2. Primary endpoints RRA at 1 year post revitalization. 3 Secondary endpoints Maintained or restored periapical health (evaluated within each group separately due to expected baseline inequivalency between groups) 1 year post revitalization.

4 Other endpoints

• RRA 2 and 3 years post revitalization

• Maintained or restored periapical health 2 and 3 years post revitalization (evaluated within each group separately)

• Pulp sensitivity 1-3 years post revitalization (evaluated within each group separately due to expected baseline inequivalency between groups)

• Tooth survival 3 years post revitalization (even if no further root development and incomplete periapical bone healing with no clinical symptoms).

  5 Trial Design Open, prospective cohort, multicenter Blinded: radiographic assessment and statistical analysis; operators and patients cannot be blinded, due to practically not feasible.

Inclusion Criteria:

• Provision of Informed Consent
• Female and male patients
• Age range: 6-18 years
• "Healthy": ASA I and II
• Permanent immature tooth (Cvek stage of root maturation ≤ 2) requiring revitalization
• Etiological factor: (a)symptomatic apical periodontitis post dental trauma or irreversible pulpitis post dental trauma

Exclusion Criteria:

• Unlikely to be able to comply with the study procedures, as judged by the investigator
• Patients older than 18 years and younger than 6
• Deciduous teeth
• Cvek root maturation stage > 2: permanent immature tooth that can be treated by conventional root canal treatment or apexification
• Known or suspected current malignancy
• History of chemotherapy within 5 years prior to study
• History of radiation in the head and neck region
• History of other metabolic bone diseases
• Bleeding disorders
• Involvement in the planning and conduct of the study

Healthy patients (ASA I and II), younger than 18 years, presenting an immature permanent tooth in need of treatment, etiological factor: (a)symptomatic apical periodontitis or irreversible pulpitis post dental trauma, no other endodontic treatment option than revitalization possible.