Many noncommunicable diseases share common risk factors and may develop as comorbidities. Additionally, persistent local infections could induce or perpetuate low-grade chronic systemic inflammation, which in turn could contribute to insulin resistance, eventually leading to a hyperglycemic state and diabetic complications. Conversely, diabetes and its associated pathways may increase susceptibility to the development of local complications.

The oral cavity may be home to those which were considered the first (i.e., untreated dental caries in permanent teeth) and sixth (i.e., severe periodontitis) most prevalent diseases in humans in 2010. Periodontitis was considered to be ‘the sixth complication of diabetes’ and presents a bidirectional relationship with that disease. Besides periodontitis, other oral health problems that may affect individuals with diabetes including but not limited to dry mouth, root caries, fungal infections (e.g., candidiasis), peri-implantitis, and oral cancer. In children, early dental eruption and gingivitis may also be present. All of these oral health problems affect the quality of life of diabetic patients and their development must be understood for effective management.

The aim of this Special Issue is to advance current knowledge on the mechanisms that contribute to the bidirectional relationship between diabetes and oral diseases, with a special focus on chronic oral diseases such as periodontitis, peri-implantitis, dental caries, endodontic lesions, and oral cancer, among others. Beyond inflammatory/immunological markers, studies evaluating the mechanisms and pathways by which the oral microbiome relates to this bidirectional association are especially welcome. New treatment strategies that may impact both diseases are also encouraged. All levels of scientific evidence (in vitro, preclinical, observational – cross-sectional or prospective – studies and randomized clinical trials) will be considered. Review articles, especially systematic reviews, are also welcome.

Potential topics include but are not limited to the following:

• Potential role of the oral microbiome on the bidirectional relationship between diabetes and oral diseases
• Mechanisms and pathways related to the bidirectional relationship between diabetes and oral diseases
• Prevention and treatment strategies for managing comorbidities – assessing both oral and systemic outcomes
• Common biomarkers for screening disease severity
• Evidence of the strength of association between oral diseases and diabetes