The effect of long standing chronic mechanical irritation on the tongue of rats.

The effect of long standing mechanical irritation of the tongue was studied in 100 young rats. This was effected by the protruding end of a twisted wire, ligated around the lower first molar and directed toward the later-ventral aspect of the tongue on one side, while the other side served as control. Groups of rats were killed after 3, 6, 9 and 12 months and the tongues were examined grossly and microscopically. Fibrous hyperplasia was observed in 48% of tongues in the 3-month group and increased to 79% in the 12-month group. Microscopically, epithelial changes were noted which included ulceration acanthosis and hyperkeratosis. In no instance was dyskeratosis or any other malignant change noted.