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  • Radiology

     

    Post Orthodontic Idiopathic Bone Cavity

    Case Report

     

     

    Alexandre Khairallah - BDS, PGD, DESS, FEADMFR, MBAIRD

    Head of the Service of Oral and Maxillo-Facial Imaging Department, Lebanese University, Beirut | Lebanon

    Founder and Manager Of CLIR center | Alexandrekhairallah@hotmail.com

     

     

    ABSTRACT

    The Idiopathic bone cavity (IBC) is a nonepithelial lined cavity of the jaws. The lesion is mainly diagnosed in young patients most frequently during the second and third decade of life. It is seldom detected on buccal examination due to their lower inability to cause clinical symptoms. The majority of the traumatic cyst is located between the mandibular canine and the third molar but other locations are not totally excluded. The diagnosis is generally done on routine radiological examination as a unilocular radiolucent area with a “scalloping effect”. We report to you a case of an anterior Idiopathic Bone Cyst detected on Cone beam eleven years after an orthodontic treatment.

     

    KEYWORDS

    Idiopathic bone cavity, Orthodontic treatment, Buccal bone expansion, Cone beam ct imaging.

    BACKROUND

    The idiopathic bone cyst (IBC) is an uncommon non neoplastic, non-epithelial lined cavity of the jaws. Since it was first described by Lucas1 in 1929, the lesion has attracted a great deal of interest in the dental literature, but its pathogenesis is still not clearly understood.1,3

     

    Idiopathic bone cysts have been reported in the literature under a variety of names: traumatic bone cyst,1 solitary bone cyst,3 haemorrhagic bone cyst,4 extravasation cyst,5 progressive bone cavity,6 simple bone cyst,7 unicameral bone cyst8 and primary bone cyst. The multitude of the names applied to this lesion attests to the lack of understanding of its etiology and pathogenesis. The World Health Organization (WHO) recommends the use of term Solitary bone cyst, although traumatic one cyst is the most widely used one.2,9,10

     

    In an evaluation carried out by Guerra5 on 26 cases of IBC, a female predilection was noticed, 30.77% had a history of trauma, 69.23% had some relation to orthodontic treatment and 50% of all cases had been diagnosed during initial orthodontic documentation.5,6 IBC accounts for nearly 1% of cystic lesions occurring in the jaws.6 About 56-70% of the cases of IBC are diagnosed during the second decade of life with a slight female gender predilection.7 The majority of IBCs are located in the mandibular body between the canine and the third molar.9,11,12,14 The second most common site is the mandibular symphysis. Fewer cases are reported in the ramus, condyle and the maxilla, predominantly in the anterior part.11,14,16

     

    Clinically, the lesion is asymptomatic in the majority of cases and is often accidentally discovered on routine radiological examination.2,4,12,14,17 Pain is the presenting symptom in 10% to 30% of the patients.4,11,12

     

    Other, more unusual symptoms include tooth sensitivity11,13,14 aresthesia,12,18 fistulas,13 delayed eruption of permanent teeth,19 displacement of the inferior dental canal2 and pathologic fracture of the mandible.20

     

    Expansion of the cortical plate of the jaw bone is sometimes noted, usually buccally, resulting in intraoral and extraoral swelling and seldom causing deformity of the face. The adjacent to the lesion teeth are usually vital and there is no mobility, displacement or resorption of their roots.2,4,6,11,13

     

    Numerous theories have been linked to the idiopathic bone cyst formation which includes cystic degeneration of fibro-osseous lesions, intraosseous vascular anomalies, alteration of bony metabolism and low level of infection.3 It was also suggested that trauma can initiated a subperiostal hematoma that caused a compromised blood supply to the area, leading to osteoclastic bone resorption.4

     

    On radiological examination, a traumatic bone cyst usually appears as unilocular radiolucent area with an irregular but well defined (or partly well defined) outline, with or without sclerotic lining around the periphery of the lesion. Characteristic for the traumatic bone cyst is the “scalloping effect” when extending between the roots of the teeth. The scalloped outline, however, is often found in edentulous areas also. Occasionally, expansion or erosion of the cortical plate is noted.4,11

     

    Since material for histologic examination may be scant or non-existent, it is very often difficult for a definite histologic diagnosis to be achieved.2,11,20 Most of the histologic findings reveal fibrous connective tissue and normal bone. There is never any evidence of an epithelial lining. The lesion may exhibit areas of vascularity, fibrin, erythrocytes and occasional giant cells adjacent to the bone surface.10,11,14,15

     

    The definite diagnosis of traumatic cyst is invariably achieved at surgery when an empty bone cavity without epithelial lining is observed. Surgical exploration has been advised not only to confirm the diagnosis but also as treatment modality.10 Bone regeneration after surgical exploration is typical feature of TBCs.11 Spontaneous regression of the lesion has been observed in cases of TBC.12

     

    CASE REPORT

    A 32-year-old female patient reported to our office for an asymptomatic buccal expansion of the anterior lower cortical. She reported having crowded teeth in the maxilla and mandible since her adolescence and she underwent an orthodontic treatment at the age of 21 for 18 month. The medical history was non-contributory. She didn’t report any history of trauma. A thorough clinical examination was performed. The percussion and mobility tests were negative and the vitality test of the teeth revealed a normal response. A Cone beam CT of the mandible was performed, panorex (Fig. 1) reconstruction along with cross-sectional cuts (Fig.2) were generated from the axial cuts. A well-defined osteolytic, radiolucent and unilocular image was noticed in the anterior mandible (Fig.1). The lesion extended from the distal surface of the right canine to the mesial surface of the left canine. Inferiorly it extended to the lower border of the mandible and superiorly it extended into the inter-radicular areas. No evidence of external root resorption or tooth displacement was noticed. The cross-sectional cuts revealed buccal cortical thinning and expansion (Fig.2). The lingual cortical is well preserved. A three-dimensional reconstruction was also made to determine the precise extension of the lesion (Fig.3). The lesion was provisionally diagnosed as a traumatic bone cyst. After raising a buccal, papillae conserving, flap the area was surgically explored; hollow cavity lacking a lining was noticed (Fig.4).

     

    Curettage was done to collect tissues for histopathology and to induce bleeding. The flap was then sutured and post-operative pain killer was suggested every 8 hours, no other medications were prescribed.

     

    The specimen was sent to a pathological examination which revealed normal appearing bone spicules with parts of vascular connective tissue (Fig.5).

     

    Based on these clinical histological and radiological findings a final diagnosis of Idiopathic Bone Cyst was confirmed.

     

    (Fig. 1) Panorex reconstruction showing unilocular radiolucent area in the symphysis region

     

     

    (Fig. 2) Cross sectional cuts showing the thinning and expansion of the buccal cortical

     

     

    (Fig. 3) Three dimensional reconstruction showing the extension and the scalloping aspect of the image

     

     

    (Fig. 4) Empty cavity shown during surgical procedure

     

     

    (Fig. 5) Histopathological cut showing normal appearing bone spicules with parts of vascular connective tissue (haematoxylin-eosin, original magnification × 40)

     

     

     

    DISCUSSION

    IBC is an asymptomatic lesion usually seen in young patients in the mandibular area and most commonly appears radiographically as a well-circumscribed, non-corticated, unilocular radiolucency. It does not produce displacement of teeth or resorption of the roots.

     

    According to our case and several ones cited in the literature a possible association between IBC and orthodontic treatment may exist.

     

    The following theories may be applicable to the aetiopathogenesis of IBC during orthodontic treatment:

    An increased vascular activity, in the presence of vascular endothelial growth factor (VEGF), is seen in areas of tension and pressure during experimental tooth movement. Macrophages appear consistently near blood vessels in the areas of osseous stress.6 Osteoclasts are differentiated from macrophages by the presence of tumour necrosis factor (TNF)-a.7 The osteoclast’s membrane is the resorptive organelle that is able to mediate bone resorption. This membrane is able to acidify the bone surface, thereby mobilizing inorganic bone minerals, resulting in bone resorption.

    The piezoelectric effect may play an important role in the development of IBC. Piezoelectricity is the ability of some materials, including bone, to generate an electric potential as a response to an applied mechanical force. When pressure is applied, it causes mechanical deformation and displacement of charges. Marino and Becker13 stated: “In theory, this effect could translate an environmental stimulus into a biologically recognizable signal, controlling growth and resorptive processes.” Bone produces charges proportional to mechanical displacement. These charges stimulate osseous change. It is postulated that the piezoelectric effect may be able to change the chemistry and influence the cellular activity of osteoblasts and osteoclasts. The piezoelectric effect has been associated with bone growth, remodelling, regeneration and resorption.9

     

    CONCLUSION

    An IBC may occur in any bone of the body; the posterior mandible represents a common location but other location as the anterior symphysis must not be excluded. The name of traumatic bone cyst should no longer be used for this entity as there has been no proven association with traumatic events. This lesion is not a true cyst as there is no epithelial lining. The nomenclature of IBC is descriptive and appropriate, as this is a true cavity and the cause is not understood. IBC is asymptomatic. There is a predilection for female patients.

     

    Radiographically, most of the lesions are unilocular, well-circumscribed, non-corticated, non-expansile radiolucencies. Scalloping and expansion were seen in some of the mandibular molar cases. The cortical bone was not normally affected by this process.

     

    In the current knowledge base of scientific research, the cause of the enigmatic lesion termed IBC is not known. The cause of IBC is probably multifactorial, such as the presence of VEGF,6 which appears in areas of bone tension and pressure. The piezoelectric9 effect may also play a role as it has been associated with bone remodelling, regeneration and resorption. Further research utilizing prospective double-blind protocols is necessary to further elucidate the cause of IBCs.

     

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