Healthy gums never bleed when brushing, biting into an apple, or spontaneously. Gum bleeding is the cardinal sign of gingivitis, the body’s initial inflammatory response to bacterial plaque buildup on the tooth surface. Capillaries in the tissue dilate in response to bacterial toxins, increasing blood flow (hyperemia) and impairing permeability; the tissue becomes fragile and bleeds at the slightest touch. The gingivitis stage is reversible; the tissue heals completely if the plaque is removed. However, if left untreated at this stage, the infection histologically penetrates deeper tissues. Inflammatory cells (osteoclasts) begin to break down the periodontal fibers that connect the tooth to the bone, subsequently eroding the alveolar bone; the process evolves into irreversible periodontitis, meaning bone loss and the eventual loss of teeth.
