Dental mercury was injected accidentally to left upper buccal mucosa of a 16-year-old girl by charlatan in order to anesthetize a tooth for extraction; thereafter,injected elemental mercury was almost removed by drug adimnistration and surgical operations.One year have passed, still, there are many scaffered small radiopaque white globular cimages in dental, maxillo-facial, and chest radiographs. Redish swollen gingiva and mobility of left upper central incisor which is adjacent to mercury injection site are oral manifestations in this mercury poisoning case. Recently, the patient complains of metallic taste, gastric discomfort and abdominal pain which are thought to be symptoms of mercury poisoning, but there seems to be no serious sequelae now.