The purpose of the study is to evaluate peri-radicular healing after root-end surgery using Leukocyte and Platelet Rich Fibrin. The study population includes patients diagnosed with persistent periapical pathology and scheduled for Endodontic Microsurgery at the University of Pennsylvania School of Dental Medicine, Department of Endodontics. Patients undergoing routine endodontic microsurgery and who meet the inclusion criteria will be given the opportunity to opt in to receive L-PRF in the osteotomy site to promote bone formation. Healing will be assessed radiographically and clinically at six, twelve, eighteen, and twenty-four months.

Inclusion Criteria:

1. Provision of signed and dated informed consent form.
2. Stated willingness to comply with all study procedures and availability for the duration of the study, including the follow-up visits.
3. Male or Female age >18 years old.
4. In good general health (ASA 2 or less) with no contraindications for Endodontic Microsurgery.
5. Persistent endodontic periapical pathology Class A, B, or C according to the Kim and Kratchman classification (5)
6. Intact coronal restorations with no evidence of leakage or caries under the restoration.

Exclusion Criteria:

1. Minors.
2. Suspected root fractures.
3. ASA classification 3 or greater.
4. Periapical pathology Class D, E, or F according to the Kim and Kratchman classification (5).
5. Patients with history of Oral or IV Bisphosphonate use.
6. Patients may be excluded if their treatment team do not believe Endodontic microsurgery and L-PRF graft is in the patient's best interests.

Dental Clinic population.