Introduction : Parents have important role in children’s character building. Social Government of Yogyakarta has a Social Rehabilitation and Childcare Center Institution (BRSPA) that provides a rehabilitation for children who have social problems, such as children abandonment by their parents. The children in BRSPA are looked after by foster parent in their daily life. The parent’s role is mainly needed in educating, giving attention, giving understanding, and providing facilities to children, so that later children are able maintain their oral health. Oral health can identified by plaque index. Objective: The purpose of this research was to determine the difference of plaque index between family and institution care children. Method: This study was descriptive observational method with cross sectional study approach. The study was conducted by examining the condition of plaque subjects which amounted to 35 family-care children (group 1) and 35 institution-care child (group 2). O'Leary plaque index was used in this study. The data were analyzed used Mann Whitney test. Results: Based on Mann Whitney test result there was significant difference (p <0,05) on plaque index before brushing (p = 0,012) and after brushing (p = 0,003) between family-care child and institution-care child. The difference of plaque index before-after brushing between family-care child and institution-care child there was a significant difference (p = 0.035). Conclusion: There was difference of plaque index between family-care and institution-care children.