The interleukin (IL)-23JIL-17 axis is recognized as a novel immune pathway in addition to the traditional T helper 1 (Th1) and Th2 responses. This new Th subtype, which mainly secretes the IL-17 cytokine, is named T helper 17 (Th17). Plenty of research has investigated the correlation between this new pathway and autoimmune diseases, especially rheumatoid arthritis. Those studies assumed that Th17 plays an important role in bone resorption. However, patients with periodontal disease also encounter a bone resorption crisis. Much research has attempted to determine whether periodontitis is a major Th1 or Th2 response, and the answer to this is still controversial. The latest experiments showed that levels of IL-23 and IL-17 are higher in tissues with periodontitis. The results imply that the newly found IL-23/ IL-17 axis may play an important role in periodontitis, and this novel Th subtype could be a new target for understanding the pathogenesis of periodontal diseases. In this article, we review the immune pathway of IL-23/IL-17 and its role in bone resorption, and highlight the role of Th17 in periodontal disease based on some reports.