all patients will be informed about the study through informed constant that will describe the natural of the study beside the potential risks of it. After accurate diagnosis clinically and radiographically, patients who will meet the eligibility criteria will be randomized. The standardized operating procedure of regenerative therapy requires two treatment visits. During the first appointment, infection is controlled and inflammation is relieved. Regenerative procedure and revascularization are accomplished during the second appointment. At the first visit, perioperative CBCT will be taken, access cavity with full mechanical preparation will be accomplished followed by application of double biotics paste for 3 weeks.~At the second appointment the intra-canal medicaments will be removed then 10 ml of blood of whole venous blood will be drawn from the patient's forearm and transferred into two plain plastic test tubes without an anticoagulant and will centrifuge immediately u at 700 rpm for 3 minutes then liquid platelet rich fibrin layer will be taken with plastic syringe and according to the group of the patient that will be assigned, the patient will receive either the iprf alone or to be mix with Vitamin C and injected inside the canal. Collagen membrane will be placed over the iprf or iprf with Vitamin C then the tooth will be restored with resin filling material, the patients will be followed every 3 months for 1 year, at every follow up periapical radiograph will be taken with standardized bite block and after 1 year CBCT will aslo be taken with same parameter of the perioperative one t be compared and asses the reduction of the periapical lesions
The purpose of the study is to investigate the effect of injectable platelet rich fibrin augmented with Vitamin C (ascorbic acid) in healing of chronic peri-apical lesion, by assessing it radiographically 2dimensionally and 3 dimensionally