Combined surgical and conservative endodontic management of Oehler’s type 3b dens invaginatus aided by guided tissue regeneration

Abstract

The present case describes the successful healing of a periapical lesion associated with the left maxillary lateral incisor (# 22, Federation Dentaire Internationale) having a type 3b dens invaginatus tooth morphology. The treatment was complicated by the presence of blunderbuss root apex and large periapical lesion (>10 mm) with through and through bone defect (Bucco palatal cortical bone perforation, Von Arx Type 1b). An adolescent boy reported palatal swelling and pus discharge in relation to tooth #22. A thorough clinical and radiographic examination revealed tooth #22 as having a type 3b dens invaginatus with an open apex and a diagnosis of pulp necrosis and acute apical abscess. The case was managed by non-surgical root canal treatment followed by endodontic surgery using principles of guided tissue regeneration. A 5-year recall revealed an asymptomatic functional tooth with complete healing.

Background

Dens invaginatus (DI) is a disorganised morphodifferentiation of the tooth due to the infolding of the enamel organ into the dental papilla before the calcification of the tooth is completed.¹ The incidence of DI ranges from 0.04% to 10%, with permanent maxillary lateral incisors being the most frequently affected teeth.²

Based on the origin of invagination, DI is broadly categorised as coronal and radicular DI. Oehlers³ classified coronal DI into three principal categories:

In type I, the enamel lined invagination is minimal and confined within the crown.

In type II, the invagination invades beyond the cementoenamel junction (CEJ) into the root as a cul de sac. There is no communication with the periodontal ligament; however, it may or may not show a connection with the pulp.

In type III, the invagination extends into the root and communicates with the periodontal ligament through either pseudoforamen on the lateral aspect of the root (type IIIa) or extends completely and exits through the apical foramen (type IIIb).

This congenital anomaly provides a conducive site for microbial infiltration within the tooth and predisposes the risk of endodontic infection at a young age. When planning the endodontic treatment for DI, it is crucial to accurately determine the vitality of the pulp. In cases where the pulp remains healthy and vital and the infection is limited to the invagination, the endodontic treatment can be focused solely on addressing the invagination. This is applicable when there are no intercommunications between the invagination and the pulp canal, and when the invagination possesses its separate apical or lateral foramens.^{4 5}

However, when the pulp is necrotic and there are intercommunications between the invagination and the pulp canal, it becomes necessary to address and treat both the invagination and the pulp canals. A decision must then be made on whether to treat them separately or combine their anatomies into a single root canal space through the removal of the invagination via troughing. In situations where conservative treatment proves ineffective or when non-surgical treatment is not feasible due to anatomical challenges or inability to access all areas of the root canal system, surgical intervention maybe needed.⁶

Establishing a standardised treatment protocol for type III dens invagination can be challenging due to the unique anatomical features presented in each case. Therefore, the success of treatment relies on patient-specific case-based planning. The current case was treated using a combination of non-surgical and surgical endodontic approaches, incorporating guided tissue regeneration principles. The purpose of employing a combined treatment approach was to achieve multiple objectives: preserving as much tooth structure as possible while addressing the invagination, improving disinfection of the root canal system and periapical area, and gaining access to the apex of the tooth for effective management of the blunderbuss immature root apex. This approach aimed to achieve long-term tooth retention while creating a favourable environment for periradicular healing.⁷ During the surgical intervention, the principles of guided tissue regeneration were used to enhance the predictability of regenerative healing and repair.

Healing after periapical surgery should ideally result in ‘osseous healing’ of the bony defect and regenerative healing of the dentoalveolar attachment apparatus. In large periapical bony defects and through and through cortical perforation defects (loss of labial and palatal cortical bone), the osteoprogenitor cells from the endosteum may not be sufficient to repopulate the coagulum and facilitate complete healing. Scar tissue healing has been reported in 26% of periapical lesions >10 mm and 60% of cases where the periapical defect involved both cortical plates (through and through bone defect (TTBD), Von Arx type 1b).⁸ The healing in these clinical scenarios may benefit from placing a barrier membrane over the osseous defect after the endodontic surgery. The objective of the guided tissue regeneration using a mechanical barrier is twofold: (1) optimise tissue healing by stabilising and protecting the wound, (2) prevent the faster proliferating epithelial and connective tissue from populating the osseous crypt and thereby favour the gradual and controlled regeneration of periodontal ligament and bone.^{9 10}

The barrier membrane can be categorised as bioabsorbable and non-resorbable. The first-generation non-resorbable barrier membrane made of expanded polytetrafluoroethylene requires a second surgery for its removal and has largely been replaced by newer generation bioabsorbable membranes. These absorbable membranes are composed of various materials, including collagen, polylactic and polyglycolic acid, acellular dermal matrix, chitosan and platelet-rich fibrin (PRF).^{11 12}

A graft material placed in the osseous crypt over which a mechanical barrier membrane is placed ensures a stable base and space maintenance beneath the membrane. Some studies have suggested that this maybe critical for regenerative healing. Several graft materials with varying characteristics are available, including autogenous bone, allografts (demineralised freeze dried human bone (DMFD)), xenografts and synthetic materials (CaSO4, bioactive glasses).¹²

The present case report describes the successful management of an adolescent boy with a large periapical through and through lesion associated with a maxillary lateral incisor with type 3b DI and blunderbuss root apex. The non-surgical root canal treatment (NSRCT) was combined with surgical endodontics and MTA (mineral trioxide aggregate) retrofilling. The prognostic uncertainty of complete healing in a large periapical lesion with through and through osseous defect (Bucco-palatal cortical bone perforation, Von Arx type 1b) was managed by applying the techniques and principles of guided tissue regeneration during endodontic surgery.

Case presentation

An adolescent boy reported to the Department of Conservative Dentistry and Endodontics with a chief problem of swelling and recurrent pus discharge on the left side of the palate for the past 6 months. The patient reported no significant medical history but recounted an episode of traumatic dental injury to his front teeth while playing in school 2 years back.

Clinical examination and diagnosis

On intraoral examination, the maxillary left lateral incisor (#22, Federation Dentaire Internationale) displayed increased mesiodistal and faciopalatal dimensions and a pronounced palatal cingulum (talon cusp)(figure 1). Tooth #22 was not associated with caries or fractures; however, a deepened pit was observed in relation to the talon cusp. A fluctuant paramedian palatal swelling (2×3 cm in size) was present, which extended from the upper left central incisor to the mesial aspect of the upper left first molar (figure 1).

Figure 1.

Preoperative view showing atypical faciopalatal dimensions and a pronounced palatal cingulum (talon cusp) irt tooth #21 and showing a fluctuant paramedian palatal swelling extending from the midline to the mesial aspect of the upper left first molar.

The baseline pocket probing depth measured (to the nearest mm) using a manual periodontal probe (UNC 12 probe, Hu-Friedy, Chicago, Illinois, USA) was found to be within the normal limits (2 mm). Electric (Parkell, Edgewood, New York, USA) and cold pulp sensibility testing (Endofrost, Roeko, Germany) elicited negative responses in teeth #22 and #23. Tooth #22 was tender to percussion and exhibited grade 1 mobility.

An intraoral periapical radiograph (IOPAR) suggested an Oehlers type 3b DI with blunderbuss root apex in tooth #22 to be associated with a large periapical radiolucency with well-defined corticated borders (figure 2). A limited field of view cone beam CT (CBCT, CS 8200 3D; Carestream Health, Rochester, New York, USA) examination was performed (90 kVp, 10 mA and 15 s scanning time) to obtain detailed information of the tooth morphology and the periapical lesion. The CBCT confirmed the presence of type 3b DI with intercommunicating channels between the invaginatus and the pulp canal. The axial sections revealed that the invagination and the pulp canal configuration varied from the coronal to the apical end of the root. The axial section at the CEJ presented a centrally located invagination encircled by a laterally displaced strip of pulp canal space (figure 3). The middle third axial section showed a crescent shaped mesial and distal pulp canal space flanking the centrally located invagination (figure 3). The apical section showed a single pulp canal opening exiting through the immature root apex. The coronal and the sagittal section revealed that the invagination extended from the crown to the apex of the root canal, with both the mesial and distal pulp canals joining the invagination in the apical third (figure 4). An incomplete root formation with the blunderbuss opening exiting in the palatal direction was evident from the CBCT sections. The periapical radiolucency was measured and found to be 10.4×11.2×12.4 mm in its greatest dimension (figure 5). The planar CBCT sections and the three-dimensional (3D) reconstructed image demonstrated the erosion of the palatal cortex and a bony fenestration defect in the buccal cortex (figure 6). Based on the clinical and radiographic findings, tooth #22 was diagnosed as Oehler’s type IIIB DI with pulpal necrosis and acute periapical abscess. The periapical lesion was categorised as a through-and-through osseous defect of endodontic origin (Von Arx type 1b).

Figure 2.

Preoperative IOPAR (intraoral periapical radiograph) suggestive of Oehlers type 3b dens invaginatus associated with a large periapical radiolucency with well-defined corticated borders.

Figure 3.

The axial section at the cementoenamel junction presented a centrally located invagination encircled by a laterally displaced strip of pulp canal space and the middle third axial section showed a crescent-shaped mesial and distal pulp canal space flanking the centrally located invagination.

Figure 4.

The coronal and the sagittal section revealed that the invagination extended from the crown to the apex of the root canal, with both the mesial and distal pulp canals joining the invagination in the apical third.

Figure 5.

The periapical radiolucency was measured and found to be 10.4×11.2×12.4 mm in its greatest dimension.

Figure 6.

(A) Three-dimensional reconstructed image demonstrated the erosion of the palatal cortex and a (B) bony fenestration defect in the buccal cortex.

The patient and his guardians were informed of the complications and prognostic challenges of successfully treating the teeth. The alternative treatment option of extraction followed by transitional prosthetic rehabilitation and definitive implant restoration at 17 years of age was also discussed. A decision to retain the tooth by a two-phase approach of NSRCT followed by endodontic surgery using the principles of guided tissue regeneration was finalised, and written informed consent was obtained from the guardian.

Phase I: NSRCT

In the initial visit, an emergency treatment was performed. The tooth and the palatal mucosa were anaesthetised with 2% lidocaine with 1:80 000 epinephrine by combining infraorbital and nasopalatine nerve blocks with local infiltration of the palatal mucosa around the abscess. The fluctuant palatal abscess was then incised with a number 11 scalpel and the pus was drained. The teeth #22 and #23 were isolated under rubber dam (6′′×6′′ Latex Dental dam, Sanctuary Health SDN BHD Chemor Perak Malaysia), and the access openings was performed. During the access cavity preparation of #22, a frank amount of pale-yellowish pus fluid started to ooze out from the canal. The fluid was allowed to drain and intermittently flushed with 3% NaOCl and saline. When the fluid drainage was controlled, the access cavity was visualised and two root canal orifices (one mesial and one distal) were located (figure 7). The canals were negotiated with 10 and 15 K-files (Dentsply Maillefer) and coronally flared with Gates Glidden drills #2 and #3. (Dentsply Maillefer) Calcium hydroxide intracanal medicament was placed and the access cavity was sealed with Cavit. A CBCT scan was requested for the patient to assist in diagnosis and treatment planning.

Figure 7.

Access cavity displaying two root canal orifices (one mesial and one distal).

In the next appointment, the access cavity was modified based on the information obtained from the CBCT images. The cavity was extended to reveal the centrally located invagination and the peripherally encircling pulp canal space extending mesially, palatally and distally in a strip of C-shaped configuration (figure 8). The pulp canal and the invagination were troughed using ultrasonic tips Start-X #1, #2, #3 (Dentsply Maillefer) to remove the coronal obstruction and enable negotiation of the internal anatomy. The mesial and distal strip of pulp canal space scouted with no #8, 10 and 15 K file had the presence of multiple negotiation points, either meeting resistance to advancement at the coronal or middle third or merging with the invagination at the apical third. Working length was determined by combining electronic apex locator reading (Propex Pixi, Dentsply) with radiographic assessment. The pulp canals were coronally flared with Gates Glidden drills #2 and #3 and the glide path was established with ProGlider rotary files (Dentsply Sirona). They were biomechanically prepared to an apical size #25/0.06 in the mesial and #30/0.06 in the distal canal using Hyflex CM rotary files (Coltene Whaledent, Altstetten, Switzerland). The manual hand K and H files were used between the rotary file sequence to provide tactile feedback of the canal configuration and ensure patency. The invagination was prepared by a step back technique using K and H files (Dentsply Maillefer) till a master apical file size of #80. The canals were continuously irrigated with 3% sodium hypochlorite using a 30-G NaviTip double-side port needle (Ultradent, South Jordan, Utah) during the instrumentation cycle. XP endo finisher was used in a sequence of three cycles of 1 min each for final irrigant activation. The static XP endo finisher was placed inside the canal filled with 3% sodium hypochlorite and then mobilised at 800 rpm and 1 Ncm. The XP endo finisher was carried to the full working length and gently brushed against the canal walls during the irrigant activation. The canals were flushed with 5 mL of 3% sodium hypochlorite following each irrigant activation cycle to remove the suspended debris. Following the irrigant activation, the canals were irrigated with 5 mL of 17% EDTA and 5 mL of saline to remove the inorganic smear layer. The canals were dried with paper points (Dentsply Maillefer, Ballaigues, Switzerland)) and a dressing of premixed calcium hydroxide paste was given (RC Cal, Prime Dental Products, Mumbai, India). The access opening was sealed with a 3-mm-thick temporary restorative material (Cavit, 3 M Oral Care), and the patient was scheduled to return after 2 weeks for the subsequent phase of surgical management.

Figure 8.

Access cavity revealing the centrally located invagination and the peripherally encircling pulp canal space extending mesially, palatally and distally in a strip of C-shaped configuration.

Phase II: Endodontic surgery with guided tissue regeneration

On the next visit, the patient was completely asymptomatic, and the swelling and the sinus tract associated with the tooth had subsided. Local anaesthesia was administered, and a labial full-thickness rectangular mucoperiosteal flap was reflected extending from #11 to #23. The bony defect on the buccal cortical plate was identified by firm probing with an explorer, and a sharp round bur 4 (Dentsply Maillefer) in a high speed handpiece (T3 Racer, Dentsply Maillefer, Ballaigues, Switzerland)) was used in a light brushing motion under copious saline irrigation to create a window. The window extension was minimal and dictated by the necessity to expose the root apex and gain access to the periapical lesion (figure 9). The pathologic tissue was removed using sharp surgical curettes (Hu-Friedy, Chicago, Illinois, USA), and the tissue was placed in 10% formalin for sending it for histopathologic examination. Following the removal of the periapical lesion, a communication of the osseous defect with the nasal floor could be visualised at the superior right side of the cavity. A periapical through and through defect (Bucco-palatal cortical bony defect) was also evident along the apex of the root surface of #22 and #23. A surgical carbide tapered fissure bur (FG 25; Prima Classic Prima Dental Group, Gloucester, UK) positioned perpendicular to the faciolingual plane of the root was used to smoothen and shave 1.5–2 mm of the root apex of #22. The root end cavity was prepared to a depth of 3 mm using diamond-coated retro tips (No. 1 ProUltra, Dentsply) operated by an ultrasonic unit(Satelec/Acteon, Merignac, France) at a low power setting and copious water irrigation (figure 10). Haemostasis was achieved by applying epinephrine-soaked cotton pellets and the root end cavity was dried by a Stropko syringe. ProRoot MTA (Dentsply Tulsa Dental, Tulsa, Oklahoma, USA) was placed in the root end cavity using Microapical placement system (Dentsply Maillefer) and condensed using indirect ultrasonic activation applied on the lateral surface of the condensers (figure 10). Following the debridement of the periapical lesion and root end cavity filling, the steps to augment the osseous defect by a guided tissue regeneration approach were initiated. The steps included (1) placement of a bioresorbable collagen membrane of approximately 10×13 mm (Periocol-GTR, Eucare Pharmaceuticals, Chennai, India) (figure 11) against the palatal surface of the osseous defect. (2) The bony defect was completely filled with synthetic nanocrystalline hydroxyapatite (Nc-HA; SybografTM) particles (figure 12). (3) Another piece of bioresorbable collagen membrane (Periocol-GTR, Eucare Pharmaceuticals, Chennai, India) (figure 13) was placed covering the graft and extending 2–3 mm beyond the bony defect margin. (4) A PRF membrane was placed over the collagen membrane (figure 14). The mucoperiosteal flap was repositioned and stitched using a 5–0 polypropylene suture (Ethicon). Written and oral postoperative instructions were provided, and the patient was recalled after 5 days for suture removal. The histopathology report confirmed a diagnosis of periapical granuloma for this case. The histopathology section showed characteristic Langerhans giant cell along with fibroblasts and lymphocytic infiltrate (figure 15).

Figure 9.

Periapical lesion was accessed by creating a bony window along the lesion’s margins.

Figure 10.

3 mm retrograde cavity prepared using diamond coated retro tips (No. 1 ProUltra, Dentsply) and retrofilled with ProRoot MTA (Dentsply Tulsa Dental, Tulsa, Oklahoma, USA).

Figure 11.

Placement of first bioresorbable collagen membrane of approximately 10×13 mm against the palatal surface of the osseous defect.

Figure 12.

Bony defect adequately packed with synthetic nanocrystalline hydroxyapatite (SybografTM) until compaction.

Figure 13.

Placement of second piece of bioresorbable collagen membrane covering the graft and extending 2–3 mm beyond the bony defect margin.

Figure 14.

Platelet-rich fibrin membrane placed over the collagen membrane.

Figure 15.

Histopathology section showing Langerhans giant cell along with lymphocytic infiltrate.

Outcome and follow-up

The patient was recalled for clinical and radiographic evaluation scheduled at 3, 6 and 12 months and subsequent yearly visits. A 5-year follow-up recall was categorised as complete healing and considered a successful outcome (figures 16–19)

Figure 16.

Immediate postoperative radiograph.

Figure 17.

3 months follow-up radiograph.

Figure 18.

5 years recall radiograph.

Figure 19.

Immediate postoperative clinical view.

Discussion

Several strategies have been proposed for the management of type III DI. Preventive sealing of the pits is indicated if the tooth does not exhibit any signs of infection and is asymptomatic. In scenario of peri-invagination periodontitis with vital pulp, and the invagination exits as a separate apical foramen with no connection with the pulp canal, the infected invagination may be endodontically treated in isolation. If both the invagination and the pulp canal are infected, the invagination and the root canal needs to be treated in combination. This can be accomplished by debriding, disinfecting and obturating the root canals and invagination separately, or by removing the invagination and merging the internal anatomy into a single common space. Other treatment alternatives include apexification or pulp revascularisation in open apex cases, endodontic surgery, intentional reimplantation and extraction.⁷

The present case had several prognostic challenges for achieving successful healing outcome. The case difficulty could be broadly accounted by (1) anatomic complexity associated with the DI tooth morphology, (2) the character and extent of the periapical lesion allied to the infected tooth and (3) the susceptibility of the young patient to spiral in a situation with limited prosthetic rehabilitation options over his life span in case of early failure and extraction of the tooth. The tooth #22 had a type III DI morphology with intercommunicating channels between the infected invagination and necrotic pulp canal space. Additionally, the DI was associated with funnel-shaped blunderbuss root apex contributing to the difficulty in predictably debriding, disinfecting and obturating the internal anatomy. There was a large periapical lesion (>10 mm) with a TTBD (buccal and palatal cortical bone peroforation, Von Arx type 1b) associated with #22. An extensive periapical tissue damage with TTBD requires substantial reorganisation of various tissues and healing by repair and scar tissue may be a likely outcome.

The treatment was therefore planned in two phases: an NSRCT phase followed by surgical endodontics. An initial NSRCT to reduce intracanal pathogenic microflora was followed by the establishment of an impervious retrograde apical seal during the surgical intervention. A GTR approach using bone replacement grafts and barrier membranes was included in the surgical treatment plan to achieve optimal healing of the large TTBD. The two-phase strategy aimed to promote a conducive environment for regenerative healing of the large TTBD and facilitate long term retention and survival of the tooth.

Phase I (NSRCT)

A NSRCT preceded the surgical phase with the objective of significantly reducing the intracanal bacterial load by conscientious biomechanical instrumentation, copious irrigation and its activation and intracanal calcium hydroxide medicament. A reduced pathogenic microflora by NSRCT preceding the endodontic surgery increases the chance of successful healing outcome.¹³

CBCT scan was used in the present case to reconstruct a 3D image of the complex internal anatomy. The visual image of CBCT in conjunction with magnification by dental operating microscope allowed accurate access and negotiation of the internal morphology. The CBCT must be performed only after thoroughly considering the risk versus benefit and the radiation dose must be optimised for the clinical situation. This is especially important while obtaining CBCT images in young adults as they are most susceptible to the stochastic effects of the radiation.¹⁴ In the present case, the CBCT helped in revealing the type and character of invagination, its relation with the pulp canal anatomy, the large extension and the through and through perforating character of the periapical lesion. The visual picture of the challenging internal anatomy and the periapical lesion helped strategise and execute the treatment plan.

In the present case, both the invagination and the pulp canals were infected, necessitating complete debridement and disinfection of the internal anatomical channels. The decision was taken to treat the invagination and the pulp canal separately and not combine them into a single wide canal space by removing the invagination. The invagination in the present case extended through the total root length and removing the invagination would significantly compromise the strength and the long-term retention of the tooth.

The large and irregular internal anatomy of type 3 DI makes cleaning and shaping a formidable challenge. In the present case, a combination of ultrasonic troughing tips and manual files were used to negotiate, scout and circumferentially file the semicircular strip of pulp canals and enamel-lined invagination. Rotary instrumentation was used subsequent to glide path preparation to prevent iatrogenic instrument fracture. Mechanical instrumentation accesses and debrides a fraction of the complex root canal system and copious irrigation and its activation is advocated for effective disinfection.⁷ In the present case, voluminous irrigation with 3% NaOCl was performed with a final three-cycle irrigant activation with XP- endo finisher. XP endo finisher file due to its thin core diameter and design compresses and expands to project and scrape the canal walls inaccessible to conventional instrumentation. Furthermore, these files can agitate the irrigant, increasing its effectiveness in canal debridement.¹⁵ An interappointment intracanal medicament was placed in the canals to enhance disinfection due to the history of a chronic long-standing periapical lesion and an acute palatal abscess associated with an intermeshed and complex canal anatomy.

Phase II: Endodontic surgery using principles of guided tissue regeneration

The surgical endodontic treatment aimed at achieving regenerative healing of the large periapical TTBD (Von Arx type 1 b). Gutman and Harrison described prognostic factors that may negatively influence the outcomeof periapical surgery.^{16 17} These include (1) through and through (tunnel) lesions, (2) large cysticlesions and (3) apico-marginal defect. In the present case, a large periradicular lesion (10.4×11.2×12.4 mm, type 1b) was observed in the reconstructed CBCT image. Studies^{18 19} have reported that these defects often heal by repair with incomplete bone regeneration and the formation of fibrous scar tissue. As a result of the rapid proliferation of soft tissue from both the facial and lingual aspects before the space could be repopulated with bone in-growth from the approximal surfaces, the healing associated with these defects is typically incomplete or characterised by the formation of scar tissue. With reported healing rates as low as 25%, the presence of a large bone defect in conjunction with a through-and-through bone defect may negatively impact the outcome of periradicular surgery.^{17 19–21} Guided tissue regeneration⁹ has been widely accepted as the treatment to regenerate the lost periodontium. The rationale is that if the migration of the epithelial cells can be prevented by the space-creating technique long enough to stabilise the cells of regenerative capacity (osteoblasts), regeneration can be realised.⁹ By preventing the migration of epithelial cells in the bony crypt, a buccal and palatally placed barrier membrane may have accelerated the healing process in the surgical treatment of the current case. Several clinical studies, randomised controlled trials and experimental studies demonstrate that the use of guided tissue regeneration could improve the treatment outcomes for through-and-through lesions.²⁰

In this present case, the bioresorbable collagen barrier Periocol was used. According to Tsesis et al,²² the use of a resorbable membrane favoured better clinical outcomes than a non-resorbable membrane or a graft alone. Khanna et al²³ compared open flap debridement with the use of collagen membrane and bone graft, and concluded that the use of bone graft in combination with membrane improved clinical parameters more effectively. In large tunnel lesions, barrier membranes placed buccally and palatally tend to collapse towards the defect; therefore, it is recommended to place bone fill in the crypt to support non-rigid membranes.²⁴ The use of Nc-HA may have accelerated bone healing and normal trabecular bone formation in the present case. The Nc-HA material has osseointegrative properties, which it achieves by inducing osteoblastic activity and forming a strong bond with the newly deposited bone. In addition, the chemical composition of Nc-HA is similar to that of bone mineral. Numerous studies have demonstrated the role of Nc-HA in periodontal and bone regeneration, angiogenesis and resorbability, indicating its potential for regeneration.²⁵ The use of NcHA bone graft in conjunction with a resorbable collagen membrane produces clinically significant bone regeneration and periodontal regeneration.²⁶ PRF was used in this instance because it acts as a fibrin glue to hold the flap and membrane in place and promotes neoangiogenesis by acting as an interpositional scaffold, thereby preventing necrosis and shrinkage of the surgical flap. In addition, PRF provided a synergetic effect to the Periocol by also acting as a barrier membrane. A systematic review concluded that PRF in conjunction with a bone graft improved clinical outcomes for patients with periodontal intrabony defects.²⁷

MTA was chosen as a retrograde filling material because it induces a more uniform, thicker and impermeable dentin bridge than calcium hydroxide. It is an established benchmark in retrofill due to its biocompatibility, impeccable sealing ability, low solubility and radiopacity.²⁴ A GTR approach involving bone replacement grafts and barrier membranes was included in the surgical treatment plan for optimal healing of the large TTBD in the present case. A systematic review and meta-analysis concluded that using a membrane without a bone graft was found to be 1.02 times more effective than endodontic surgery without a GTR technique (control) and more effective than platelet-rich plasma techniques. However, membrane plus bone graft proved to be 3.6 times more effective than membrane alone.²⁸

Patient’s perspective.

• When I first came to realise I have a big swelling inside my mouth, it gave me tremendous shock, I went to many doctors seeking treatment for the same but none of them were able to completely remove it. The swelling would come back again along with some discharge, I was afraid and convinced that this is some sort of mouth cancer. I was young and I didn’t want to die of mouth cancer. When I came to this hospital, they convinced me that it is very much treatable and need not be scared of. I was relieved and immediately developed confidence because I was skeptic of all the treatment I had previously gotten. They explained to me in depth about the type of disease and how it can appear and be treated. They ran a few tests and xrays, and educated me and my guardians with the help of that. In the first treatment they gave me, I realised my swelling had disappeared after a few days and the pus wasn’t coming out. So we got even more convinced that these doctors could treat me successfully and I came for my subsequent appointments. Everything went smoothly and I can’t thank my doctors enough. Even after five years I haven’t faced any problems so far and I am very much satisfied with my treatment.

Learning points.

• The present case report demonstrates complete healing of a large periapical through and through lesion (Bucco-palatal cortical bone perforation, Von Arx type 1b) associated with a type 3 dens invaginatus in an adolescent patient.

• An understanding of contemporary evidence-based techniques of non-surgical root canal treatment and endodontic surgery using guided tissue regeneration can accomplish complete healing in prognostically questionable cases.

• Preserving teeth through regenerative healing in young patients prevents early extraction and complex prosthetic or orthodontic treatments, supporting a comprehensive treatment approach.

Ethics statements

Patient consent for publication

Consent obtained from parent(s)/guardian(s)