The aim of this prospective, randomized, controlled double-blind study is to evaluate the effectiveness of biodentine compared with MTA used as pulp space barrier on discoloration of teeth after regenerative based non-obturation root canal treatment in mature single canal with pulp necrosis and apical periodontitis.

• Regenerative endodontic treatment will be performed through two visits: First visit aims to clean and disinfect the tooth canal by copious irrigation with NaOCL and EDTA solution . At the end of first visit, canal will be dressed by CaOH as intracanal medicaments.

Second visit will be after two weeks. After removal of CaOH dressing by copius irrigation, evoking bleeding inside canal by over instrumentation. When blood become semi-coagulated, according to the random sequence number of the participants, either biodentine or white MTA will be placed as pulp space barrier.

At the end of treatment, the access cavity will be sealed with composite restoration.

Inclusion Criteria:

1. Tooth type: single-rooted teeth (anterior or premolar) encasing of one root canal with mature root (closed apex).
2. Negative response of pulp tissue to electrical or thermal pulp tester.
3. Widening in lamina dura or periapical radiolucency not more than 3 mm.

Exclusion Criteria:

• 1. Patients having significant systemic disorder or immunocompromised patients. 2. Teeth with generalized chronic periodontitis or have periodontal pocket larger than 3 mm.

  3. Teeth with developmental anomalies (i.e, dens invaginatusor a palatogingival groove).

  4. Teeth with previous root canal. 5. Teeth need to post and core as final restoration

Participants/ outcome assessor will be blinded