To elucidate the mechanism underlying the failure of root formation after irradiation, we established a method of local irradiation of the molar tooth germ and demonstrated that radiation directly affected dental root development. In the current study, to locally irradiate the lower first molars of 5-day-old C57BL/6J mice, we used lead glass containing a hole as a collimator. We confirmed that our local irradiation method targeted only the tooth germ. The irradiated root was immature in terms of apical growth, and dentin formation was irregular along the outside of the root apices. Moreover, calcified tissue apically surrounded Hertwig's epithelial root sheath, which disappeared abnormally early. This method using a local irradiation experimental model will facilitate research into radiation-induced disorders of dental root formation.

为了阐明辐照后牙根形成失败的机制，我们建立了一种对磨牙牙胚进行局部辐照的方法，并证明辐照直接影响牙根的发育。在当前的研究中，为了对 5 天大的 C57BL/6J 小鼠的下第一磨牙进行局部照射，我们使用含有孔的铅玻璃作为准直器。我们确认我们的局部照射方法仅针对牙胚。辐照后的牙根根尖发育不成熟，牙本质沿根尖外侧形成不规则。此外，钙化组织在赫特维希上皮根鞘周围出现，其异常早期消失。这种使用局部辐射实验模型的方法将有助于研究辐射引起的牙根形成障碍。