Diabetes mellitus is a chronic disease characterized by hyperglycemia and causes a number of health complications. The increase in blood sugar levels consequently leads to an increase in salivary sugar levels and the development of oral manifestations of diabetes such as xerostomia, candidiasis, burning mouth syndrome (stomatopyrosis) and periodontal diseases. This last manifestation is termed as the sixth complication of diabetes mellitus. People with type 1, 2 diabetes or metabolic syndrome have a higher risk of developing periodontal disease. A patient with unregulated blood glucose levels will also develop more severe consequences of periodontal disease compared to a healthy person. There is a greater loss of clinical attachment, alveolar bone, heavier bleeding on probing and increased mobility of the teeth. Hyperglycemia also leads to an increase in bacteria in the oral cavity, frequent inflammation and the formation of glycosylated compounds that ultimately prolong the wound healing process and aggravate tissue damage. An increased number of proteolytic and hemolytic bacterial species have also been observed in diabetics. Regular check-ups and maintenance of appropriate oral hygiene can prevent the development of periodontal disease, thus preventing further destruction of the supporting tissues of the teeth. Apart from the fact that periodontal therapy reduces local inflammation in the periodontal area and enables the healing of pockets, its positive effects on diabetes control have also been proven.