Management of necrotic immature permanent maxillary incisors using a modified technique of revascularisation

Abstract

The management of necrotic immature permanent teeth has always been a challenge to endodontists. Various treatment modalities have been tried and tested for achieving a successful outcome. Revascularisation is one among these treatment options, which is gaining widespread attention among endodontists. The growing body of evidence demonstrating the success of revascularisation has led to different variations of this treatment option. Clinicians have over time used different scaffolds such as blood clot, collagen, platelet-rich fibrin (PRF) and platelet-rich plasma for revascularisation. This case report outlines the management of immature maxillary central incisors with pulp necrosis and large periapical lesions in a 19-year-old female patient with a modified technique of revascularisation by combining PRF and blood clot. At the end of 12 months, the patient was completely asymptomatic along with regression of the periapical lesions.

Background

The presence of narrow dentinal walls and the absence of a natural apical constriction makes the endodontic procedures on necrotic immature permanent teeth a considerable challenge. The currently exciting arena of medical science includes the regeneration of tissues instead of its artificial substitution. Regeneration of tissues helps in revitalising a non-vital tooth with an immature apex. These procedures help to increase the width of the fragile dentinal walls as well as the lengthening of underdeveloped roots.¹

Since the ground-breaking case reports by Banchs and Trope,² and Iwaya et al,³ many other case reports have shown the healing of periapical lesions along with continuous root development by using regenerative endodontic procedures (REPs) on immature non-vital teeth. Bakhtiar et al in their case series reported the healing of periapical lesions, continuation of root developments and apical closures in all cases of necrotic immature teeth while using PRF as a scaffold.⁴ The increasing evidence of success with these procedures has led to the existing recommendations of the American Association of Endodontists for REPs.⁵ However, different protocols which vary in the sodium hypochlorite (NaOCL) concentrations, the antibiotic regimens and the scaffold materials have been proposed.

Platelet concentrates as scaffolds have shown considerable success in the regeneration of tissues. These are autologous, easily prepared and contain growth factors in high concentrations. The migration, proliferation, differentiation of cells and matrix synthesis influenced by these signalling molecules have been documented by various in vitro studies.^{6 7}

The ability of platelet-rich plasma (PRP) to enhance periapical healing, apical closure and thickening of dentinal walls have been demonstrated by various case reports and randomised controlled clinical studies.^8–13 PRF a second-generation platelet concentrate does not require the presence of agents such as thrombin. The platelets and leucocytes are trapped within an organised fibrin network created by PRF. This forms a reservoir for continuous release of growth factors. The immune cells and cytokines circulating within the PRF clot also act against infection. The consistency of PRF also makes the condensation of the materials used to achieve a coronal seal such as mineral trioxide aggregate (MTA) much easier.⁶ These advantages of PRF have led to it being considered as an optimal bioscaffold to be used in REPs.

Nageh et al in their clinical study used a modification of the conventional revascularisation protocol by combining the induction of a blood clot (BC) with the use of PRF.¹⁴ Despite the considerable advantages of using PRF with BC as a scaffold, only a few case reports and clinical trials have described its use as a scaffold or compared its efficacy in root development and resolution of periapical radiolucencies after tooth revascularisation/revitalisation with other scaffolds. This report outlines a modified technique of revascularisation using platelet-rich fibrin (PRF) with BC as a treatment strategy for immature necrotic maxillary central incisors with large periapical lesions.

Case presentation

A 19-year-old female patient presented with a dull pain in the upper front tooth region since 1 week. The patient gave a history of a fall ten years back. The medical history was noncontributory. No abnormalities were detected extraorally. Intraoral examination revealed no significant soft-tissue abnormalities. The periodontal examination showed probing depth within normal limits. There was no tenderness on percussion and mobility in relation to these teeth.

Investigations

Radiographic examination revealed large periapical radiolucencies in relation to teeth #12, #11, #21 and #22 with open apices in relation to #11 and #21 (figure 1A). There was no response to the electric pulp testing in relation to teeth #12, #11, #21, #22. A diagnosis of pulp necrosis with asymptomatic apical periodontitis was made on the basis of the clinical and radiographic findings.

Figure 1.

(A) Preoperative radiograph. (B) PRF. (C) Immediate postoperative radiograph. (D) A 3-month follow-up radiograph. (E) A 6-month follow-up radiograph. (F) A 12-month follow-up radiograph. PRF, platelet-rich fibrin.

Treatment

Treatment options which included non-surgical root canal treatment and revascularisation were explained to the patient. The patient opted for regenerative endodontic treatment for #11 and #21 and non-surgical root canal treatment for #12 and #22. Written informed consent was procured from the patient. In the first visit, the teeth #11 and #21 were anaesthetised by the infiltration technique using 2% lidocaine with 1:100 000 epinephrine. Isolation was achieved with a rubber dam, and the canals were accessed. The canals were negotiated with stainless steel hand K files # 40 (Dentsply Maillefer, Oklahoma, USA). An electronic apex locator Root ZX Mini (J. Morita, Kyoto, Japan) was used to determine the working lengths and then confirmed with an intraoral periapical radiograph. Copious gentle irrigation with 1.5% NaOCL (20 mL) with a side vented needle was carried out for 5 mins in each tooth. This was followed by irrigation with 20 mL of 17% EDTA for 5 min. After drying the canals with paper points, a single tablet of metronidazole (500 mg) and ciprofloxacin (500 mg) was used to prepare double antibiotic paste (DAP). These tablets were ground and mixed with saline to achieve a reasonably creamy homogenous paste. The paste was subsequently injected into the canals to a level just below the cementoenamel junction (CEJ). Temporary restoration of the cavities was then done with glass ionomer cement after placing a cotton pellet within the pulp chamber. The patient was recalled after 3 weeks.

In the second visit for the regenerative procedure, the teeth were anaesthetised using 2% lidocaine without a vasoconstrictor. Rubber dam isolation of the teeth was done. Gentle irrigation of the canals with 20 mL of 17% EDTA was carried out, followed by irrigation with saline. Paper points were then used to dry the canals. A #20 K file was used to intentionally overinstrument 2–3 mm beyond the apex to induce bleeding to a level below the CEJ. Before its withdrawal, 2–3 gentle clockwise rotations were given to the file. A small cotton pellet held with tweezers was used to remove the excess blood that reached the pulp chamber. PRF was prepared using 10 mL of whole venous blood drawn from the patient’s right median cubital vein. After transferring the blood sample to a test tube without anticoagulant, immediate centrifugation was carried out. Centrifugation was carried out at 3000 rpm for 10 min which resulted in the formation of a top layer of platelet-poor plasma, a middle layer with PRF clot and a bottom layer with red blood within the test tube (figure 1B). After the fragmentation of the prepared PRF membrane, hand pluggers (Dentsply, India) were used to place it within the canal up to the CEJ. The coronal seal was achieved by condensing a layer of MTA Plus (Avalon Biomed, Bradenton, Florida, USA) 3 mm above the PRF matrix (figure 1C). After confirming the setting of MTA, the access cavity was double sealed with glass ionomer cement (GC, Tokyo, Japan) and composite resin (Filtek bulk-fill, 3M ESPE, St. Paul, Minnesota, USA).

During the course of the treatment, conventional root canal therapy in relation #12 and #22 were completed.

Outcome and follow-up

The patient was reviewed after 3, 6 and 12 months and was completely asymptomatic at each of the follow-up appointments. There were no signs of oedema, erythema or sinus tracts during the recall period. There was no tenderness on percussion or palpation and probing depth remained within normal limits. Thermal and electric pulp testing was carried out at each of the follow-up appointments, which yielded no response. Evaluation of the radiographs showed healing of the radiolucent lesions in relation to both teeth during the follow-up appointments (figure 1D–F). An increase in the thickness of dentinal walls at the apex of tooth number #11 was noticed in the radiographs.

Discussion

Several reports have demonstrated successful revascularisation using BCs^{15 16} and PRF as a scaffold.^{17 18} However, there is a limited concentration of growth factors in a BC.¹³ Various platelet concentrates have currently been identified as potential scaffolds for REPs. We found five studies which have compared the clinical and radiographic outcomes of PRP or PRF with BC.1 12 13 19 20 Among these, the reported success in one of the studies has been connected to the use of PRP along with BC instead of an isolated effect.¹ The other four studies in which the individual effects of PRP and PRF were evaluated, failed to demonstrate any considerable advantage of PRP and PRF over the BC approach. Miron et al demonstrated that PRP and injectable PRF possessed various growth factors necessary for tissue regeneration that could prompt fibroblast behaviour. The injectable PRF instigates elevated cell migration and mRNA expression of transforming growth factor (TGF-β) platelet derived growth factor and COL1a2 gene.^{21 22} A newer treatment strategy to improve the prognosis of treatment is to use a combination of traditional REP method with PRP or PRF. When the induced bleeding from the periapical area is inadequate, the remaining portion of the canal can be filled with preparation from the patient’s centrifuged blood. An analysis of previous case reports revealed successful results when the authors used REP in combination with PRP or PRF.²³

In the present case, we chose to use a combination of a BC and PRF. In the first visit, following access opening, no instrumentation was carried out. Instrumentation was avoided to prevent the thinning of the already weak dentinal walls as well as to preserve the stem cells present in their apical area. Instrumentation could also eradicate the growth factors and other cells vital for the regeneration process.²⁴ In order to reduce the chances of irrigant extrusion beyond the canal, NaOCL irrigation of the canals was performed using closed-end, side vented needles for 5 min. Saline irrigation of the root canals was then carried out to flush away the NaOCL to diminish any toxicity that can hinder the regeneration process. The modulus of elasticity and flexural strength of human dentin are adversely affected by the use of 5.25% NaOCL due to its proteolytic action. The odontoblastic differentiation is diminished due to the cytotoxic effect of 5.25% NaOCL on apical tissue stem cells.¹⁴ Therefore, according to the existing evidence, it is not necessary to use NaOCL at a concentration above 1.5%. Following hypochlorite irrigation, 20 mL of 17% EDTA was used to irrigate the canals for 5 min to eliminate the smear layer to produce improved penetration of the irrigator and root canal medicaments.²⁴

DAP (eliminating minocycline) was used as the intracanal medicament. Minocycline was avoided as it chelates with the calcium ions to form insoluble complexes, incorporation of which in the tooth matrix causes discolouration. It also causes the demineralisation of intertubular dentin and diminishing of tooth fracture resistance.^{14 25–28}

In the second visit, plain anaesthesia 2% lignocaine was used to facilitate bleeding. 17% EDTA solution was then used since it aids in releasing the growth factors which are embedded within the dentin during dentinogenesis due to its chelating effect.²⁴ In the present case, we used a modified technique of revascularisation, where a combination of PRF and BC were used as a scaffold. A similar modified technique of revascularisation was carried out in a previous study by Nageh et al with favourable results.¹⁴ We believe that the synergistic effect achieved when PRF and BC were used together is responsible for the success of the treatment despite the presence of large periapical radiolucencies. The conventional root canal therapy of #12 and #22 could also possibly have influenced and contributed to the healing of the periapical lesions. The stem cell population is higher in a periapically induced BC compared with PRF. PRF, however, has a higher platelet concentration which aids in tissue regeneration by continuously releasing growth factors.⁶ In the present case, the coronal seal was achieved with a layer of MTA plus condensed above the PRF followed by a layer of glass ionomer cement and composite resin. The vitality testing gave negative responses at the end of 12 months. Since the follow-up period was only 12 months, the recovery of tooth vitality after the follow-up period was not evaluated. Future studies will require long-term observations. According to Hargreaves et al, positive responses achieved in various studies and case reports following tooth revascularisation indicate the existance of innervated tissues in the previously vacant space.²⁹ However, the presence of thick layers of MTA and glass ionomer cement may have contributed to the lack of response to the vitality tests.³⁰ Many cases with radiographic evidence of root maturation have previously responded negatively to vitality tests. Thus the absence of a response to pulp vitality cannot be considered as an indicator of non-vitality in these cases.³¹

Learning points.

• The use of a combination of platelet-rich fibrin and blood clot as a scaffold is effective in managing necrotic immature teeth with large periapical lesions.

• Revascularisation/revitalisation is an effective treatment option aiding in the preservation of tooth structure in immature permanent teeth with already thin dentinal walls.

• Careful case selection, diagnosis and treatment plan are the cornerstones for successful regenerative endodontic therapies.

• A negative response to vitality tests following revascularisation does not necessarily indicate failure of the treatment.