Under the best of circumstances a periodontal diagnosis is a clinician's best guess as to what condition or disease the patient has. Because there is always some uncertainty, experienced clinicians routinely develop a differential diagnosis that is listing of the possible diagnosis of a patients' condition ranked from most likely to least likely. The diagnostic label captures, in a few words, a clinician's entire past experience with the disease or condition. It is a summary term that helps the clinician toward answering questions that are important to both the dentist and patient.