Tobacco smoking is a worldwide public health problem. Recently, there has been growing interest in smoking cessation. On the other hand, oral mucosal ulcers are common presentations encountered in daily practice. These ulcers may be caused by various etiologies.
We report a case of refractory oral mucosal ulcer caused by improper use of nicotine gum. A male in his 50s presented to our department with an intractable ulcer in the oral floor existing for over 3 months. He had smoked 20 cigarettes per day for 25 years. He had given up smoking and been using nicotine gum for 6 months. He used two pieces of nicotine gum （2mg tablet） per day, and the gum was improperly placed at the oral floor for 3 to 4 hours per piece. An excisional biopsy was performed and revealed a mucosal ulcer without atypical cells. He was instructed to stop using nicotine gum at the first visit to our department, and the ulcer healed completely in 4 weeks.