This case report describes an ameloblastic fibro-odontoma arising from a calcifying odontogenic cyst (COC) in the mandible of a twenty-three-year old male. The patient was referred to the Department of Oral Surgery, Tokyo Dental College, on March 30th, 2000, complaining of a painful swelling, which had appeared three weeks earlier on his left mandibular molar region. In a pathological view, the lesion was a round cyst the size of a chicken-egg, dark red in color, and surrounded by a thick membrane. The cyst had an epithelium of varying thickness which included many ghost cells and an enamel-like structure on the inside, and a thick wall of connective tissue with an ameloblastic fibro-odontoma on the outside. Enamel organ-like epithelial islands were structured radially in the form of strands with immature dentin. Cytokeratin 19 was strongly immunoreactive in the epithelium of the lesion; osteopontin and osteocalcin reacted in the mesenchymal cells and weakly in the epithelial element of this tumor.

The purpose of this study was to investigate the behavior of rat bone marrow cells (RBM) growing on surfaces with different pore sizes. RBM behavior on Millipore filters (MF-Millipore TM membrane filter) made from cellulose mixed esters with 5 different pore surfaces (0.45m, 1.2m, 3.0m, 5.0m and 8.0m) were compared in terms of morphological changes on the different pore sizes. Furthermore, the expressions of osteopontin and osteocalcin mRNAs were investigated. On the 1.2m and 3.0m pore surfaces, RBM attached to the substrate well, but cells on the 5.0m and 8.0m pore surfaces invaded deeply into the pores. Higher levels of both osteopontin and osteocalcin mRNA expression were always observed in cells cultured on the 1.2m filter. These results suggest that the 1.2m Millipore filter pore size is the most suitable for inducing RBM to differentiate into an osteoblastic phenotype among these surfaces and is probably related to production of the ECM but not to the phenomenon of cell spreading.