Background: The problem that many people experience in general is the uncluttered array of teeth. These reasons make people start doing dental care, one of which is orthodontic treatment. The use of orthodontic appliance in addition has a function that is very beneficial for the teeth but also has a deficiency, which can cause physical damage to the oral mucosa. The risk of orthodontic appliance is one of them is the occurrence of traumatic ulcers. Research purposes: To determine the difference in incidence of traumatic ulcers in users of removable orthodontic appliances and fixed orthodontics. Research methods: This type of research is analytic observational research with prospective cohort design. The subjects of this study were the removable orthodontic patients who would perform the insertion of the tool at Dental and Oral Hospital of Muhammadiyah University of Yogyakarta and the fixed orthodontic patient who would perform tool insertion in orthodontic dentist practice. The research subjects were 21 persons in each group who had fulfilled inclusion criteria. Data analysis using chi-square statistical test . Research result: Chi-square test results obtained value p = 0.190 (p>0.05) means there is the differences between one group with another group. Conclusion : The number of incidences of traumatic ulcers in users of fixed orthodontic appliances is higher than that of removable orthodontics.