The purpose of this study was to evaluate the effect of N-nitroso-N-methylurea(NMU Sigma Co.) on the tooth gem ,teeth as well as the periodontal tissue of the mother rats and also the teeth germs of the prenatal rats.
Forty eight female Wistar rats, 200gm in body weight, were used in this experiment, in which pregnancy had been induced in all of them. In the experimental group of 32 a 0.4m1 NMU solution which was diluted in normal saline at a dose of lgm/100m1 was intravenously injected into the tail vein of all thirty two on the 13th day after pregnancy. Arid in the control group of 16, only 0.4m1 of normal saline solution was injected.
The 48 pregnant rats were divided into 8 groups, each group consisting of 4 from the experimental group and 2 from the control group. One group was sacrificed on each of the following respective occasions; on the 17th, 19th, and 21rst day of pregnancy as well as on the 5th, 9th, 13th, 20th, and 24th week after delivery. When examined, the mandible, cervical lymph node, mammary gland, heart, liver, lung, kidney, ovary, stomach and colon were removed from moth and prenatal rats obtained from pregnant rats which were sacrificed during pregnancy. Then the histopathologica evaluation was performed by the routine method.
The results were as follows;
1. The tooth germs of the mother rats began to form dysplastic dentin and irregular ameloblastic layer on the 21rst day, and metaplastic adenomatoid proliferation of the epithelium in some tooth germs with the time lapse.
2. The pulpal tissue of the mother rats revealed severe congestion of the blood vessels and a dense cellular layer odontoblasts, and then cystic structures and denticles was formed gradually
3. The periodontal tissue of the mothers was thickened by proliferation of fibroblasts with blood vessel congestion, and it showed formation of cysts and denticles in some portions and hypercementosis of molar teeth. The gingiva revealed hyperkeratinization and basilar hyperplasia by epithelial proliferation, but did not show dysplastic or malignant features
4. There was 1 mammary gland carcinoma, 3 lung carcinomas, 3 hepatic carcinomas, 2 kidney sarcomas and 2 colon carcinomas among all organs removed from mothers.
5. In the tooth germs at the cap stage of the prenatal rats, the inner enamel epithelium revealed metaplastic proliferation with hyperchromatic nuclei.
6. The tooth germs of the mothor rats showed more severe developmental disturbance than that of prenatal rats.
7. To conclude, the general administration of NMU induced carcinoma on various organs and nietaplastic adenomatoid proliferation of the epithelium in some tooth germs can be recognized as an early developing feature of odontogenic carcinoma
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