Simple bone cyst with unusual root resorption: a case report

This case report presents an unusual case of a gnathic simple bone cyst (SBC) with significant tooth resorption of a mandibular second molar. A 30-year-old male presented to the dental school clinic for further evaluation of an incidental periapical radiographic finding of a radiolucent lesion in the left mandibular second molar region. The lesion was not identifiable on his panoramic radiographic imaging 1 year prior. Plain films and cone-beam computed tomography (CBCT) images demonstrated a relatively well-demarcated radiolucent lesion in the left posterior body of the mandible with substantial resorption of the second molar. Based on the aggressive behavior of the lesion, a biopsy was immediately performed. Surgical exploration revealed a bone cavity containing sanguineous fluid with no evidence of a cystic lining or mass lesion consistent with an SBC. Sparse soft tissue fragments were curetted, and pieces of the bone cavity walls were submitted for histopathologic analysis. Histopathologic examination revealed a thin layer of fibrous tissue without an epithelial lining and lamellar bone consistent with an SBC. SBCs of the jaws commonly extend between the roots of teeth without resorption, and a minority of cases show bone expansion. Rarely, gnathic SBCs substantially resorb tooth roots.