Considerations and differences in the treatment of a fused tooth

OLIVÁN-ROSAS G, LÓPEZ-JIMÉNEZ J, GIMÉNEZ-PRATS MJ, PIQUERAS- HERNÁNDEZ M.CONSIDERATIONS AND DIFFERENCES IN THE TREATMENT OF A FUSED TOOTH. MED ORAL 2004;9:224-8.

SUMMARY

Dental malformations relating to bigeminism, fused teeth, etc., have a prevalence of 0.5-5%, depending on geographic, racial or genetic factors. This in turn may influence the treatment to be provided in each case. Anomalies in the shape, size and number of teeth are more common in the so-called pediatric genetic syndromes, many of which are associated to mental retardation.
The present study describes two clinical cases of similar dental fusion involving a central incisor and comprising different and individualized treatment plans due to the important differences in the characteristics of each patient.

The first case corresponded to a healthy 9-year-old boy with a fused upper central incisor and a supernumerary incisor in the second quadrant. The fused tooth presented two independent and converging roots with a single pulp chamber. Endodontic treatment was provided, with dental sectioning and composite reconstruction of the crown. Orthodontic management was reserved for a second stage.
The second patient was a 27-year-old male with severe mental retardation of uncertain origin, gingival hyperplasia, a large bilobular upper central incisor, and a total lack of oral hygiene. Treatment in this case was limited to surgical resolution of the periodontal problem and the introduction of an exhaustive prevention program involving instructions for oral hygiene (with implication of the parents and care takers).
In conclusion, the development of a management plan in these two cases of fused teeth required due consideration of the degree of patient cooperation, which was severely limited in one case - thereby causing treatment to differ greatly from one individual to another.

Key words: Double tooth, fused tooth, bigeminism.

INTRODUCTION

Dental morphological anomalies are usually the result of development defects of dominant autosomal hereditary origin, attributable to trauma or produced by some infectious process or radiological exposure (1-3). The classification of such morphological anomalies comprises dehiscence, dental fusion, concrescence, gemination, schizodontia and dens in dente, among other conditions (1,2). According to Canut-Brusola, the following definitions can be established:

Dehiscence: laceration resulting from trauma and affecting the crown of a tooth germ.

- Dental fusion: the merging of two or more teeth at enamel and/or dentinal level.

- Concrescence: the merging of two or more teeth at root cement level.

- Gemination: attempted division of a tooth germ in two.

- Schizodontia: complete division of a tooth germ in two.

- Dens in dente: enamel penetration into the pulp chamber (2)

In this context, some authors recommend the term "double tooth" in reference to all such junctional defects (4-8).

"Double teeth" can form as the result of fusion of the developing dental germinal elements, or as a consequence of gemination of a single germ (4). In cases of dental fusion, two teeth may joint at dentinal and/or enamel level - merging at enamel level alone being infrequent. These fused teeth may present two independent root canals or, less often, a single root and one or two pulp chambers (1). The joining of two normal teeth may occur, thereby reducing the final number of teeth in the arch, though the most common situation is the fusion of two supernumerary teeth or of one supernumerary tooth and a normal tooth. In these latter two cases the total number of teeth in the arch is not reduced (2,8). As a consequence of fusion, the resulting tooth may be of normal size or larger than normal (1).

Dental fusion is more common during the deciduous dentition phase. It affects 0.1-2.5% of individuals depending on the author, and is normally associated to agenesis of the corresponding permanent tooth (in 33-70% of cases)(1-3,9,10). The canines and incisors are particularly implicated (1,11,12).

Some authors report no significant differences in relation to location (maxillary or mandibular) or patient sex - though racial differences have been documented (10,13). In this context, a 5% prevalence has been reported in the Japanese population, versus 0.5% among Caucasians (1,9,10,13).

Trisomy 21, orodigitofacial syndrome, ectodermal dysplasia, Pierre-Robin syndrome and certain situations involving labiopalatal fissures can be associated to dental fusion (1,9,14).

The differential diagnosis must be made with bigeminal teeth, and is not always easy to establish. Nevertheless, as a general rule, dental fusion may be presumed if the number of teeth in the arch is found to be reduced and/or two roots are radiologically present (1,4,9,14,15).

The present study describes two clinical cases of similar dental fusion involving a central incisor and comprising different and individualized treatment plans due to the important differences in the characteristics of each patient.

CLINICAL CASES

CASE 1

A healthy 9-year-old boy presented an upper central incisor of much greater than normal size, with a central depression along the entire vestibular surface that tended to divide the piece in two (fig. 1). There was no reduction in the number of teeth in the arch, and no other teeth were seen to present the same problem. An erupting supernumerary upper left lateral incisor was also noted. Examination of the oral mucosa in turn revealed a hypertrophic upper lip frenulum. The panoramic X-ray study showed the fused tooth to present two independent and converging roots, with a single pulp chamber, confirmed by periapical radiography.

Fig. 1. A healthy 9-year-old boy. 
Note the enlarged right central incisor with a central depression. 
The second quadrant also contains a supernumerary incisor. 
The lip frenulum is implanted very low down.

Paciente varón de 9 años, sano. 
Se observa el incisivo central derecho aumentado de 
tamaño con una hendidura central. 
En el segundo cuadrante también se observa un incisivo supernumerario. 
El frenillo labial presenta una implantación muy baja.

Management in this case consisted of endodontic treatment of the mesial root of the fused central incisor, dental sectioning and extraction of the distal crown-root fragment, followed by composite reconstruction of the mesial coronary fragment. The supernumerary tooth was also removed, and an upper lip frenectomy was performed (Fig. 1-2-3-4). Orthodontic treatment with functional apparatus was reserved for after surgery, to favor correction of the incomplete canine and molar deviation, increase vertical dimension to favor molar extrusion, and reduce the anterosuperior diastemas and overjet.

 

Fig. 2. Peroperative view of the same patient as in the previous figure. 
Endodontic treatment was provided, with coronal-root sectioning and composite sealing. 
The left supernumerary tooth was extracted and a lip frenectomy was performed.

Imagen peroperatoria. Se procede a la endodóncia, odontosección 
coronoradicular  y obturación con composite de IC, exodoncia 
del diente supernumerario izquierdo y frenecectomia labial.

 

Fig. 3. Immediate postoperative view of the 
same patient as in the two previous figures.

Postoperatorio inmediato.

 

Fig. 4. Some months later.

Aspecto unos meses después.

 

CASE 2

A 27-year-old male presented severe mental retardation attributable to encephalopathy of unknown origin and involving neuromotor, sensory and cognitive impairment with a level of comprehension far superior to the level of expression and a degree of language development allowing useful communication. Periodontal disease was diagnosed, with severe gingival hyperplasia almost completely covering the dental crowns (with code 4 CPTIN). A bilobular macrodontic upper right central incisor was identified, with the presence of a deciduous upper canine in the first quadrant. The radiological study corroborated dental fusion of the central incisor at enamel level, with two divergent roots, and an impacted upper right canine.

Treatment in this case was limited to periodontal therapy under general anesthesia, due to the aggressive behavior of the severely retarded patient.

DISCUSSION

It is truly difficult to establish a differential diagnosis between a fused tooth and a bigeminal tooth, particularly when associated to dental ageneses or supernumerary teeth. As an illustrative example of such difficulty, a bigeminal central incisor can be observed with agenesis of the lateral incisor. For this reason many authors prefer to use the term "double tooth" in view of the uncertainty regarding the embryological cause underlying the junction defect.

As regards the treatment of such cases, a number of aspects should be taken into account. On one hand, fused teeth in the deciduous dentition require no treatment of any kind (4). In contrast, cases affecting the permanent dentition do require management for esthetic reasons. Some studies advocate extraction of the anomalous tooth, followed by orthodontic management to close the spaces (16). In any case, two situations are prevalently observed:

(a) Independent pulp chambers and root canals; in this case it is preferable to wait until late adolescence of the patient, once pulp horn recession has taken place, to then separate the crowns and subsequently restore both teeth. If one of the affected teeth is a supernumerary piece, the latter should be removed (3,4,17).

(b) A single pulp chamber with independent root canals; in this situation endodontic treatment of both canals is indicated, with double chamber aperture and root canal sealing, followed by crown sectioning to separate the teeth and program subsequent crown reconstruction (3,4).

In our first patient, and after dental sectioning, we extracted the distal crown-root fragment, since we considered the latter to correspond to the fused supernumerary tooth. This was followed by restoration of the mesial fragment with posterior orthodontic management. Some authors prefer orthodontic treatment before restoration of the treated tooth (18), while others tend to postpone the former (3,4,19).

In our second case, and in view of the special characteristics of the patient, oral health was considered to be more important than esthetic concerns. Management was therefore limited to periodontal surgery, with the provision of instructions for maintaining adequate periodontal health.

In our opinion, an individualized treatment plan is required in patients with dental fusion, since special patients (e.g., mentally handicapped individuals) may require increased attention to aspects of buccodental health, with less emphasis on esthetic concerns.

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