Considerations and differences in the treatment of a fusedtooth

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 orgenetic factors. This in turn may influence the treatment to beprovided in each case. Anomalies in the shape, size and number ofteeth 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 dentalfusion involving a central incisor and comprising different andindividualized treatment plans due to the important differences inthe characteristics of each patient.

The first case corresponded to a healthy 9-year-old boy with afused upper central incisor and a supernumerary incisor in the secondquadrant. The fused tooth presented two independent and convergingroots 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 mentalretardation of uncertain origin, gingival hyperplasia, a largebilobular upper central incisor, and a total lack of oral hygiene.Treatment in this case was limited to surgical resolution of theperiodontal problem and the introduction of an exhaustive preventionprogram involving instructions for oral hygiene (with implication ofthe parents and care takers).
In conclusion, the development of a management plan in these twocases of fused teeth required due consideration of the degree ofpatient cooperation, which was severely limited in one case -thereby causing treatment to differ greatly from one individual toanother.

Key words: Double tooth, fused tooth, bigeminism.

INTRODUCTION

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

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

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

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

- 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" inreference to all such junctional defects (4-8).

"Double teeth" can form as the result of fusion of the developingdental germinal elements, or as a consequence of gemination of asingle germ (4). In cases of dental fusion, two teeth may joint atdentinal and/or enamel level - merging at enamel level alonebeing infrequent. These fused teeth may present two independent rootcanals or, less often, a single root and one or two pulp chambers(1). The joining of two normal teeth may occur, thereby reducing thefinal number of teeth in the arch, though the most common situationis the fusion of two supernumerary teeth or of one supernumerarytooth and a normal tooth. In these latter two cases the total numberof teeth in the arch is not reduced (2,8). As a consequence offusion, the resulting tooth may be of normal size or larger thannormal (1).

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

Some authors report no significant differences in relation tolocation (maxillary or mandibular) or patient sex - thoughracial differences have been documented (10,13). In this context, a5% prevalence has been reported in the Japanese population, versus0.5% among Caucasians (1,9,10,13).

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

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

The present study describes two clinical cases of similar dentalfusion involving a central incisor and comprising different andindividualized treatment plans due to the important differences inthe characteristics of each patient.

CLINICAL CASES

CASE 1

A healthy 9-year-old boy presented an upper central incisor ofmuch greater than normal size, with a central depression along theentire 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 eruptingsupernumerary upper left lateral incisor was also noted. Examinationof the oral mucosa in turn revealed a hypertrophic upper lipfrenulum. The panoramic X-ray study showed the fused tooth to present two independent and convergingroots, with a single pulp chamber, confirmed by periapical radiography.

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

Paciente varón de 9 años, sano. 
Se observa elincisivo central derecho aumentado de 
tamaño con una hendiduracentral. 
En el segundo cuadrante también se observa unincisivo supernumerario. 
El frenillo labial presenta unaimplantación muy baja.

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

Fig. 2. Peroperative view of the same patient as in the previousfigure. 
Endodontic treatment was provided, with coronal-rootsectioning and composite sealing. 
The left supernumerary tooth wasextracted and a lip frenectomy was performed.

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

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

Postoperatorio inmediato.

Fig. 4. Some months later.

Aspecto unos meses después.

CASE 2

A 27-year-old male presented severe mental retardationattributable to encephalopathy of unknown origin and involvingneuromotor, sensory and cognitive impairment with a level ofcomprehension far superior to the level of expression and a degree oflanguage development allowing useful communication. Periodontaldisease was diagnosed, with severe gingival hyperplasia almostcompletely covering the dental crowns (with code 4 CPTIN). Abilobular 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 centralincisor at enamel level, with two divergent roots, and an impactedupper right canine.

Treatment in this case was limited to periodontal therapy undergeneral anesthesia, due to the aggressive behavior of the severelyretarded patient.

DISCUSSION

It is truly difficult to establish a differential diagnosisbetween a fused tooth and a bigeminal tooth, particularly whenassociated to dental ageneses or supernumerary teeth. As anillustrative example of such difficulty, a bigeminal central incisorcan be observed with agenesis of the lateral incisor. For this reasonmany authors prefer to use the term "double tooth" in view of theuncertainty regarding the embryological cause underlying the junctiondefect.

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

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

(b) A single pulp chamber with independent root canals; in thissituation endodontic treatment of both canals is indicated, withdouble chamber aperture and root canal sealing, followed by crownsectioning to separate the teeth and program subsequent crownreconstruction (3,4).

In our first patient, and after dental sectioning, we extractedthe distal crown-root fragment, since we considered the latter tocorrespond to the fused supernumerary tooth. This was followed byrestoration of the mesial fragment with posterior orthodonticmanagement. Some authors prefer orthodontic treatment beforerestoration of the treated tooth (18), while others tend to postponethe former (3,4,19).

In our second case, and in view of the special characteristics ofthe patient, oral health was considered to be more important thanesthetic concerns. Management was therefore limited to periodontalsurgery, with the provision of instructions for maintaining adequateperiodontal health.

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

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