We conducted a review of English papers published between 2012 and April 2015 for associations between periodontal disease and diabetes-related medical expenditure. This resulted in only one paper being selected, which demonstrated that, to date, very little information exists on this topic. Although the evidence is limited, the current research findings support the hypothesis that periodontal disease is an important predictor for the growth of medical spending related to diabetes among the US population. Our ongoing project based on a Japanese elderly population also produced concordant results. It is necessary to conduct further research to accumulate more evidence and to be able to generalize these findings. Because periodontal disease is largely modifiable, controlled intervention studies are needed to elucidate whether health-care spending related to diabetes could be reduced thorough adequate preventive dental care, proper dental education, and oral health promotion.