Ghost cells in complex odontoma: a light microscopic and SEM study.

Ghost cells in complex odontoma were studied by light microscopic and scanning electron microscopic examination of decalcified sections. They were found at different locations in odontomas: next to tubular dentin, at the site where enamel would be expected; adjacent to remnants of enamel matrix or surrounded by enamel matrix; within granular calcified masses in contact with bone or tubular dentin; in contact with ameloblasts or adjacent to small rests of odontogenic epithelium. They were either isolated or arranged in groups. Their cytoplasm presented a fibrillar component and a lack of keratohyaline. In a complex odontoma, ghost cell keratinization occurs as a result of metaplastic transformation. The calcifying process in these cells was found to be a passive one, with the cells becoming gradually entrapped within the calcified material--bone, osteoid, dentin, dystrophic osteodentin, or dystrophic granular or lamellar types of calcification. Complex odontomas contain both normal and metaplastic odontogenic epithelial cells, which may have lost their developmental and inductive properties.