Immunopathology of Apical Periodontitis and Refractory Cases

Apical periodontitis is a relatively frequently encountered disease in clinical dentistry; however, its pathogenesis and etiology are not easily elucidated. Therefore, it is not always cured, even when carefully following the highest standards of treatment and intractable apical periodontitis may occur. In addition, in long-term root canal treatment of difficult cases with intractable pain, there may be misunderstandings between the dentist and patient. While acute pain is an indispensable symptom in detecting lesions and disease, sustained chronic pain can decrease an individual’s quality of life with various negative outcomes, including decreased motivation to work. Therefore, endodontic treatments and pain control measures for a diseased tooth in intractable apical periodontitis must be developed. This review outlines the progression from the onset of the lesion and examines the immunology of apical periodontitis based on studies of model animals, indicating that interleukin-1β is a key factor in elucidating the disease state and is expected to lead to the development of an effective treatment for refractory cases.