Simply put, gingivitis is inflammation of the gums. It is the initial stage of gum disease and the easiest to treat. The direct cause of gingivitis is plaque. If plaque is not removed by daily brushing and flossing, it produces toxins that can irritate the gum tissue, causing gingivitis. At this early stage in gum disease, damage can be reversed. If it’s left untreated, however, gingivitis can become periodontitis and cause permanent damage to your teeth and jaw.