Diseases of the gastrointestinal tract are often accompanied by changes in the oral cavity. This is largely due to morphological and functional unity of the mucous membrane of the mouth and entire digestive tract. According to numerous publications in recent years, at the end of the XX-beginning of the XXI century, there is a significant increase in the number of people suffering from cancer of the colon and rectum. This localization accounts for 15% of all initially diagnosed tumors of all localizations (30% of them are represented by rectal cancer).