Introduction
Dens invaginatus or dense in dente (DI) or ‘Tooth within a Tooth’ is an uncommon anomaly arising during tooth development prior to calcification, resulting from surface invagination of crown or root which is lined by enamel. This defect occurs in two forms- coronal and radicular and may vary from slight enlarged lingual pit to deep infolding extending upto the apex.1, 2, 3 The prevalence varies from 0.3% to 38.5% with the permanent maxillary incisors most frequently being affected and bilateral occurrence in 43% of cases. Invaginated odontome, dilated composite odontome (Hunter 1951), Gestant anomaly (Colby 1956), tooth inclusion, dentoidindente and telescopic tooth are synonyms for this malformation.4, 5
Mesiodens (multiple are termed ‘Mesiodentes’) is the most frequently occurring supernumerary tooth, located in the anterior midline of maxilla2 and 0.15% and 1.9% is the reported occurrence in general population.6
Concomitant presence of dens invaginatus and mesiodentes is a rarity. This paper describes a unique association of dens invaginatus in a mesiodensleading to unaesthetic appearance.
Case History
A 19 year old boy reported to the department of oral medicine and radiology with the complaint of unaesthetic appearance of his upper front teeth. Medical and dental histories were not contributory. General examination indicated no abnormalities.
Intraoral examination revealed the presence of two additional teeth in the anterior maxilla, one conical-shaped and palatally placed in the first quadrant, while the other was bulbous and located at anatomical position of the permanent central incisor (21) in the second quadrant. Teeth 21 and 22 were malpositioned, labially and palatally respectively. The bulbous supernumerary showed deepened groove incisally (Figure 1, Figure 2). Radiographic investigation demonstrated enlarged pulp chamber with respect to the bulbous supernumerary.(Figure 3)
Figure 2
Intraoral view- palatalo-occlusalaspect showing affected mesiodense and additional supernumerary
Since these mesiodentes lead to malalignment and unesthetic appearance they were extracted. The one with abnormal morphology was sent for histological examination.(Figure 4 ) The patient was further referred for orthodontic treatment for the realignment of malpositioned maxillary left central and lateral incisors.
Figure 4
Macroscopic view of longitudinal section of the extracted specimen showing invagination of enamel into tooth structure
A Ground section of the specimen was prepared and scanned under the microscope. The icroscopic picture showed normal enamel and cementum on their respective locations. A pit on the external surface of enamel invagination as a blind sac, lined by enamel and extended below the cemento-enamel junction. However it did not communicate with the pulp (Figure 5). Based on the above findings a final diagnosis of dense in dente type II was made according to Oehlers classification.
Discussion
Dens in dente is a developmental anomaly resulting from an invagination of enamel organ into the dental papilla before calcification. It is of two types coronal and radicular.1 Dens invaginatus (DI) was first described by ‘Ploquet’ in 1794 in a whale’s tooth.4, 7 It was described by Salter as “a tooth within a tooth” in 1855.8 In human it was first described by a dentist named Socrates in1856.4, 7
Its etiopathogenesis is controversial. Several theories have been proposed, which include buckling of enamel organ under pressure from growing dental arch (Euler 1939, Atkinson 1943), focal growth failure of the internal enamel epithelium with continued proliferation of the surrounding normal epithelium (Kronfeld 1934), rapid and aggressive proliferation of a part of the internal enamel epithelium invading the dental papilla (Rushton1937), distortion and subsequent protrusion of a part of the enamel organ (Oehlers1957), fusion of two tooth-germs (‘twin-theory’ Bruszt 1950), infection (Fischer 1936 and Sprawson 1937) and trauma (Gustafson &Sundberg 1950).Association of genetic factors has also been reported (Grahnen 1962, Casamassimoet al. 1978, Ireland et al. 1987, Hosey & Bedi 1996).4
Among the different classifications recommended, Oehlers classification is the most extensively used. It classifies the entity in three classes, depending on how far the invagination extends from crown to the root. Type I is when an enamel-lined invagination is limited to the coronal part of the tooth and ends as a blind sac. In Type II, the enamel-lined invagination extends beyond cemento-enamel junction but is retained within the root canal. Type III represents an invagination which penetrates through the rootperforating at the apical area forming a second foramen in the apical or in the periodontal area. Amongst the three forms, Type I is the most common constituting 79%, followed by Type II (15%) and Type III (5%).5
In most cases, a dens invaginatus is detected inadvertently on the radiograph. Clinically, the invagination is often difficult to locate. Use of magnification and application of methylene blue dye can help illustrate the invagination.3 Passage of infection is possible from the invagination into the pulp and into periodontal tissues leading to ‘peri-invagination periodontitis’.3 Periodontal infection is most commonly associated with Type II entity. Abscess formation, cyst and internal resorption are other complications.7, 9, 10 Prophylactic or preventive sealing of the invagination, endodontic treatment, intentional replantation and extraction are the possible treatment options.11
Syndromes associated with it include Ekman-Westborg-Julin syndrome, Williams syndrome, Nance Huran syndrome, Tricho-dento-osseous syndrome and Postaxial polydactyly-dental-vertebral syndrome.5, 12
Wide discrepancy exists in the reported prevalence of dens invaginatus. Colak et al in a radiological study on Turkish patients found dens invaginatus in 0.17% of the patients. Maxillary lateral incisor were most commonly affected (80% of cases), followed by maxillary canine (20% of cases).13 The incidence of bilateral occurance was 25%. A retrospective radiographic study evaluating dental anomalies in Southeast Asian population in the Minneapolis reported prevalence of dens invaginatus and supernumerary to be 10.1% and 3.8%, respectively.14
Dental anomalies along with which dens invaginatus have been reported include supernumerary teeth, microdontia, macrodontia, hypodontia, oligodontia, taurodontism, fusion,germination and amelogenesis imperfecta.5, 15
Mesiodens are the most common supernumerary teeth with the prevalence between 0.15% and 1.9%. Co-existence of dens invaginatus in a supernumerary tooth is a rare occurrence. As per the available literature, twelve such cases have been reported9, 15, 16, 17, 18, 19, 20 out of which three have been reported in impacted mesiodens15, 17, 19 and three cases of occurrence of dens invaginatus in mesiodentes.9, 18, 20
Conclusion
This case report highlights the rare association of supernumerary tooth with dens invaginatus. Dens invaginatus and supernumerary teeth together can result in a range of complications like delayed eruption, crowding, spacing, impaction, diastema, abscess, cystic lesion and root resorption. So early diagnosis and necessary management is imperative to avoid these. Since the mesiodentes in the present case, imposed esthetic problem and malocclusion, they were extracted.
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