Tissue damage in the rabbit oral mucosa by acute and chronic direct toxic action of different alcohol concentrations.

The direct effects of different alcohol concentrations (20%, 40%, 96%) upon the oral mucosa of rabbits were proved in short-term and long-term experiments. The direct toxic action of the alcohol in short-term experiments leads to a local damage of the mucous membrane which is proportional to the degree of alcohol concentration. The alcohol-toxic irritation in long-term studies produced in the course of 12 months a leukoplakia-like epithelial dysplasia (dyskeratosis, keratosis, increased density of the basal layer, slightly increased number of mitotic figures) but there was no loss of polarity of cells and the basement membrane was always intact. No animal developed a spontaneous tumour. The repeated local tissue damage by high local alcohol concentration is in connection with other etiologic factors (excessive tobacco usage) an important initiating factor of cancer of the mouth.