Gingivitis is a treatable and reversible form of gum disease. It is the first and mildest stage. Gum disease occurs when plaque that is constantly forming on your teeth accumulates and hardens over time. The bacteria found in this buildup causes damage to the gum tissue. Poor oral hygiene, such as infrequent brushing and flossing, along with irregular visits to your dental health professional, are the most common causes of gingivitis. According to the American Academy of Periodontology, factors such as smoking or chewing tobacco, stress, inadequate nutrition, pregnancy, diabetes, puberty, substance abuse, autoimmune diseases and certain medications contribute to increased risk for developing gum disease.