[A phd completed. The effect of radiotherapy on oral mucosa cell morphology.]

The treatment of oral cancer usually consists of surgical removal of the tumour, possibly followed by radiotherapy. The purpose of this dissertation research was to investigate the effects of radiotherapy on the oral tissues, in particular the superficially positioned epithelial cells in the oral mucosa. Earlier studies with electron microscopy revealed that unradiated oral mucosa cells, when observed at high magnification, contain microplicae (ridges or folds). Together with various saliva components, these microplicae form a protective layer that offers defence against, for instance, microorganisms. Radiotherapy damages these microplicae and may even destroy them altogether. Studies have shown that this effect of radiation can be observed in animals as well as in humans. As the radiation dose increased (50 Gy or more) the destruction of the microplicae was more severe. With a dose of 60 Gy or more the microplicae completely disappeared. This process may play an important role in the occurrence of osteoradionecrosis in the jaw and failure of dental implants placed after radiotherapy.