The purpose of this study was to evaluate the effect of ethylnitrosourea(N-ethyl-N-nitrosourea ; ENU, Sigma Co.) on the tooth germs and its surrounding tissues.
Forty male Wistar rats; one month of age and 100-130gm in body weight, were used in this experiment, which were devided into 3 experimental groups and 2 control groups.
Ten animals of experimental group 1 were given local injection of 1% ENU solution which were dissolved in physiologic saline into the region of incisor tooth germ of the right mandible every other day for 19 days (a total of 10 times). Ten animals of experimental group 2 received ENU injections as the same manner as group 1 and were given mechanical injuries on the same regions at 2nd, 8th and 15th days after beginning of experiment. And fifteen animals of experimental group 3 received mechanical injuries as well as ENU injections as the same manner of group 2, and were given 4% ethanol as drinking water and subcutaneous injections of 2.5mg prednisolone acetate at 2 times per week. Three animals a control group 4 were treated as the same manner with experimental group 3, but received injections of physiologic saline instead of ENU, and two animals of control group 5 were not treated.
All animals were sacrificed at the end of the sixth month, and the mandibles were removed, fixed in 10% N-fornialin, decalcified with electrolytic decalcification method, embedded in paraffin, sectioned in 4-6/tm thickness, and stained with Hematoxylin and eosin, and Masson´s trichrome.
The results were as follows ;
1. Various polycystic structures with fibrous connective tissue wall and neoplasm-like proliferation were revealed at the ENU-injected areas of the tooth germs, the periodontal ligaments and the salivary glands.
2. The epithelium of the tooth germ revealed irregular epithelial hyperplasia and disturbance of dentinogenesis.
3. The stratum intermedium of the tooth germ revealed severe adenomatous proliferations, therefore suggesting a potential of odontogenic tumors.
4. Malassez´s epithelial rests in the periodontal membrane of the posterior teeth revealed mild hyperplastic proliferation.
5. Gingival hyperplasia at the posterior teeth and the formation of epithelial islands resembling with enamel organ at the affected interdental papillae were observed.
6. The ductal epithelium of the intercalated ducts and the secretory ducts of the accessory salivary glands revealed basal cell adenomatous proliferations,
7. Group 2 and 3 revealed more prominent histopathological changes than group 1, therefore it suggested that these changes would develop to odontogenic tumors.
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