Use of photoactivated disinfection and platelet-rich fibrin in regenerative Endodontics.

AIM: Photoactivated disinfection has been used as an adjunct to conventional endodontic treatment. Its use in regenerative endodontics is not reported in literature. The aim of this case report was to describe a new proposal for pulp revascularization with disinfection of pulp canal space using a unique combination of a photosensitizer solution and low-power laser light.
MATERIALS AND METHODS: A 9-year-old boy came with the chief complaint of discolored upper central incisors (#8, #9). A diagnosis of pulp necrosis was made on the basis of clinical and radiographic findings. The canal was irrigated with 5.25% sodium hypochlorite solution and dried with paper points. Photodynamic therapy was used to disinfect the root canal and platelet-rich fibrin was used to revitalize the pulp. Three millimeters of gray mineral trioxide aggregate was placed directly over the platelet-rich plasma clot. Three days later, the tooth was double-sealed with permanent filling materials.
RESULTS: Clinical examination revealed no sensitivity to percussion or palpation tests. Radiograph revealed continued thickening of the dentinal walls, root lengthening, regression of the peri-apical lesion and apical closure. Both the roots showed complete apical closure at the 10-month follow-up. However, the teeth were not responsive to electric pulp test.
CONCLUSION: This report of pulp revascularization shows that disinfection with photodynamic therapy combined with platelet-rich fibrin leads to satisfactory root development in necrotic immature teeth.

INTRODUCTION

Regenerative endodontic procedures can be defined as biologically based procedures designed to replace damaged, diseased or missing structures, including dentin and root structures as well as cells of the pulp–dentin complex.[1] The three pivotal components contributing to the success of this revitalization include stem cells, signaling molecules and scaffold.[2] The harvesting of autologous materials as scaffold should be what a dentist should aspire for. Many studies have reported the use of blood,[3] platelet-rich plasma[4] and platelet-rich fibrin (PRF)[5] for revitalization procedures. The wide popularity of these methods includes possibility of further root development and reinforcement of the dentinal walls with hard tissues, thus strengthening the tooth against a potential fracture.

Care is needed to deliver regenerative endodontic procedures that maintain or restore the vitality of teeth, but which also disinfect and remove necrotic tissues. Many reported cases of revitalization procedures used Hoshino's paste, commonly called as triple antibiotic paste.[56] In other cases, calcium hydroxide proved to be equally efficacious as the antibiotics promoting root lengthening and thickening.[7] Lately, the photoactivated disinfection (PAD) concept has been introduced into modern dentistry. PAD is a unique combination of a photosensitizer solution and low-power laser light. Laser light activates the photosensitizer and creates a cascade of energy transfer and variable chemical reactions in which singlet oxygen and free radicals are produced, which eliminates microbes. The benefit of this action is that it is quite impossible for the microbes to create resistance against it. The root canal needs to be disinfected for the regenerative process to undergo unabated. The purpose of this case report is to document the efficacy of a new disinfection protocol using photodynamic therapy (PDT) and PRF in revitalization of a tooth with necrotic pulp and open apex.

CASE REPORT

A 9-year-old boy came with the chief complaint of discolored upper central incisors (#8, #9). The medical history of the patient was non-contributory. On clinical examination, the teeth presented with little or no sensitivity to percussion and tenderness to palpation. Periodontal examination revealed physiologic mobility and normal probing depth (<3 mm) around the teeth. The teeth did not respond to cold test or electric pulp test. Radiographic examination of the teeth showed immature roots with open apices, along with peri-apical radiolucency [Figure 1]. A diagnosis of pulp necrosis was made on the basis of clinical and radiographic findings. Taking into consideration the incomplete root development with wide-open apices, regenerative endodontic treatment using Choukroun's PRF was decided. After obtaining consent of the patient and parents, treatment was initiated at the same visit. Local anesthesia was achieved using Lignocaine (1:100,000 adrenaline, DJ Lab, India). Access to the pulp chamber was gained in #8 and #9 and rubber dam was placed. The surrounding area was irrigated with 5 ml of chlorhexidine solution at 2% to ensure that the crown of the teeth was with minimal microbial load. The working length was determined by using electronic apex locator, Root ZX (J. Morita Mfg. Corporation, Kyoto, Japan), and K files (Dentsply Maillefer, Ballaigues) on radiograph. The canal was thoroughly irrigated with 20 ml of 5.25% sodium hypochlorite solution (Novo Dental Product, India) and neutralized with saline. After drying with sterile paper points, solution (tolonium chloride 0.01% w/v in aqueous solution) of the photosensitizer was placed inside the root canal (0.5 ml) with an endodontic needle and left inside the root canal for 2 minutes as pre-irradiation time. The illumination was performed with a 300 μm diameter fiber-coupled diode laser (MM Optics, São Carlos, SP, Brazil). The laser delivered 660 nm light at a total power of 40 mW without the fiber. The fiber was initially placed in the canal; spiral movements, from apical to cervical, were manually performed to ensure an equal diffusion of light inside the canal lumen. These movements were repeated approximately 10 times per minute. A new fiber was used for each patient. The root canal was again irrigated with 10 ml of sterile saline solution to remove the photosensitizer.

Figure 1

Preoperative intraoral peri-apical showing the open apices of the left and right central incisors. Working length is determined so as to place the fiber tip 4 mm short of apex

A 12 ml sample of whole blood was drawn intravenously from the patient's right antecubital vein and centrifuged (REMI Model R-8c with 12 × 15 ml swing out head) under 3000 rpm for 10 minutes to obtain the PRF, which was jelly-like in consistency. The PRF was condensed into the canal using a finger plugger (Dentsply Maillefer, Ballaigues) till the level of the cemento-enamel junction. Gray mineral trioxide aggregate (MTA) (ProRoot MTA; Dentsply) was placed directly over the PRF to a thickness of 3 mm followed by a wet cotton pellet and cavity. The patient was recalled after 3 days and the setting of MTA was confirmed. The access cavity was then double-sealed with Coltosol and composite resin. (Filtek)

The patient returned to the clinic after 6 and 10 months for review and was asymptomatic; teeth #8 and #9 showed negative response to percussion and palpation tests. Radiograph revealed continued thickening of the dentinal walls, root lengthening, regression of the peri-apical lesion and apical closure. Both the roots showed complete apical closure at the 10-month follow-up [Figures 2 and 3]. However, the teeth were not responsive to electric pulp test.

Figure 2

6-month follow-up

Figure 3

10-month follow-up shows apical closure in both the central incisors along with calcific degeneration in the apical third of left central incisor

DISCUSSION

In the classic revascularization protocol in majority of studies, passive decontamination is performed with sodium hypochlorite,[3] which was also used in the present case. In addition to irrigation, the literature reports that use of intracanal dressing materials, mainly those composed of antibiotics, metronidazole, ciprofloxacin and minocycline, contributes to decontamination.[56] Nevertheless, this paste may promote some side effects such as coronal discoloration, bacterial resistance and allergic reactions.[8] A recent article has proposed the use of calcium hydroxide and chlorhexidine gel for decontamination of root canal. However, conflicting speculations have been proposed with the use of calcium hydroxide and chlorhexidine. It was observed that the viability of stem cells of the apical papilla was affected when chlorhexidine was used,[9] whereas others have effectively used irrigation protocols with chlorhexidine.[10] Because of the high alkaline pH, calcium hydroxide can cause necrosis of multipotent stem cells on contact with it.[3] On the other hand, some case reports have shown favorable results when using calcium hydroxide in the cervical third of the root canal.[11]

PDT uses a chemical chromophore, commonly called a photosensitizer, which is taken up by target cells and then activated to initiate bacterial disinfection. Generally, absorption of the light triggers excitation of the photosensitizer, which then either kills cells directly through formation of highly reactive free radicals (Type I mechanism) or reacts with molecular oxygen to create secondary reactive oxygen species that disrupt cell function (Type II mechanism).[12] Bacteria are generally more susceptible to light-activated photosensitizers than mammalian cells because bacteria have fewer rescue systems to help them survive an oxidative insult. Preferential uptake of the photosensitizer by bacteria may be enhanced by linking it with a targeting moiety via a poly-lysine polymer.[13]

PRF was first developed in France by Dohan et al. for specific use in oral and maxillofacial surgery.[14] The scientific rationale behind the use of platelet preparations lies in the fact that the platelet α-granules are a reservoir of many growth factors that are known to play a crucial role in hard and soft tissue repair mechanism.[15] These include platelet-derived growth factors (PDGFs), transforming growth factor β, vascular endothelial growth factor (VEGF), epidermal growth factor (EGF) and insulin-like growth factor-1 (IGF-1). PDGFs exhibit chemotactic and mitogenic properties that promote and modulate cellular functions involved in tissue healing and regeneration and cell proliferation.[16] It has been reported that revitalization of necrotic-infected immature tooth is possible under conditions of total canal disinfection; and as PRF is an ideal biomaterial for pulp-dentin complex regeneration,[5] it was used as a scaffold in the present case.

Apical closure and increasing radicular thickness were noted at the 10-month follow-up in both the central incisors; however, the left central incisor showed radio-opacity at the apical third, which could be calcific degeneration. The negative response demonstrated may be because the tissue that invaginated into the canal space had minimal nervous innervation or more likely because of the presence of MTA sealing and partial obliteration of the root canal space. MTA was placed over the blood clot to isolate the root canal from the external surface of the tooth and create a hard tissue barrier at its contact point with the blood clot. It might have also provided signaling molecules for the growth of stem cells.[4] This report of pulp revascularization shows that disinfection with PDT combined with PRF leads to satisfactory root development in necrotic immature teeth.