Regenerative Endodontics

Root Maturation in Teeth Treated byUnsuccessful Revitalization: 2 Case Reports

Radovan �Zi�zka, DMD,* Tom�a�s Buchta, DMD,* Iva Voborn�a, DMD,* Lubo�s Harvan, DMD, PhD,*and Ji�r�ı �Sed�y, MD, DMD, PhD, MBA, FADI, FICD†

Abstract

This article deals with the unusual course of failedrevascularization/revitalization cases. Up to this datethe evidence of success and failure rates of revascular-ization/revitalization treatment is scarce. These casereports present ‘‘unsuccessful’’ revascularization/revi-talization treatment of permanent immature teethwith apical periodontitis. Although the teeth weretreated by protocol suggested by the American Associ-ation of Endodontists and the symptoms disappeared,maturation of teeth continued, and periapical lesionwas reduced, the teeth went symptomatic during thefollow-up. Subsequently, regular root canal treatmentwas performed. Despite chronic infection that wasprobably left inside the root canal after a disinfectionprotocol, the secondary aims of the treatment wereachieved even when the primary ones were not. Thepossible causes of failures of revascularization/revital-ization treatment and their prevention are discussed. (JEndod 2016;42:724–729)

Key WordsApical periodontitis, immature tooth, revascularization,revitalization, root maturation

From the *Department of Dentistry, Faculty of Medicineand Dentistry, Palacky University, Olomouc, Czech Republic;and †Department of Anatomy, Faculty of Medicine andDentistry, Palacky University, Olomouc, Czech Republic.

Address requests for reprints to Dr Radovan �Zi�zka, Depart-ment of Dentistry, Faculty of Medicine and Dentistry, PalackyUniversity, Palackeho 12, 779 00, Olomouc, Czech Republic.E-mail address: loupaczech@gmail.com0099-2399/$ - see front matter

Copyright ª 2016 American Association of Endodontists.http://dx.doi.org/10.1016/j.joen.2016.02.004

724 �Zi�zka et al.

The first case report of modern regenerative endodontics that used principlesof tissue engineering was published in 2001 (1). From the beginning of the

performance of the revascularization/revitalization procedure, great emphasishas been placed on root canal disinfection. It had been assumed that in theabsence of bacteria and necrotic tissue and if scaffold with stem cells or growthfactors are present, regeneration of dental pulp would be feasible (2). The firstrevascularization cases used high concentrations of hypochlorite and a multipleinterim medication mixture of antibiotics to control bacterial infection (3).The concentration of antibiotics in these mixtures reached 1 g/mL, which wassubsequently found to be cytotoxic for stem cells of apical papilla (SCAP) (4),and lower concentrations of 1 mg/mL or the usage of Ca(OH)2 were proposed(5). Later the conditioning of dentin with high concentrations of hypochloritewas shown to have a profound negative effect on the survival and differentiationof SCAP (6) and prevented stem cell attachment to the dentin surface (7).In addition, a high concentration of hypochlorite was discovered to be toxicto SCAP (8).

In 2007, the American Association of Endodontists in agreement with the Amer-ican Academy of Pediatric Dentistry suggested the first treatment protocol for regen-erative endodontic therapy and has revisited it since then. This treatment protocolfollows laboratory procedures rather than clinical experience described in case re-ports and series. It consists of short time usage of a low concentration of hypochlo-rite, interim medication with low concentration of triple antibiotic paste or Ca(OH)2,and prolonged usage of EDTA. Experiments showed that residual bacteria persisted innoninstrumented recesses of root canals and in isthmi, and that it was impossible toremove them by hypochlorite (9) or by 2-visit treatment protocols (10). Conse-quently, reaching the goal of achieving a microbe-free canal by the root canal treat-ment is currently unattainable (11).

Until now, many complications of regenerative endodontic procedures havebeen described. The first was the discoloration of the clinical crown caused byminocycline or mineral trioxide aggregate (MTA). This esthetic complicationdoes not impede the success of the treatment itself. Currently, it is possible touse other calcium silicate cements that are discoloration-free, bond access cavity(12), or use antibiotic pastes without minocycline. Another complication of therevascularization/revitalization treatment was the inability to induce bleedingfrom the apical papilla. This complication can be solved by the injection ofplatelet-rich plasma (13). Animal histologic studies suggest that although thereis no difference between blood clot and platelet-rich plasma, there is a significantdifference if there is no matrix inside the root canal system (14). Furthermore,the collapse of MTA on top of the blood clot was described (15). It can bereduced with the use of atelocollagen or oxidized cellulose. Another problemleading to poor clinical outcome is a lack of root maturation or the depositionof hard tissue (16, 17). On the other hand, the formation of a root apex ispossible without regeneration of pulp (18). The information about failure isvery scarce in the literature (19). It is related to limited deposition of mineral-ized tissue or development of tooth rather than to recurrent bacterial infection.No evidence has appeared to date in the literature about symptomatic revascu-larization/revitalization where maturation of root or hard tissue deposition hadoccurred and subsequently went symptomatic.

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Figure 1. Case 1: diagnostic X-ray. Figure 2. Case 1: 9-month follow-up.

Regenerative Endodontics

Case Report 1An 8-year-old girl was admitted to the pediatric emergency

department at the Dental Clinic of Palacky University, Olomouc,Czech Republic for the evaluation and treatment of a maxillaryanterior swelling associated with her permanent maxillary leftincisor (Fig. 1). The tooth was slightly discolored, and an accesscavity that was previously performed showed it filled with fooddebris. Responses to percussion and probing pocket depthwere all within normal limits. A scar was apparent in the mucosaresulting from a previous incision. Palpation was mildly painful. Adiagnostic x-ray showed that the tooth was in the third stage ofroot development and encircled by large radiolucency. Thetooth was diagnosed as acute exacerbation of chronic apical peri-odontitis. The dental history disclosed that the patient was treateda week earlier as a dental emergency patient where the accesscavity and incision for drainage were performed. The dental his-tory also disclosed the patient had suffered dental trauma nearly6 months earlier, sustaining a noncomplicated crown fracture ofher permanent maxillary left incisor. No treatment was offeredsince then. After an interview with her parents, an informed con-sent for revascularization treatment was obtained.

The treatment was accomplished according to the clinicalprotocol recommended by the American Association of Endodon-tists. During the first appointment, local anesthesia 4% articainewith 1:200,000 epinephrine (Supracain 4%; Zentiva a.s., Prague,Czech Republic) and a rubber dam were applied, and the access

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cavity was redesigned. After that, the orientation working lengthwas established by an electronic apex locator and verified bymeasuring x-ray. The root canal system was rinsed with 1.5% hy-pochlorite for 5 minutes and subsequently with 5 mL saline andthen dried. Calcium hydroxide was injected into the coronal thirdof the root canal and covered with sterile Teflon tape, temporarilyrestoring the access cavity with glass ionomer cement.

After 3 weeks, the patient was completely free of symptomswhen she returned for further treatment. In local anesthesia, 4% me-pivacaine (Mepivastesin; 3M ESPE, St Paul, MN), a rubber dam wasapplied, and a temporary glass ionomer restoration with Teflon tapewas removed. The root canal system was irrigated for 20 minuteswith 17% EDTA with a final rinse of 5 mL saline. Afterwards,bleeding from apical papilla was induced with the help of sterileISO 25 K-file, with the tip bent by 30�. Ten minutes were allowedfor the blood clot to reach a level of around 2 mm under the ce-mentoenamel junction. White MTA (ProRoot MTA; Dentsply TulsaDental, Johnson City, TN) was mixed with sterile water and appliedover the blood clot together with sterile paper points. Then the ac-cess cavity was cleaned, and a thin layer of self-adhering composite(Vertise Flow; Kerr Corporation, Orange, CA) was placed atop theMTA to prevent the displacement of MTA. The tooth was then adhe-sively restored with composite material.

During the follow-up 3, 6, and 9 months later, the patientwas completely asymptomatic. Compared with her adjacent andcontralateral teeth, her central left incisor was within normal

Root Maturation of Failed Revitalization 725

Figure 3. Case 1: 1-year follow-up. Figure 4. Case 1: control X-ray after root canal treatment.

Regenerative Endodontics

limits regarding percussion, palpation, and pocket depths. It wasnonresponsive to heat or cold pulp vitality tests. Radiographicevaluation showed a reduction of the size of periapical radiolu-cency and further development of tooth type I, according to Chuehet al (20) (Fig. 2). At the 12-month follow-up evaluation, the toothwas slightly sensitive to percussion and palpation. There were noleakage around the margins of the composite filling and no cracksof the clinical crown, and probing depths were within normallimits. We assume a bacteria-tight seal prevented reinfection.Radiographic evaluation showed enlargement of periapical radio-lucency and no further development of the root and small resorp-tive lesions on the mesial aspect of the internal root canal wall(Fig. 3). A diagnosis of recurrent post-treatment endodontic dis-ease was made. After an interview with the patient’s parents, thegirl was scheduled for conventional root canal treatment, whichwas performed 1 month later. The root canal was filled with TotalFill RRM (FKG Dentaire SA, La Chaux-de-Fonds, Switzerland) andmaster apical cone (Fig. 4). At the 3-month follow-up the patientwas completely symptom-free, and an x-ray revealed resolvingperiapical radiolucency (Fig. 5)

Case Report 2An 8-year-old boy was admitted to the pediatric emergency

department at the Palacky University Dental Clinic for evaluation

726 �Zi�zka et al.

and treatment of a maxillary vestibular swelling associated withhis permanent maxillary right incisor (Fig. 6). The tooth wasslightly mobile, and an access cavity had been performed. Theresponse to percussion was increased slightly, and the probingpocket depth was within normal limits. A sinus tract was presentin the mucosa. A diagnostic x-ray showed the tooth was in thefourth stage of root development, no periapical radiolucencywas observed, and the presence of radiopaque structures in theapices of both central incisors was discovered. The vitality testof the left central upper incisor was positive. The right centralincisor was diagnosed as acute apical periodontitis. The boy’sdental history disclosed that he was treated the day before as adental emergency patient where the isolated access cavity was pre-pared. The dental history also revealed the patient had suffered atrauma the year before when he fell off his bike. Higher mobility ofthe central incisors and bleeding ‘‘around the teeth’’ wereobserved by his parents, corresponding with the diagnosis of sub-luxation. Since then no treatment was given. After an interview withthe patient’s parents, an informed consent for revascularizationtreatment was obtained.

The treatment was carried out by using the same protocol aspreviously. After the initial treatment, the patient was symptom-free. We saw him a second time 3 months after the first visit. Apostoperative x-ray showed further development of the root

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Figure 5. Case 1: 3-month follow-up after root canal treatment. Figure 6. Case 2: diagnostic X-ray.

Regenerative Endodontics

apex without deposition on the root canal walls and MTAcollapsed into blood clot (Fig. 7). Although a fistula was detectedduring a 3-month follow-up, the tooth was otherwise symptom-free. An x-ray revealed further development of the apical partof the root and radiolucency on the mesial aspect of the root.With concurrence of the patient’s parents, he was scheduled forconventional root canal treatment, and it was performed 1week later. The apical part of the root canal was filled with a5-mm-thick plug of MTA and restored with resin composite andfiber-reinforced composite posts. A small amount of MTA wasextruded through the apical foramen on the mesial aspect ofthe root. Furthermore, a noticeable radiolucent line that sepa-rated the root canal system and the continued developing apexwas visible (Fig. 8). At the 3-month follow-up, the patient wascompletely symptom-free, and an x-ray revealed healed radiolu-cency (Fig. 9).

DiscussionCurrently, the authors have treated 12 cases by revasculari-

zation/revitalization procedure, and only 2 cases described inthis article were unsuccessful. There are numerous probablecauses of revascularization/revitalization treatment failures. Themost probable is residual infection in the root canal system. Elim-inating bacteria from the root canal system was determined as one

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of the important principles of regenerative endodontic procedures(3). Nevertheless, the deposition of hard tissue or maturation ofroots occurred in these cases despite the residual bacterial infec-tion. It seems that the root development is dependent on the con-dition of the Hertwig epithelial sheath rather than the pulpregeneration (18) or bacterial load in the root canal system. Acase of maturation of infected root without any previous treatmentwas described in the literature (21). Chueh et al (20) recognize 5types of revascularization outcomes and propose that the condi-tion of the Hertwig epithelial sheath determined the outcome ofthe type of revascularization/revitalization. In an animal modelwhere the revascularization in infected and empty root canalswas compared, the character and amount of tissue were verysimilar (22).

Another possible cause of failure is reinfection of root canalsystem. In these cases no signs appeared of marginal leakage orinfraction of clinical crowns. In the second case, dislocation of theMTA coronal plug occurred, which might indicate a problem that isdue to the failure of treatment. Meticulous compaction of MTA andsubsequent precise adhesive restoration of the tooth can prevent rein-fection of the root canal system.

In these 2 cases interim medication with calcium hydroxidewas used. It was applied only to the coronal half of the rootcanal as recommended by Bose et al (23). Although the antimi-crobial action of calcium hydroxide was well-described (24),

Root Maturation of Failed Revitalization 727

Figure 7. Case 2: control X-ray after revascularization/revitalization procedure.

Figure 8. Case 2: 3-month follow-up.

Regenerative Endodontics

a smaller amount and significant distance from the apical part ofthe root canal system can decrease its antimicrobial effect. Theuse of antibiotic paste in severely infected root canals wouldlead to better antimicrobial action because it is thereby appliedto nearly the whole root canal system. Moreover, the removalof antibiotic paste from the root dentin is generally hard toachieve (25), and this can lead to substantively better antimicro-bial action (26).

Occlusal trauma can be another cause of revascularization/revitalization treatment failure. It can play a role in the secretionof particular neuropeptides such as substance P (27). Theinteraction of the neuropeptide with the pulp or immune cellscan cause neurogenic inflammation leading to necrosis of thepulp (28). Primary occlusal trauma can be caused by abnormalcontact of the tooth because of its faulty restoration or anorthodontic problem. It can be eliminated by proper occlusaladjustment of tooth restoration or by orthodontic treatment.Secondary occlusal trauma will probably not play a significantrole because tooth attachment is usually completely healedbefore the revascularization/revitalization treatment after traumais finished.

Although less likely, treatment failure could also be caused byrepeated tooth trauma, which could induce disruption of newly es-tablished and highly delicate homeostasis in the periapical envi-ronment, leading to the reactivation of an inflammatory process.Moreover, it has been reported that multiple dental trauma epi-sodes affecting the same tooth range up to 45%. The risk of sus-taining multiple dental injuries is more probable if the first injuryoccurs before the age of 9 (29).

728 �Zi�zka et al.

All current efforts of regenerative endodontic treatment arefocused instead on achieving the secondary goal of revasculariza-tion/revitalization treatment, ie, obtaining deposition of hard tissueon the root canal walls and maturation of root by protecting theviability and adherence of stem cells (30, 31). Shortenedirrigation time and decreased concentration of hypochloriteshould lead to a higher amount of the deposited hard tissuebecause the damage to stem cells and the structure of dentinare reduced. However, this leads to a lower reduction ofbacterial load and smaller effect on biofilm, and thus theprobability of achieving the primary goal is reduced. From thispoint of view, the use of the conventional irrigation protocolshould be considered because the bacterial spectrum of infectedcanals is the same in immature and mature permanent teeth(32). We should focus instead on reversing the negative effectof hypochlorite on the dentin by prolonging the use of EDTA oractivation of hypochlorite, which will not harm the apical papillaor the Hertwig epithelial sheath, rather than on reducing the anti-microbial function of hypochlorite or the limitation in the activa-tion of disinfectants.

AcknowledgmentsThe authors deny any conflicts of interest related to this study.

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Figure 9. Case 2: 3-month follow-up after root canal treatment.

Regenerative Endodontics

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