Periodontitis is a chronic multifactorial inflammatory disease primarily caused by biofilm and characterized by progressive loss of the supporting tooth apparatus. Due to its high prevalence and incidence, it is one of the most common chronic diseases, which makes it significant public health problem. Although plaq as a biofilm plays a central role in the complex development of this disease, it is the host's immune response that induces (too)strong inflammation that causes the destruction of tooth's supporting tissue. This complex mechanism of attachment and bone loss is under the influence of numerous modulators, of which it is inevitable to mention systematic diseases. Diabetes, the most common endocrine disorder characterized by hyperglycemia, caused by the insulin insufficiency, is most closely related to periodontitis. The model of low-intensity inflammation, induced by both periodontitis and diabetes, constitutes the strongest bond that connects these two diseases with convincing two-way mechanisms. Such silent, smoldering inflammation forms a kind of circulus vitiosus in which it is almost impossible to find out which disease is the primary originator of such a condition. Like periodontitis, diabetes also follows a trend of extremely high rates of increase in prevalence and incidence, which gives these two diseases the character of an almost epidemic spread in the western world. Given that, the comorbidity of diabetes and periodontitis is not uncommon today. Sufferers of these diseases represent a risk group of patients for many procedures performed in dental offices. With this in mind, adequate knowledge of the pathophysiology, the impact of both diseases on the oral cavity and procedures within it, as well as the guidelines by which they are carried out, is an absolute imperative for Doctor of Dental Medicine.