Mice embryos were irradiated in utero by gamma rays (٠،٢،٤،٦ Gy) at
١٠،١٢،١٤،١٦،١٨ days of gestation. Histological study was carried out on the
first premandibular molar after ٢،٤،٦،٨ days of irradiation, to investigate the
effect of irradiation on different stages of molar development.