ABSTRACT
OBJECTIVE: To investigate the mechanisms that cause damage to root formation as a result of irradiation to the mouse head, morphological changes in molar dental roots and cell dynamics in Hertwig's epithelial root sheath (HERS), and surrounding mesenchymal tissue were examined. MATERIALS AND METHODS: To perform the experiments, 5-day-old C57BL/6 mice were randomly divided into three groups: the control group (0 Gy) and irradiated groups (10 and 20 Gy). Micro-CT analysis, HE staining, immunohistochemistry analysis, and TUNEL assay were then performed. RESULTS: Roots in irradiated mice were dose-dependently shorter than those of control mice. Cells located outside the root dentin, with abnormal morphology in irradiated mice, were positive for an odontoblast marker. HERS fragmentation occurred earlier in irradiated mice than in control mice, and HERS was trapped by the calcified apical tissue. A dose-dependent reduction in the number of proliferating cells within the apical dental pulp and periapical periodontal ligament surrounding HERS was observed in irradiated mice. Apoptotic cells in the dental pulp and periodontal ligament surrounding HERS were hardly seen. CONCLUSIONS: These results indicate that the early disappearance of HERS and the proliferative suppression of the surrounding mesenchymal cells, which was induced by irradiation, caused dental root malformation.
Subject(s)
Epithelial Cells/cytology , Epithelial Cells/radiation effects , Mesoderm/cytology , Mesoderm/radiation effects , Tooth Root/cytology , Tooth Root/radiation effects , Animals , Dentin/cytology , Dentin/radiation effects , Enamel Organ/cytology , Enamel Organ/radiation effects , Mice , Mice, Inbred C57BL , Odontoblasts/cytology , Odontogenesis/radiation effects , Periodontal Ligament/cytology , Periodontal Ligament/radiation effects , Stem Cell Transplantation , Tooth CalcificationABSTRACT
Fetuses of pregnant albino mouse exposed to 400 rad of gamma-irradiation, on the 12th gestational day, were compared with unirradiated fetuses to asses the radiation effect on developing incisors. Pregnant animals were sacrificed on day 18 post coitum, and their fetuses were decapitated. Heads were routinely prepared, frontally sectioned, and stained with hematoxylin and eosin. Histologic examination demonstrated that the development of the maxillary and mandibular incisors was retarded in all the experimental fetuses and were in early bell stage, whereas those of the control animals were elaborated their matrices. It was concluded that gamma-irradiation interferes with cytodifferentiation of the enamel organ and dental papilla and subsequently inhibits normal odontogenesis.