Management of synodontia between dilacerated permanent maxillary central incisor and supernumerary tooth with aid of cone-beam computed tomography.

A malformed tooth characterized by one or more developmental disturbances is often difficult to treat. When such teeth are present in anterior region, they pose a technical challenge for the clinician to restore esthetics as well as function. This case describes endodontic, surgical, and restorative management of fused and dilacerated maxillary central incisor. Cone-beam computed tomography (CBCT) was used in the present case to aid in understanding of complicated tooth morphology and managing the case successfully.

INTRODUCTION

Developmental tooth anomalies are deviations from the normal appearance involving color, shape, size, or number of teeth.[1] Fusion or synodontia is union between dentin and/or enamel of two or more separate developing teeth.[2]

Fusion, though an uncommon anomaly with incidence being <1% in Caucasian population may cause clinical problems related to appearance, spacing, and periodontal conditions.[3] Gemination is the malformation of a single tooth bud, recognized as an attempt by a single tooth germ to divide, with a resultant large single tooth with a bifid crown and usually a common root and root canal.[2] Clinically, it is often difficult to differentiate between fusion and germination, and these two anomalies are commonly referred as “double teeth”. Fusion might occur between two normal teeth or between a normal tooth and a supernumerary tooth. The union of a supernumerary tooth and a normal tooth is referred to as diphyodontic germination.[1]

Dilaceration (Latin: Dilacero-tear up) is defined as a deviation or bend in the linear relationship of a crown of a tooth to its root. According to some authors, a tooth is considered to have dilaceration to ward mesial ordistal direction if there is a 90-degree angle or greater along the axis of the tooth or root, whereas according to Chohayeb, dilaceration is a deviation from the normal axis of the tooth by 20 degrees or more in the apical part of the root.[4] Presence of dilaceration can severely complicate endodontic treatment.

Conventional intraoral periapical radiographs are not sufficient for understanding the complicated morphology of the root and root canal system, as in case of fused teeth. Therefore, cone-beam computed tomography (CBCT) which can produce three-dimensional (3D) images of individual teeth and the surrounding tissues was used.

In this case report, we present clinical detection and management of fused and dilacerated maxillary central incisor with a supernumerary tooth by using CBCT imaging.

CASE REPORT

A 22-year-old male patient reported to the Department of Conservative Dentistry and Endodontics with chief complaint of unesthetic appearance of maxillary anterior teeth. On clinical examination, #21 revealed unusual crown morphology [Figure 1a and b]. The crown was hypoplastic, fused to a supernumerary tooth, and exhibited anterior cross bite. A groove can be seen between the fused crowns. Caries was evident in the distal surface of crown and tooth was tender on percussion without any mobility.

Figure 1

(a) Preoperative photograph (labial view). (b) Preoperative photograph (occlusal view). (c) Preoperative radiograph. (d) Coronal view coronal to CEJ. (e) Coronal view at level of CEJ. (f) Coronal view 1.5 mm apical to CEJ. (g) Axial view showed root curvature of # 21 in distal direction. (h) Sagittal 3D reconstruction showed curvature of root of # 21 in labial direction. (I) Coronal 3D reconstruction of fused teeth. CEJ = Cemento enamel junction, 3D = threedimensional

There was history of trauma 15-16 years back and past dental history revealed that patient had previous endodontic treatment with 11 around 12 years back. Medical history was noncontributory. On thermal and electric pulp testing (C pulse pulp tester, Foshan Coxo Medical Instruments Co. Ltd), no response was elicited with #21 and supernumerary tooth. Radiographic examination [Figure 1c] showed superimposition of supernumerary tooth over #21. Also, distal caries and apical periodontal ligament space widening was seen with #21. Open apex, poor quality obturation lacking coronal seal, and periapical extrusion of gutta-percha was evident with 11. To ascertain the exact extent of fusion of 21 and supernumerary tooth in a 3D manner, CBCT (Planmeca Promax 3D Mid, Finland) imaging was carried out. Informed consent was taken from the patient. The involved teeth were focused, and images were obtained in transverse, axial, and sagittal sections of 0.5mm thickness, along with 3D reconstruction. The CBCT images revealed fusion of crowns of #21 with supernumerary tooth and both teeth separated 1.5 mm above cement enamel junction (CEJ) [Figure 1d-f]. Fusion was between enamel and dentin with two separate pulp canals. And the root of #21 showed curvature distally as well as in labial direction in apical third [Figure 1g and h]. On the basis of clinical, radiographic, and CBCT findings; a diagnosis of chronic apical periodontitis with fused and dilacerated #21 was made.

Management

Nonsurgical endodontic treatment of #21 was performed under rubber dam (Hygenic, Coltene/Whaledent) isolation. Endodontic access cavity was prepared on the palatal surface of #21 using a no. 2 round bur and an EX 24 bur (non-end cutting tapered fissure; Mani, Tochigi, Japan). Access cavity preparation was modified to accommodate the instrument unrestrained in the curved canal [Figure 2a]. Pulp tissue was extirpated by a barbed broach (Dentsply Maillefer, Ballaigues, Switzerland) and K files (Mani Inc, Tochigi-Ken, Japan). The canal was thoroughly irrigated with copious sodium hypochlorite (2.5%) and saline (0.9%). The working length was determined by using apexlocator (Root ZX; Morita, Tokyo, Japan) and confirmed radiographically [Figure 2b]. Canal preparation was completed using both crown-down and step-back technique. Coronal flaring of the root canal was done by using Gates Glidden drills no. 1-4 (Mani Inc). Enlargement of apical third was done using nickel-titanium (NiTi) hand files up to size #40/0.02 taper (Dia Dent Intl Inc). Coronal two-third of root was prepared with rotary ProTaper files (Dentsply Maillefer, Ballaigues, Switzerland). Canals were copiously irrigated with sodium hypochlorite and saline. Calcium hydroxide (Ultracal XS; Ultradent, South Jordan, UT) was used as the intracanal medicament and the access cavity was temporarily sealed using Cavit G (3M ESPE, Seefeld, Germany).

Figure 2

(a) Access cavity preparation (Shamrock preparation) in # 21.(b) Working length determination. (c)Post-obturation radiograph. (d) Surgical exposure of fused teeth. (e) Crown of supernumerary tooth separated from crown of 21. (f) Complete removal of supernumerary tooth. (g) Gingiva contoured and sutures placed. (h-j) Retreatment of #11. (k) Tooth preparation to receive PFM. (l) Permanent esthetic rehabilitation of 11 and 21. (m) Recall radiograph (1 year)

After a week, there was no tenderness on percussion with #21 and the root canal treatment was completed. The canals were rinsed with 2.5% sodium hypochlorite solution and saline (0.9%), dried with sterile paper point, and obturated with gutta-percha and Sealapex (Kerr, Romulus, MI, USA) using cold lateral compaction technique. The access cavity was sealed with light-cure composite resin (3M ESPE, St Paul, MN) restoration [Figure 2c].

After completion of endodontic treatment, esthetic management was discussed with the patient. The available treatment option explained to the patient was extraction of super numerary tooth, retreatment of #11, followed by fixed prostheses with #11 and #21. For removal of supernumerary tooth, full thickness triangular flap was elevated and crown of supernumerary tooth was separated from crown of #21 with the help of taper fissure bur (SS White Inc) and then root of supernumerary tooth was removed in isolation. Marginal gingiva was contoured around #21 for better esthetics and sutures (3:0 Silk, Ethicon Inc) were given [Figure 2d-g]. After a week, sutures were removed and retreatment of #11 was done by removing gutta-percha, cleansing of canal with sodium hypochlorite and saline, using calcium hydroxide as an intracanal medicament for a week, placing mineral trioxide aggregate (MTA;ProRoot, Dentsply Maillefer, Ballaigues, Switzerland) apical plug, and obturating the canal after 48 h by using thermoplasticized gutta-percha technique (E&Q Plus; Meta Biomed Co. Ltd, Cheongju, Korea) [Figure 2h-j].

The teeth were prepared to receive porcelain fused to metal (PFM) crown; and temporary crowns were cemented, which were replaced with PFM crowns after 2 days [Figure 2k and l]. The teeth were totally asymptomatic at 1-year recall visit [Figure 2m].

DISCUSSION

An anomalous tooth poses definite diagnostic and treatment challenge to the clinician. The extent of malformation in permanent tooth germ is highly related to its developmental stage and to the severity and type of trauma sustained by the primary incisor. This can be explained by the close anatomic relationship between the apices of primary incisors and the germs of succeeding teeth. The percentage of developmental disturbances of permanent incisors ranges from 12 to 74% and could be attributed to injuries of their predecessors.[5] The highest frequency of malformations was found following subluxation injuries and intrusion injuries were associated with the most severe malformations.[6]

Fusion between supernumerary and permanent teeth occur less often than fusion between other types of teeth with the frequency of 0.1% as reported by Yuzawa and colleagues.[1] Many theories have been proposed regarding etiology of fusion such as genetic factors, local metabolic interference during tooth bud differentiation, and traumatic or inflammatory causes. Clinically, it might be difficult to differentiate between fusion and gemination when a super numerary tooth is fused with a permanent tooth. Though “double teeth” (result of fusion or gemination) is relatively common, occurrence of union of three teeth which is reported as “triple tooth” is very rare. Triple tooth may occur due to fusion, gemination, or concrescence. Shilpa and Nuvvula proposed a classification of triple tooth: Type I with three pulp chambers and three root canals due to fusion; Type Ia, fusion of two normal teeth with a supernumerary tooth; Type Ib, fusion of three normal teeth; and Type II with two pulp chambers and two root canals which can be Type IIa, a combination of one geminated (double tooth) tooth and a supernumerary tooth; or Type IIb, one geminated tooth (double tooth) and a normal tooth.[7] Fused teeth can cause esthetic and functional problems; carious lesions in the grooves present in the fusion zone; periodontal problems associated with the grooves that extend subgingivally; asymmetries when fusion occurs in the anterior segment; malocclusions, especially when supernumeraries are involved; and endodontic complications.[1]

Radiographic examination is indispensable for management of endodontic problems right from diagnosis and treatment planning to assessing outcome. However; due to superimposition, periapical radiographs reveal limited aspects of the 3D anatomy. Also, there can be geometric distortion of the anatomic structures being imaged. CBCT is a valuable task-specific imaging modality, producing minimal radiation exposure to the patient and providing maximal information to the clinician. The X-ray beam is cone-shaped (hence the name of the technique) is directed onto an X-ray detector on the opposite side of the patient and captures a cylindrical or spherical volume of data, described as the field of view (FOV). The dimensions of the FOV, or scan volume, are primarily dependent on the detector size and shape, beam projection geometry, and the ability to collimate the beam. In general, the smaller the scan volume, the higher the resolution of the image and the lower the effective radiation dose to the patient. For most endodontic applications, limited or focused FOV CBCT is preferred over large volume CBCT for the following reasons:[8]

Increased resolution to improve the diagnostic accuracy of endodontic-specific tasks such as visualization of small features including calcified/accessory canals, missed canals, etc.

Highest possible resolution.

Decreased radiation exposure to the patient.

Time savings due to smaller volume to be interpreted.

Smaller area of responsibility.

Focus on anatomical area of interest.

In order to rule out the presence of any other anomaly or pathology in adjacent teeth and/or maxilla, we took medium FOV scanin this case without compromising much of resolution.

Injury to the deciduous predecessor might lead to root or crown dilaceration in permanent dentition in which the calcified portion of the tooth changes position and the remainder of the tooth is formed at an angulation.[910] Also, some authors proposed an idiopathic developmental disturbance as the possible cause in cases that have no clear evidence of traumatic injury.[11] In the present case, it can be hypothesized that an excessive pressure or force due to trauma produced, in addition to the close apposition of tooth buds, a possible displacement of the different layers of the tooth germ, thereby resulting in dilaceration.

Risk of procedural accident during endodontic procedure increases in case of severe dilaceration. In dilacerated teeth, the accepted basic endodontic techniques must be strictly followed, that is, good preoperative and working radiographs, unobstructed access to the root canal orifice, as direct access as possible to the apical third of the canal (within the constraints of the dilaceration), precurvature of all files used (the sharper the canal curvature, the nearer the bend of the file should be to its tip), and thorough irrigation.[12] Failure to recognize the multiplanar nature of the dilaceration is one of the factors that might contribute to the higher rate of unfavorable outcomes. Such findings can be confirmed by CBCT scan.[13] Modification in access cavity preparation is advocated i.e. “Shamrock preparation” (cloverleaf appearance) where an entire access cavity wall need not be extended, rather only a portion of wall is extended in the event of instrument impingement in case of dilacerated root.[14] When using manual instrumentation techniques, it is essential to precurve all instruments, and especially those larger than size 20, to allow the files to follow the curve and not just cut in a straight direction.[15] Shaping of root canal in this case was done by both crown-down and step-back technique with apical preparation done using NiTi hand file. The use of copious irrigation, file recapitulation, and further irrigation should be repeated more frequently in these severely curved canals. A multi visit approach should also be followed, with the use of inter appointment intracanal medicaments to increase the predictability of the treatment.[1] In this particular case, cold lateral compaction technique was chosen for obturation and spreaders made from NiTi were used because they penetrate to greater depths and distribute forces more evenly than stainless steel spreaders.[14]

Various treatment approaches such as selective grinding, surgical separation, or extraction followed by prosthesis are available for these abnormalities. However, wide variations in morphology of fused teeth require treatment decision to be made on individual basis [Table 1]. In this case, the level of fusion extended 1.5 mm above CEJ of 11. Therefore, surgical approach was done to separate the fused teeth properly, to remove the supernumerary tooth, and to achieve optimal contouring of gingival margins around #21. Esthetic problem was corrected by restoring #11 and #21 with PFM crowns.

Table 1

Various treatment modalities for management of fused teeth reported in literature

CONCLUSION

Synodontia or fusion in maxillary anterior teeth, though infrequent, may present with significant unesthetic appearance, spacing, and periodontal problems. Conventional intraoral radiography provides clinicians with cost-effective, high-resolution imaging that continues to be the frontline method for dental imaging. However, there exist many specific situations where the 3D images produced by CBCT facilitate diagnosis and influences treatment. 3D imaging with CBCT for accurate diagnosis and interdisciplinary treatment planning for correction of esthetics and function is needed for successful management of malformed teeth. 23]