Background: Orthodontic treatment aims to improve teeth to obtain optimal occlusion with good physiological adaptation and mastication function, as well as facial aesthetic improvement. Orthodontic treatment, especially the use of fixed orthodontic planes can have an impact of changes in the oral environment and oral flora composition, an increase in the number of plaques that can cause dental caries and gingivitis, as a result of the difficulty of oral hygiene procedures in patients. Objective: Know the difference of OHI-S index between man and woman of fixed orthodontic appliance device at Faculty of Social and Political Sciences Muhammadiyah University of Yogyakarta. Method: The type of research conducted was analytic observational, with cross sectional study design. The subjects in this study were active students of the Faculty of Social and Political Sciences force 2017 who used a fixed orthodontic appliance for 1 to 2 years. Then the sampling technique used is non probability sampling that is with total sampling technique. Results: Respondents of women with OHI-S index of good criteria were 8 respondents, with moderate criteria 5 respondents, and none with bad criteria, male respondents with good criteria 2 respondents, moderate criteria 7 respondents, and with bad criteria 1 respondent. so there is a correlation between the OHI-S index of fixed orthodontic appliance to gender. Conclusion: There is a significant difference between the OHI-S index in man and woman.