恒牙胚缺失动物模型的建立及相应乳牙牙根的吸收

Establishment of permanent tooth germ missing animal model and study on root resorption of the corresponding deciduous teeth

目的：通过建立恒牙胚缺失动物模型，为在恒牙胚缺失情况下研究乳牙牙根的吸收奠定实验基础。方法：选择11周龄雄性Beagle犬作为实验动物，通过手术摘除继承恒的方法建立恒牙胚缺失动物模型。定期拍摄根尖片观察相应乳牙牙根的吸收情况，与乳牙生理性根吸收进行比较。当摘除恒牙胚的相应乳牙牙根出现吸收时，取颌骨标本，进行组织学观察。结果：恒牙胚存在情况下，乳磨牙牙根吸收起始于20周龄；恒牙胚摘除的乳牙牙根吸收明显延缓，起始于26—27周龄。恒牙胚缺失情况下乳牙牙根吸收的组织学表现为大量多核巨细胞主要分布于吸收牙根的牙髓侧，牙周膜侧仅有少量多核巨细胞分布。结论：成功地建立了恒牙胚缺失动物模型，模拟了恒牙胚先天缺失情况，恒牙胚缺失的乳牙牙根吸收明显晚于恒牙胚存在的乳牙。

Objective： To establish the permanent tooth germ missing animal model for future research on the root resorption of deciduous tooth in the absence of permanent tooth germ. Methods： The perma- nent tooth germ missing animal model was established by surgical removal of the permanent tooth buds in a male 11-week-old Beagle dog. Root resorption of the deciduous teeth without permanent successors was observed by taking periapical films periodically, and compared with physiological root resorption. Once the sign of root resorption of the deciduous teeth without permanent successors was detected on radiographic films, the animal was sacrificed and the mandibular bone was collected for histological study. Resuits： Root resorption of the deciduous teeth with the presence of permanent tooth germ started at 20 weeks after birth, while root resorption of deciduous teeth without permanent tooth germ started 26 -27 weeks which was significantly delayed. Histological studies showed that a large number of multinucleated giant ceils were present on the pulpal surface of the root, while only few of them were seen on the outer surface. Conclusion： The permanent tooth germ missing animal model was successfully established in this study which simulated the case of congenital absence of permanent tooth germ in human. Root resorption of deciduous tooth without permanent tooth germ was significantly delayed than the deciduous tooth with permanent tooth germ.