Gum disease occurs when bacteria in the plaque that causes tooth decay attacks the gum tissue around a tooth, creating pockets between the tooth and gums. These pockets become repositories for harmful bacteria. Periodontal disease usually starts as gingivitis, a mild form of gum disease that causes gums to become red, swollen, and bleed easily. In its early stages, gingivitis can be eliminated by brushing and flossing daily to remove plaque. If not treated, gingivitis can progress to periodontitis, a more serious condition of the gums that occurs when bacteria attack the bone and tissue supporting the teeth. Periodontists treat gum disease with root planing and scaling, a treatment in which the periodontist pulls back the gum tissue and uses specialized scraping tools to remove the harmful bacteria.