Goncalves, M. Goncalves, D. P. Oliveira & N. Goncalves
Department of Oral Diagnosis and Dentomaxillofacial Surgery, Division of Dentomaxillofacial Radiology, Araraquara Dental School–UNESP, Brazil.
Department of Endodontics and Department of Oral Diagnosis, Division of Dentomaxillofacial Radiology, Piracicaba Dental School–UNICAMP, Brazil.

Introduction.
‘Dens invaginatus’ is a rare malformation of teeth, probably resulting from an infolding of the dental papilla during tooth development (Ikeda et al. 1995, Hulsmann 1997). However, controversy exists in the dental literature regarding the terminology to be used for this anatomical defect. It has been called ‘dens in dente’ (Thomas 1974), ‘dilated composite odontome’ (Hunter 1951, Hulsmann 1997), and ‘dens invaginatus’ (Oehlers 1957).
The variation in nomenclature has occurred because of a lack of consensus regarding the aetiology of this anomaly. The term ‘dens in dente’ indicates the radiographic appearance of a tooth which has apparently formed within another. ‘Dilated composite odontome’ infers that there is an abnormal dilation of the dental papilla, which then calcifies. ‘Dens invaginatus’ implies a defect which results from invagination of the crown before calcification occurs.
The classification of invaginations proposed by Oehlers (1957) is the most popular classification and the most commonly affected teeth are the maxillary lateral incisors. Type I is an enamel-lined minor invagination occurring within the confines of the crown not extending beyond the amelo-cemental junction. Type II consists of an enamel-lined form, which invades the root but remains as a blind sac; it may or may not communicate with the dental pulp. In type III, the invagination penetrates through the root, perforating the apical area and having a second foramen in the apical or periodontal area. There is no immediate communication with the pulp. The invagination may be completely lined by enamel, but frequently cementum will be found lining the invagination. The reported incidence for ‘dens invaginatus’ ranges from 0.04 to 10% (Hovland & Block 1977).
Although it is not common to find invaginations bilaterally, contra-lateral teeth should be examined clinically and radiographically, whenever one tooth is diagnosed with an invagination, since early discovery may allow preventive treatment to be provided. Classification of invaginations is based on radiographic appearance and it is common to see peg- or barrelshaped teeth.
Clinically, the ‘dens invaginatus’ presents unusual crown morphology, but affected teeth may also show no clinical signs of the malformation. The invagination allows entry of irritants into an area which is separated from pulp tissue by only a thin layer of enamel and dentine. It may predispose to the development of dental caries and ingress of irritants resulting in pulp inflammation. The affected pulp tissue then frequently undergoes necrosis.
If no entrance to the invagination can be detected and no signs of pulp pathosis are visible clinically and radiographically, then no treatment is indicated (Hulsmann 1997). However, the invagination should be sealed before carious destruction occurs. With deep invaginations having a separate apical or lateral foramen, it is likely that conservative root-canal treatment may be required (Szajkis & Kaufman 1993, Schwartz & Schindler 1996). Occasionally, the presence of immature roots necessitates apexification (Fergusson et al. 1980). In extreme cases, surgical procedures may also be necessary (Beltes 1997).
The purpose of this article is to report a case of ‘dens invaginatus’ in a vital permanent mandibular central incisor, which required conservative root-canal treatment.

A 10-year-old boy was referred to Piracicaba Dental School for root-canal treatment of the right mandibular central incisor. Clinical signs of morphological alteration were observed with a pronounced ‘dens invaginatus’ on the lingual surface, but no foramen coecum was visible (Fig. 1). The tooth was caries free and no draining sinus was observed. The colour of the tooth did not differ from the adjacent teeth and the total number of teeth in the anterior region was normal (Fig. 2). The tooth responded normally to pulp sensibility testing using ice.
The radiographic examination consisted of one periapical film, which demonstrated a type III invagination extending all the way from the crown to the apex of the root (pseudocanal), with no apparent communication with the main canal (Fig. 3). Although no opening on the lingual surface of the affected tooth could be seen, it was likely that an opening was present since there was a periapical radiolucency.
Since clinical tests suggested a normal pulp, and because there was an invagination extending to the open root end, conservative root-canal treatment of the invagination was initiated as the first course of treatment. It was assumed that the presence of infection in the invaginated canal and the periapical inflammation had delayed root development. The primary purpose of treatment was to remove the infection and allow apical closure of the root.
The tooth was isolated with a rubber dam and access gained to the pulp chamber. The canal was cleaned and shaped prior to placing a calcium hydroxide temporary dressing which was changed on two occasions. Root-canal treatment of the invagination was performed using K-files until a size 30 instrument reached the apex. A 1% sodium hypochlorite solution was used as the irrigant. Gutta-percha and Grossman’s sealer were used to fill the canal with the lateral condensation technique. The pulp continued to provide positive responses to pulp-sensibility testing, which indicated that the pulp in the main root canal had survived. The final restoration of the tooth was completed using amalgam (Fig. 4) and the tooth was reviewed after 1, 2, 5 and 10 years (Fig. 5).

Figure 1. Lingual view of the lower right central incisor showing pronounced dens invaginatus.



Figure 2. Occlusal radiograph which shows that all teeth in the lower anterior region are present.



Figure 3. Periapical radiograph which demonstrates the invagination extending all the way from the crown to the apex of the root. Note the periapical radiolucency.



Figure 4. Post-operative periapical radiograph taken immediately after completion of the endodontic treatment of the invagination.



Figure 5. Periapical radiographs taken at the 1-, 2-, 5- and 10-year follow-up examination.

Discussion.
According to Oehlers (1957), ‘dens invaginatus’ can present three distinct types depending on the depth of invagination and whether there is any communication with the periodontal ligament or periapical tissue.
The case reported in this article is a type III one and its clinical appearance was of ‘dens invaginatus’, with an associated ‘talon cusp’. Communication between the invagination and the oral environment was not apparent clinically, but it must have been present since a periapical radiolucency had developed. Bacterial contamination of the invagination that occurred subsequent to eruption of the tooth resulted in infection of the invagination and this, in turn, led to the development of periapical inflammation. Morfis & Lentzari (1989) reported that the presence of infection in the invagination could delay root development, as occurred in this case. Once the infection had been eliminated by canal preparation and irrigation, the periapical inflammation subsided, and the normal pulp within the main canal continued its normal process of root development.
Pulp sensibility testing highlighted a problem in this case and the positive response to testing does not necessarily mean that the whole pulp is alive. As reported by Kulild & Weller (1989), an invagination can occasionally become infected but the main canal contains normal pulp tissue.
Communication may exist between the root canal and the invagination (Gotoh et al. 1979). However, the tooth reported in this case did not appear to have any communication because the pulp responded to sensibility tests both before and after treatment. In addition, the resolution of the periapical radiolucency suggests that it was associated with the invagination.
The follow-up examinations demonstrate that conservative root-canal treatment of the invagination was successful with radiographs showing periapical healing.

References.

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