Why is a medical history important in dentistry? A patient's medical history is a vital part of his or her dental history and increases the dentist's awareness of diseases and medication which might interfere with the patient's dental treatment. What medical conditions affect oral health? Alzheimer's disease. Other conditions that might be linked to oral health include eating disorders, rheumatoid arthritis, certain cancers and an immune system disorder that causes dry mouth (Sjogren's syndrome) How often should patient information be updated? Common sense dictates that patients who have complicated medical histories need complete updating more often than average healthy adults.