This document summarizes common gastrointestinal diseases that may affect dental care: 1) Peptic ulcer disease affects 15% of industrialized populations and is caused by an interaction of aggressive factors like H. pylori and defensive factors. Symptoms include epigastric pain and bleeding. Treatment involves anti-secretory agents and antibiotics. 2) Inflammatory bowel disease (IBD) describes ulcerative colitis and Crohn's disease. IBD is managed but not cured through medications, immunosuppressants, or surgery. Patients may experience oral lesions. 3) Pseudomembranous colitis is a severe, potentially fatal form of colitis associated with certain antibiotics in at-risk patients.