Experimental dentigerous cysts and enamel hypoplasia: their possible significance in explaining the pathogenesis of human dentigerous cysts.

Cysts lined by epithelium were often found in association with tooth-germ isografts in hamster cheek pouch. They developed from odontogenic epithelium and were in close relation to the crowns of involved teeth. Cysts associated with tooth-germ isografts from 5-day-old animals (17 out of 36) commenced their formation shortly after transplantation as a result of enamel organ degeneration. Teeth associated with these cysts often showed enamel hypoplasia. Accordingly, 86 teeth involved in human dentigerous cysts were examined and 43 were found to possess areas of enamel hypoplasia on their occlusal surfaces or incisal edges. It is suggested that the pathological process initiating cystic degeneration in the enamel organ was also accompanied by degeneration of ameloblasts. When tooth germs from 2-day-old hamsters were transplanted, cystic spaces developed only after completion of enamel formation, 6 weeks following transplantation (in six out of 11 transplants), as a result of separation between the cells of the reduced enamel epithelium. Enamel hypoplasia was not a conspicuous feature. These experimental and clinical observations suggest that there may be at least two types of dentigerous cyst, perhaps with different causes, arising at different stages of tooth development.