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CASE REPORT

Key words computed tomography, fused teeth, maxillary lateral incisor, operative microscope, supernumerary tooth, talon cusp

José Francisco Gómez Sosa, Enrique José Padrón Zambrano

Endodontic management of a maxillary lateral incisor fused with a supernumerary tooth with a talon cusp

The success of root canal therapy implies a thorough knowledge of the internal as well as the ex-ternal dental anatomy, in addition to its variations. An aberrant morphology of the root canals can be observed in any tooth, even in a maxillary lateral incisor. This case report looks at the root canal treatment of a maxillary lateral incisor fused with a supernumerary tooth, which shows large periapi-cal radiolucency. This treatment was successfully carried out with the aid of computed tomography (CT) and an operative microscope.

José Francisco Gómez Sosa, DMDDirector of Postgraduate Studies, School of Dentistry, Universidad Santa María, Caracas, Venezuela, South AmericaPhD Candidate in Endod-ontics, School of Dentistry, Universidad Central de Venezuela, Caracas, Venezuela, South America

Enrique José Padrón Zambrano, DMDChairman, Department of Endodontics, School of Dentistry, Universidad Santa María, Caracas, Venezuela, South America

Correspondence to:Dr Jose Francisco Gomez Sosa Director of Postgraduate Studies, School of Dentistry, Universidad Santa, María, Caracas, VenezuelaEmail: josefgomezs@gmail.com

Introduction

One of the main goals of nonsurgical root canal treatments is the elimination of infection and pre-vention of reinfection of the root canal system1-2. On the other hand, several studies on this subject have claimed that a poor knowledge about the morphology of root canal systems is the cause of a significant number of problems occurring during root canal treatment due to the fact that an aber-rant morphology can be found in any tooth, even in a maxillary central incisor. The conclusion is thus reached that for the success of such treatments, be-fore anything else, endodontists should first consider carrying out a thorough study of root canal systems and their anatomical variations3-5.

Dental hard tissue anomalies

Some diagnostic terms have been traditionally used to refer to dental hard tissue anomalies. For instance, some irregularities concerning the number and shape of teeth are named as ‘fusion’, ‘gemination’, ‘concres-cence’, ‘talon cusp’ or ‘dens evaginatus’6,7.

Fusion is known as the process of twinning of two or more tooth germs, which develop separately at the dentinal level but become a single large tooth during odontogenesis at a time when the crown is not yet mineralised6,8,9. According to epidemiologic studies, this process occurs most frequently during deciduous dentition.

Concerning the localisation of fused teeth, such an anomaly is more often found in the anterior re-gion of the mouth, particularly in the mandibular anterior segment. Actually, canines and lateral in-cisors are the teeth most frequently affected by fusion10, whereas twinning of a permanent and a super numerary tooth, a type of fusion that usually involves maxillary anterior teeth, only shows a fre-quency of 0.1%11.

Gemination differs from fusion in that in the for-mer, the tooth germ splits itself and the dental struc-ture usually shows two crowns, totally or partially separated, with only one root and one root canal12. In addition, gemination normally affects primary teeth though it may also affect permanent dentition usually in the incisor region13. Moreover, gemina-tion is generally asymptomatic and does not require treatment, although poor aesthetics, periodontal

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destruction and caries leading to pulp necrosis may occur14.

Despite being similar dental anomalies, gemina-tion and fusion are distinguished from each other only for classification purposes. Concerning treat-ment, distinction between the two does not seem to be important15.

Talon cusp or dens evaginatus is characterised by the presence of an anomalous structure, which resembles an eagle’s talon projecting itself lingually from the cingulum areas of a maxillary or a man-dibular permanent incisor16. Moreover, research on this subject shows that such an anomaly is more fre-quently found in permanent rather than in primary dentition. Actually, 75% of the cases under study were permanent teeth, whereas only 25% were pri-mary teeth17.

Talon cusp shows preference for the maxilla over the mandible. In fact, maxillary lateral incisors are the most frequently involved teeth (67%) followed by central incisors (24%) and canines (9%)18,19.

The above data also support the hereditary character of talon cusp, since family histories of the reported cases revealed that such an anomaly sometimes affected patients who had consanguine-ous parents17. The same data also show that the occurrence of both dens evaginatus18,20-22 and fu-sion23-30, in the same tooth is rare31,32. Concres-cence, unlike fusion and gemination, is known as the twinning of two teeth by cementum6,7.

Careful clinical and radiographic examinations are highly recommended for a good treatment planning. Actually, the conventional intraoral peri-apical radiograph is an important diagnostic tool in endodontics for assessing root canal configuration.

However, the usual dental radiograph is not enough for understanding the complex morphology of root canal systems, e.g., that of fused teeth. This problem can be overcome by using more recent diagnostic methods such as computed tomography (CT), which can offer three-dimensional (3D) im-ages of individual teeth and their surrounding tis-sues33. Precisely, this paper reports the root canal treatment of a maxillary lateral incisor with two roots and three root canals, which were found by means of radiographic, CT and operative micro-scope examinations.

Case report

A 12-year-old Venezuelan male patient with a non-contributory medical history was referred by his dentist to the author’s private practice for root canal treatment of a left maxillary lateral incisor showing a coronal abnormality. Clinical examin-ation showed a talon cusp at the lingual aspect of tooth 22 (Fig 1) and, at the buccal and lingual aspects of that tooth, a fusion line with a supernu-merary tooth (Fig 2).

At the time of the first examination, there was no spontaneous pain, mobility, swelling or sinus tract and periodontal probing depths were within normal limits. However, there was a positive his-tory of pain since the patient reported that he had some swelling and a sinus tract every 3 months for over 2 years. In addition, there was no history of trauma, the tooth was tender to percussion and pulp sensitivity tests showed no response to cold or to electric pulp testing.

Fig 1 Clinical image showing (a) talon cusp and (b) fusion line. Fig 2 Clinical image showing buccal fusion line.

ab

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The radiographic evaluation of the incisor re-vealed an unusual and complex root canal anatomy (Figs 3a and 3b). Besides, the radiographic outline of the periodontal ligament suggested the presence of two rare roots with a large periapical radiolucency of about 10 mm in diameter.

Due to such an abnormal radicular anatomy, it was decided to perform a CT (BrightSpeed Elite; GE Healthcare, Pewaukee, WI, USA) of tooth 22, which confirmed the presence of three canals in the apical third of the root and a periapical radiolucency that destroyed the cortex of the maxillary palatine pro-cess (Figs 4a– 4g).

Based on the above clinical and radiographic findings, a necrotic pulp and an asymptomatic ap-ical periodontitis were diagnosed and a nonsurgical root canal treatment was planned with the use of calcium hydroxide as an inter-appointment dressing. Two appointments were then fixed.

In the first appointment, access to the root canal system was reached after anaesthetising the area with 1.8 ml of 2% lidocaine with 1:100,000 epi-nephrine, and the use of a rubber dam. Though a necrotic pulp was diagnosed, anaesthesia was used in order to avoid gingival discomfort when the rub-ber dam clamp was placed. By means of an operative microscope, two root canal orifices were found, one distal and the other mesial. The latter split into two root canals at the mid-root level showing two differ-ent apical foramina.

EX 1 and ET 20D ultrasonic tips (Satelec, Merig-nac, France) were used to enlarge the canal orifices in order to obtain a straight-line access into the root canals (Figs 5a and 5b). The initial negotiation of these root canals was performed with a size 15 K-file (Dentsply Maillefer, Ballaigues, Switzerland) and the irrigants used were 5.25% sodium hypochlorite (NaOCl) and 17% ethylene-diaminetetraacetic acid (EDTA).

The working length of the root canals was meas-ured and confirmed with an apex locator (Fig 6) (Root ZX; J. Morita, Osaka, Japan). Stainless steel hand K-files up to size 20 (Flexofiles, Dentsply Maillefer) were first used to enlarge the canals. Afterwards, ro-tary files (RaCe; FKG Dentaire, La Chaux-de-Fonds. Switzerland) were used to clean and shape them, calcium hydroxide (Ultracal; Ultradent, South Jor-dan, UT, USA) was used as intracanal medicament

Fig 3a Preoperative radiograph. Fig 3b Mesial angled diagnostic radio-graph.

and finally the access cavity was sealed with Cavit (3M Espe, Seefeld, Germany).

The patient returned to the clinic symptom-free 3 weeks later and after anaesthesia and rubber dam placement, calcium hydroxide was removed from the canals with ultrasonic activation of 5.25% NaOCl and 17% EDTA (P5 Booster Suprasson; Satelec Mer-ignac, France). After drying the canals with paper points, the fitting of the greater taper gutta-percha cones was checked (Autofit; Analytic Endodontics, Glendora, CA, USA) (Fig 7). Each canal was then obturated using the continuous wave obturation technique of warm gutta-percha (Elements Obtura-tion Unit; Sybron Endo, Glendora, CA, USA) and sealer (Extended Working Time Pulp Canal Sealer; Kerr, Romulus. MI, USA). A thin coat of glass iono-mer (Meron; Voco, Cuxhaven, Germany) and a resin composite (Tetric Ceram, Ivoclar Vivadent, Ellwan-gen, Germany) were then placed over the orifice of each canal, and a radiograph was taken (Fig 8).

The patient was under clinical examination and radiographic control every 6 months for over 3 years. After 3 years of follow-up, the tooth was asympto-matic and a control radiograph showed complete healing and no evidence of periapical pathology (Figs 9a to 9d).

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Fig 4 CT images of tooth 22: size of the re-sorptive defect (a and b). Cross-sectional images showing destruction of the palatal cortex at the apical third of the root: (c to f) transverse images showing the extension of the lesion, rare root anatomy and root canals of the tooth; (g) CT image showing 3D reconstruction of tooth 22.

a

NASAL CAVITY

LEFT

8.3 mm (3D)

12.2 mm (3D)

b

NASAL CAVITY

LEFT

22 OSTEOLYTIC PROCESS

c

NASOPALATINE DUCT

LEFT

22

RIGHT

d

11.0 mm (3D)RIGHT

5.0 mm (3D)

e

NASOPALATINE DUCT

22

OSTEOLYTIC PROCESSf NASOPALATINE DUCT

22

OSTEOLYTIC PROCESS

g RIGHT

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Fig 5a Microscopic view at 12× magnification showing two root canal orifices.

Fig 5b Microscopic view at 20× magnification showing two root canal orifices.

Fig 6 Working length radiograph. Fig 7a Master gutta-percha points in position.

Fig 7b Radiograph of apical plugs.

Fig 8 Immediate postoperative radiograph showing canal spaces completely obturated.

Fig 9 Follow-up radiographs: (a) 6 months; (b) 1 year; (c) 2 years; and (d) 3 years showing the bone reparation process, until complete healing.

a b c d

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Discussion

A maxillary central and lateral incisor with three root canals is an unusual case. In fact, according to the literature 100% of these teeth show a single canal, though a survey reported that 3% of maxillary lat-eral incisors may have two canals1.

A malformed tooth is often a challenge to endo-dontists, because from a clinical aspect, such a mal-formation may be due to either gemination, fusion, concrescence or dens invaginatus. Among these morphological defects, dens invaginatus can be said to be the most serious challenge from a diagnostic, treatment and prognostic point of view.

To help distinguish between fusion and gemina-tion, counting the teeth in an arch and including the anomalous crown as an additional tooth has been suggested. A full complement of teeth indicates gemination, whereas one tooth less than the normal number indicates fusion. This rule does not apply if a normal tooth fuses with a supernumerary tooth, because the anomaly in this case might represent the twinning of a normal and a supernumerary tooth. Nevertheless, concerning treatment an exact distinc-tion between fusion and gemination may not be critically important25,34.

As far as the aetiology of fusion is concerned, many theories have claimed genetic factors, local metabolic interference during tooth bud differentia-tion, traumatic and inflammatory causes. Moreover, to explain fusion some authors have put forward lack of space as the cause of deep penetration of the dental follicles33.

Talon cusp originates during the morphologic dif-ferentiation stage of tooth development. However, the aetiology of this condition still remains unknown. In most of reported talon cusp cases, this structure shows no association to any systemic condition. Nevertheless, the anomaly has been reported as ob-served in patients with Sturge-Weber Syndrome (en-cephalo-trigeminal angiomatosis), Mohr Syndrome (oro-facial-digital II syndrome), Ellis-van Creveld Syndrome or Rubinstein-Taybi Syndrome. The case reported herein is not associated with any known abnormal systemic developmental syndrome35.

Radiographic examination is an essential compo-nent of the management of root canal problems. The amount of information gained from conventional

films and digitally captured periapical radiographs is limited by the fact that the 3D anatomy of the area being radiographed is compressed into a two-dimensional image. These problems can be over-come by the use of CT, which delivers 3D images of individual teeth and can be helpful to achieve a better understanding of root canal morphology. This technique seems to have the potential to help visual-ise the topography of root canals and offer new per-spectives for dental images of special clinical cases33.

Conclusion

The present case report describes the treatment of a fused maxillary left lateral incisor with three root canals associated with a large periapical osteolytic process. In fused teeth, treatment protocols require special attention owing to the abnormal morphology of the crown and the complexity of the root canal system. Apart from clinical, radiographic and CT ex-aminations, the enhanced illumination and visibility obtained with an operating microscope together with the skill of a trained endodontist should be considered as a guarantee to predictable successful results.

Acknowledgements

The authors wish to thank Dr Yepsel Rada, Dr Enrique Pérez, Dr Cleydes Guerra and Dr Michelle Carvallo for their critical review and comments.

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