The purposes of this study were to investigate the distribution of cytokeratins in the different tissue types of ameloblastoma and to discuss the histogenesis of this tumor. CK19 and CK8, which are markers for odontogenic epithelium, reacted positively to the constituting cells in all types of ameloblastoma. This suggests that all types of ameloblastoma derive from odontogenic epithelium. However, the desmoplastic type diminished the odontogenic characteristics because the basal cells are negative to CK19. Immunoreactions of five kinds of cytokeratin revealed similar results in plexiform, follicular, acanthomatous, and granular cell types. The plexiform type is probably the original type of ameloblastoma; the other types have the characteristics of squamous epithelium, and the follicular, acanthomatous, and granular cell types can develop due to the differentiation of cells of the plexiform type into squamous epithelium.

Abstract:Cell density and distribution, vascular area and Malassez's epithelial rest in wounded periodontal ligament were examined in three different areas of the beagle dog. Complete regeneration was observed in the wounded periodontal ligament. However, ankylosis between the wounded tooth and regenerated bone was sometimes seen 2 months after the operation. The blood vessels occupied approximately 17% of the middle area and 15% of the alveolar area, but only 4% of the cementum area. Significantly higher numbers of cells were observed in the cementum area than in both the alveolar and middle areas. The number of cells in the middle area that were positive for PCNA was significantly higher than that in both the alveolar and cementum areas. The percentage of PCNA-positive cells associated with blood vessels was approximately 64% in the middle area, 59% in the alveolar area and 30% in the cementum area. These results are extremely similar to those in normal periodontal ligament, except for the absence of Malassez's epithelial rests. These results suggest that the width of the periodontal ligament is most probably regulated by some effect of Malassez's epithelial rest.