Therefore, uncontrolled hyperglycemia increases the risk of developing periodontitis and triggers an overexpression of ACE-2 in the periodontal tissue of patients with T2DM, these events being potentially essential for SARS-CoV-2 infection and the development of the mild to severe form of COVID-19 (Casillas Santana et al., 2021). This evidence concerns the gene ACE2 and type 2 diabetes mellitus.