periradicular ( pr ) surgery is an inevitable option after an unsuccessful conventional endodontic treatment when orthograde retreatment of root canals is not possible . pr surgery is indicated in cases where there is infection persisting on the apical areas of the tooth , radicular cyst , and foreign body reactions . pr surgery involves the surgical debridement of periapical lesion , root end resection , root end cavity preparation to receive a filling material . the practice of conventional pr surgery after surgical debridement of a large cystic lesion often resulted in healing by scar tissue formation . this can be achieved with the application of guided tissue regeneration ( gtr ) technique . gtr works on the concept of cell occlusion , by restriction of rapidly proliferating epithelial and gingival cells . this promotes the re - population of the surgical defect with periodontal ligament cells , which assists in the regeneration of tooth supporting tissues . the principle of gtr can be successfully used , as an adjunctive technique in pr surgery . a 42-year - old male referred to the faculty of periodontics , tatyasaheb kore dental college and research centre in june 2011 . the patient presented with chronic history of gingival swelling in relation to maxillary right central incisor . the swelling subsided intermittently on intake of antibiotics and nonsteroidal anti - inflammatory drugs . on clinical examination , 11 appeared to be discolored , having undergone endodontic treatment , 5 years ago [ figure 1 ] . the patient revealed a history of trauma to the maxillary anterior teeth , 5 years back . occlusal radiograph revealed a large periapical radiolucency with relation to 21 , 11 and 12 [ figure 2 ] . considering the large size of the lesion and evaluating the prognosis , an interdisciplinary approach consisting of endodontic surgery with periodontal regenerative procedure was decided . occlusal radiograph showing extent of periapical lesion after securing local anesthesia in the maxillary anterior region , a sulcular incision was made extending from maxillary right premolar to left premolar , with two vertical incisions . this was further enlarged to gain complete access to the cystic lesion , which was eventually debrided . a large periapical defect ( 30 mm  20 mm ) with relation to the apices of 12 , 11 , apicoectomy and the root end preparations of 12 , 11 , 21 were performed , under magnification . the resultant cystic bony defect was decorticated at multiple sites with a sharp curette to stimulate bleeding . a collagen membrane was approximated to cover the large opening of the pr osseous defect . membrane fixation kit ( intakt ) was utilized to stabilize and secure the membrane in the desired place [ figure 4 ] . the flap was repositioned and sutured with 5 - 0 resorbable suture material [ figure 6 ] . the patient was prescribed amoxicillin 500 mg and diclofenac 50 mg thrice daily for 5 days . an intramuscular injection of dexamethasone 8 mg was also administered to control the postoperative edema . the patient was advised to refrain from mechanical plaque control measures for 2 weeks and prescribed 0.2% chlorhexidine digluconate mouthwash , as an aid for chemical plaque control . a histopathologic study of the cystic capsule was performed to confirm the provisional diagnosis of the periapical cyst . a complete resolution of the surgical defect was noticed , with the complete replacement of the lost labial cortical plate [ figures 7 and 8 ] . a 24 months postoperative occlusal radiograph prior to the removal of tacks revealed complete fill of the pr defect as indicated by increase in radiodensity [ figure 9 ] . per - radicular defect with apicoectomy membrane fixation kit with titanium minipins collagen membrane fixated with titanium minipins surgical re - entry 24 months postoperative surgical re - entry 24 months postoperative ( minipins removed ) occlusal radiograph 24 months postoperative periapical pathology may persist in spite of an immaculate endodontic treatment . in such cases , conventional endodontic treatment demonstrated a high - risk of failure , particularly in cases of large periapical lesions . gtr technique successfully used in clinical periodontal practice may be applied as an adjunctive therapy in endodontic surgery . the described case report presents with a large pr lesion from endodontic origin , with no periodontal communication . in order to gain surgical access to the large cystic lesion , to facilitate its complete elimination , a loss of buccal cortical plate ensued this pr lesion can be included in class i as per von arx classification of membrane application in endodontic surgery . the healing of pr defects with concomitant loss of buccal cortical plate is compromised , involving poor regeneration of periapical tissues . the rationale of bone decortication though controversial , seems to cause some beneficial effects such as stimulation of a  regional acceleratory phenomenon  and advance the process of angiogenesis accompanied by the recruitment of pluripotential cells in the defect site . the blood clot thus formed may provide a hoard of cytokines and growth factors , accelerating the healing process . a mere curettage of the defect site could have prompted fibrous tissue growth into the defect site . a barrier membrane was utilized to ward off epithelial cells and fibroblasts , facilitating repopulation of periodontal ligament cells . application of titanium minipins prevented the mobility and collapse of the membrane , thus facilitating space maintenance . the minipins thus facilitated to achieve a secured seal allowing a crease - free transition to periosteum . several authors have reported the successful resolution of periapical defects with a combined application of gtr and bone grafts or with gtr alone . the present case report describes a successful resolution of a large pr lesion of endodontic origin , accompanied with loss of labial cortical plate . this is particularly important since keratocyst may have chances of recurrence . in the present case , postoperatively 2 years radiographic examination of the defect site revealed augmented radiodensity . a surgical re - entry demonstrated complete re - establishment of the labial cortical plate . the outcome success may be attributed to the following factors : 
 complete debridement of the pr defectdecortication of the bony defect at multiple sitesfixation of the gtr membrane with titanium minipinsprimary wound closure . complete debridement of the pr defect decortication of the bony defect at multiple sites fixation of the gtr membrane with titanium minipins primary wound closure . pass involves primary closure of surgical site ( p ) , angiogenesis by providing adequate blood supply and the cell type necessary for regeneration ( a ) , space creation and maintenance ( s ) and finally stability of the blood clot ( s ) . however , the present case fails to confirm the histology of formed tissue . a histological study ( not carried out in this case ) of the tissue formed after re - entry may have revealed the histology of tissues formed . . it may be difficult to engage the titanium tacks on the surface of tough cortical bone . it can be concluded that efficacy of gtr procedures can be substantially improved by stabilization and fixation of membrane . a successful resolution of a large pr lesion , unresponsive to conventional endodontic therapy can be obtained with application of gtr . gtr accompanied by the accessory procedures may significantly improve the prognosis of teeth with pr lesion .
periradicular ( pr ) bone defects are common sequelae of chronic endodontic lesions . sometimes , conventional root canal therapy is not adequate for complete resolution of the lesion . 
 pr surgeries may be warranted in such selected cases . 
 pr surgery provides a ready access for the removal of pathologic tissue from the periapical region , assisting in healing . 
 recently , the regeneration of the destroyed pr tissues has gained more attention rather than repair . in order to promote regeneration after apical surgery 
 , the principle of guided tissue regeneration ( gtr ) has proved to be useful . 
 this case presents the management of a large pr lesion in a 42-year - old male subject . 
 the pr lesion associated with 21 , 11 and 12 was treated using gtr membrane , fixated with titanium minipins . 
 the case was followed up for 2 years radiographically , and a surgical re - entry confirmed the re - establishment of the lost labial plate . 
 thus , the principle of gtr may immensely improve the clinical outcome and prognosis of an endodontically involved tooth with a large pr defect .