Maxillary Lateral Incisor with Two Root Canals: Fusion, Gemination or Dens invaginatus?

Antonio José de Azevedo PEREIRA1
Rivail Antonio Sérgio FIDEL2
Sandra Rivera FIDEL2

1Disciplina de Clínica Integrada, Instituto de Odontologia, Universidade Gama Filho, Rio de Janeiro, RJ, Brasil
2Faculdade de Odontologia, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ, Brasil

Braz Dent J (2000) 11(2): 141-146  ISSN 0103-6440

Introduction | Case Report | Discussion | Resumo | References

Endodontic retreatment of a maxillary right lateral incisor with two root canals is described. The diagnosis of fusion, gemination or dens invaginatus could not be made, due to conflicting findings, and to previous root canal treatment that erased the original configuration of the pulp chamber.

Key Words: tooth abnormalities, root canal therapy.


Endodontic therapy of abnormal root canal morphology is a challenge to the most experienced professional, and in a great number of situations, the tooth must be extracted (Cooke and Cox, 1979; Melton et al., 1991; Estrela et al., 1995; Hülsmann, 1997; Santa Cecília et al., 1998). The vast majority of cases in the literature report development changes representing anomalies such as radicular grooves (Pécora and Cruz Filho, 1991; Estrela et al., 1995; Santa Cecília et al., 1998), c-shaped canals (Cooke and Cox, 1979; Melton et al., 1991), and concrescence (Law et al., 1994).

More than one canal in maxillary central and lateral incisors is not a very common finding. In fact, according to Vertucci (1984), 100% of these teeth show single canals, although the survey of DeDeus (1992) reported that 3% of maxillary lateral incisors may have two canals. Mention of multiple canals in these teeth is limited to case reports (Goldberg et al., 1985; Thompson et al., 1985; Reeh and ElDeeb, 1989; Wong, 1991; Mangani and Ruddle, 1994; Peyrano and Zmener, 1995; Beltes, 1997; Hülsmann, 1997; Walvekar and Behbehani, 1997) of anomalies known as fusion, gemination or dens invaginatus.

The phenomenon of gemination arises when two teeth develop from one tooth bud and, as a result, the patient has a larger tooth but a normal number, in contrast to fusion where the patient would appear to be missing one tooth. Fused teeth arise through union of two normally separated tooth germs, and depending upon the stage of development of the teeth at the time of union, it may be either complete or incomplete. On some occasions, two independent pulp chambers and root canals can be seen. However, fusion can also be the union of a normal tooth bud to a supernumerary tooth germ. In these cases, the number of teeth is also normal and differentiation from gemination may be very difficult, if not impossible. In geminated teeth, division is usually incomplete and results in a large tooth crown that has a single root and a single canal. Both gemination and fusion are prevalent in primary dentition, with incisors being more affected (Shafer et al., 1979).

Dens invaginatus is a developmental variation most frequently involving the permanent maxillary lateral incisors thought to result from the infolding of a tooth crown before calcification. As the occurrence is frequently bilateral, if one tooth is affected, its homologous should be investigated. The invagination allows entry of irritants into an area which is separated from pulp by a thin layer of enamel and dentin, and presents a predisposition for the development of caries. In most cases the anomaly is detected by chance by radiographs (Shafer et al., 1979). An unusual crown anatomy can be seen, but these teeth may also show no clinical signs of any abnormality. In some cases the invagination is limited to the tooth crown, with normal morphology of the root and root canal. In most severe cases, the invagination can reach the end portion of the root (Hülsmann, 1997).

The following describes the endodontic management of a maxillary right lateral incisor that could be diagnosed as gemination, fusion or dens invaginatus, as well as the treatment of periapical and lateral bone loss with the aid of calcium hydroxide.

Case Report

A 28-year-old mulatto female in good health was referred for endodontic retreatment of an asymptomatic maxillary right lateral incisor. Clinical examination revealed the tooth to have a somewhat larger and discolored crown (Figure 1). Probing revealed no periodontal pocketing around the tooth. Radiographic evaluation showed that tooth had two separate canals, and previous inadequate endodontic treatment. Periapical and lateral radiolucencies were associated with the tooth, and extruding filling material could be noted in the bone surrounding its root apex (Figure 2). The corresponding tooth on the opposite side of the arch seemed radiographically and clinically normal (Figures 3 and 4).

Without anesthesia, and using carbide burs, the composite restoration was removed and the retrieval of the gutta percha points was easily performed with the aid of xylol and reamers. Two orifices were seen in the pulp chamber (Figure 5). The root canals were thoroughly instrumented with Gates-Glidden drills and K-type files using 5.25% sodium hypochlorite irrigation. After drying with paper points, the canals were filled with a thick mixture of calcium hydroxide and glycerin. The calcium hydroxide paste was changed every 90 days for 16 months.

Master gutta percha points were then cemented in place with an epoxy resin cement (Sealer 26, Dentsply, Rio de Janeiro, RJ, Brazil). Lateral condensation with accessory gutta-percha points of the apical third of the canal was followed by the use of a McSpadden compactor (Tagger's hybrid technique). The lingual access opening was sealed with temporary zinc oxide-eugenol filling, and the patient returned to the referring general dentist for the final restoration of the tooth (Figure 6).

At the 1-year recall appointment, the tooth was symptom-free, all clinical findings were within normal limits and bone healing appeared to be improved (Figure 7).


In the present case, the root canals were filled only after radiographic signs of bone healing, related to the apical and mesial aspect of the root. Because of its high pH (12.5), calcium hydroxide is an effective antibacterial agent, and has been reported to favorably influence the local environment at the resorption site, leading to healing. It has also been shown to change the environment in the dentin and bone to a more alkaline pH, which has been postulated to slow down the action of the resorptive cells and promote hard tissue formation and repair (Tronstad, 1988).

During endodontic therapy, the dentist must be prepared for unusual root canal anatomy, taking into account the importance of careful radiographic evaluation, that may lead to identification of such abnormalities, increasing the rate of success.

Some degree of confusion can occur over the classification of gemination and fusion. In fact, attempts to distinguish differences between the two anomalies have no clinical relevance. In this case report, the nature of the condition as fusion, gemination or dens invaginatus could not be established. Although two individual canals may lead to diagnosis of fusion, the diagnosis of gemination can also be made, because there were no missing teeth and the tooth had only one root. In addition, it is interesting to observe that in contrast to these anomalies, the crown of the tooth was almost normal in size, favoring the diagnosis of dens invaginatus. Nevertheless, cervical lingual groove (clinically) and invagination of enamel to the interior of the root (radiographically) were not observed here.

All in all, the question remains the same: fusion, gemination or dens invaginatus?


Pereira AJA, Fidel RAS, Fidel SR: Incisivo lateral superior com dois canais radiculares: Fusão, geminação ou dens invaginatus? Braz Dent J 11(2): 141-146, 2000.

É descrito o retratamento endodôntico de um incisivo lateral superior com dois canais. O diagnóstico de fusão, geminação ou dens invaginatus não pôde ser precisamente estabelecido, devido a características anatômicas conflitantes e à intervenção endodôntica anterior, que suprimiu a configuração original da câmara pulpar.

Unitermos: anomalias dentais, tratamento endodôntico.


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Correspondence: Antonio José de Azevedo Pereira, Av. N. S. de Copacabana, 195/406, 22020-000 Rio de Janeiro, RJ, Brasil. Tel: +55-21-295-8890. Cell phone: +55-21-9978-7924. e-mail:

Accepted March 30, 2000
Eletronic publication october, 2000