http://www.oramd.com/recedinggums/4-recedinggumline.htm For example if you have never had a problem with sensitive gums in the past, but suddenly find yourself buying sensitive toothpaste, there is a good change bacteria is affecting your gums. Bleeding gums during routine activities like brushing your teeth is an indication as well. In the more serious stages of periodontal disease, you may even notice that your gums are pulling away from the surface of the teeth and changing the way your teeth and gums look.