Crohn's disease and ulcerative colitis are chronic inflammatory diseases of the gastrointestinal tract. In addition to bowel symptoms, patients may also have oral manifestations. This thesis investigated potential associations between disease activity in the gut, oral health, salivary gland function, and saliva composition. Patients with Crohn's disease had a significantly higher DMFT index, but showed no difference in periodontal diseases compared to a healthy control group. The saliva composition in patients with active bowel disease differed from that in patients with inactive bowel disease, suggesting that saliva analysis could potentially be used in the future to determine the degree and severity of bowel disease. The knowledge of gastroenterologists and dentists regarding oral manifestations of bowel diseases was found to be limited. Gastroenterologists and dentists valued interdisciplinary patient consultation as very useful, but the frequency of consultation was considered insufficient.