number of diseases comes under the category of  silent killers  as they gradually consume one without causing any serious symptoms in the early stages . it is defined as  a localized resorptive process that commences on the surface of the root below the epithelial attachment and the coronal aspect of the supporting alveolar process , namely the zone of the connective tissue attachment  . there is a homeostatic balance of pulp and periodontal ligament preventing clastic insults , which is due to an intact cementoblast and odontoblast cell layer . any breach in these layers may down - regulate osteoprotegrin and up - regulate receptor activator of nuclear factor ligand causing resorption . the severance of the protective layer may be commonly due to orthodontic treatment , dental trauma , or bleaching . a study has also revealed that an interleukin-1  polymorphism significantly increases the risk external resorption . heithersay classified icr into four classes according to the extent and severity of the lesion within the tooth . class 1 - 3 has a better prognosis , while class 4 is not amenable for treatment and might require extraction and replacement with implant retained crown restoration . the lesion classically presents as an asymmetrical radiolucency with ragged or irregular margins in the cervical region of the tooth . early lesions might be radiolucent ; however , more advanced lesions might have a mottled appearance caused by the osseous nature of the advanced lesions . unless proper treatment is initiated , the resorption continues unabated leading to irreversible destruction of tooth structure . early diagnosis , elimination of the resorption and restorative management are the keys to a successful outcome . this article discusses an icr managed by endodontic treatment , surgical management of resorptive defect by reverse sandwich technique and periodontal regeneration using platelet rich fibrin ( prf ) , prf membrane and bone graft . a 35-year - old non - smoking male patient presented for consultation at the endodontic department with a chief complaint of swelling and pus discharge in the upper left canine [ figures 1a and 2a ] . after performing sensitivity tests , tooth # 11 was diagnosed as having pulpal necrosis . clinical examination revealed localized gingival recession and gingival enlargement in relation to tooth # 11 . probing pocket depth on the mesial surface of the tooth # 11 was 10 mm with a high bleeding score . based on the clinical and radiological finding , we came to the diagnosis of localized chronic periodontitis and pulpal necrosis with external inflammatory root resorption . the treatment plan was informed to the patient , which included patient motivation , oral hygiene reinforcement , scaling and root planning , endodontic procedure and lastly surgical intervention . patient and his parents were informed of possible discomforts and potential risks concerning the planned treatment procedure and prognosis . ( a ) pre - operative clinical photograph showing swelling and pus discharge in the upper left canine . ( b ) surgical exploration revealed that two lesions were present on the mesial surface of upper left canine and there was no palatal intercommunication . ( c ) the resorptive defects were restored with microfilled composite to a thickness of about 1 mm and light cured for 20 s. the rest of the defects were restored with resin modified glass ionomer cement . ( d ) the bony defect was filled with freeze - dried bone allograft and platelet rich fibrin . ( f ) follow - up after 2 years shows normal probing depth , no gingival recession , and no loss of clinical attachment loss ( a ) pre - operative intraoral periapical showing bone loss in the mesial aspect of upper left canine with two resorptive regions . ( d ) at 2 years follow - up showing significant bone fill in phase one therapy oral prophylaxis was performed . endodontic access cavity was prepared after placing a rubber dam and disinfecting the area with 2% of chlorhexidine digluconate ( calypso , septodont , india ) . working length was determined by using the electronic apex locator root zx ( j. morita mfg . corporation , kyoto , japan ) and file in - radiograph with 15 number k - files . the root canal was cleaned and shaped by rotary ni - ti protaper system along with glyde ( dentsply maillefer company , usa ) using the crown down technique . the root canal was copiously irrigated with 2.5% sodium hypochlorite ( novo dental product , india ) . access cavity was temporized with calcium hydroxide and temporary endodontic restorative material ( term ) . root canal was irrigated again with normal saline and dried using paper points . before obturation , master points were seated to test their suitability to canals and radiograph was taken . the canals were obturated with selected master gutta - percha cone ( variable taper ) and ah - plus sealer ( dentsply maillefer company , usa ) . the coronal gutta - percha cones were sheared off using heated instrument and vertical compaction was done using the heated pluggers at the canal orifices . the access cavity was restored with a composite ( clearfil majesty ; kuraray , osaka , japan ) . the surgical procedure was performed under local infiltration anesthesia ( 2% of lidocaine with 1:100,000 adrenaline ) on vestibular mucosa . an intrasulcular incision was made from the distal surface of the maxillary left central incisor to the distal surface of the maxillary left canine and full - thickness mucoperiosteal flap was elevated . surgical exploration revealed that two lesions were present on the mesial surface of upper left canine and there was no palatal intercommunication [ figure 1b ] . granulomatous tissue within the defect area was removed and 90% of trichloroacetic acid was applied to the resorptive defect for coagulation necrosis . the resorptive defects were restored with microfilled composite ( durafill vs ; heraeus kulzer gmbh , dormagen , germany ) to a thickness of about 1 mm and light cured for 20 s. the rest of the defects were restored with resin modified glass ionomer cement ( rmgic ) ( fuji ii lc ; gc corporation , tokyo , japan ) to a smooth finish with a cervical matrix and light cured for 20 s [ figure 1c ] . a test dose of 12 ml sample of whole blood was drawn intravenously from the patient 's right antecubital vein and centrifuged ( remi model r-8c with 12 ml  15 ml swing out head ) under 3000 rpm for 10 min to obtain the prf , which was jelly like in consistency . prf clot started to release its serum ( prf - clot exudates ) and was ready for compression into the membrane . the bony defect was filled with freeze - dried bone allograft ( lifenet , virginia beach , va ) and prf [ figure 1d ] . without delay autologous prf membrane was placed [ figure 1e ] and the flaps were secured with 4 - 0 polyglactin 910 sutures ( vicryl , ethicon , inc . , piscataway , nj ) . after the surgery , the patient was prescribed amoxicillin 1 g twice a day for 1 week and 0.2% of chlorhexidine mouthwash 15 ml twice a day for 2 weeks . the desired gingival contour was achieved ; the patient was asymptomatic 1 week after the surgery and the sutures were removed . patient was followed - up for 6 months , [ figure 2b ] 1 year [ figure 2c ] and 2 year . at 2-year follow - up period , periodontal status of related tooth demonstrated mild mobility with normal probing depth , no gingival recession and no loss of clinical attachment [ figures 1f and 2d ] . endodontic access cavity was prepared after placing a rubber dam and disinfecting the area with 2% of chlorhexidine digluconate ( calypso , septodont , india ) . working length was determined by using the electronic apex locator root zx ( j. morita mfg . corporation , kyoto , japan ) and file in - radiograph with 15 number k - files . the root canal was cleaned and shaped by rotary ni - ti protaper system along with glyde ( dentsply maillefer company , usa ) using the crown down technique . the root canal was copiously irrigated with 2.5% sodium hypochlorite ( novo dental product , india ) . access cavity was temporized with calcium hydroxide and temporary endodontic restorative material ( term ) . root canal was irrigated again with normal saline and dried using paper points . before obturation , master points were seated to test their suitability to canals and radiograph was taken . the canals were obturated with selected master gutta - percha cone ( variable taper ) and ah - plus sealer ( dentsply maillefer company , usa ) . the coronal gutta - percha cones were sheared off using heated instrument and vertical compaction was done using the heated pluggers at the canal orifices . the access cavity was restored with a composite ( clearfil majesty ; kuraray , osaka , japan ) . the surgical procedure was performed under local infiltration anesthesia ( 2% of lidocaine with 1:100,000 adrenaline ) on vestibular mucosa . an intrasulcular incision was made from the distal surface of the maxillary left central incisor to the distal surface of the maxillary left canine and full - thickness mucoperiosteal flap was elevated . surgical exploration revealed that two lesions were present on the mesial surface of upper left canine and there was no palatal intercommunication [ figure 1b ] . granulomatous tissue within the defect area was removed and 90% of trichloroacetic acid was applied to the resorptive defect for coagulation necrosis . the resorptive defects were restored with microfilled composite ( durafill vs ; heraeus kulzer gmbh , dormagen , germany ) to a thickness of about 1 mm and light cured for 20 s. the rest of the defects were restored with resin modified glass ionomer cement ( rmgic ) ( fuji ii lc ; gc corporation , tokyo , japan ) to a smooth finish with a cervical matrix and light cured for 20 s [ figure 1c ] . a test dose of 12 ml sample of whole blood was drawn intravenously from the patient 's right antecubital vein and centrifuged ( remi model r-8c with 12 ml  15 ml swing out head ) under 3000 rpm for 10 min to obtain the prf , which was jelly like in consistency . prf clot started to release its serum ( prf - clot exudates ) and was ready for compression into the membrane . the bony defect was filled with freeze - dried bone allograft ( lifenet , virginia beach , va ) and prf [ figure 1d ] . without delay autologous prf membrane was placed [ figure 1e ] and the flaps were secured with 4 - 0 polyglactin 910 sutures ( vicryl , ethicon , inc . , after the surgery , the patient was prescribed amoxicillin 1 g twice a day for 1 week and 0.2% of chlorhexidine mouthwash 15 ml twice a day for 2 weeks . the desired gingival contour was achieved ; the patient was asymptomatic 1 week after the surgery and the sutures were removed . patient was followed - up for 6 months , [ figure 2b ] 1 year [ figure 2c ] and 2 year . at 2-year follow - up period , periodontal status of related tooth demonstrated mild mobility with normal probing depth , no gingival recession and no loss of clinical attachment [ figures 1f and 2d ] . treatment depends on the severity , location , whether the defect has perforated the root canal system and the restorability of the tooth . as smaller lesions offer the most favorable long - term outcome , endodontic treatment followed by surgical treatment the true nature of the defect could be assessed only after surgical exploration . to treat the icr lesions , it is usually necessary , to curette away the granulomatous tissue from the adjacent periodontium to sever the blood supply to the resorbing cells and fills the defect with an inert filling material . periodontal regeneration is the next aim , which includes reconstruction of lost or injured tissue so that the form and function of the lost structures are restored . the removal of granulomatous tissue the surgical defect was filled by the reverse sandwich technique microfilled composite as a liner followed by lamination with rmgic . microfilled resin was used because they tend to flex with the tooth rather than debond and rmgic was biocompatible to periodontal tissues . the development of subgingival plaque over rmgic is prevented by achieving a smooth finish using the cervical matrix . the regenerative process is a complex biologic process in itself , requiring intricately regulated interaction between cells , signaling molecules ( local and systemic ) and extra cellular matrices in which these entities interact . prf is a scaffold that not only acts as carriers for growth factors and proteins , but also allow cellular infiltration and subsequent integration of the newly formed tissue within the native one . it is biocompatible , non - cytotoxic and non - immunogenic to prevent adverse effects on recruited cells and neighboring tissue . this scaffold material along with growth factors and cells pave the way to accelerate bone and periodontal regeneration . prf can up - regulate phosphorylated extracellular signal - regulated protein kinase expression and suppress osteoclastogenesis by promoting the secretion of osteoprotegerin in osteoblasts cultures . prf membrane has a very significant slow sustained release of key growth factors for at least 1 week and up to 28 days , which means that the membrane stimulates its environment for a significant time during wound healing . hydroxyapetite ( ha ) was added to prf in our study , this was because it has been demonstrated that the treatment of intrabony defects with prf results in significant improvements of pocket depth , clinical attachment level and bone fill compared with baseline and secondly , that ha increases the clinical effects observed with prf in the treatment periapical defects . significant bone fill was obtained in our case after a 2-year follow - up period ; thanks to the synergistic combination of prf and ha .
invasive cervical resorption ( icr ) is a localized resorptive process that commences on the surface of the root below the epithelial attachment and the coronal aspect of the supporting alveolar process , namely the zone of the connective tissue attachment early diagnosis , elimination of the resorption and restorative management are the keys to a successful outcome . 
 treatment done was a combined non - surgical root canal therapy , surgical treatment to expose the resorptive defect and the resorptive defect was filled up with reverse sandwich technique and finally the bony defect filled with platelet rich fibrin ( prf ) , hydroxylapatite and prf membrane . 
 significant bone fill was obtained in our case after a 2 year follow - up period . 
 this case report presents a treatment strategy that might improve the healing outcomes for patients with icr .