The multidisciplinary management of a fused maxillary central incisor with a talon cusp


Dr Sezin Ozer
Department of Pediatric Dentistry
Faculty of Dentistry
Ondokuz Mayıs University
55139 Atakum


Background:  A fused maxillary incisor required complex multidisciplinary treatment to preserve health and restore aesthetics. This report presents a rare case of a dental fusion between the maxillary right central incisor and a supernumerary tooth of a 9-year-old male patient with the chief complaint of the presence of a large anterior tooth.

Methods:  Radiographic investigation and computerized tomography indicated there was no connection between pulp chambers. After dividing the crown with a diamond bur, the supernumerary tooth was removed and the diastema between the maxillary central incisors was closed by orthodontic treatment. The tooth was then restored with composite resin.

Results:  The maxillary right central incisor was still healthy after a follow-up examination period of 24 months.

Conclusions:  A multidisciplinary approach with the cooperation of different practitioners can contribute to the success of a treatment plan.


Development of the human dentition is a very complex process. Any aberration in different stages of tooth development can result in unique manifestations, either in the primary or in the permanent dentition.

The terms ‘double teeth’, ‘double formations’, ‘joined teeth’, ‘fused teeth’1 or ‘dental twinning’2 are often used to describe fusion or gemination, both of which are primary developmental abnormalities of the teeth which may require treatment for aesthetic, orthodontic and functional reasons.3 Tooth fusion is defined as a union between the dentine and/or enamel of two or more separate developing teeth, causing the formation of a single tooth with an enlarged clinical crown.4 Fusion may be partial or total, depending on the stage of tooth development at the time of union.5 Both of the conjoint buds may be normal, or one may be supernumerary.

The aetiology of fusion is still unknown, but the influence of pressure or physical forces producing close contact between two developing teeth was reported as a possible cause. Genetic predisposition and racial traits were also reported as contributing factors.6 Fusion of a regular tooth and a supernumerary tooth may result in crowding, protrusion or the impaction of an adjacent tooth owing to insufficient arch length.7 Several treatment methods are described in the literature with respect to the different types and morphologic variations of fused teeth.

Dens evaginatus is the malformation of a tooth characterized by the presence of an accessory cusp. It is a developmental anomaly that occurs more frequently in mandibular premolars.8 However, it can also affect other teeth, including supernumerary teeth.9 Talon cusp refers to the same condition as d. evaginatus but talon cusp is the manifestation of d. evaginatus on anterior teeth.10 Talon cusp may cause occlusal interference and subsequent loosening or displacement of the involved tooth.8 These conditions may be an indication for odontoplasty treatment.11 The aim of odontoplasty is to reduce the additional palatal cusps and the mesiodistal dimension of the tooth. However, if odontoplasty leads to exposure of the pulp chamber, endodontic treatment options could be considered.12

Although there are several reports in the literature concerning d. evaginatus8 and dental fusion,13 observing these anomalies in the same tooth is a rarity.14 This case report describes the treatment of a fused maxillary central incisor with a talon cusp using a multidisciplinary approach to manage and restore function and aesthetic appearance.

Case Report

A 9-year-old male was referred to the Department of Pediatric Dentistry at Ondokuz Mayıs University, Turkey for the treatment of an enlarged maxillary right central incisor which caused aesthetic and chewing problems. There was no significant medical history and no family history of dental anomalies.

Intraoral examination revealed a macrodontic maxillary right central incisor which had a broad crown, separated by grooves extending into the gingival sulcus on the buccal and palatal aspects (Fig. 1). Thermal pulp testing gave a normal response, there was no tenderness to percussion and probing revealed no periodontal pocketing around the tooth. The total number of teeth was normal. The patient was in the late mixed dentition stage with a Class I skeletal basis on an average vertical pattern. The molar relations were half a unit Class II on the right and Class I relation on the left side. There was some anterior crowding in the lower arch and no midline shift according to the left central incisor. However, there was moderate crowding in the upper arch and a lack of space for eruption of the right canine tooth.

Figure 1.

 Preoperative view of the buccal aspect of the fused tooth showing a broad crown, a large enamel projection and a longitudinal groove extending into the gingival sulcus.

Radiographic examination of the upper incisors revealed that the maxillary right central incisor had fused with a supernumerary tooth (Fig. 2). Computerized tomography (CT) revealed the fused tooth had two root canals and two separate roots, with no communication detected between the pulp systems of the teeth (Fig. 3). The corresponding tooth on the opposite side of the arch appeared radiographically and clinically normal. Orthondontic treatment was planned for the treatment of the fused tooth hemisection.

Figure 2.

 Preoperative radiograph of the fused tooth.

Figure 3.

 Computerized tomography showing two root canals in the coronal part of the root of the maxillary right central incisor.

The treatment plan was explained to the patient and his family. With their permission, the tooth was anaesthetized and isolated for hemisection and a full-thickness buccal flap was raised. After examining the outline and position of the roots, it was decided to remove the supernumerary tooth. The crown was divided with a diamond bur. During the sectioning procedure, every attempt was made to remove the tooth structure and alveolar bone but only at the expense of the supernumerary tooth (Fig. 4). The tooth was then restored with flowable composite resin (Ælite Flow, Bisco, Schaumburg, IL, USA). The patient was told to brush his teeth carefully after every meal and to use dental floss to avoid plaque build-up. The patient reported no symptoms postoperatively.

Figure 4.

 Clinical photographs showing post-surgical view of tooth.

The diastema between the maxillary central incisors was closed with orthodontic treatment. Prior to the procedure, the upper right first premolar was extracted to allow for the proper eruption of the upper right canine. In this case, 0.022 inch slot MBT brackets were bonded. Tooth levelling and aligning procedures were achieved with 0.016 HANT wires (3M Unitek, Monrovia, CA, USA), followed by rectangular HANT wires. The space closure was made on rectangular stainless steel wire, and then normal finishing procedures were followed and appliances removed after 18 months of active treatment. A pleasing improvement in dental occlusion was obtained. Normal retention was provided with a lower bonded retainer placed on the canines. A Hawley retainer was placed on the upper arch. The tooth was then restored with a resin composite (Filteks Z250 3M ESPE, St Paul, MN, USA). The maxillary right central incisor was still healthy after a follow-up examination period of 24 months. Probing revealed no periodontal pocketing around the central incisor and attachment was within normal biological limits (Fig. 5).

Figure 5.

 Intraoral views of the patient showing good aesthetics with an ideal overjet and overbite relation.


Traditional terminology such as concrescence, fusion and gemination should be used as the potential embryologic cause of the anomaly and not as an exact diagnosis.15 To help distinguish between fusion and gemination, it is suggested that the teeth in the arch be considered as one with the anomalous crown. A full complement of teeth indicates gemination, whilst one tooth less than normal indicates fusion.16 This rule is compromised if a normal tooth fuses with a supernumerary tooth.17,18 In this case, the number of teeth was normal and differentiation from gemination was difficult. Also, the fused tooth had two root canals and two separate roots. In addition, considering Mader’s ‘two-tooth rule’,5 no missing permanent tooth was seen in this patient and therefore fusion with a supernumerary tooth was presumed.

Fusion is described in the literature as a developmental occurrence but its aetiology is uncertain.19 The morphology of fused teeth varies, and complex forms with separated or fused coronal pulp chambers are present. Even separated chambers can meet in the radicular area or can remain separated. Clearly, a careful clinical and radiographic examination is beneficial for optimal treatment planning. However, normal dental radiographs are usually not sufficient to establish a proper diagnosis and treatment plan.12 In this particular case, CT confirmed the exact path of the root canal. This technique has the potential to visualize the topography of the root canals and offers new perspectives for dental imaging for special clinical cases.20 However, it is not recommended for routine use because of the insufficient cost–benefit ratio. In this case, the diagnosis of fusion along with talon cusp was tentatively made based on radiographic analysis and CT findings which revealed two separate root canals and the clinical appearance of the tooth. The evagination is oriented perpendicular to the palatal surface, as is usually seen in cases of talon cusp.20 Clinically, talon cusps may cause problems attributed to caries developing in the groove.21 In this case, the talon cusp in the maxillary incisor did interfere with the patient’s occlusion, requiring recontouring before orthodontic treatment. Pulp exposure was not observed following recontouring which contraindicated the need for endodontic therapy. After odontoplasty was completed, the tooth was restored with flowable composite resin.

In the present case, tooth fusion of a maxillary central incisor is described, demonstrating surgical hemisection and extraction of the mesial part of the tooth. This procedure is one of several different treatment options. The fused tooth possessed two separate roots and canals. After the hemisection of the tooth there was no need for endodontic treatment. In some cases similar to the present one, root resection without root canal treatment was described and there was no evidence of pulpal necrosis in the resected teeth postoperatively.22,23


Different cases require a broad knowledge of alternative operative techniques and suitable clinical skills for successful management. Following a careful clinical and radiographic assessment, the hemisection can be selected as an appropriate treatment alternative in cases where a permanent tooth is fused with a supernumerary tooth. A multidisciplinary approach with the cooperation of different practitioners can contribute to the success of a treatment plan.