Periodontal (gum) disease has been referred to as the 6th major complication of diabetes. Periodontal diseases are the most common chronic bacterial infection in humans. They are a group of insidious, initially asymptomatic diseases which result in loss of the attachment between the tooth and the jaw and may ultimately lead to the loss of the teeth. Diabetes at least doubles your risk of periodontitis and poor control leads to even greater risk. Obviously loss of teeth may lead to significant restrictions in diet which may further complicate diabetic control.  Like diabetes, it is a condition that can be controlled. Without treatment, a patient may have an area of chronically ulcerated epithelium as large as the inner side of the forearm, which is unseen inside the mouth, but obviously has potentially significant systemic effects. This lecture will provide a background to the nature of periodontal disease and its management. It will examine the two way interaction between diabetes and periodontitis and oral health generally in the diabetic patient. Whichever way you look at it, poor oral health is detrimental to diabetic health.