About a decade ago, a hypothesis was proposed suggesting that the innate immune system, including acute-phase reactants, contribute to the development of T2DM [Type 2 DM (diabetes mellitus)] and the metabolic syndrome. In this model, it was hypothesized that the innate immune system modulates the effects of many factors, including genes, fetal programming, nutrition and aging, upon the later development of metabolic problems associated with insulin resistance. In this present article, we expand this hypothesis by looking at the involvement of periodontitis in DM and its complications. Periodontitis is a common inflammatory process involving the innate immune system and is associated with DM. We will also illustrate how dental disease is important in patients with DM and could be implicated in various diabetic complications.