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Table of Contents   
CASE REPORT  
Year : 2012  |  Volume : 23  |  Issue : 5  |  Page : 699
An erupted odontoma associated with pigmentation: A histogenetic and histological perspective


1 Department of Oral Pathology, Gian Sagar Dental College and Hospital, Banur, India
2 Department of Oral Pathology, Meenakshi Ammal Dental College, Chennai, India
3 Department of Anatomy and Human Sciences, King's College, London, United Kingdom
4 Department of Oral Pathology, Manipal College of Dental Sciences, Manipal, India

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Date of Submission22-Jul-2011
Date of Decision24-Nov-2011
Date of Acceptance24-Aug-2012
Date of Web Publication19-Feb-2013
 

   Abstract 

Odontomas are hamartomatous malformations of odontogenic origin composed of all the structures that form the tooth. Pigmentation associated with odontomas is rare, with only two cases reported in the literature. The genesis of this composite malformation is attributable to the organizational failure of the developing odontogenic apparatus leading to abnormal morphodifferentiation. Although some odontomas erupt into the oral cavity, it defies the existing views of normal physiologic tooth movement thus raising questions over the use of this term. Here, we review a case of large odontoma in a 23-year-old male surfacing into the oral cavity from its intraosseous location. The unusual occurrence of melanotic pigmentation in the odontogenic epithelial rests was demonstrated by Mason Fontana special stain. The histogenesis of this unusual entity and explanation to its possible occurrence is discussed.

Keywords: Erupted odontoma, hamartoma, mixed odontogenic tumor, odontoma, pigmentation

How to cite this article:
Kaur GA, Sivapathasundharam B, Berkovitz BK, Radhakrishnan RA. An erupted odontoma associated with pigmentation: A histogenetic and histological perspective. Indian J Dent Res 2012;23:699

How to cite this URL:
Kaur GA, Sivapathasundharam B, Berkovitz BK, Radhakrishnan RA. An erupted odontoma associated with pigmentation: A histogenetic and histological perspective. Indian J Dent Res [serial online] 2012 [cited 2020 Sep 28];23:699. Available from: http://www.ijdr.in/text.asp?2012/23/5/699/107447
Odontomas are hamartomatous malformations composed of an irregular mass of hard and soft tissues of odontogenic origin. It is regarded by many as an odontogenic tumor composed of enamel, dentine, cementum and pulp tissue. [1] It is believed to arise from both the ectomesenchymal and epithelial components of the developing tooth bud, apparently exhibiting normal histodifferentiation but abnormal morphodifferentiation. [2]

The occurrence of odontomas is frequent, accounting for about 22-67% of all odontogenic tumors. [3] Clinically, three variants of odontomas are recognized, which include the central (intraosseous) odontoma, peripheral (extraosseous) odontoma and erupted odontoma. [4] While the erupted odontoma is essentially an intraosseous odontoma that erupts into the oral cavity, [5] the peripheral odontoma occurs only in the soft tissue covering the tooth-bearing portion of the jaws, [6] and is histologically identical to the intraosseous odontoma. Based on the histologenetic presentation, odontomas are recognized as compound or complex odontomas. [7] Odontomas are commonly detected on routine radiographic examination in the second and third decades of life. [2],[3] Early diagnosis is important so that complications in dental arch development, tooth eruption and occlusion, including aesthetic problems, can be avoided.

Here, we report the case of a large odontoma in a 23-year-old male surfacing into the oral cavity from its intraosseous location. An unusual occurrence of melanotic pigmentation in the odontogenic epithelial rests, and the possible explanation for its formation is discussed.


   Case Review Top


A 23-year-old male patient presented at the outpatient department with a complaint of pain and slight swelling in the lower right posterior region of 8 months duration. The patient revealed that the pain was dull and subsided on taking analgesics. His medical and dental history was not contributory. Extraoral examination revealed an ill-defined enlargement on the right posterior angle and inferior border of the mandible measuring about 3 cm x 3 cm. The overlying skin was pinchable and palpation of the enlargement suggested the presence of a hard structure with a smooth surface and without any signs of mobility or tenderness. Intraoral examination revealed a creamish yellow, irregularly shaped mass in the position of the mandibular right third molar, which was conspicuously missing [Figure 1]. The mucosa around the mass was inflamed with signs of soft tissue enlargement and the mucobuccal sulcus was obliterated.
Figure 1: A creamish yellow, irregularly shaped mass in the region of the mandibular right third molar

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Complementary radiological examination using a panoramic radiograph [Figure 2] showed an unerupted mandibular right third molar that presumably had been depressed to lie close to the lower border of the mandible. Coronal to this tooth was a roughly circular, radiopaque mass, having the same radiodensity of adjacent teeth and surrounded by a thin peripheral rim of radiolucency. A mandibular occlusal radiograph showed an expansion of the buccal cortical plate in association with the irregular radioopaque mass distal to the mandibular right second molar [Figure 3]. Correlated with the clinical and radiologic findings, the provisional diagnosis was compatible with the diagnosis of odontoma. Treatment consisted of surgical removal of the mass under local anesthesia [Figure 4] and the impacted teeth [Figure 5] before sending the mass for histopathological examination for confirmation. The gross examination of the excised mass showed an irregular, creamish white, hard tissue mass [Figure 6], while the soft tissue bits attached to it were supple and friable with strong odor emanating from it.
Figure 2: A panoramic radiograph showing an unerupted mandibular right third molar inferior to the irregular mass and lying close to the inferior border of the mandible

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Figure 3: Mandibular occlusal radiograph showing expansion of buccal cortical plate in association with irregular radioopaque mass

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Figure 4: Surgical removal of irregular mass under local anesthesia

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Figure 5: Surgical removal of unerupted third molar under local anesthesia

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Figure 6: Gross examination of the excised mass before submitting for histopathological examination

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Histological examination of the soft tissue bit revealed a non-keratinized, hyperplastic, squamous epithelium overlying a cell-rich connective tissue stroma resembling primitive mesenchyme. The stroma surrounding the unerupted part of the odontoma was abundant and loose, composed of a delicate interlacing network of collagen fibers, fibroblasts/fibrocytes and numerous nests of odontogenic epithelial rests [Figure 7]. Many of the odontogenic epithelial rests showed intracellular pigmentation resembling melanin. The presence of melanin was further confirmed by Masson-Fontana special stain, which showed these deposits primarily in the cytoplasm of the odontogenic epithelial rests [Figure 8]. Careful examination did not reveal any dendritic cells adjacent to these odontogenic cells. A moderate amount of infiltration by chronic inflammatory cells, endothelium-lined vessels and extravasated red blood corpuscles were also evident.
Figure 7: Photomicrograph of the soft tissue surrounding odontoma was composed of a delicate interlacing network of collagen fibers, fibroblasts/fibrocytes and numerous nests of odontogenic epithelial rests (hematoxylin-eosin stain, × 20)

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Figure 8: Photomicrograph of the odontogenic epithelial rests with intracellular pigmentation resembling melanin (Mason Fontana, × 40)

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The hard tissue component was sectioned using a bone saw and both ground and demineralised sections prepared. The ground sections revealed the presence of irregularly arranged enamel, dentin and cementum-like tissues with spaces surrounded by dentine presumably representing pulp tissue [Figure 9]. The decalcified tissue showed relatively large quantities of irregularly deposited mature tubular dentin, enclosing clefts and hollow circular spaces [Figure 10], representing the sites of enamel deposition removed during decalcification. Some clefts showed presence of small amount of basophilic fibrillar material presumably representing enamel matrix. In contact with the masses of dentin was the connective tissue simulating the normal pulp and exhibiting a delicate network of collagen fibers, fibroblasts, fibrocytes, few inflammatory cells and blood capillaries. Aggregates of cementum were also evident in a few areas. The above histological description of haphazard deposition of dental tissue was consistent with the diagnosis of a complex composite odontome.
Figure 9: Photomicrograph of ground sections of odontoma showing the presence of irregularly arranged enamel, dentin and cementum-like tissues with spaces presumably representing pulp tissue (ground sections, × 40)

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Figure 10: Photomicrograph of the decalcified section of odontoma showing irregularly deposited mature tubular dentin, enclosing clefts and hollow circular spaces (hematoxylin-eosin stain, × 40)

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   Discussion Top


Odontomas are frequently occurring asymptomatic odontogenic malformations that constitute a chance finding on routine radiographic examination. [8] A review of odontomas by Sprawson [9] credits Paul Broca to be the first to use the term "odontoma" in 1867, who defined odontomas as tumors formed by an overgrowth of transitory or complete dental tissue. Subsequently, as many as five types of odontoma based on histomorphological features were described, which included the geminated composite odontomes, compound composite odontomes, complex composite odontomes, dilated odontomes and cystic odontomes. [10] Currently, the World Health Organization has placed odontomas under the odontogenic tumors of odontogenic epithelium with odontogenic mesenchyme with or without hard tissue formation, along with ameloblastic fibroodontoma, which is regarded as an immature precursor of complex odontoma. [7] Based on their location, odontomas are either central (intraosseous) or peripheral (extraosseous). Intraosseous odontomas most likely provide a barrier to eruption if they are lying in the eruptive pathway of an adjacent tooth. When these intrabony odontomas emerge into the oral cavity, they are termed "erupted odontoma." [11],[12]

Erupted odontomas are more often found in the maxila, [5],[13] although cases have also been described in the mandible, particularly in the molar region. [8] The majority of reported odontomas are correlated with unerupted teeth, mainly the second permanent molars. [4],[14],[15] It may therefore be postulated that the eruptive forces of these teeth play an important role in the eruption of odontoma. This implies that the partial movement of the unerupted tooth provides the force that pushes the odontoma into the mouth.

Although the etiology of the odontoma is unknown, several theories have been proposed, including local trauma, infection, family history, hereditary anomalies, odontoblastic hyperactivity and molecular events responsible for controlling tooth development. [16],[17] Hitchin [17] in his explanation of the etiology of calcified composite odontome suggested that odontomas are inherited from a mutant gene or interference, possibly post-natal, with a genetic control over tooth development. A mutation in the dental lamina or of the tooth germ itself may change the inherent capacity of odontogenic epithelium to go through the cap and bell stages necessary for tooth formation and yet retain its ability to stimulate the formation of all the dental tissues leading to the development of a composite odontoma. A plausible explanation for this is that the odontogenic tumor epithelial cells are recapitulating genetic programs expressed during normal odontogenesis, but demonstrate an abnormal expression of genes.

The mechanism whereby the odontoma appears to "erupt" into the mouth is unclear. Because of its size, the most likely explanation is that the odontoma reached the surface simply by its own preferential growth, with or without any contribution from the underlying molar tooth. An alternative explanation relates to the normal physiological situation where tooth eruption appears to be a multifactorial process involving the tissues of the periodontal ligament (PDL) or its precursor, the dental follicle (DF).

Although the presence of PDL was not clearly demonstrable in association with the odontoma in this case, the DF that surround the original structure would possibly result in the so-called eruption. [18] However, there is no experimental evidence to support the proposal that the eruptive movement was related to bone deposition below and bone resorption above.

Control of bone remodelling during tooth eruption necessitates complex signalling between the DF and the tooth germ, and this has been reviewed by Wise et al.[19] Whether some of these processes may be relevant to eruption of the odontoma awaits further study. However, the explanation for the occurrence of an erupted odontoma and the mechanism of its eruption appears to be different from tooth eruption because of the lack of PDL around odontoma. The forces required to move the odontoma may be not thus be linked to the contractility of the ligament fibroblasts.

Existing evidence for the physiologic tooth movement suggests that factors secreted by cells within the DF region promote both the recruitment of mononuclear cells and their differentiation into osteoclasts, with subsequent alveolar bone resorption as required for tooth eruption. Paralleling tooth eruption is the development of a functional PDL. As the root formation in odontoma does not follow the pattern of normal odontogenesis, it is proposed that the emergence of odontoma is attributable to the intrinsic enlargement of the lesion, which leads to resorption of the overlying bone and hence its eruption into the oral cavity. [7],[20] Also, in odontomas, eruption times are uncertain as some erupt at a younger age and others at an older age. Thus, it is likely that resorption of the overlying alveolus occurs secondary to the pressure of follicular tissue that surrounds odontomas. [5]

Another explanation for the emergence of large odontomas into the oral cavity is through bony remodeling. The DF regulates osteoclastogenesis and osteogenesis by regulating the expression of critical genes in both a chronological and a spatial fashion. Spatially, the bone resorption is in the coronal portion of the bony crypt and genes such as RANKL are expressed more in the coronal region of the DF than in its basal one-half. For osteogenesis, bone formation begins at the base of the bony crypt and osteoinductive genes such as bone morphogenetic protein-2 (BMP-2) appear to promote this and are expressed more in the basal half of the DF than in the coronal half. [21] However, the question with regard to erupted odontoma is whether the follicular tissue that surrounds the odontoma would provide necessary factors for conductance and chemoattraction of osteoclasts necessary to induce bone resorption. This observation is pertinent as not all intraosseous odontomas erupt and evidence points to the emergence of only the large odontomas.

A correlation between the patient's age and the type of odontoma has been studied, leading to the suggestion that compound odontomas are frequent in younger patients, while complex odontomas seem to occur much later. [22] Also, in the same way, the occurrence of this entity with regard to location suggests that older individuals are more likely to present odontomas in the molar region. [23] Frequently, odontomas take the place of missing teeth, or, alternatively, if all the teeth are present, an odontoma may represent a supernumerary tooth. [3] An unerupted tooth is frequently associated with the odontoma.

The present case had a similar radiographic picture with the size of the lesion larger than usual. However, if the lesion is pericoronal in location, ameloblastic fibro-odontoma or odontoameloblastoma has to be considered in the differential diagnosis, and has to be ruled out by histologic examination. [24],[25]

The most unusual histological feature observed in this case was the presence of melanin pigmentation within the odontogenic epithelial rests. A case of a complex odontoma, which also contained melanin pigment in the ghost cells, has been reported previously. [26] The origin of melanin in odontogenic cells [27] needed further probing as melanin is normally found in the skin, mucous membranes and uveal tract, but not within bone. The presence of melanocytes in the dental primordium points to a contribution by the neural crest to the formation of the tooth in mammals, and may also serve to explain the formation of certain pigmented odontogenic lesions. [28]

Although these observations suggest an association with racial pigmentation, particularly among the blacks and the Asians, [29] melanocytes normally present in the oral mucosa are also found in the dental lamina or tooth bud of the fetuses, more commonly in the pigmented race. It might not be surprising that melanocytes, which are also of neural crest in origin, may be present in dental lamina and odontogenic lesions. Another possibility is that a small proportion of lesional odontogenic tissue could have the potential for neuroectodermal differentiation under certain circumstances, which needs to be investigated for further clarification. [30]

Although the majority of odontomas present as asymptomatic masses in the oral cavity, their eruption into the oral cavity can give rise to pain, inflammation and infection, as was observed in this case. The management of odontomas associated with an impacted tooth comprises the surgical removal of the lesion with slight repositioning of the impacted tooth if the patient is young. However, in this case, surgical removal of both the mass and the impacted tooth was deemed necessary as the impacted tooth was in immediate proximity to the odontoma. Extraction is advised only in those cases where the tooth is abnormally oriented, morphologically altered and present with cystic changes.


   Conclusion Top


The present case is an exceptional one not only because of its relatively large size but also due to its emergence into the oral cavity. In addition to the characteristic histopathologic features of a complex odontoma, odontogenic epithelial rests containing melanin pigment were found. This could be attributed to the induction of odontogenic cells to produce melanin due to unknown underlying factors. The present report constitutes one of the very few cases reported in the literature where an intraosseous odontoma sequestered into the oral cavity also exhibited melanin pigmentation.

 
   References Top

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30.Han PP, Nagatsuka H, Siar CH, Tsujigiwa H, Gunduz M, Tamamura R, et al. A pigmented calcifying cystic odontogenic tumor associated with compound odontoma: A case report and review of literature. Head Face Med 2007;3:35.  Back to cited text no. 30
    

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Correspondence Address:
Raghu A Radhakrishnan
Department of Oral Pathology, Manipal College of Dental Sciences, Manipal
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-9290.107447

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10]

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