Maintenance of cell viability in extraoral conditions for a case of intentional replantation to retrieve a separated endodontic instrument.

Intentional replantation has been used as an alternative treatment modality to tooth extraction and prosthetic replacement when conventional endodontic treatment modalities are unfeasible or contraindicated. This case report presents a successful case of intentional replantation for the mandibular first molar with an endodontic mishap. An endodontic instrument was separated in the apical third of the root canal and extended beyond its mesiobuccal root apex. Intentional replantation served as a means to remove the separated instrument. The periodontal ligament (PDL) cells were kept viable throughout the endodontic treatment using a distinctive technique, wherein a preoperative impression is used for continuous wetting with saline. Platelet-rich fibrin (PRF) was shredded and placed in the alveolar socket to enhance PDL cell reattachment and prevent ankylosis. The 2-year successful follow-up reinforced that intentional replantation can be a viable option for removal of separated instruments that lie beyond the root apex. The use of these techniques to keep PDL cells viable and the use of PRF can aid in prevention of ankylosis.

INTRODUCTION

Cleaning and shaping of the root canal system remains the mainstay of successful endodontic treatment. During cleaning and shaping of the root canal system, procedural accidents can occur that might affect the prognosis. Examples of procedural accidents include ledge formation, artificial canal creation, root perforation, and extrusion of irrigating solution periapically. Not all procedural problems lead to a reduced prognosis, but any error that compromises microbial control is likely to increase the risk of a poor outcome.

Fracture or separation of endodontic instruments within the root canal is an unfortunate occurrence that may hinder root canal procedures and affect the outcome. Fracture of root canal instruments is one of the most troublesome incidents in endodontic therapy, especially if the fragment cannot be removed.[1] Fractured root canal instruments might include endodontic files, lateral or finger spreaders, spiral fillers, or Gates-Glidden burs, whether manufactured from nickel-titanium (NiTi), stainless steel (SS), or carbon steel.[1]

Whereas separation rates of SS instruments have been reported to range between 0.25% and 6%, the separation rate of NiTi rotary instruments has been reported to range between 1.3% and 10.0%.[1]

A number of treatment protocols for removing obstructions have been described in the literature. Earlier, it was suggested that the object, regardless of the primary endodontic diagnosis, should be left in the canal, and that the canal coronal to the object should be treated according to standard endodontic procedures. Others modalities include bypassing the instrument and incorporation into the root-filling material. Surgical techniques for the removal of either the object itself or the entire portion of the root encompassing the object have been recommended. In addition, several authors have introduced special instruments and techniques for retrieval of the separated instrument. However, the removal procedure might result in undue loss of tooth structure and clinical implications such as root perforation. Thus, it is important to assess the risks versus benefits of attempting the removal of a retained instrument and its impact on the prognosis of the tooth.[1]

Intentional replantation is a procedure involving removal of a tooth and its almost immediate replacement, with the object of obturating the canals apically, while the tooth is out of the socket. According to Ingle, intentional replantation may be defined as the purposeful extraction of a tooth to repair a defect or cause of a treatment failure and then returning the tooth to its original socket. The individual first credited with the principle of extraction and replantation was an Arabian physician by the name of Abulcasis who practiced in the 11th century.[2]

Previously failed non-surgical endodontic treatment and retreatment cases and where periradicular surgery is not feasible, are the major indications for intentional replantation. Contraindications are teeth with flared or curved roots, periodontal involvement, or teeth with vertical root fracture or nonrestorable teeth.[3] However, evidence suggests that this treatment modality can be carried out successfully even in periodontally compromised hopeless teeth to save the natural dentition.[4]

Being a noninvasive and faster procedure, there are advantages of this modality over periradicular surgery. There is no need of osteotomy and provides better access and visualization of the roots, more patient comfort, and is cost-effective to the patient. Possible complications being risk of vertical root fracture or postoperative complications such as root resorption and ankylosis have been reported.[3] This interesting case reports intentional replantation with additional precautions to ensure periodontal ligament (PDL) cell viability and repair.

CASE REPORT

A 23-year-old female patient presented to the Depatment of Conservative Dentistry and Endodontics, with a chief complaint of pain in her lower left back tooth on chewing. A written informed consent form duly signed by the patient was obtained before any treatment. The patient's medical history was noncontributory; no allergies or medications were reported by the patient. Dental history revealed endodontic treatment in tooth #19 done 2 weeks back at a private dental clinic.

Clinical examination revealed that tooth #19 was temporized and occlusally relieved with the absence of any swelling or sinus associated with the same tooth. Pain on percussion was noted. Periodontal examination revealed no mobility, normal periodontal probing depth, and normal gingival anatomy. Radiographic findings revealed radiopacity in all the root canals suggestive of under-filled root canal filling which was unsatisfactory. The radiograph also showed a separated instrument (approximately 2–3 mm in length) protruding through the apical foramina of mesiobuccal canal of tooth #19, with the instrument being 1.5 mm into the canal and 1.5 mm outside the tooth. No periapical radiolucency was seen associated with the apex of tooth #19. Crestal bone levels were seen to be within the normal limits [Figure 1a]. The patient was informed about all the treatment options such as orthograde endodontic retreatment followed by extraction and its intentional replantation, extraction, and a dental implant, or extraction with a fixed partial denture and periradicular surgery. The benefits and risks with each procedure were explained to the patient.

Figure 1

Endodontic retreatment (a) Preoperative radiograph showing gutta percha in the root canals and instrument separation (b) postobturation radiograph (c) extracted tooth showing instrument protruding through its mesial root apex (d) extraction socket (e) root-end resection (f) retro preparation (g) retro filling (h) platelet-rich fibrin

The patient agreed to undergo orthograde endodontics and intentional replantation, and her informed consent was obtained.

The patient was administered an inferior alveolar nerve block anesthesia using 2% lidocaine and 1:100,000 epinephrine, and then, tooth was isolated using rubber dam. Endodontic retreatment was carried out with the tooth #19 using SS H-files (Mani Inc., Japan) and gutta percha solvent (Endosolv, Septodont, France). Apical patency was determined with a size 10 K-file (DENTSPLY Maillefer, Ballaigues, Switzerland). The working length was established 1-mm short of the apical foramen, confirmed with a radiograph, and biomechanical preparation was done using hand ProTaper instruments (DENTSPLY Maillefer, Ballaigues, Switzerland) SX, S1, S2, F1, and F2 at the working length. After successfully bypassing the separated instrument, the mesio-buccal canal was shaped up to ProTaper F2. Calcium hydroxide (RC Cal, Prime Dental products, Mumbai, India) intracanal dressing was placed into the root canals for 2 weeks. After 2 weeks, the patient was asymptomatic and the calcium hydroxide intracanal dressing was removed using H-files. Root canals were then obturated with ProTaper gutta percha (DENTSPLY Maillefer, Ballaigues, Switzerland) and AH plus root canal sealer (DENTSPLY De Trey, Konstanz, Germany). On the same day, a composite postobturation restoration (Filtek Z100 Restorative, 3M, ESPE, USA) was done [Figure 1b].

On the next day, the patient was given 600 mg of ibuprofen one hour before the replantation procedure. An impression was made using condensation silicone putty material which was used during the extraoral period to keep the extracted tooth moist continuously. This was in accordance with the novel technique advocated by Niemczyk.[5] The impression was disinfected by immersion in Cidex (2% glutaraldehyde) for 10 min. The patient was asked to rinse with chlorhexidine gluconate 0.12% just before the extraction. Two operators were present throughout the procedure. The PRF was prepared in accordance with the protocol developed by Choukroun et al. just before the surgery.[6] A blood sample was taken without anticoagulant in 10-mL tubes which was immediately centrifuged at 3000 rpm for 10 min.

The patient was prepared for surgery and profound inferior alveolar and lingual nerve block anesthesia was achieved with 5 ml of 2% lidocaine containing 1:100,000 epinephrine. The tooth was extracted with minimal trauma with the use of forceps, which held the tooth above its cervical region and the extraction socket is depicted in Figure 1d. The instrument was seen at the apex of the mesial root of the extracted tooth [Figure 1c]. Operator #1 carried the tooth with the forceps, and it was kept inverted in an elastomeric impression flooded with normal saline such that most of the root region was continuously in contact with the saline.

The apices of the two roots were resected up to 3 mm with a 170 L fissure bur using a straight handpiece, while the tooth was held in the crown portion with gloved fingers using a wet saline gauze [Figure 1e]. Root-end preparation was done using ultrasonic tips (Satelec P5 Ultrasonic Booster) removing 3 mm of gutta percha and debris [Figure 1f]. Irrigation was performed with sterile saline and the three canals were dried with paper points, while the entire root surface was kept moist with saline. Mineral trioxide aggregate (MTA, Medicept, India) was mixed to the desired consistency according to the manufacturer's instructions, and root-end filling was done [Figure 1g].

The tooth was replanted into the socket with digital finger pressure, while PRF [Figure 1h] was packed into the alveolar socket wall to aid in periodontal regeneration and prevent ankylosis.

The tooth was replanted into the socket in around 10 min from extraction [Figure 2a]. Two interrupted 4–0 silk sutures were used to stabilize the tooth [Figure 2b]. A semirigid fiber splint (Interlig, Angelus, Brazil) along with flowable composite (Brilliant Flow, Coltene Whale dent, Alstatten, Switzerland) was used to splint the tooth with the adjacent teeth postoperatively. A postoperative intraoral periapical radiograph [Figure 2c] was taken, and the following postoperative instructions were given: chlorhexidine gluconate rinse 0.12%, three times per day after meals for 7 days, ibuprofen 600 mg every 4–6 h for 48 h, and soft diet for 2 weeks. The patient was recalled in 1 week for suture removal and evaluation of the surgical site. At 1 week, the soft tissues showed a normal tone with no inflammation, and pain on biting had diminished. The patient was recalled again for splint removal after 2 weeks.

Figure 2

(a) Platelet-rich fibrin placed into buccal bony socket wall and tooth replanted (b) suturing done (c) immediate postoperative periapical radiograph (d) 1-year follow-up clinical photograph (e) 1-year follow-up periapical radiograph (f) 2-years follow-up periapical radiograph

The patient was followed up subsequently after 1, 3, 6 months, 1 year, and 2 years. Healing was uneventful, and the tooth showed normal mobility as well as probing depth. At 1 year follow-up, the patient was asymptomatic. Clinical examination revealed no response to percussion or palpation, probing depths and mobility were within normal limits [Figure 2d]. Radiographic findings revealed normal PDL space and continuous lamina dura around the tooth #19 at all the recall visits [Figure 2e and f].

DISCUSSION

This report describes a unique case of intentional replantation to retrieve a separated instrument and employment of additional procedures to ensure successful treatment outcome. These included use of saline bath using an impression “well” during extraoral endodontic treatment to keep PDL cells viable and the use of PRF with the objective of achieving periodontal regeneration and preventing ankylosis.

Fractured instruments in the root canals of molars are sometimes impossible to remove. They can be beyond reach in curved or smaller canals or in surgically inoperable roots. Root or tooth resection may be a feasible alternative to extraction. Intentional replantation may be an option when surgical access is limited or presents unacceptable risks.[7] Mandibular molars are good candidates for this technique because of the typically thick overlying buccal bone, shallow vestibular depth, and proximity of the root apices to the mandibular canal. Another pre requisite is that the tooth can be atraumatically removed in toto. Thus, intentional replantation treatment modality was chosen for the mandibular first molar over periradicular surgery to avoid unnecessary sacrificing of the buccal cortical bone during osteotomy. Another major reason was difficulty in access and visualization of the small separated K file at the mesiobuccal root apex during a periradicular surgery.

Various factors affect the outcome of intentional replantation of teeth. Major factors that encourage healing include atraumatic extraction/reinsertion, root hydration medium, prevention of damage to tooth roots, minimal extraoral time, adequate apical seal in terms of depth, material compaction, and characteristics as well as suitable case selection.[3] Additional factors affecting the treatment outcome could be the administration of preoperative antibiotics and preoperative disinfection and number of operators. Also protection of the socket, tooth handling method, apicectomy technique along with tooth insertion and method of splinting have been found to influence the success of intentional replantation procedures.[3]

In this case, normal saline bath as a medium to prevent dehydration and damage to PDL cells which is essential in the periradicular healing process. The use of saline as a root hydration medium has been followed unanimously till recently by Choi et al.,[8] Asgary et al.,[9] Cho et al.,[10] and Jang et al.[11] Kratchman[12] and Niemczyk[6] on the other hand recommended Hank's balanced salt solution (HBSS) as a better root hydration media. In the present case, the tooth was constantly kept submerged in an impression during the extraoral period to keep the roots moist continuously. This was in accordance with the novel technique advocated by Niemczyk.[6] This aided in prevention of resorptive processes such as replacement resorption, ankylosis, internal, and external root resorptions.[13]

Survival of the PDL cells has been found to be a critical factor influencing successful healing of intentionally replanted teeth.[3] Restricting the extraoral “dry” time to minimum and keeping the tooth constantly wet by keeping it immersed in a physiologic solution has been advocated as another such strategy to ensure survival of PDL cells. It has been found that the viability of PDL exposed to the extraoral environment decreased rapidly after 18 min; hence, the extraoral procedure time should be kept minimal to obtain optimal healing.[14] In the present case, the extra oral wet time was minimal and was only 10 min. During the 10 min of instrument retrieval and apicectomy followed by root-end filling, the tooth was kept immersed in normal saline in an impression. In this case, normal saline was used as a wetting media for the PDL although HBSS or ViaSpan could also be used to keep the root surface moist.[3]

The shredded platelet-rich fibrin (PRF) was later placed in contact with the buccal bony socket wall to achieve periodontal regeneration. PRF requires neither anticoagulant nor bovine thrombin (nor any other gelling agent). Platelets are entrapped massively in the fibrin meshes. PRF also contains and releases growth factors such as platelet-derived growth factor and transforming growth factor which promote periodontal regeneration. PRF has a strong positive effect on the proliferation of gingival fibroblasts, PDL fibroblasts, and osteoblasts.[15] Cell type-specific manner makes PRF beneficial to periodontal regeneration. In addition, activation of phosphorylated extracellular signal-regulated protein kinase, osteoprotegerin, and alkaline phosphatase expression by PRF suggests the pivots for new periodontal attachment formation.[16] Zhao et al. demonstrated that the combined use of PRF and cell sheet fragments of PDL stem cells or PRF alone, in replanted incisors in an animal experiment, which had an extraoral dry time of 2 hours, showed effective healing characterized by regeneration of PDL like tissues and reduction of ankylosis.[17] Although our extraoral “wet” time was within limits (<15 min), PRF was placed additionally to promote fibroblastic activity in the PDL of the intentionally replanted molar and minimize probability of ankylosis.

A prospective cohort study depicted a cumulative 12-year retention rate of 93% and healed rate of 77% after 3 years in intentionally replanted teeth. Healing occurred 1.7 times more frequently in teeth replanted within 15 min. Although most complications occurred within 1 year after replantation, it was suggested that the follow-up should extend for at least 3 years to capture late complications.[10] Hence, the present case is being regularly followed up and a 2-year follow-up has seen no complications and the tooth remains clinically functional and completely asymptomatic.

Another systematic review and meta-analysis by Mainkar revealed a survival rate of 89.1% (83.8%–94.4%) of intentionally replanted teeth.[13] Most failures are due to some form of resorption or periodontal problem which is generally diagnosed after 1 year; however, inflammatory resorption and replacement resorption (ankylosis) can be usually observed earlier within 1–2 months.[9] No such signs were seen clinically and radiographically in the present case at the end of 2 years.

A systematic review and meta-analysis by Torabinejad et al. revealed an overall mean survival of 88% for intentionally replanted teeth with a mean 4-years follow-up. Root resorption was reported as an adverse outcome in all included studies, with an overall prevalence of 11%.[18] Other studies have shown clinical success rate of intentional replantation cases after 1 year to be 89% which decreased to 59% at 5 years.[19] Jang et al.[11] found higher success rates for teeth in which the extraoral time was minimal, that is, 15 min or less compared with those which were kept out for >15 min. Similarly, Hammarström et al.[20] showed that intentionally replanted teeth with 1 h of extraoral time revealed extensive root resorption whereas the other teeth with 15 min of extraoral time showed better periodontal healing associated with reestablishment of the periodontal membrane. By keeping the tooth bathed in saline during the minimal 10 min of extraoral time, we aimed to circumvent this factor as extraoral wet time.

CONCLUSION

Intentional replantation of teeth has always been considered as the last treatment resort in endodontics. Appropriate case selection and clinical expertise helps to achieve successful outcomes in such intentional replantation cases. Also, with the use of simplified efficient aids to keep PDL cells viable along with PRF which provides essential growth factors, intentional replantation of teeth can be a good treatment option for treating endodontic mishaps such as removal of separated instruments beyond root apex. Furthermore, the advantageous of IR for the patient include reduction in clinical time, complications, and cost compared to nonsurgical endodontic treatment and surgical endodontic treatment. Evidence-based practices shall suggest that it should no longer be considered as a final treatment modality, but in fact as a conventional treatment.

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Conflicts of interest

There are no conflicts of interest.