A Giant Posterior Maxillary Intra-Sinusal Complex Odontoma: A Clinical Case

Odontomas are the most common odontogenic neoplasms. They are generally small and asymptomatic. This article presents an unusual case of a giant maxillary complex odontoma, which obscured a part of the maxillary antrum and impacted a tooth. This was discovered during an episode of maxillofacial cellulitis. In this case, surgical excision of the lesion was performed under general anesthesia, and the closure was performed with a fat pad pedicled flap. A brief review of the literature was performed to analyze the characteristics of this clinical entity and their implication in the treatment.


Introduction
An odontoma is currently considered as a hamartoma because it is highly differentiated. It is a mixed odontogenic benign tumor because it is both epithelial and mesenchymal in origin [1]. According to the 2017 World Health Organization classification, there are two types of odontomas: complex odontomas, which consist of an anarchic assembly of mineralized tissue (enamel, dentin, and cementum) and pulp, and compound odontomas, which present as more differentiated tissue in the form of multiple small teeth [1]. Hybrid forms such as cystic odontomas have also been described. The average age of diagnosis of complex odontomas is approximately 26 years, with a male predominance [2]. Most odontomas described in the literature are between 1 and 2 cm in diameter [3]. Beyond this size, they are called giant odontomas [4].
The aim of this report is to describe a case of giant maxillary intrasinusal complex odontoma revealed by cellulitis and to describe the specifics of treatment resulting from this localization. We have also analyzed similar cases that have been reported in the literature and discussed the importance of imaging.

Case Presentation
A 27-year-old patient with no allergy presented with right posterior maxillary severe pain (visual analogue scale [VAS] score = 80/100). He had no medical or surgical history. No radiological examination was prescribed at the time.
On the day of the consultation, facial examination revealed a swelling in the right upper jaw, which was firm, non-indurated, and without eyelid edema. Endobuccal examination revealed a fluctuating swelling from distal to tooth 16 associated with exposure of hard tissue of inhomogeneous appearance extending 2 cm up to the right maxillary tuberosity. The panoramic radiograph revealed a heterogeneous radiopaque image of about 4 cm in its long axis, well delimited by a radiolucent halo ( Figure 1). The diagnosis of cervicofacial cellulitis was retained, and an antibiotic therapy based on amoxicillin 1 g (two tablets per day for six days) and metronidazole 500 mg (three tablets per day for six days) was prescribed for six days as well as level II analgesics (paracetamol codeine 500/30 mg, two tablets every six hours in case of pain) and a local antiseptic (chlorhexidine 0.12%) in the form of mouthwash. A computed tomography (CT) scan was also ordered. At the follow-up visit, seven days later, the CT evidenced a hyper-dense mass, which found a 33 x 23 x 21 mm right intra-sinusal encysted bone density mass with inclusion of the probable teeth 17 and 18 ( Figure 1). The diagnostic hypothesis that was considered was a giant and complex odontoma. The differential diagnosis for this lesion included calcifying odontogenic cyst, calcifying odontogenic tumor, ameloblastic fibroma, fibro-odontoma, and fibro-osseous lesion. Given these different diagnostic hypotheses, a biopsy was performed. The pathological examination concluded that the patient had a complex odontoma without any sign of malignancy.

Discussion
Most odontomas are asymptomatic and may present as a slowly evolving painless expanding process. They can be detected either fortuitously during routine radiological examinations, or either in the context of delayed dental evolution, or in case of an infectious episode. Delays in diagnosis of these conditions can lead to abnormalities in tooth eruption or even structural abnormalities of adjacent teeth. For this reason, a radiological check-up should always be performed in case of an eruption disorder and before each tooth extraction [1].
In this case, the odontoma was present in the maxillary tuberosity which is a very rare location (<2%) [3]. Indeed, odontomas are most often located in the anterior maxilla and in the parasymphyseal region of the mandible [3]. Intra-sinus and tuberosal localizations are very rare. The majority of cases of giant complex odontomas reported in the literature are located in the mandible and were asymptomatic complex odontomas [4][5][6].
Four relevant articles on the subject were reviewed, which contained four case reports of giant maxillary complex odontomas [7][8][9][10]. We have reported clinical and radiological characteristics of these cases in Table  1. The data collected in the articles [7][8][9][10] showed that the average age of the patients reported in the literature was 22 years and that the male-to-female ratio was 3:1. Only one patient out of the four presented with pain, and this same patient had an oral exposure of the lesion [9]. In three out of four clinical cases, the location of the lesion was the maxillary sinus [8][9][10]; only one case reported lesion in the central maxillary region [7]. Three of the four cases had extra-oral swelling, but all cases were associated with dental eruption anomalies. These delays in tooth eruption associated with extra-and intra-oral manifestations have led patients to consult dentists to refer them to specialized services. The use of three-dimensional (3D) radiological examination was essential for the management of the patients, which consisted in the removal of the lesion.

CBCT, cone beam computed tomography
The clinical presentation of this lesion type is highly variable, depending on the patient. Exo-buccal swelling may or may not be present. During an endobuccal examination, delayed tooth eruption and a buccal exposure of the lesion with an inhomogeneous appearance may be observed.
Dental panoramic imaging reveals an inhomogeneous radio-opaque mass. Further analysis must be conducted using CT scans to precisely determine the appearance, extent, and relationship to surrounding structures and to establish a definitive diagnosis and rule out differential diagnoses such as calcifying odontogenic cyst, calcifying odontogenic tumor, ameloblastic fibroma, fibro-odontoma, and fibro-osseous lesion. Furthermore, a biopsy and an anatomopathological examination must be performed. Prior to the removal of a maxillary giant odontoma, a comprehensive treatment plan with oral rehabilitation solutions is necessary.
Some authors have shown that an odontoma, giant or not, can interfere with eruption of the adjacent teeth, causing impaction [11]. This requires dental restoration or filling of a large edentulous tooth depending on the size of the giant odontoma, the location of the lesion, and the number of teeth affected. These formations, although benign, can be very destructive and mutilating. They require a maxillofacial prosthesis or a consequent bone reconstruction, especially in the maxillary posterior sectors.
The etiology of this disease is still unknown, but many factors have been considered to play an important role in its pathogenesis, such as local trauma, infection, genetics, or a family history of conditions such as Gardner syndrome and Hermann syndrome [4,7].
The 3D-CT examination is important for the correct diagnosis of the expansion and involvement of the tumor. The exact position of all involved structures (maxillary sinus, maxillary molars, alveolar ridge, and hard palate) was verified by 3D-CT, allowing for the best planning of the surgical intervention [11]. To our knowledge, there are no recommendations for the management of these structures.

Conclusions
Through this article, we understand the importance of systematic complementary examinations (panoramic radiography, CT scan) to avoid diagnostic errancy particularly when faced with eruption anomalies. Although these are benign tumors, their removal can be very mutilating and should be combined with other surgical techniques such as closure of the buccal-sinusal communication with a fat pad pedicled flap in this case. When the damage to the adjacent teeth and surrounding bone is severe, complex oral rehabilitation is required; hence, multidisciplinary therapeutic strategies are important.

Additional Information Disclosures
Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.