To Evaluate and Compare the Effect of Orthograde and Retrograde MTA Root End Filling After Periapical Surgery in Posteriors

Inclusion Criteria: * Patients in which non-surgical retreatment is unfeasible (anatomical complexity, iatrogenic errors) or previously failed treatment in cases of persistent symptomatic apical periodontitis involving posteriors. * Tooth with a peri-radicular lesion of endodontic origin (chronic apical periodontitis) or endo-perio origin with the size of lesion ≥5mm. * Teeth with less than 10 degree root curvature. * Patients between 18-55 years of age. * No general medical contraindications for oral surgical procedures (ASA-1 according to the classification of the American Society of Anesthesiologists) * Tooth with adequate final restoration without clinical evidence of coronal leakage. * Good periodontal health condition at tooth level. * Able to completely understand and sign an informed consent form. Exclusion Criteria: * • Patients with systemic diseases (diabetes mellitus, uncontrolled hypertension grade III, hepatic/renal disease, or systemic bleeding disorders) (Bharathi et al 2021). * Patients on anticoagulant/ antiplatelet drugs. * Fractured/perforated teeth. * Presence of vertical root fracture. * Pregnancy.