Radiation-induced Changes in the Epithelium of the Buccal Mucosa

¹ Loyola University School of Dentistry, Chicago, Illinois

Smears of the normal buccal mucosa from thirteen subjects with oral carcinoma treated by X-radiation were taken before therapy and at 24-hour intervals during the course of therapy. Papanicolaou's method for staining keratinized and non-keratinized cells was used, and a differential count was done. A shift in the distribution of cells from non-keratinized to keratinized occurred as a result of radiation therapy. There was a decrease in the number of exfoliated cells in the 100x microscopic field as therapy progressed. Also, the size of the keratinizing cell widened to twice the diameter late in therapy, as compared with similar cells taken earlier in therapy.

The mitosis-inhibition effects of ionizing radiation on the normal oral epithelium of the buccal mucosa caused a reduction in the number of cells. A reduced number of cells called upon to function as the lining of the oral mucosa remain in situ longer, permitting the normally non-keratinized cells to keratinize and increasing the number of keratinized exfoliated cells. The widening of keratinizing cells is a functional adaptation of subnormal epithelium to carry on the function of lining the oral mucosa and is an indirect effect of ionizing radiation. The increase in keratinization of normally non-keratinized cells is a function of oxidative effects within the cytoplasm of the epithelial cells. It is felt that sulfhydryl groups are converted to disulfides as in cystine, as a result of oxidation, thereby accelerating the keratinization process. The rate at which non-keratinized cells decrease during radiation therapy varies in individuals and suggests variation in cellucidal effect of ionizing radiation.