Gingivitis is a mild form of gum disease characterised by red, swollen (inflamed) gums that may bleed when teeth are cleaned. It is caused by bacteria in dental plaque releasing acid and enzymes that irritate the gums and stimulate an inflammatory response. If untreated, gingivitis can develop into the more severe periodontitis. Gingivitis can usually be reversed by improving personal oral care (regular brushing and flossing) and a professional clean.
For more information please view the New Zealand Society of Periodontology website.