Outcome of Endodontic Retreatment in One or Two Visits

Inclusion Criteria: * Patients that demonstrate understanding of the study and willingness to participate as evidenced by signing the voluntary informed consent and received a signed and dated copy of the informed consent form. * Understands and is willing to comply with all study procedures and restrictions. * Not presence of clinically significant and relevant abnormalities of clinical history or oral examination. * Retreatment cases due to an endodontic failure. * Diagnosis of apical periodontitis. * Single or bi-radicular teeth. Exclusion Criteria: * General: Patients with systemic diseases, diabetes, immunocompromised and pregnant women, or any clinically significant or relevant oral abnormalities. * Specific: root resorption, root fractures, impossibility of restoration and cases were secondary root canal treatment is not the treatment of choice.