The present study was conducted to test whether pulp-like tissue can be regenerated in mature teeth with closed apex? And whether the size of the apical diameter affects the success of REPs? And whether Magnetic resonance imaging (MRI) can be used to quantitatively assess the vitality of the regenerated pulp-like tissue.

Regenerative endodontic procedures via blood clot were done on 18 mature anterior necrotic teeth with periapical lesions. The teeth were randomly assigned into two groups according to the size of the apical diameter of the rotary files used for instrumentation.

In the test group, rotary instrumentation was done using Pro-taper Next till size X3, while in the control group, instrumentation was done till size X5.

Calcium hydroxide was used as an intracanal medication for 1-2 weeks. Calcium hydroxide was then washed away using 1.5%NaOCl, followed by induction of blood using pre-curved K-fi;e #25 2mm past the radiographic apex. Biodentine was then used as a cervical plug over the blood clot followed by resin-modified glass ionomer cement and composite resin as coronal restoration.

MRI was used to assess the vitality of the regenerated pulp-like tissue, where the signal intensity of the regenerated pulp-like tissue was measured after 3,6 and 12 months follow up and compared to the normal contralateral teeth. In addition, sensibility tests using cold test and electric pulp testing were used to assess vitality of regenerated pulp-like tissue after 3,6,9 and 12 months. Cone beam computed tomography (CBCT) was also used to assess the healing of the periapical lesion after 12 months.

Inclusion Criteria

• Upper anterior mature teeth with single canals.
• Necrotic teeth
• Presence of periapical lesion.

Exclusion Criteria:

• Presence of systemic diseases.
• Presence of stainless steel wires o brackets
• Vital immature teeth with open apex