Abstract: Most of the people living in the wetlands of Maliku District, Pulang Pisau Regency were still use river water to brush their teeth. Based on the content of water chemical parameters, pH, fluorine characteristics of wetland river water were not suitable for brushing teeth, because it can cause caries.: This research were research and Development method. Samples were taken using simple random sampling technique. The population of this study were 22 grade students of SD Tahai Jaya. The number of respondents was 22 students, which were divided into 2 groups, 11 students who brushed their teeth using river water and 11 students who brushed their teeth using water that met the requirements for toothbrushes. Then followed up for 6 months to examine the Caries index. There were significant differences in students who brushed their teeth using river water and clean water. From the research results it can be concluded that there were a significant difference in the caries index of students who brushed their teeth using river water and students who brushed their teeth with clean water.