Sixty dentigerous and 10 primordial cysts were examined clinically and pathologically. Fifty-six of the dentigerous cysts had non-keratinizing epithelium and 9 of the dentigerous cysts had keratinizing epithelium. However, 5 keratinizing dentigerous cysts and 1 non-keratinizing primordial cyst were observed as exceptions.
Radiographically, the dentigerous cysts were generally of unilocular round shape with a well-defined border. However, the well-defined border was often lost due to severe infection. In contrast, the primordial cysts were more frequently shown to be of irregular and multilocular shape, and the well-defined border was well preserved even with severe infection. Thus, keratinizing epithelium was suggested to be involved in the formation of irregular and multilocular shape and to be more resistant to infection.
Pathologically, non-keratinizing epithelium often showed proliferation, a lacy appearance, and ridge elongation in association with inflammatory cell infiltration. In contrast, such changes in keratinizing epithelium were rarely observed even with heavy inflammation. Interestingly, ameloblastoma-like epithelial proliferation and calcification in the absence of inflammation were partially observed in 6 and 7 cases, respectively, independent of keratinization of epithelium. Thus, odontogenic epithelial cells were suggested to have high proliferative and differentiative activities.
