As many diseases have been shown to have several or indirect causes (i.e. are multifactorial) the question is what is the relative importance of each factor in a given disease? Also, what happens when some diseases, although apparently disparate, share causative factors and/or tissue pathologies? Host inflammation response mechanisms are largely shared by the body’s different tissues and systems and only recently has special attention been paid to the possible linkages among chronic periodontitis and other chronic systemic diseases. The aim of this review was to consider and discuss the mounting evidence that the basis for the inter-relationships between chronic periodontitis and atheromatous disease and diabetes lie at a fundamental intracellular level, namely oxidative stress and mitochondrial dysfunction, as a meeting background among such chronic diseases and periodontitis.