Combined endodontic-surgical management of a palato-gingival groove in a maxillary lateral incisor with two canals

Case report

An 18 year-old male patient reported with a chief complaint of discharging pus and dull pain from the upper anterior tooth region for one month's duration. The patient had a history of dental trauma three years previously and the medical history was non-contributory. There was no discoloration, caries or any sign of mobility observed in the maxillary incisors. However, the maxillary right central and lateral incisors (UR1 and UR2) were slightly tender to vertical percussion. A sinus opening was seen in the labial vestibule in relation to UR1 (Figure 1). Periodontal probing revealed a pocket depth of 6 mm on the palatal aspect of the UR2. Pulp sensibility testing (cold and electric) gave a negative response in relation to UR2 and UR1. A periapical radiograph revealed circumscribed periapical radiolucency in relation to UR2. Gutta percha tracing into the sinus tract revealed a communication with the periapical area of UR1. An unusual parapulpal line was also noted on tooth UR2 (Figure 2). Considering the unusual canal morphology, a small field of view (FOV) cone beam CT (CBCT) (Kodak 9000 C, 70 KV, 8 mA, 10.8 s) of the anterior maxillary region was taken. The scan in relation to UR2 revealed a C-shaped canal configuration in the coronal and middle third of the root (Figures 3a, b), and in the apical third the canal divided into two with separate exits (Figure 3c). The axial view sections at the coronal and middle third of the root also revealed a mid-palatal radiolucent line, correlating with PGG.

A combined surgical/non-surgical approach was planned in relation to UR2 based on the clinical attachment loss and the extent of PGG, anticipating a good prognosis. The treatment plan was explained to the patient and informed consent obtained. Initially, non-surgical root canal treatment was performed on UR1. With regard to UR2, in phase one, therapy oral prophylaxis and root planing was carried out. Endodontic therapy was initiated under rubber dam isolation. During working length determination of UR2 it was seen that, in addition to the main canal, there was an accessory canal with a lateral apical opening (Figure 4). The canals were cleaned and shaped using step back technique with stainless steel hand files till ISO 60 K-file. The canals were dried and calcium hydroxide intra canal medicament was placed (UltraCal XS, Ultradent Products, Inc, South Jordan, UT). After 10 days, the canals were obturated using cold lateral condensation technique with gutta percha and AH plus sealer (Figure 5).

Considering the loss of attachment at the palatal aspect and the extent of the PGG, it was decided to access the groove surgically. A full thickness mucoperiosteal flap was raised from the palatal aspect. Granulation tissue was removed from the bony defect and the PGG was isolated to its most apical extent (Figure 6). At this point, it was noted that granulation tissue was extending beyond the apex, which correlated with the labial radiolucency at the apical third on the axial CBCT image. This indicated the need for an apical root resection. A Luebke-Ochsenbein flap was raised from the labial aspect; the apical root end was resected and sealed with MTA (Figure 7). Scaling and root planing was performed over the groove and the defect was packed with MTA. Platelet-rich fibrin (PRF) was prepared by withdrawing 5 ml of whole blood from the patient's left antecubital vein and centrifuged (REMI Model R-8c with 12 x 15 ml swing out head) at 3,000 rpm for 10 min to obtain the PRF clot, which was compressed to obtain PRF membrane. The bony defect on the labial aspect was filled with a bioactive synthetic bone graft material (Perioglass, NovaBone Products, LLC). Immediately following this, the autologous PRF membrane was placed covering the graft material and also the sealed PGG (Figure 8). The flap was repositioned and sutured with 4-0 polyglactin 910 sutures (Vicryl, Ethicon Inc, NJ). Postoperative instructions were given and the patient was recalled for regular follow-up. Healing was uneventful and the complete resolution of the sinus tract was observed at 1 month recall. A 3 mm non-bleeding sulcus was present at the site of the palatal groove. A periapical radiograph taken at the 12 months follow-up demonstrated bone filling of the osseous defect (Figure 9).

Discussion

The contribution of PGGs to the development of localized periodontitis is based on the fact that they can form stagnant areas sheltered from host defence and hygiene measures giving rise to plaque build-up and microbial pathogenesis. Pulpal invasion of bacteria and by-products are channelled via an accessory foramen, as well as lateral canals along the side walls and floor of the groove beside the exposed dentinal tubules situated on the groove inclines.⁸ This combined endo-perio challenge can elicit a periradicular inflammatory response, destroying the periodontal attachment apparatus, resulting in a poor prognosis. Hence a combined endo-perio management is pivotal for the success of these cases.

One of the main differential diagnoses in this case was vertical root fracture, especially considering the history of trauma and the often similar radiographic signs of PGG and vertical root fracture. An isolated, narrow, deep periodontal pocket, as was present in this case, may be associated with vertical root fracture.⁹ A para-pulpal radiolucent line may also be seen on an angulated radiograph of a vertically fractured tooth, and the presence of J-shaped (apico-crestal) radiolucency is considered pathognomonic.^9,10 However, the CBCT images revealed the palatal invagination and the resultant C-shaped root canal morphology, which were critical in confirming the diagnosis of PGG. Thus, based on the clinical and the radiographic examination, the definitive diagnosis was necrotic pulp with chronic apical abscess in relation to UR2 and UR1, along with localized periodontitis secondary to the PGG on tooth UR2.

The treatment plan in this case was to eliminate the PGG and to regenerate the attachment apparatus using a combination of PRF and bone graft. The palatal groove was isolated to its most apical extent and filled with MTA. Although various materials are recommended to be used to eliminate the groove, including flowable composite, glass ionomer cement and biodentine, MTA was preferred in this case because of its excellent sealing ability, biocompatibility and favourable osseous and cemental deposition.¹¹ The physicochemical basis for the biological properties of MTA has been attributed to the production of hydroxyapatite when the calcium ions released by the MTA comes into contact with tissue fluid.¹²

Choukroun's PRF (platelet-rich fibrin) is prepared by immediate centrifugation of collected blood without any anticoagulant, which renders initiation and propagation of a natural coagulation cascade, resulting in the formation of three layers: upper straw-coloured acellular plasma, red-coloured lower portion containing red blood cells (RBCs) and the middle portion containing a fibrin clot.¹³ PRF is purely autologous and allows for the easy collection of a leukocyte and platelet-rich fibrin (L-PRF) clot, without the need for any biochemical modification of the blood. This is the most simple and also the least expensive protocol developed so far. Characteristically, PRF is a dense fibrin scaffold, with a high number of leukocytes concentrated in one part of the clot, with a specific slow release of growth factors (GFs) (such as transforming growth factor type beta 1 (TGF-β1), platelet-derived growth factor (PDGF), vascular endothelium growth factor (VEGF)) and glycoproteins (such as thrombospondin-1) released over at least 7 days.¹⁴ The main role of PRF in this case was to contain the graft in the bony defect, prevent epithelial migration and to stimulate healing and new bone formation.¹⁵ The osteoconductive nature of biphasic hydroxyapatite-beta tricalcium phosphate bone graft and its ability to act as a mechanical substructure to support the membrane and overlying soft tissues is harnessed by employing this to fill the osseous defect.¹⁶ This combined regenerative procedure using bone graft and PRF membrane was selected because of the size of the osseous defect and the fact that the involvement of the periapical lesion and PGG compromised both facial and lingual cortical plates.

Multiple reasons can be attributed to pulp necrosis in the maxillary right lateral incisor in this case. The most probable aetiology is previous trauma to the maxillary anterior region, resulting in pulp necrosis, as was evident from the concomitant necrotic involvement of the adjacent central incisor. The communication between the deep infected PGG and the pulp could have provided the bacterial conduit and subsequent pulpal infection in UR2. Radiographically, a parapulpal radiolucent line often denotes PGG. At times the line may not exactly follow the root canal outline.³ The invagination of the groove to involve the radicular pulp often results in a C-shaped canal configuration or forms two separate canals.¹⁷ In the case presented, the palatal groove was deep and extended beyond the middle-third of the root, which was confirmed with the aid of axial CBCT sections. Compared with the conventional radiographs, the axial CBCT sections at the coronal, middle and apical third of the root were helpful in analysing the extent of the PGG and also to study the morphology of the root canal system precisely.

Besides the various factors determining the long-term prognosis of the condition, the major determinant is the depth of apical extension of the groove; with shallow ones, which are much amenable to elimination, providing better outcomes compared to deeper ones, which can terminate in complex endo-perio pathosis.¹⁶ The success rate of 27% to 37% has been reported in the surgical management of endo-perio lesions without any regenerative procedure.¹⁸ However, a combined approach involving the application of PRF along with bone graft has been shown to produce faster bone formation in animal models.¹⁹ Accelerated bone formation with predictable healing was obtained in this particular case. However a conclusive long-term outcome study using regenerative procedures with PRF is still missing from the endodontic literature.

Conclusion

A palato-gingival groove may be suspected if a deep periodontal pocket is present on the palatal aspect of the maxillary anterior tooth (especially lateral incisor) along with a parapulpal radiolucent line on the radiograph. Cone beam CT is an excellent tool in identifying anatomical variations like PGG, and in confirming the extent and complexity of the groove. A combined endo-perio approach is often indicated in complex cases of PGG. An autologous platelet-rich fibrin (PRF) is a simple and cost-effective healing aid and helps in the regeneration of the attachment apparatus.