EXPERIMENTAL PRODUCTION OF PALATAL LEUKOPLAKIA WITH CHRONIC MECHANICAL IRRITATION PLUS TOBACCO AND WINE

PURPOSE: With the purpose of confirming the etiological factors of palatal leukoplakia, screening various treatments for it and methods of preventing malignant degeneration, we have undergone a series of experiments to establish a standard experimental animal model. MATERIALS AND METHODS: 18 hamsters and 55 rats were used and divided into 6 groups according to the method of experiments, （1）. Repeated pricking with a steel wire brush, （2）. Local application of tobacco in wine, （3）. Combination of （1） and （2）,. （4） Local paint with concentrated alcohol solution of tobacco, （5） Combination of （1） and （4）. （6） Control group, without any irritation. The agents used in the experiments were applied to the posterior part of hard palate and anterior part of soft palate three times a week, for 11 months, in group （1）, （2）, and （3）, and for 7 1/2 months, in groups （4） and （5）. RESULTS: （A）. Gross findings: The rugae over the part of the palate of every animal in eaeh group subjected to irritations become shallow after 16 treatments, and white spots or patches were seen. They became severer when the experiment was continued. （B）. Microscopic findings: 1. Each biopsy material in every group, except for the first biopsy of the hamster of group （1）, showed the characteristic histopathological changes of leukoplakia, being mild at the early stage and severe at the later stage of the experiment. The lesions in animals of groups receiving combined irritations were severer than those receiving single irritation. Concentrated alcoholic solution of tobacco caused severer lesions than the tobacco in wine, and a few animals showed local cellular atypia in the squmaous epithelium, and pathological changes of the palatal glands too. DISCUSSION: （1） Locat chronic mechanical and chemical irritations appear to be of importance in the cause of leukoplakia of the mouth, so the removal of the irritations are significant in the prevention and treatment of this disease. （2） This type of leukoplakia is rather constant, we can control it if the irritatants are removed or the lesions treated properly. （3） This kind of animal model is suitable for screening effective drugs or methods of treatment. （4） Cases of oral leukoplakia caused by strong irritative agents for a long duration must be treated immediately. （5） The pathological changes in the palatal glands are characteristic of the palatal leukoplakia, which we must treat accordingly.