Abstract
Opercula of the first molars delay in eruption were investigated histologically to detect the cause of eruption failure. The material was comprised of operation specimens from the exposure of 4 nonerupted first molars in Ichinose Pediatric Dental Office. There were no lesions in oral inspection and x-ray examination such as odontogenic tumor, odontoma and ectopic eruption. But location of tooth germ, development of root and comparison with another first molar presented delayed eruption.All specimens contained hamartomatous lesions with an odontogenic epithelial island. All of them stopped eruption when teeth germs were fresh from alveolar bone. I performed fenestration and after the surgery, three of them presented a tendency to erupt. There was no tendency to erupt in one case,so I opted traction. The eruption process was successfully completed.When the cases revealed delayed development of the first molar, we should keep these cases under observation without any intervention. But we should treat permanent first molars delayed in eruption as soon as we can for occlusal development.
