Oral ulcers occur on the mucous membranes of the mouth and are a common disease caused by low immunity, or a lack of vitamins and trace elements, leading to a mucosal disease of the mouth. Generally, oral ulcers can heal on their own in about 14 days, or two weeks. If the ulcers do not improve after two weeks, a biopsy is necessary to avoid potential malignancy. Oral ulcers may also be due to sharp tooth cusps or dental roots within the mouth, which are referred to as traumatic ulcers; these can be examined. If dental roots or other irritating factors are present near the ulcer, it is important to promptly remove these external irritants. Oral ulcers that do not heal on their own after two weeks require further biopsy.