Periodontal disease is caused by bacteria. Bacteria form a ‘plaque’ which is a sticky, colourless film that forms on your teeth, particularly around the gum line. Other bacteria thrive deep in the gap between the gum and the tooth (the ‘pocket’). Some people are much more at risk of developing periodontal disease — smoking is one of the major risk factors. Other conditions such as diabetes, stress, pregnancy and various medications can all be contributing factors.