Gingival lesions not induced by plaque are common and can help explain the many different periodontal tissue reactions observed. Gingival inflammation sometimes differs from that of routine plaque-associated gingival diseases and often presents distinctive clinical features. (Holmstrup, 1999a). The causes of non-plaque-induced gingival diseases include bacterial, viral, and fungal infections, genetic disorders and mucocutaneous diseases (e.g., lichen planus). Traumatic tooth brushing and allergic reactions to drugs are other possible causes.