Discussion

Osteoma is a benign neoplasm consisting of well-differentiated compact or cancellous bone that increases in size by continuous osseous growth.^1,2,4-6,7  Peripheral osteoma occurs most frequently in the frontal, ethmoid, and maxillary sinuses^4,8-10 but are not common in jawbones.^1,4,5  A review of the English literature of the last 30 years revealed only 16 well documented cases: 15 in the mandible and 1 in the body of the maxilla.⁴  Kaplan et al.⁴  reported the age at which the lesions are first identified ranges between 15 and 75 years, the majority being noticed after the age of 25.  The duration of the lesions varies between 1 and 22 years.  Although the cases in this report are men, it is reported that females predominate by a ratio of 3:1.¹

The pathogenesis of peripheral osteoma is still unknown.^1,3,5,7,10  Some investigators classified it as a reactive condition triggered by trauma, because peripheral osteomas are generally located on the lower border or buccal aspect of the mandible which are traumatized areas^1,4,5  and others consider it as a true neoplasm.^1,4  Peripheral osteomas are probably not neoplastic in nature because in the majority of cases their growth potential and growth rate seem to be limited.⁴  The lesions in our cases were shown to be present for no more than 7 years and they were not developmental in origin.  Twenty-four percent of cases of peripheral osteoma of the mandible were associated with a history of trauma which may cause subperiosteal bleeding or edema that simulate an oestrogenic reaction^1,3-5  Trauma may be minor, that is, unlikely to be remembered by the patient years later.  ⁴ Bony hyperplasia associated with muscle traction is a documented phenomena.^1,4,5  It is suggested a combination of trauma and muscle traction may play a role on its development.^1,4  Either one or both might imitate an oestrogenic reaction that could be perpetuated by the continuous muscle traction in the area.  Because the first case had a history of trauma, it was thought this might play a role in its development.  It was also possible that masseter muscle traction stimulated the oestrogenic reaction in the area.  There was no history of trauma in our second case, but there is the chance the patient experienced minor trauma and was not aware of it. It is thought masseter traction, in particular, might play a role in the occurrence of this lesion.

The discovery of an osteoma of the facial skeleton should raise the possibility of Gardener’s syndrome.^1,6,8-10  Patients with Gardner’s syndrome may present with symptoms of rectal bleeding, diarrhea, and abdomimal pain.  The triad of colorectal polyposis, skeletal abnormalities, and multiple impacted or supernumerary teeth is consistent with this syndrome.  Onset occurs in the second decade, with malignant transformation of the colorectal polyps approaching 100% by age 40.  The skeletal involvement includes both peripheral and endosteal osteomas, which can occur in any bone but are found more frequently in the skull, ethmoid sinuses, mandible, and maxilla.  However, no corroborating syndromal lesions were found in these patients. The lesion rarely recurs after surgical excision^2,3,6,7,10 , and it is not associated with malignant change.^6,7,10

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Citation Number: Vol. 4, No. 3, Page 102