Two-stage surgical removal of large complex odontoma

Oral Maxillofac Surg DOI 10.1007/s10006-010-0206-0

CASE REPORT

Two-stage surgical removal of large complex odontoma Bruno Ramos Chrcanovic & Filipe Jaeger & Belini Freire-Maia

# Springer-Verlag 2010

Abstract Purpose The surgical treatment of a large complex odontoma in the mandibular angle is reported. Four possible surgical approaches to remove a benign tumor in the mandibular angle are discussed. Patient A two-stage surgical treatment was chosen; first, removing most part of the lesion and preserving the second molar, decreasing the risk of a pathological mandibular fracture. A maxillo-mandibular fixation for a period of 4 weeks was used. The patient was oriented to maintain a soft diet. The second surgical stage occurred 3 months after the first one due to the significant bone consolidation observed, reducing the possibility of a mandibular fracture. The remaining lesion and the second molar were then completely removed. Conclusions This case demonstrates the value of the tridimensional computed tomography in treatment planning prior to any definitive surgery. A computed tomography

B. R. Chrcanovic (*) Av. Raja Gabaglia, 1000/1209-Gutierrez, Belo Horizonte, MG-CEP 30441-070, Brazil e-mail: [email protected] F. Jaeger Alameda Monte Bianco 18-Condomínio Villa Alpina, Nova Lima 34000-000, Brazil e-mail: [email protected] B. Freire-Maia Av. do Contorno 4747/1010, Serra, Belo Horizonte, MG-CEP 30110-921, Brazil e-mail: [email protected] B. Freire-Maia Department of Oral and Maxillofacial Surgery, School of Dentistry, Pontifícia Universidade Católica de Minas Gerais, Belo Horizonte, Brazil

should be made in every case of intraosseous lesion in order to establish the intraosseous extent of the tumor, cortical perforation, and soft tissue involvement for precise guidance for the surgical planning. It is recommended that the surgeon considers excision by an intraoral, lingual approach when indicated, and in two stages, when an extremely thin mandibular base is present. Keywords Odontogenic tumors . Complex odontoma . Computed tomography

Introduction Odontomas are benign odontogenic tumors, characterized by their slow growth and non-aggressive behavior [1, 2]. Initially, the term was used as a general description for odontogenic tumors. Odontoma is the most common odontogenic tumor and accounts for 22–67% of all odontogenic tumors [1–5]. Odontomas are usually discovered by the second decade of life with no significant sex predilection [2–8]. Because compound odontomas are more likely to be diagnosed at a younger age than complex odontomas, the average age for patients with compound odontoma is often younger than that for patients with complex odontoma [6, 8, 9]. Although predominantly associated with permanent teeth, they also occur in association with primary teeth and are often involved with impacted teeth [8, 10]. Since these lesions develop from both epithelial and ectomesenchymal sources, odontomas are classified as mixed odontogenic tumors, a category that also includes ameloblastic fibroma and ameloblastic fibro-odontoma. It has been theorized that the ameloblastic fibro-odontoma is, in fact, an immature complex odontoma [7].

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Odontomas have been associated with antecedents of trauma during primary dentition [11] as well as with inflammatory and infectious processes, hereditary anomalies (Gardner's syndrome, Hermann's syndrome), odontoblastic hyperactivity, alterations of the genetic components responsible for controlling dental development, or from extraneous buds of odontogenic epithelial cells [3, 4, 12]. Radiographically and histologically, they are divided into two types, compound and complex, based on the degree of morphological similarity to mature teeth. Compound odontomas are about twice as common as the complex type and are characterized by the presence of tooth-like structures known as “denticles.” Their radiographic appearance is that of an opaque mass surrounded by a lucent zone, which may be encircled by a sclerotic border. This morphology is similar to that of a developing or unerupted tooth. Their size is usually about the same as a small tooth. Compound odontomas are most commonly located in the anterior tooth-bearing areas, often preventing the eruption of a permanent tooth. They have a high degree of histological differentiation, showing discernable areas of enamel, dentin, cementum, and pulp [3, 4, 12]. Complex odontomas, while showing the same degree of histological differentiation, are more amorphous in form. They are often found in the mandibular posterior tooth-bearing regions and have a greater potential for growth [10]. Most complex odontomas are small, measuring a few millimeters in diameter, and only rarely reach a considerable size or produce deformity of the jaw. These lesions are often diagnosed because of abnormal or absence of eruption of teeth [1, 13]. Radiographically, the complex odontoma presents as a welldemarcated radiopaque mass, occasionally surrounded by a narrow, radiolucent zone. Complex odontoma is less frequently seen than compound odontoma [1–6, 8]. Other types of odontomas are sometimes also seen, presenting combinations of the characteristics of compound and complex odontomas, i.e., mixed odontomas [3, 12]. Clinically, three types of odontomas are recognized in the literature: central (intraosseous) odontoma, peripheral (extraosseous or soft tissue) odontoma, and erupted odontoma [14]. Histologically, odontomas are composed of various dental tissue formations, including enamel, dentin, cement, and sometimes also pulp. Compound odontomas consist of a fibrous connective tissue sac surrounding the denticles. Complex odontomas show primary or immature dentin as predominant component, though enamel is also found, exhibiting two possible types of distribution: in a highly calcified area close to the central core or in a hypocalcified zone with immature enamel. Immature cement is also observed together with the external connective tissue capsule surrounding the lesion, resembling the dental follicular tissue [3, 6, 9].

The tooth-like appearance of odontomas, especially the compound variety, makes radiographic identification fairly routine. Typically, a radiograph of the area will reveal the lesion preventing eruption of a tooth. Complex odontomas have been associated with unerupted teeth more often than compound odontomas [4]. Odontomas can actually erupt into the oral cavity [1, 2, 5, 14, 15]. A differential diagnosis must be established with lesions of inter-root location, such as focal residual osteitis, cementoma, calcifying epithelial odontogenic tumors, adenomatoid odontogenic tumors, supernumerary teeth, cementing fibroma, or benign osteoblastoma. If the lesion is located at pericoronal level, the differential diagnosis should be established with adenomatoid odontogenic tumors, calcifying epithelial odontogenic tumors, ameloblastic fibrodentinoma, or odontoameloblastoma [3, 16]. According to Singer et al. [17], a differential diagnosis of odontoma pertains only to the complex odontoma, since the radiographic presence of numerous well-defined denticles and its clear delineation are pathognomonic for the compound odontoma. Bone tumors that may radiographically resemble complex odontoma include osteoid osteoma, osteoblastoma, cementoblastoma, and cemento-ossifying fibroma. However, these are not usually found with an impacted tooth [17]. The treatment of choice for odontoma is surgical excision. There is no reported potential for recurrence of complex odontoma, and, in many cases, conservative management allows for preservation of the surrounding dentition. The purpose of the present article is to report of large complex odontoma of the mandibular angle that was treated with an intraoral approach, with a discussion emphasis on the importance of the radiological findings and the surgical treatment.

Case report A 21-year-old man was referred to the Department of Oral and Maxillofacial Surgery, at the Pontifícia Universidade Católica de Minas Gerais, Belo Horizonte, Brazil, because of a large swelling in the right mandibular angle. Extraoral examination revealed obvious facial asymmetry. Mouth opening was adequate. Intraorally, expansion of the buccal and lingual cortical plates of the mandibular angle was visible, and the second and third molars were seen to be absent. The patient noted the swelling approximately 3 years earlier, giving no importance, but 1 month before, the increase became significant, resulting in facial asymmetry, painful symptoms, and limitation of mouth opening. Intraoral expansion of the buccal and lingual cortical plates of the mandibular angle was visible.

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A panoramic radiograph revealed a large, wellcircumscribed radiopaque mass in the right mandibular angle adjacent to the roots of the first molar, absence of the third molar, displacement of the second molar to the mandibular base, and erosion of the retromolar cortical region (Fig. 1). Computed tomography (CT) of the mandible showed a well-defined radiopaque mass, with an anterior–posterior dimension of 4.0 cm, medial–lateral dimension of 2.75 cm (Fig. 2), and cranial–caudal dimension of 3.0 cm. A tridimensional (3D) CT showed some erosion of the buccal cortex (Fig. 3), an extremely eroded lingual cortex (Fig. 4a), and preservation of a very thin mandibular base, mostly in its vestibular aspect (Fig. 4b). A two-stage alternative surgical treatment was chosen; first, removing most part of the lesion and preserving the second molar, decreasing the risk of a pathological mandibular fracture. In the first surgical stage, Erich bars were fixed to the maxillary and mandibular teeth, anticipating a possible occurrence of a pathological mandibular fracture. Under general anesthesia, an intraoral excision of the lesion via the lingual cortex was performed. A subperiosteal dissection directly exposed the lesion. A curved periosteal elevator was used to raise the lingual flap subperiosteally and protect the lingual nerve. Via this lingual approach, the odontoma was exposed and removed piece by piece with a bur. Most of the lesion was removed, and the tooth was left in the mandibular base. Figure 5 shows the macroscopic aspect of part of the lesion. The wound was primarily closed and healing was uneventful. A maxillo-mandibular fixation (MMF) for a period of 4 weeks was used. The patient was oriented to maintain a soft diet after the release of the MMF. The sensation in the distribution of the inferior alveolar and lingual nerves was preserved. A panoramic radiograph was taken immediately after the surgery (Fig. 6) and it revealed a radiolucent area in the right mandibular angle,

Fig. 1 Initial panoramic radiograph revealing a large, wellcircumscribed radiopaque mass in the right mandibular angle

Fig. 2 Axial computed tomography of the mandible

which corresponded to the area where most of the lesion was removed, and the presence of small radiopaque area associated to the coronary surface of the second molar was withheld. Histopathologic examination revealed a complex odontoma. The second surgical stage occurred 3 months after the first one due to the significant bone consolidation observed, reducing the possibility of a mandibular fracture. The remaining lesion and the second molar were completely removed. Panoramic radiographs were taken during the follow-up period. At 5 years control, significant bone regeneration was observed in the region of the lesion without signs of recurrence (Fig. 7).

Discussion Odontomas are usually smaller than the surrounding teeth or have the same size. They may replace one of the 32 teeth or be supernumerary to the normal dentition. Occasionally, a complex odontoma will exhibit potential for remarkable expansion [15], as it is described in this paper, a characteristic that distinguishes them from compound

Fig. 3 Tridimensional CT showing some erosion of the buccal cortex

Oral Maxillofac Surg Fig. 4 Tridimensional CT showing an extremely eroded lingual cortex (a) and preservation of the mandibular base only in its vestibular aspect (b)

odontomas. Pathologic changes such as impaction, malpositioning, aplasia, malformation, and devitalization of adjacent teeth are associated with 70% of odontomas [18]. Because of the presence of the solid mass, there was no eruption of the second molar, and the third molar was missing. This fact may suggest that the lesion might had developed from the malpositioned third molar bud, i.e., from extraneous buds of odontogenic epithelial cells. When these buds are divided into several particles, they may develop individually to become numerous, closely positioned malformed teeth or tooth-like structures. When the buds develop without such uncommon divisions and consist of haphazard conglomerates of dental tissues, they may develop into complex odontomas. However, the transition from one type to another is commonly associated with varying degrees of morphodifferentiation or histodifferentiation (or both), and it is often difficult to discriminate between the two types [19]. Odontomas are usually asymptomatic and are frequently discovered on routine dental radiographs, but in some cases, the patient may refer pain and present suppuration

[1]. It is the clinical manifestation of pain that led the patient to the conduction of X-ray examinations, which in turn, revealed the presence of a large complex odontoma in the mandibular angle. If no signs or symptoms appear, and the lesions go undetected, they can remain within bone for many years without producing clinical manifestations. The presence of a large radiopaque maxillofacial mass, particularly in a younger person, may be alarming to the clinician and raise suspicion of a malignant tumor, such as osteosarcoma. A comparison of the radiographic features of both lesions should allow the clinician to differentiate between these two diseases, which have divergent behavior and prognosis. An odontoma will present as a wellcircumscribed lesion that may distort the surrounding anatomy if sufficiently large but will not cause destruction of the surrounding tissue. Osteosarcoma, in contrast, will be ill-defined, with marked destruction of the surrounding bone and teeth. Radiolucent areas are often present and represent the proliferating cellular component of the tumor. An increase in the width of the regional periodontium may appear. In addition, periosteal reactions may be seen,

Fig. 5 Macroscopic aspect of part of the lesion

Fig. 6 Panoramic radiograph after the first surgery, revealing radiolucent area corresponding to the lesion removed, remaining part of the lesion and the impacted second molar

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Fig. 7 Five-year follow-up panoramic radiograph revealing new bone formation

leading to development of a peripheral sunburst pattern [20]. A cementoblastoma presents as a well-defined radiopaque mass attached to the tooth root and surrounded by a radiolucent rim [5, 21]. Osteoid osteomas are characterized by a small ovoid or round radiolucent area surrounded by a rim of sclerotic bone; the central radiolucency exhibits some calcification. Cemento-ossifying fibroma presents as a well-defined radiolucency with increasing flecks of calcification as it matures; it is not surrounded by a radiolucent rim and it is diffused with normal bone [5, 21]. Also, none of these is associated with an impacted tooth. Radiographic examination seems to be the most effective clinical method of discriminating between the two types of odontomas. In the case of a complex odontoma, the radiographic image shows comparatively well-organized malformed teeth or tooth-like structures, usually in a radiolucent cyst-like lesion. A complex odontoma shows an irregularly shaped oval radiopacity usually surrounded by a well-defined thin radiolucent zone. Typical images of the two types of odontoma make a discrimination simple [4]. Large complex odontomas of the mandible are rare; thus, little information is available about the preferred surgical approach for these lesions [22–24]. They can be removed by an extraoral or intraoral approach including buccal exposure, lingual exposure, or a sagittal split [22, 24, 25]. There are four possible surgical approaches to remove a benign tumor in the mandibular angle. 1. Segmental osteotomy via an extraoral submandibular approach [26], which involves partial resection of the mandible, and may include part of the inferior alveolar nerve, and which requires rigid internal fixation and

reconstruction with a bone graft. Moreover, a scar in the lateral aspect of the neck may become visible. This method constitutes a rather aggressive approach, since odontomas are considered to be benign lesions [27]. 2. Unilateral sagittal split osteotomy via an intraoral approach [22–24]. This procedure avoids large defects in the cortical bone and gives excellent access to the tumor site. This approach, however, can be complicated by injury to the inferior alveolar nerve and by fracture of the cortical bone, particularly, if it is eroded by the tumor [22–24]. 3. Intraoral excision of the lesion via the buccal cortex [27, 28]. This method requires removal of the thick buccal plate, leaving only a thin lower border. Since the lingual bone is usually thin, the risk of fracture must be taken into consideration [22, 29]. 4. Intraoral excision of the lesion via the lingual cortex [27]. By this approach, part of the thin lingual cortex is sacrificed, but the thick, buccal plate is preserved, thereby, reducing the risk of fracture. However, the subperiosteal dissection, in exposing the lingual cortex, may result in dysesthesia of the ipsilateral tongue. This complication, which is known to occur with the lingual split bone method for impacted mandibular third molars, can be avoided if the mucoperiosteum is carefully elevated lingually and protected by a curved retractor [27]. Odontomas are benign lesions that should be approached in a conservative manner. Since the lingual cortex is much thinner than the buccal cortex, it is logical that the lingual approach should be chosen to avoid unwanted fractures. The final choice of what method to use, however, should depend on the extension of the lesion, its lingual buccal location, and whether the lingual or buccal cortical plates are eroded [27]. The intraoral lingual approach was chosen in the present case because the lingual cortical plate was completely eroded. Computed tomography and magnetic resonance imaging have been found to be superior to plain radiographs when establishing the intraosseous extent of the tumor, cortical perforation, and soft tissue involvement and extent [30]. A 3D CT was made for precise guidance of the lesion limits and the association with adjacent structures. But in this case, the 3D CT was essential to discover the preservation of a very thin mandibular base only in its vestibular aspect, and this was significant to decide to perform a two-stage surgery because of the significant risk of a pathological mandibular fracture. Although many impacted teeth were removed together with the odontomas, Morning [13] reported that 3 quarters of impacted teeth related to odontomas erupt after removal of the odontoma. This finding indicates that a careful

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consideration has to be made before removing the impacted tooth associated with the odontoma. But this was not the aim in the present case. Leaving an impacted tooth after the first procedure could have brought infection to the manipulated site, but it was preferable to do in order to prevent a possible mandibular fracture in its removal. Blinder et al. [27] related in a similar case, fracture of the mandibular angle in an attempt to remove a tooth adjacent to the lesion. A MMF was maintained for 4 weeks in order to also prevent the possibility of fracture, as also related by other authors [22–24]. The 3-month period between surgeries allowed sufficient new bone formation, allowing the delayed complete removal of the lesion and the tooth, without the occurrence of a pathologic mandibular fracture, as occurred with Blinder et al. [27]. Clinical and radiographic follow-up is prudent where surgical treatment is deferred.

Conclusions This case demonstrates the value of imaging and radiographic diagnosis and surgical treatment planning prior to any definitive treatment. A computed tomography should be made in every case of intraosseous lesion in order to establish the intraosseous extent of the tumor, cortical perforation, and soft tissue involvement for precise guidance for the surgical planning. It is recommended that the surgeon consider excision by an intraoral, lingual approach when indicated, and in two stages, when an extremely thin mandibular base is present.

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