Diabetes mellitus, is a common chronic disease, and its prevalence in the United States, particularly type 2 diabetes, is increasing. Complications associated with diabetes impose a heavy burden on many people, especially among certain minority populations. Periodontal diseases, dental caries, and tooth loss also are common conditions in the United States, but their prevalence is generally decreasing. Nevertheless, among important subgroups of the population, particularly certain minority and economically disadvantaged groups, there is a disproportionately higher burden of periodontal diseases, dental caries, and tooth loss. This article reviews the post-1960 English-language literature on the relationship between diabetes and oral health, specifically focusing on periodontal disease, dental caries, and tooth loss. Substantial evidence exists to support the role of diabetes and poorer glycemic control as important risk factors for periodontal disease. Additionally, the evidence provides support for viewing the relationship between diabetes and periodontal diseases as bidirectional. However, additional research is necessary to firmly establish that treating periodontal infections can contribute to glycemic control management and possibly to the reduction of type 2 diabetes complications. The literature does not describe a consistent relationship between type 2 diabetes and dental caries. It reports increased, decreased, and similar caries experiences between those with and without diabetes. This review suggests that currently there is insufficient evidence to determine whether a relationship between diabetes and risk for coronal or root caries exists. Most of the reviewed studies reported greater tooth loss in people with diabetes. However, the differences were slight and not significant in several of the reports. Furthermore, this review of the association between diabetes and tooth loss reveals that valid population-based evidence generalizable to the US population is sparse. Further investigations of the association of diabetes with dental caries and tooth loss are warranted. If adverse effects of diabetes on dental caries and/or tooth loss are substantiated, the results of such studies would help design intervention studies to prevent or reduce the occurrence of dental caries and tooth loss in people with diabetes. These results also may affect existing clinical practice protocols and promote new public policy related to diabetes.