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rev port estomatol med dent cir maxilofac . 2021;62(3):170-175 173

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an altered bone metabolism. There is also the theory of syno-
vial cysts arising from an error in the ossification process,
2
where a synovial lining would occur in the affected region. In
the theory of tumor degeneration, a pathological alteration
such as fibrous dysplasia and central granuloma of giant cells
would result in SBC after their liquefaction process. 8,9,13
A retrospective study of 44 cases of SBC, pointed out a pos-
sible combination of these lesions with orthodontic treatment
and some cases associated with florid bone cement dysplasia
9
(DCOF). In this case, there is a misfunction in bone metabo-
lism leading to biochemical and hormonal changes resulting
Figure 7. Follow-up panoramic radiograph showing, after 8,9
4 months, the new bone formation in progress, and no in osteolysis. Due to the disorganized mineralization of bone
signs of the recurrence of the lesions. tissue, blockage of lymphatic drainage may occur, inducing the
7
formation of the cystic space. The age of the majority of the
patients affected by SBC coincides with those who undergo
9
orthodontic treatment, ranging from 9 to 20 years of age. Pos-
sible pathogenesis is associated with tooth movement per-
formed by orthodontic treatment, which promotes areas of
tension and pressure that increase the vascularization in the
region. The presence of vascular endothelial growth factors,
tumor necrosis factors, and pro-inflammatory cytokines pro-
mote the activation of cellular receptors on macrophages, in-
active osteoclasts, and undifferentiated cells that differentiate
into mature osteoclasts, whose function is to mediate bone
9
resorption. Besides, piezoelectricity also plays a role in the
Figure 8. Follow-up panoramic radiograph showing development of cystic spaces, as the generation of electrical
complete bone formation and no signs of recurrence after potential in the bone caused by a displacement of mechanical
16 months.
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charges influences the cellular activity of osteoclasts. In the
present case there was the presence of two possible etiological
factors, trauma and orthodontic treatment; although the pa-
tient could not remember a specific trauma, he mentioned
Discussion and conclusions that traumas in the face were very common during his sports
activities.
The simple bone cyst (SBC), also known as a traumatic bone Regarding the prevalence of SBC between gender, some
3
cyst, is an uncommon osteolytic lesion, of benign characteris- studies found no difference. However, some authors claim
tics and with no epithelial lining. 2,4,9 It usually occurs unilat- that women are more affected, due to the high index of estro-
erally. A case with bilateral involvement, such as the one de- gen and lack of progesterone, especially at a young age, result-
scribed above, is poorly documented in the literature. 9,10,14 ing in bone resorption and development of the lesion. 9,10 Oth-
Since the beginning of the 20th century, when it was first er authors, however, reported a predominance in males in
described, its true pathogenesis remains unknown. 7,10 Trauma their case series. 7
is supposed to be the main triggering factor. It forms an in- Although SBC can be found at any age, there is agreement
traosseous hematoma and liquefaction of the blood clot that among the authors that younger patients, between the first
fails to be replaced by bone tissue. Resorption of the adjacent and second decade of life, are the most affected, once they are
bone occurs through enzymes activated by the adjacent the ones that suffer more traumatic injuries. 1,3,7,11,12 A study
cells. 1-3,7-9 Also, next to the trauma, a subperiosteal hematoma with a case series finds a history of trauma in patients aged
reduces the blood supply to the region causing an osteolysis 14-22 years, as observed in the present case. 9
2
process and subsequent formation of the lesion. However, the The posterior region of the mandible 2,3,7-9,11 is the most
absence of an important traumatic injury reported by patients, affected site by SBC, but lesions in the anterior region may
makes the theory of trauma very questionable. 1,7,8 More than occur. 7,13 Maybe there are more cases in the mandible com-
8
50% of the SBC cases have no traumatic involvement; in a pared to the maxilla because the mandible has more cortical
7
systematic review, it was observed that only 1 in 4 cases of SBC bone, which is repaired more slowly. However, the involve-
3
were preceded by trauma. Besides, boxing athletes and other ment of condyle, anterior maxilla, and zygomatic bone regions
individuals who suffer frequent head and neck trauma are no have also been described. 2,3,9,12
longer affected by this type of injury. 9 Patients are usually asymptomatic, but in 20% of the cases
Another concept applied to the possible pathogenesis of they may present symptoms of pain, edema, tooth sensitivity,
8
SBC involves microtrauma of the teeth and alveolar crest. paresthesia, and in very rare cases, pathological fracture of the
Some authors suggest the addition of an underlying systemic jaw. 1-3 The absence of symptoms explains the detection of le-
component in patients with multiple SBC, with a tendency to sions by chance during routine radiographic examinations. 3,8,10
vascular anomalies. 2,8 Others associate osteolysis caused by The pulp tissue of teeth involved in the injury is vital. Color